JP2021002432A - Non-aqueous electrolyte power storage element, usage method thereof, and manufacturing method thereof - Google Patents
Non-aqueous electrolyte power storage element, usage method thereof, and manufacturing method thereof Download PDFInfo
- Publication number
- JP2021002432A JP2021002432A JP2019114141A JP2019114141A JP2021002432A JP 2021002432 A JP2021002432 A JP 2021002432A JP 2019114141 A JP2019114141 A JP 2019114141A JP 2019114141 A JP2019114141 A JP 2019114141A JP 2021002432 A JP2021002432 A JP 2021002432A
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- Prior art keywords
- positive electrode
- aqueous electrolyte
- charging
- power storage
- storage element
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- 238000003860 storage Methods 0.000 title claims abstract description 169
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Images
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
Description
本発明は、非水電解質蓄電素子、その使用方法及びその製造方法に関する。 The present invention relates to a non-aqueous electrolyte power storage device, a method of using the same, and a method of manufacturing the same.
リチウム二次電池に代表される非水電解質蓄電素子は、近年ますます用途が拡大され、より大容量の正極材料の開発が求められている。従来、非水電解質蓄電素子用の正極活物質として、α−ＮａＦｅＯ２型結晶構造を有するリチウム遷移金属複合酸化物が検討され、ＬｉＣｏＯ２を用いた非水電解質二次電池が広く実用化されている。リチウム遷移金属複合酸化物を構成する遷移金属（Ｍｅ）として、地球資源として豊富なマンガンを用い、リチウム遷移金属複合酸化物を構成する遷移金属に対するリチウムのモル比（Ｌｉ／Ｍｅ）がほぼ１であり、遷移金属中のマンガンのモル比（Ｍｎ／Ｍｅ）が０．５以下である、いわゆるＬｉＭｅＯ２型活物質を用いた非水電解質二次電池も実用化されている。 Non-aqueous electrolyte power storage elements represented by lithium secondary batteries have been increasingly used in recent years, and development of a positive electrode material having a larger capacity is required. Conventionally, a lithium transition metal composite oxide having an α-NaFeO type 2 crystal structure has been studied as a positive electrode active material for a non-aqueous electrolyte storage element, and a non-aqueous electrolyte secondary battery using LiCoO 2 has been widely put into practical use. There is. Manganese, which is abundant as an earth resource, is used as the transition metal (Me) constituting the lithium transition metal composite oxide, and the molar ratio of lithium to the transition metal constituting the lithium transition metal composite oxide (Li / Me) is approximately 1. In addition, a non-aqueous electrolyte secondary battery using a so-called LiMeO type 2 active material in which the molar ratio (Mn / Me) of manganese in the transition metal is 0.5 or less has also been put into practical use.
一方、近年、α−ＮａＦｅＯ２型結晶構造を有するリチウム遷移金属複合酸化物の中でも、遷移金属に対するリチウムのモル比（Ｌｉ／Ｍｅ）が１を超える、いわゆるリチウム過剰型活物質が知られている（特許文献１、２）。この活物質は、電池を組み立てて、最初に行う充電過程において、４．５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以上５．０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下の電位範囲内に、充電電気量に対して電位変化が比較的緩やかな領域が観察されるという特徴がある。このようなリチウム過剰型活物質を用いた非水電解質蓄電素子は、電位変化が比較的緩やかな領域が観察される充電過程が終了するまで初期に充電を行うことにより、以降の充電電位をそれほど高くしなくても、ＬｉＭｅＯ２型活物質に比べて大きい放電容量を有することから、注目されている。
On the other hand, in recent years, among lithium transition metal composite oxides having an α-NaFeO type 2 crystal structure, a so-called lithium excess type active material in which the molar ratio of lithium to the transition metal (Li / Me) exceeds 1 is known. (
リチウム過剰型活物質を正極に用いた従来の非水電解質蓄電素子においては、上記のような効果を発揮させるため、一般的に正極電位が４．６Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以上に至るまでの初期充放電を経て製造される。特許文献１では、リチウム過剰型活物質を正極に用い、ケイ素と炭素とを負極に用いた非水電解質二次電池の初期充放電の際に、正極電位が４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまで充電が行われている。特許文献２では、リチウム過剰型活物質を正極に用い、黒鉛を負極に用いた非水電解質二次電池の初期充放電の際に、電圧が４．７Ｖに至るまで、すなわち正極電位が４．８Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまで充電が行われている。
In a conventional non-aqueous electrolyte power storage device using a lithium excess type active material for the positive electrode, the positive electrode potential is generally 4.6 V vs. in order to exert the above effects. Manufactured through initial charge / discharge up to Li / Li + or higher. In
上述のようなリチウム過剰型活物質を正極に用いた非水電解質蓄電素子は、充放電サイクルにおける容量維持率が低いという不都合を有する。 The non-aqueous electrolyte power storage element using the lithium excess type active material as the positive electrode as described above has the disadvantage that the capacity retention rate in the charge / discharge cycle is low.
本発明の目的は、リチウム過剰型活物質を正極に用いた非水電解質蓄電素子であって、充放電サイクルにおける容量維持率が高い非水電解質蓄電素子、並びにこのような非水電解質蓄電素子の使用方法及び製造方法を提供することである。 An object of the present invention is a non-aqueous electrolyte storage element using a lithium excess type active material as a positive electrode, a non-aqueous electrolyte storage element having a high capacity retention rate in a charge / discharge cycle, and such a non-aqueous electrolyte storage element. To provide a method of use and a method of manufacture.
本発明の一態様に係る非水電解質蓄電素子は、正極活物質を含む正極合剤を有する正極を備え、上記正極活物質が、α−ＮａＦｅＯ２構造を有し、かつＬｉ１＋αＭｅ１−αＯ２（０＜α＜１；ＭｅはＮｉ及びＭｎを含む遷移金属である。）で表されるリチウム遷移金属複合酸化物を含み、上記正極に対して、上記正極合剤の質量あたり９ｍＡ／ｇの電流密度により、電位が２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの放電を行った後、上記電流密度により、電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電と電位が２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの放電とからなる充放電を２サイクル行ったときの充電電気量が、下記式（１）を満たす、非水電解質蓄電素子である。
（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００≧１．０ ・・・（１）
（式（１）中、Ｃ１Ａは、上記充放電の１サイクル目の充電の際に、充電開始から電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ１Ｂは、上記充放電の１サイクル目の充電の際に、充電開始から電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ２Ａは、上記充放電の２サイクル目の充電の際に、充電開始から電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ２Ｂは、上記充放電の２サイクル目の充電の際に、充電開始から電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。）
The non-aqueous electrolyte power storage element according to one aspect of the present invention includes a positive electrode having a positive electrode mixture containing a positive electrode active material, and the positive electrode active material has an α-NaFeO 2 structure and Li 1 + α Me 1-α. It contains a lithium transition metal composite oxide represented by O 2 (0 <α <1; Me is a transition metal containing Ni and Mn), and is 9 mA / mass of the positive electrode mixture with respect to the positive electrode. Due to the current density of g, the potential is 2.00 V vs. After discharging up to Li / Li + , the potential becomes 4.80 V vs. due to the above current density. Charging and potential up to Li / Li + is 2.00 V vs. It is a non-aqueous electrolyte power storage element in which the amount of electricity charged when two cycles of charge / discharge consisting of discharge up to Li / Li + is performed satisfies the following formula (1).
(C 2A / C 2B ) × 100- (C 1A / C 1B ) × 100 ≧ 1.0 ・ ・ ・ (1)
(In the formula (1), C 1A is the amount of electricity charged from the start of charging to the potential of 4.45 V vs. Li / Li + during the first cycle of charging / discharging. C 1B. Is the amount of electricity charged from the start of charging to the potential of 4.80 V vs. Li / Li + during the first cycle of charging / discharging. C 2A is the second cycle of charging / discharging. C 2B is the amount of electricity charged from the start of charging to the potential of 4.45 V vs. Li / Li + at the time of charging. C 2B is the amount of electricity charged from the start of charging during the second cycle of charging / discharging. The amount of electricity charged until the potential reaches 4.80 V vs. Li / Li + .)
本発明の他の一態様に係る非水電解質蓄電素子の使用方法は、正極電位が４．３０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋超４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満に至るまで充電することを備える、本発明の一態様の非水電解質蓄電素子の使用方法である。 In the method of using the non-aqueous electrolyte power storage device according to another aspect of the present invention, the positive electrode potential is 4.30 V vs. Li / Li + Super 4.60V vs. It is a method of using the non-aqueous electrolyte power storage element according to one aspect of the present invention, which comprises charging to less than Li / Li + .
本発明の他の一態様に係る非水電解質蓄電素子の製造方法は、上記正極の最大到達電位を４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満で初期充放電を行うことを備える、本発明の一態様の非水電解質蓄電素子の製造方法である。 In the method for manufacturing a non-aqueous electrolyte power storage device according to another aspect of the present invention, the maximum ultimate potential of the positive electrode is 4.60 V vs. It is a method for manufacturing a non-aqueous electrolyte power storage element according to one aspect of the present invention, which comprises performing initial charge / discharge at less than Li / Li + .
本発明の一態様に係る非水電解質蓄電素子は、リチウム過剰型活物質を正極に用いた非水電解質蓄電素子であって、充放電サイクルにおける容量維持率が高い。
本発明の他の一態様に係る非水電解質蓄電素子の使用方法によれば、リチウム過剰型活物質を正極に用いた非水電解質蓄電素子を高い容量維持率で使用することができる。
本発明の他の一態様に係る非水電解質蓄電素子の製造方法によれば、リチウム過剰型活物質を正極に用いた非水電解質蓄電素子であって、充放電サイクルにおける容量維持率が高い非水電解質蓄電素子を製造することができる。
The non-aqueous electrolyte storage element according to one aspect of the present invention is a non-aqueous electrolyte storage element using a lithium excess type active material as a positive electrode, and has a high capacity retention rate in a charge / discharge cycle.
According to the method of using the non-aqueous electrolyte storage element according to another aspect of the present invention, the non-aqueous electrolyte storage element using the lithium excess type active material as the positive electrode can be used with a high capacity retention rate.
According to the method for producing a non-aqueous electrolyte storage device according to another aspect of the present invention, the non-aqueous electrolyte storage device using a lithium excess type active material as a positive electrode has a high capacity retention rate in a charge / discharge cycle. A water electrolyte power storage element can be manufactured.
初めに、本明細書によって開示される非水電解質蓄電素子、その使用方法及びその製造方法の概要について説明する。 First, the outline of the non-aqueous electrolyte power storage device disclosed by the present specification, its use method, and its manufacturing method will be described.
本発明の一態様に係る非水電解質蓄電素子は、正極活物質を含む正極合剤を有する正極を備え、上記正極活物質が、α−ＮａＦｅＯ２構造を有し、かつＬｉ１＋αＭｅ１−αＯ２（０＜α＜１；ＭｅはＮｉ及びＭｎを含む遷移金属である。）で表されるリチウム遷移金属複合酸化物を含み、上記正極に対して、上記正極合剤の質量あたり９ｍＡ／ｇの電流密度により、電位が２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの放電を行った後、上記電流密度により、電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電と電位が２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの放電とからなる充放電を２サイクル行ったときの充電電気量が、下記式（１）を満たす、非水電解質蓄電素子である。
（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００≧１．０ ・・・（１）
（式（１）中、Ｃ１Ａは、上記充放電の１サイクル目の充電の際に、充電開始から電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ１Ｂは、上記充放電の１サイクル目の充電の際に、充電開始から電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ２Ａは、上記充放電の２サイクル目の充電の際に、充電開始から電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ２Ｂは、上記充放電の２サイクル目の充電の際に、充電開始から電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。）
The non-aqueous electrolyte power storage element according to one aspect of the present invention includes a positive electrode having a positive electrode mixture containing a positive electrode active material, and the positive electrode active material has an α-NaFeO 2 structure and Li 1 + α Me 1-α. It contains a lithium transition metal composite oxide represented by O 2 (0 <α <1; Me is a transition metal containing Ni and Mn), and is 9 mA / mass of the positive electrode mixture with respect to the positive electrode. Due to the current density of g, the potential is 2.00 V vs. After discharging up to Li / Li + , the potential becomes 4.80 V vs. due to the above current density. Charging and potential up to Li / Li + is 2.00 V vs. It is a non-aqueous electrolyte power storage element in which the amount of electricity charged when two cycles of charge / discharge consisting of discharge up to Li / Li + is performed satisfies the following formula (1).
(C 2A / C 2B ) × 100- (C 1A / C 1B ) × 100 ≧ 1.0 ・ ・ ・ (1)
(In the formula (1), C 1A is the amount of electricity charged from the start of charging to the potential of 4.45 V vs. Li / Li + during the first cycle of charging / discharging. C 1B. Is the amount of electricity charged from the start of charging to the potential of 4.80 V vs. Li / Li + during the first cycle of charging / discharging. C 2A is the second cycle of charging / discharging. C 2B is the amount of electricity charged from the start of charging to the potential of 4.45 V vs. Li / Li + at the time of charging. C 2B is the amount of electricity charged from the start of charging during the second cycle of charging / discharging. The amount of electricity charged until the potential reaches 4.80 V vs. Li / Li + .)
当該非水電解質蓄電素子は、リチウム過剰型活物質（α−ＮａＦｅＯ２構造を有し、かつＬｉ１＋αＭｅ１−αＯ２で表されるリチウム遷移金属複合酸化物）を正極に用いた非水電解質蓄電素子であって、充放電サイクルにおける容量維持率が高い。このような効果が生じる理由は定かでは無いが、以下のことが推測される。 The non-aqueous electrolyte storage element is a non-water-free active material (a lithium transition metal composite oxide having an α-NaFeO 2 structure and represented by Li 1 + α Me 1-α O 2 ) as a positive electrode. It is an electrolyte storage element and has a high capacity retention rate in the charge / discharge cycle. The reason for this effect is not clear, but the following can be presumed.
（式（１）の技術的意義）
まず、上記式（１）の技術的意義について、図１、２を参照に説明する。図１は、本発明の実施例１に係る非水電解質蓄電素子（試験電池）に対して、上記２サイクルの充放電を行ったときの充放電曲線である。図２は、本発明の比較例１に係る非水電解質蓄電素子（試験電池）に対して、上記２サイクルの充放電を行ったときの充放電曲線である。なお、図１、２において、横軸は、充電開始から電圧が４．８０Ｖ（正極電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）に至るまでの充電における充電電気量（Ｃ１Ｂ又はＣ２Ｂ）、又は放電開始から電圧が２．００Ｖ（正極電位が２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）に至るまでの放電における放電電気量を基準（１００％）とした相対電気量（％）である。また、負極材料が金属リチウムの場合、負極における金属リチウムの溶解・析出反応抵抗が極めて低いことから、充放電中の端子間電圧は、金属リチウムを用いた参照極に対する作用極の電位と等しいとみなすことができる。
(Technical significance of equation (1))
First, the technical significance of the above formula (1) will be described with reference to FIGS. 1 and 2. FIG. 1 is a charge / discharge curve when the non-aqueous electrolyte power storage element (test battery) according to the first embodiment of the present invention is charged / discharged in the above two cycles. FIG. 2 is a charge / discharge curve when the non-aqueous electrolyte power storage element (test battery) according to Comparative Example 1 of the present invention is charged / discharged in the above two cycles. In FIGS. 1 and 2, the horizontal axis indicates the amount of electricity charged (C 1B or C 2B ) in charging from the start of charging to the voltage of 4.80 V (positive electrode potential is 4.80 V vs. Li / Li + ). Or, it is a relative electric amount (%) based on the electric discharge amount in the discharge from the start of the discharge to the voltage of 2.00 V (positive electrode potential is 2.00 V vs. Li / Li + ). Further, when the negative electrode material is metallic lithium, the dissolution / precipitation reaction resistance of metallic lithium in the negative electrode is extremely low, so that the voltage between terminals during charging and discharging is equal to the potential of the working electrode with respect to the reference electrode using metallic lithium. Can be regarded.
比較例１の非水電解質蓄電素子では、上記２サイクルの充放電を行なう前に実施する初期充放電において、正極電位が４．６Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電が行われている。上述のように、リチウム過剰型活物質は、初期に正極電位が高い電位に至るまで充電を行うと、４．５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以上５．０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下の電位範囲内に、充電電気量に対して電位変化が比較的緩やかな領域が観察されるという特徴がある。そして、この電位変化が比較的緩やかな領域が観察される充電を行った場合は、その後、正極電位が同様の高い電位に至る充電を行っても、この電位変化が比較的緩やかな領域は再び観察されることは、通常無いとされている。また、リチウム過剰型活物質は、ＬｉＭｅＯ２とＬｉ２ＭｎＯ３との固溶体と考えることができ、Ｌｉ２ＭｎＯ３においてはリチウムイオンが遷移金属サイトにも存在していると考えられている。リチウム過剰型活物質においては、このような遷移金属サイトに存在するリチウムイオンが、正極電位が４．６Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電により脱離しやすくなるため、その後の充放電において大きい充放電容量が得られるようになる（活性化される）ものと考えられる。以降、「正極電位が４．６Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以上に至るまでの充電を行い、リチウム過剰型活物質が活性化されること」を高電位化成ともいう。 In the non-aqueous electrolyte power storage element of Comparative Example 1, the positive electrode potential was 4.6 V vs. in the initial charge / discharge performed before the above two cycles of charge / discharge. Charging up to Li / Li + is performed. As described above, when the lithium excess type active material is initially charged until the positive electrode potential reaches a high potential, 4.5 V vs. Li / Li + or more 5.0V vs. Within the potential range of Li / Li + or less, a region in which the potential change is relatively gradual with respect to the amount of charging electricity is observed. Then, when charging is performed in which a region in which the potential change is relatively gradual is observed, then even if charging is performed in which the positive electrode potential reaches a similar high potential, the region in which the potential change is relatively gradual is again found. It is usually not observed. Further, the lithium excess type active material can be considered as a solid solution of LiMeO 2 and Li 2 MnO 3, and it is considered that lithium ions are also present at the transition metal sites in Li 2 MnO 3 . In the lithium-rich active material, the lithium ions present at such transition metal sites have a positive electrode potential of 4.6 V vs. It is considered that a large charge / discharge capacity can be obtained (activated) in the subsequent charge / discharge because it is easily desorbed by charging up to Li / Li + . Hereinafter, "charging up to a positive electrode potential of 4.6 V vs. Li / Li + or higher to activate the lithium excess type active material" is also referred to as high potential conversion.
初期充放電において高電位化成がなされている比較例１の非水電解質蓄電素子においては、上記２サイクルの充放電において電圧が４．８０Ｖ（正極電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）に至るまでの充電を行っても、４．５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以上４．８Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下の電位範囲内に、充電電気量に対して電位変化が比較的緩やかな領域が観察されない。このため、１サイクル目の充電曲線と２サイクル目の充電曲線との差異がほとんど無い。 In the non-aqueous electrolyte power storage element of Comparative Example 1 in which the high potential is formed in the initial charge / discharge, the voltage becomes 4.80 V (positive electrode potential is 4.80 V vs. Li / Li + ) in the above two cycles of charge / discharge. Even after charging up to 4.5V vs. Li / Li + or more 4.8V vs. Within the potential range of Li / Li + or less, a region in which the potential change is relatively gradual with respect to the amount of charging electricity is not observed. Therefore, there is almost no difference between the charging curve of the first cycle and the charging curve of the second cycle.
これに対し、実施例１の非水電解質蓄電素子においては、初期充放電も含め、上記２サイクルの充放電を行なう前に、正極電位が４．６Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電が行われていない。従って、上記２サイクルの充放電のうちの１サイクル目ではじめて高電位化成がなされることとなり、１サイクル目の充電において４．５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以上４．８Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下の電位範囲内に、充電電気量に対して電位変化が比較的緩やかな領域が観察されている。また、この電位変化が比較的緩やかな領域は、２サイクル目には観察されない。 On the other hand, in the non-aqueous electrolyte power storage element of Example 1, the positive electrode potential was 4.6 V vs. before performing the above two cycles of charge / discharge including the initial charge / discharge. Charging up to Li / Li + has not been performed. Therefore, the high potential conversion is performed only in the first cycle of the above two cycles of charging and discharging, and 4.5 V vs. Li / Li + or more 4.8V vs. Within the potential range of Li / Li + or less, a region in which the potential change is relatively gradual with respect to the amount of charging electricity is observed. Further, the region where the potential change is relatively gentle is not observed in the second cycle.
このため実施例１においては、１サイクル目における充電開始から電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量に対する、充電開始から電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量（Ｃ１Ａ／Ｃ１Ｂ）は比較的小さいのに対し、２サイクル目における充電開始から電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量に対する、充電開始から電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量（Ｃ２Ａ／Ｃ２Ｂ）は大きくなる。すなわち実施例１の場合、Ｃ１Ａ／Ｃ１ＢとＣ２Ａ／Ｃ２Ｂとの差が大きい。これに対し比較例１の場合は、１サイクル目と２サイクル目とがほぼ同じ挙動を示すため、Ｃ１Ａ／Ｃ１ＢとＣ２Ａ／Ｃ２Ｂとの差がほとんどない。このように、式（１）を満たすということは、リチウム過剰型活物質に対して十分な高電位化成がなされていないことを意味する。 Therefore, in Example 1, the potential is 4.80 V vs. from the start of charging in the first cycle. With respect to the amount of electricity charged up to Li / Li + , the potential from the start of charging is 4.45 V vs. While the amount of electricity charged (C 1A / C 1B ) up to Li / Li + is relatively small, the potential is 4.80 V vs. from the start of charging in the second cycle. With respect to the amount of electricity charged up to Li / Li + , the potential from the start of charging is 4.45 V vs. The amount of electricity charged (C 2A / C 2B ) up to Li / Li + becomes large. That is, in the case of Example 1, the difference between C 1A / C 1B and C 2A / C 2B is large. On the other hand, in the case of Comparative Example 1, since the first cycle and the second cycle show almost the same behavior, there is almost no difference between C 1A / C 1B and C 2A / C 2B . As described above, satisfying the formula (1) means that a sufficiently high potential conversion has not been performed on the lithium excess type active material.
（効果が生じる理由の推察）
一方、非水電解質蓄電素子においては、充放電の際の副反応により、充放電に寄与するリチウムイオンを負極が消費することが、容量維持率が低下する原因の一つと推測される。ここで、十分な高電位化成がなされていないリチウム過剰型活物質を有する非水電解質蓄電素子においては、使用時の充放電の繰り返しに伴い、徐々にリチウム過剰型活物質が活性化され、充放電の際にリチウム過剰型活物質から脱離するリチウムイオンが徐々に増加することができると推測される。以降、「使用時の充放電の繰り返し等に伴い、徐々にリチウム過剰型活物質が活性化されること」を経時化成ともいう。このため、本発明の一態様に係る非水電解質蓄電素子によれば、充放電サイクルにおける負極によるリチウムイオンの消費を、正極のリチウム過剰型活物質からの補充により補うことができるため、容量維持率が高いと推測される。また、当該非水電解質蓄電素子においては、例えば充電状態で放置しておいた場合も、経時化成が進行し得る。従って、当該非水電解質蓄電素子によれば、放置後の容量維持率の低下も抑制することができる。
(Inference of the reason why the effect occurs)
On the other hand, in the non-aqueous electrolyte power storage element, it is presumed that one of the causes of the decrease in the capacity retention rate is that the negative electrode consumes lithium ions that contribute to charging / discharging due to a side reaction during charging / discharging. Here, in the non-aqueous electrolyte power storage element having a lithium-rich active material that has not been sufficiently high-potentialized, the lithium-rich active material is gradually activated and charged with repeated charging and discharging during use. It is speculated that the amount of lithium ions desorbed from the lithium excess type active material during discharge can gradually increase. Hereinafter, "the gradual activation of the lithium excess type active material with repeated charging and discharging during use" is also referred to as aging. Therefore, according to the non-aqueous electrolyte power storage element according to one aspect of the present invention, the consumption of lithium ions by the negative electrode in the charge / discharge cycle can be supplemented by replenishment from the lithium excess type active material of the positive electrode, so that the capacity is maintained. It is estimated that the rate is high. Further, in the non-aqueous electrolyte power storage element, for example, even if it is left in a charged state, aging may proceed. Therefore, according to the non-aqueous electrolyte power storage element, it is possible to suppress a decrease in the capacity retention rate after being left unattended.
なお、上記正極に対して、上記式（１）の値を求める際、以下の手順を採用する。まず、非水電解質蓄電素子を放電状態とし、非水電解質蓄電素子を解体して正極を取り出す。取り出した正極を作用極、金属リチウム電極を対極とした試験電池（単極電池）を組み立てる。なお、非水電解質蓄電素子の解体から試験電池の組み立てまでの作業は露点−６０℃以下のアルゴン雰囲気中で行う。組み立てた上記試験電池に対し、上記電位が２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの放電、及び上記式（１）の値を求めるための２サイクルの充放電を行う。上記式（１）の値を求めるための２サイクルの充放電は、２５℃の環境下で行い、充電と放電との間は、それぞれ３０分間の休止期間を設けて行う。 The following procedure is adopted when obtaining the value of the above formula (1) for the positive electrode. First, the non-aqueous electrolyte storage element is discharged, the non-aqueous electrolyte storage element is disassembled, and the positive electrode is taken out. Assemble a test battery (unipolar battery) with the removed positive electrode as the working electrode and the metallic lithium electrode as the counter electrode. The work from disassembling the non-aqueous electrolyte power storage element to assembling the test battery is performed in an argon atmosphere with a dew point of −60 ° C. or lower. With respect to the assembled test battery, the potential was 2.00 V vs. Discharge up to Li / Li + and charge / discharge for 2 cycles to obtain the value of the above formula (1). The two-cycle charge / discharge for obtaining the value of the above formula (1) is performed in an environment of 25 ° C., and a rest period of 30 minutes is provided between charging and discharging.
また、上記リチウム遷移金属複合酸化物の組成は、上記正極に対して、上記正極合剤の質量あたり９ｍＡ／ｇの電流密度により、電位が２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの放電を行った状態で解体して分析された組成とする。 The composition of the lithium transition metal composite oxide has a potential of 2.00 V vs. the positive electrode with a current density of 9 mA / g per mass of the positive electrode mixture. The composition is disassembled and analyzed while being discharged up to Li / Li + .
上記リチウム遷移金属複合酸化物における遷移金属（Ｍｅ）に占めるＭｎのモル比（Ｍｎ／Ｍｅ）と、遷移金属（Ｍｅ）に占めるＮｉのモル比（Ｎｉ／Ｍｅ）との差（Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅ）が、０．０２以上０．２以下であることが好ましい。 The difference (Mn / Me-) between the molar ratio of Mn to the transition metal (Me) in the transition metal composite oxide (Mn / Me) and the molar ratio of Ni to the transition metal (Me) (Ni / Me). Ni / Me) is preferably 0.02 or more and 0.2 or less.
リチウム遷移金属複合酸化物において、上記モル比の差（Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅ）が０．２以下であることにより、特に、比較的低い充電上限電位で使用する場合（通常使用時の充電終止電圧における正極電位が比較的低い場合）において、大きな放電容量を有し、エネルギー密度が高い非水電解質蓄電素子となる。一方、上記モル比の差（Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅ）が０．０２以上であることにより、経時化成の作用が高まり、容量維持率がより高まる。このような効果が生じる理由は定かでは無いが、以下のことが推測される。上述のように、リチウム過剰型活物質は、Ｌｉ２ＭｎＯ３とＬｉＭｅＯ２との固溶体と考えることができる。ここでさらに、ＬｉＭｅＯ２をＬｉＮｉ０．５Ｍｎ０．５Ｏ２とＬｉＣｏＯ２との固溶体とみなせば、リチウム過剰型活物質は、Ｌｉ２ＭｎＯ３とＬｉＮｉ０．５Ｍｎ０．５Ｏ２とＬｉＣｏＯ２との固溶体とみなすことができ、その組成は図３に示す三角相図で表すことができる。図３の三角相図において、０．０２≦（Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅ）≦０．２を満たすリチウム遷移金属複合酸化物（リチウム過剰型活物質）は、斜線の領域の組成のものとなる。ここで、Ｌｉ２ＭｎＯ３の比率が高い組成のリチウム遷移金属複合酸化物においては、リチウムイオンのうちＬｉ２ＭｎＯ３の遷移金属サイトに存在するリチウムイオンが相対的に多い。本発明の一態様に係る非水電解質蓄電素子においては、十分な高電位化成がなされておらず、比較的低い充電上限電位で使用する場合、遷移金属サイトに存在するリチウムイオンは脱離し難い。このため、Ｌｉ２ＭｎＯ３の比率が高い組成のリチウム遷移金属複合酸化物は、放電容量が大きくならない。これに対し、（Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅ）≦０．２を満たすリチウム遷移金属複合酸化物は、Ｌｉ２ＭｎＯ３の比率が低く、ＬｉＭｅＯ２を主とする固溶体とみなすことができ、リチウムイオンのうちリチウムサイトに存在するリチウムイオンが多くを占める。リチウムサイトに存在するリチウムイオンは、高電位化成されなくとも、比較的低い充電上限電位で使用する場合も脱離しやすい。このため、リチウム遷移金属複合酸化物が（Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅ）≦０．２を満たす場合、放電容量が大きく、エネルギー密度も高くなると推測される。一方、Ｌｉ２ＭｎＯ３の比率が高い組成のリチウム遷移金属複合酸化物においては、経時化成によって徐々に脱離可能な、遷移金属サイトに存在するリチウムイオンが十分に存在することとなる。このため、リチウム遷移金属複合酸化物が０．０２≦（Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅ）を満たす場合、経時化成の作用が十分に生じ、容量維持率がより高まると推測される。なお、「比較的低い充電上限電位」としては、充電上限電位が例えば４．５０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下であってよく、４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下であってもよい。
In the lithium transition metal composite oxide, the difference in molar ratio (Mn / Me-Ni / Me) is 0.2 or less, so that the lithium transition metal composite oxide is used at a relatively low upper charge potential (charge during normal use). When the positive electrode potential at the final voltage is relatively low), the non-aqueous electrolyte storage element has a large discharge capacity and a high energy density. On the other hand, when the difference in molar ratio (Mn / Me—Ni / Me) is 0.02 or more, the action of aging is enhanced and the capacity retention rate is further enhanced. The reason for this effect is not clear, but the following can be presumed. As described above, the lithium excess type active material can be considered as a solid solution of Li 2 MnO 3 and Li MeO 2 . Here addition, is regarded to LiMeO 2 and a solid solution of LiNi 0.5 Mn 0.5 O 2 and LiCoO 2, lithium-excess active material, and
上記リチウム遷移金属複合酸化物における遷移金属（Ｍｅ）に占めるＭｎのモル比（Ｍｎ／Ｍｅ）が０．５以下であることが好ましい。リチウム遷移金属複合酸化物におけるＭｎ／Ｍｅを０．５以下にすることにより、特に、比較的低い充電上限電位で使用する場合（通常使用時の充電終止電圧における正極電位が比較的低い場合）において、大きな放電容量を有し、エネルギー密度が高い非水電解質蓄電素子となる。このような効果が生じる理由は定かでは無いが、図３の三角相図に示されるように、Ｍｎ／Ｍｅ≦０．５を満たすものも、上述の（Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅ）≦０．２を満たすものと同様に、ＬｉＭｅＯ２の割合が高い固溶体とみなせる。これにより、（Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅ）≦０．２を満たすものと同様に、放電容量が大きくなり、エネルギー密度を高くすることなどができると推測される。 The molar ratio (Mn / Me) of Mn to the transition metal (Me) in the lithium transition metal composite oxide is preferably 0.5 or less. By setting Mn / Me in the lithium transition metal composite oxide to 0.5 or less, especially when used at a relatively low charging upper limit potential (when the positive electrode potential at the charging end voltage during normal use is relatively low). It is a non-aqueous electrolyte storage element with a large discharge capacity and high energy density. The reason why such an effect occurs is not clear, but as shown in the triangular phase diagram of FIG. 3, those satisfying Mn / Me ≦ 0.5 also satisfy the above-mentioned (Mn / Me—Ni / Me) ≦ 0. It can be regarded as a solid solution having a high proportion of LiMeO 2 as in the case of satisfying .2. As a result, it is presumed that the discharge capacity can be increased and the energy density can be increased, as in the case of satisfying (Mn / Me—Ni / Me) ≦ 0.2.
上記リチウム遷移金属複合酸化物における遷移金属（Ｍｅ）に占めるＭｎのモル比（Ｍｎ／Ｍｅ）が０．３６超であることが好ましい。リチウム遷移金属複合酸化物におけるＭｎ／Ｍｅを０．３６超にすることにより、容量維持率がより高まる。このような効果が生じる理由は、Ｍｎの比率を比較的高めることで遷移金属サイトに十分な量のリチウムイオンを存在させることができ、経時化成の作用が高まるためといったことが推測される。 The molar ratio (Mn / Me) of Mn to the transition metal (Me) in the lithium transition metal composite oxide is preferably more than 0.36. By setting Mn / Me in the lithium transition metal composite oxide to more than 0.36, the capacity retention rate is further increased. It is presumed that the reason why such an effect occurs is that a sufficient amount of lithium ions can be present at the transition metal site by relatively increasing the ratio of Mn, and the action of aging is enhanced.
上記リチウム遷移金属複合酸化物における遷移金属（Ｍｅ）に占めるＭｎのモル比（Ｍｎ／Ｍｅ）が０．３６超０．５以下であることが好ましい。リチウム遷移金属複合酸化物におけるＭｎ／Ｍｅを０．３６超０．５以下にすることにより、非水電解質蓄電素子の高い容量維持率とエネルギー密度等との好適なバランスを図ることなどができる。 The molar ratio (Mn / Me) of Mn to the transition metal (Me) in the lithium transition metal composite oxide is preferably more than 0.36 and 0.5 or less. By setting Mn / Me in the lithium transition metal composite oxide to more than 0.36 and 0.5 or less, it is possible to achieve a suitable balance between the high capacity retention rate of the non-aqueous electrolyte power storage element and the energy density.
上記リチウム遷移金属複合酸化物における遷移金属（Ｍｅ）に占めるＣｏのモル比（Ｃｏ／Ｍｅ）が０．４５未満であることが好ましい。Ｃｏのモル比率を０．４５未満とすることで、十分な容量維持率を発揮しつつ、高価なＣｏの使用を抑え、コスト削減を図ることができる。 The molar ratio (Co / Me) of Co to the transition metal (Me) in the lithium transition metal composite oxide is preferably less than 0.45. By setting the molar ratio of Co to less than 0.45, it is possible to suppress the use of expensive Co and reduce the cost while exhibiting a sufficient capacity retention rate.
上記正極活物質に占める上記リチウム遷移金属複合酸化物の含有量が７０質量％超であることが好ましい。このように、正極活物質に占めるリチウム遷移金属複合酸化物、すなわち高電位化成されていないリチウム過剰型活物質の含有割合を高めることで、十分な経時化成の効果が発揮され、容量維持率をより高めることができる。 The content of the lithium transition metal composite oxide in the positive electrode active material is preferably more than 70% by mass. In this way, by increasing the content ratio of the lithium transition metal composite oxide in the positive electrode active material, that is, the lithium excess type active material that has not been converted to a high potential, a sufficient effect of aging is exhibited and the capacity retention rate is increased. Can be enhanced.
本発明の一態様に係る非水電解質蓄電素子においては、通常使用時の充電終止電圧における正極電位が４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満であることが好ましい。通常使用時の充電終止電圧における正極電位が４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満であることにより、多数回の充放電の繰り返しに伴って、経時化成が徐々に進行するため、容量維持率を高めることができる。 In the non-aqueous electrolyte power storage device according to one aspect of the present invention, the positive electrode potential at the end-of-charge voltage during normal use is 4.60 V vs. It is preferably less than Li / Li + . The positive electrode potential at the end of charging voltage during normal use is 4.60 V vs. When it is less than Li / Li + , the aging process gradually progresses with the repetition of charging and discharging a large number of times, so that the capacity retention rate can be increased.
なお、「通常使用時」とは、当該非水電解質蓄電素子について推奨され、又は指定される充電条件を採用して当該非水電解質蓄電素子を使用する場合をいう。例えば、当該非水電解質蓄電素子のための充電器が用意されている場合は、その充電器を適用して当該非水電解質蓄電素子を使用する場合をいう。 The term "normal use" refers to the case where the non-aqueous electrolyte storage element is used by adopting the charging conditions recommended or specified for the non-aqueous electrolyte storage element. For example, when a charger for the non-aqueous electrolyte power storage element is prepared, it means a case where the charger is applied to use the non-aqueous electrolyte power storage element.
本発明の一態様に係る非水電解質蓄電素子においては、通常使用時の充電終止電圧における正極電位が４．３０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋超であることが好ましい。通常使用時の充電終止電圧における正極電位が４．３０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋超であることにより、通常使用時の充電の際に十分に経時化成が進行するため、容量維持率を高めることができる。 In the non-aqueous electrolyte power storage device according to one aspect of the present invention, the positive electrode potential at the end-of-charge voltage during normal use is 4.30 V vs. It is preferably Li / Li + or more. The positive electrode potential at the end of charging voltage during normal use is 4.30 V vs. When it is Li / Li + or more, aging progresses sufficiently during charging during normal use, so that the capacity retention rate can be increased.
本発明の一態様に係る非水電解質蓄電素子においては、通常使用時の充電終止電圧における正極電位が４．３０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋超４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満であることが好ましい。通常使用時の充電終止電圧における正極電位を上記範囲内とすることで、使用時の充電に伴う化成（リチウム過剰型活物質の活性化）の進行度合いが好適化され、負極によるリチウムの消費速度と、リチウム遷移金属複合酸化物からのリチウムの補充速度とのバランスがとれるため、容量維持率がより高まる。 In the non-aqueous electrolyte power storage device according to one aspect of the present invention, the positive electrode potential at the end-of-charge voltage during normal use is 4.30 V vs. Li / Li + Super 4.60V vs. It is preferably less than Li / Li + . By setting the positive electrode potential at the end-of-charge voltage during normal use within the above range, the degree of progress of chemical formation (activation of lithium excess active material) accompanying charging during use is optimized, and the lithium consumption rate by the negative electrode And the replenishment rate of lithium from the lithium transition metal composite oxide is balanced, so that the capacity retention rate is further increased.
本発明の他の一態様に係る非水電解質蓄電素子の使用方法は、正極電位が４．３０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋超４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満に至るまで充電することを備える、本発明の一態様の非水電解質蓄電素子の使用方法である。 In the method of using the non-aqueous electrolyte power storage device according to another aspect of the present invention, the positive electrode potential is 4.30 V vs. Li / Li + Super 4.60V vs. It is a method of using the non-aqueous electrolyte power storage element according to one aspect of the present invention, which comprises charging to less than Li / Li + .
当該使用方法によれば、使用時の充電に伴って徐々に経時化成がなされるため、リチウム過剰型活物質（α−ＮａＦｅＯ２構造を有し、かつＬｉ１＋αＭｅ１−αＯ２で表されるリチウム遷移金属複合酸化物）を正極に用いた非水電解質蓄電素子を高い容量維持率で使用することができる。 According to the method of use, since aging is gradually carried out with charging during use, it is represented by a lithium excess type active material (having an α-NaFeO 2 structure and Li 1 + α Me 1-α O 2). A non-aqueous electrolyte power storage element using a lithium transition metal composite oxide) as a positive electrode can be used with a high capacity retention rate.
本発明の他の一態様に係る非水電解質蓄電素子の製造方法は、上記正極の最大到達電位を４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満で初期充放電を行うことを備える、本発明の一態様の非水電解質蓄電素子の製造方法である。 In the method for manufacturing a non-aqueous electrolyte power storage device according to another aspect of the present invention, the maximum ultimate potential of the positive electrode is 4.60 V vs. It is a method for manufacturing a non-aqueous electrolyte power storage element according to one aspect of the present invention, which comprises performing initial charge / discharge at less than Li / Li + .
当該製造方法によれば、初期充放電において高電位化成がなされないため、リチウム過剰型活物質（α−ＮａＦｅＯ２構造を有し、かつＬｉ１＋αＭｅ１−αＯ２で表されるリチウム遷移金属複合酸化物）を正極に用いた非水電解質蓄電素子であって、充放電サイクルにおける容量維持率が高い非水電解質蓄電素子を製造することができる。 According to the production method, since high potential conversion is not performed in the initial charge / discharge, a lithium excess type active material (lithium transition metal having an α-NaFeO 2 structure and represented by Li 1 + α Me 1-α O 2). It is possible to manufacture a non-aqueous electrolyte storage element using a composite oxide) as a positive electrode and having a high capacity retention rate in a charge / discharge cycle.
以下、本発明の一実施形態に係る非水電解質蓄電素子、その使用方法及びその製造方法について詳説する。 Hereinafter, the non-aqueous electrolyte power storage device according to the embodiment of the present invention, its usage method, and its manufacturing method will be described in detail.
＜非水電解質蓄電素子＞
本発明の一実施形態に係る非水電解質蓄電素子は、正極、負極及び非水電解質を有する。正極及び負極は、通常、セパレータを介して積層又は巻回により交互に重畳された電極体を形成する。この電極体は容器に収納され、この容器内に非水電解質が充填される。非水電解質は、正極と負極との間に介在する。また、容器としては、通常用いられる公知の金属容器、樹脂容器等を用いることができる。以下、非水電解質蓄電素子の一例として、非水電解質二次電池（以下、単に「二次電池」ともいう。）について説明する。
<Non-aqueous electrolyte power storage element>
The non-aqueous electrolyte power storage element according to one embodiment of the present invention has a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode and the negative electrode usually form electrode bodies that are alternately superposed by stacking or winding through a separator. The electrode body is housed in a container, and the container is filled with a non-aqueous electrolyte. The non-aqueous electrolyte is interposed between the positive electrode and the negative electrode. Further, as the container, a commonly used known metal container, resin container, or the like can be used. Hereinafter, as an example of the non-aqueous electrolyte power storage element, a non-aqueous electrolyte secondary battery (hereinafter, also simply referred to as “secondary battery”) will be described.
（正極）
正極は、正極基材、及びこの正極基材に直接又は中間層を介して配される正極活物質層を有する。
(Positive electrode)
The positive electrode has a positive electrode base material and a positive electrode active material layer arranged directly on the positive electrode base material or via an intermediate layer.
正極基材は、導電性を有する。「導電性」を有するとは、ＪＩＳ−Ｈ−０５０５（１９７５年）に準拠して測定される体積抵抗率が１０７Ω・ｃｍ以下であることを意味し、「非導電性」とは、上記体積抵抗率が１０７Ω・ｃｍ超であることを意味する。正極基材の材質としては、アルミニウム、チタン、タンタル、ステンレス鋼等の金属又はこれらの合金が用いられる。これらの中でも、耐電位性、導電性の高さ、及びコストの観点からアルミニウム又はアルミニウム合金が好ましい。正極基材としては、箔、蒸着膜等が挙げられ、コストの観点から箔が好ましい。したがって、正極基材としてはアルミニウム箔又はアルミニウム合金箔が好ましい。アルミニウム又はアルミニウム合金としては、ＪＩＳ−Ｈ−４０００（２０１４年）に規定されるＡ１０８５、Ａ３００３等が例示できる。 The positive electrode base material has conductivity. The A has a "conductive" means that the volume resistivity is measured according to JIS-H-0505 (1975 years) is not more than 10 7 Ω · cm, "non-conductive", means that the volume resistivity is 10 7 Ω · cm greater. As the material of the positive electrode base material, metals such as aluminum, titanium, tantalum, and stainless steel, or alloys thereof are used. Among these, aluminum or an aluminum alloy is preferable from the viewpoint of potential resistance, high conductivity, and cost. Examples of the positive electrode base material include foils and vapor-deposited films, and foils are preferable from the viewpoint of cost. Therefore, aluminum foil or aluminum alloy foil is preferable as the positive electrode base material. Examples of aluminum or aluminum alloy include A1085 and A3003 specified in JIS-H-4000 (2014).
正極基材の平均厚さの下限としては、５μｍが好ましく、１０μｍがより好ましい。正極基材の平均厚さの上限としては、５０μｍが好ましく、４０μｍがより好ましい。正極基材の平均厚さを上記下限以上とすることで、正極基材の強度を高めることができる。正極基材の平均厚さが上記上限以下とすることで、二次電池の体積当たりのエネルギー密度を高めることができる。また、これらの理由から、正極基材の平均厚さは上記いずれかの下限以上かつ上記いずれかの上限以下とすることが好ましい。「平均厚さ」とは、所定の面積の基材を打ち抜いた際の打ち抜き質量を、基材の真密度及び打ち抜き面積で除した値をいう。他の部材等に対して「平均厚さ」を用いる場合にも同様に定義される。 As the lower limit of the average thickness of the positive electrode base material, 5 μm is preferable, and 10 μm is more preferable. The upper limit of the average thickness of the positive electrode base material is preferably 50 μm, more preferably 40 μm. By setting the average thickness of the positive electrode base material to the above lower limit or more, the strength of the positive electrode base material can be increased. By setting the average thickness of the positive electrode base material to be equal to or less than the above upper limit, the energy density per volume of the secondary battery can be increased. Further, for these reasons, it is preferable that the average thickness of the positive electrode base material is at least one of the above lower limits and at least one of the above upper limits. The "average thickness" means a value obtained by dividing the punching mass when punching a base material having a predetermined area by the true density of the base material and the punching area. The same definition applies when the "average thickness" is used for other members and the like.
中間層は、正極基材と正極活物質層との間に配される層である。中間層の構成は特に限定されず、例えば、樹脂バインダ及び導電性を有する粒子を含む。中間層は、例えば、炭素粒子等の導電性を有する粒子を含むことで正極基材と正極活物質層との接触抵抗を低減する。 The intermediate layer is a layer arranged between the positive electrode base material and the positive electrode active material layer. The composition of the intermediate layer is not particularly limited, and includes, for example, a resin binder and conductive particles. The intermediate layer contains conductive particles such as carbon particles to reduce the contact resistance between the positive electrode base material and the positive electrode active material layer.
正極活物質層は、正極活物質を含む正極合剤の層である。正極活物質層（正極合剤）は、正極活物質の他、必要に応じて導電剤、バインダ、増粘剤、フィラー等の任意成分を含んでいてよい。 The positive electrode active material layer is a layer of a positive electrode mixture containing a positive electrode active material. The positive electrode active material layer (positive electrode mixture) may contain an optional component such as a conductive agent, a binder, a thickener, and a filler in addition to the positive electrode active material, if necessary.
正極活物質は、α−ＮａＦｅＯ２構造を有し、かつＬｉ１＋αＭｅ１−αＯ２（０＜α＜１；ＭｅはＮｉ及びＭｎを含む遷移金属である。）で表されるリチウム遷移金属複合酸化物を含む。このリチウム遷移金属複合酸化物は、いわゆるリチウム過剰型活物質である。 The positive electrode active material has an α-NaFeO 2 structure and is a lithium transition metal represented by Li 1 + α Me 1-α O 2 (0 <α <1; Me is a transition metal containing Ni and Mn). Contains composite oxides. This lithium transition metal composite oxide is a so-called lithium excess type active material.
上記リチウム遷移金属複合酸化物に含まれる遷移金属（Ｍｅ）は、Ｎｉ及びＭｎを含む。この遷移金属は、さらにＣｏを含むことが好ましい。この遷移金属は、実質的にＮｉ及びＭｎからなるか、実質的にＮｉ、Ｍｎ及びＣｏからなることが好ましい。リチウム遷移金属複合酸化物は、Ｌｉ１＋α（ＮｉβＣｏγＭｎδ）１−αＯ２（０＜α＜１、０＜β＜１、０≦γ＜１、０＜δ＜１、β＋γ＋δ＝１）で表されるものであってよい。 The transition metal (Me) contained in the lithium transition metal composite oxide contains Ni and Mn. The transition metal preferably further contains Co. It is preferable that the transition metal is substantially composed of Ni and Mn or substantially composed of Ni, Mn and Co. Lithium transition metal composite oxide is Li 1 + α (Ni β Co γ Mn δ ) 1-α O 2 (0 <α <1, 0 <β <1, 0 ≦ γ <1, 0 <δ <1, β + γ + δ = It may be represented by 1).
上記リチウム遷移金属複合酸化物における遷移金属（Ｍｅ）に対するリチウム（Ｌｉ）のモル比、すなわち（１＋α）／（１−α）は、１．１以上１．４以下が好ましく、１．１５以上１．２５以下がより好ましい。（１＋α）／（１−α）を上記下限以上とすることで、十分な経時化成が生じやすくなり、容量維持率をより高めることができる。また、（１＋α）／（１−α）を上記上限以下とすることで、比較的低い充電上限電位で使用する場合であっても、十分な放電容量を有し、エネルギー密度が高い二次電池となる。なお、リチウム遷移金属複合酸化物における各元素のモル比（物質量比）は、原子数比に等しい。 The molar ratio of lithium (Li) to the transition metal (Me) in the lithium transition metal composite oxide, that is, (1 + α) / (1-α) is preferably 1.1 or more and 1.4 or less, and 1.15 or more and 1 More preferably .25 or less. By setting (1 + α) / (1-α) to the above lower limit or more, sufficient aging is likely to occur, and the capacity retention rate can be further increased. Further, by setting (1 + α) / (1-α) to the above upper limit or less, a secondary battery having a sufficient discharge capacity and a high energy density even when used at a relatively low charge upper limit potential. It becomes. The molar ratio (material amount ratio) of each element in the lithium transition metal composite oxide is equal to the atomic number ratio.
上記リチウム遷移金属複合酸化物における遷移金属（Ｍｅ）に占めるＮｉのモル比（Ｎｉ／Ｍｅ）、すなわちβは、例えば０．１以上０．７以下であってもよいが、０．２以上０．６以下が好ましく、０．３以上０．５以下がより好ましい。Ｎｉ／Ｍｅを上記下限以上とすることで、特に、比較的低い充電上限電位で使用する場合において、放電容量を大きくし、エネルギー密度を高めることができる。Ｎｉ／Ｍｅを上記上限以下とすることで、容量維持率等をより高めることができる。 The molar ratio (Ni / Me) of Ni to the transition metal (Me) in the lithium transition metal composite oxide, that is, β may be, for example, 0.1 or more and 0.7 or less, but 0.2 or more and 0. It is preferably 6.6 or less, and more preferably 0.3 or more and 0.5 or less. By setting Ni / Me to the above lower limit or higher, the discharge capacity can be increased and the energy density can be increased, particularly when used at a relatively low charging upper limit potential. By setting Ni / Me to the above upper limit or less, the capacity retention rate and the like can be further increased.
上記リチウム遷移金属複合酸化物における遷移金属（Ｍｅ）に占めるＣｏのモル比（Ｃｏ／Ｍｅ）、すなわちγは、例えば０以上０．６以下であってもよいが、０．０５以上０．４５未満が好ましく、０．１以上０．３以下がより好ましい。Ｃｏ／Ｍｅを上記下限以上とすることで、二次電池の放電容量を大きくし、エネルギー密度が高まる場合もある。一方、Ｃｏ／Ｍｅを上記上限以下とすることで、十分な容量維持率を発揮しつつ、原料コストを抑えることなどができる。 The molar ratio of Co to the transition metal (Me) in the lithium transition metal composite oxide (Co / Me), that is, γ may be, for example, 0 or more and 0.6 or less, but 0.05 or more and 0.45. Less than is preferable, and 0.1 or more and 0.3 or less is more preferable. By setting Co / Me to the above lower limit or higher, the discharge capacity of the secondary battery may be increased and the energy density may be increased. On the other hand, by setting Co / Me to the above upper limit or less, it is possible to suppress the raw material cost while exhibiting a sufficient capacity retention rate.
上記リチウム遷移金属複合酸化物における遷移金属（Ｍｅ）に占めるＭｎのモル比（Ｍｎ／Ｍｅ）、すなわちδは、例えば０．３以上０．７以下であってもよいが、０．３６超０．５以下が好ましく、０．４以上０．５未満がより好ましい。Ｍｎ／Ｍｅを上記下限以上とすることで、経時化成の作用が高まり、容量維持率を高めることができる。Ｍｎ／Ｍｅを上記上限以下とすることで、特に、比較的低い充電上限電位で使用する場合において、放電容量を大きくし、エネルギー密度を高めることができる。 The molar ratio (Mn / Me) of Mn to the transition metal (Me) in the lithium transition metal composite oxide, that is, δ may be, for example, 0.3 or more and 0.7 or less, but is more than 0.36 and 0. It is preferably 5.5 or less, and more preferably 0.4 or more and less than 0.5. By setting Mn / Me to the above lower limit or more, the action of aging is enhanced, and the capacity retention rate can be increased. By setting Mn / Me to the above upper limit or less, the discharge capacity can be increased and the energy density can be increased, particularly when used at a relatively low charging upper limit potential.
上記リチウム遷移金属複合酸化物における遷移金属（Ｍｅ）に占めるＭｎのモル比（Ｍｎ／Ｍｅ）と、遷移金属（Ｍｅ）に占めるＮｉのモル比（Ｎｉ／Ｍｅ）との差（Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅ）は、例えば０超０．５以下であってもよいが、０．０２以上０．２以下が好ましく、０．０３以上０．１０以下がより好ましい。Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅを上記上限以下とすることで、特に、比較的低い充電上限電位で使用する場合において、放電容量を大きくし、エネルギー密度を高めることができる。Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅを上記下限以上とすることで、経時化成の作用が高まり、容量維持率がより高まる。 The difference (Mn / Me-) between the molar ratio of Mn to the transition metal (Me) in the transition metal composite oxide (Mn / Me) and the molar ratio of Ni to the transition metal (Me) (Ni / Me). Ni / Me) may be, for example, more than 0 and 0.5 or less, but is preferably 0.02 or more and 0.2 or less, and more preferably 0.03 or more and 0.10 or less. By setting Mn / Me—Ni / Me to the above upper limit or less, the discharge capacity can be increased and the energy density can be increased, particularly when used at a relatively low charging upper limit potential. By setting Mn / Me—Ni / Me to the above lower limit or more, the action of aging is enhanced and the capacity retention rate is further enhanced.
上記リチウム遷移金属複合酸化物は、本発明の効果が奏される範囲で他の遷移金属等が含まれていてもよく、不純物として他の遷移金属等が混入していてもよい。また、上記リチウム遷移金属複合酸化物は、他の金属酸化物（例えば、アルミナ等）等で被覆されていてもよい。 The lithium transition metal composite oxide may contain other transition metals and the like as long as the effects of the present invention are exhibited, and other transition metals and the like may be mixed as impurities. Further, the lithium transition metal composite oxide may be coated with another metal oxide (for example, alumina or the like).
上記リチウム遷移金属複合酸化物は、従来公知の方法により製造することができる。例えば、上記リチウム遷移金属複合酸化物は、この目的とする複合酸化物を構成する金属元素（Ｌｉ、Ｎｉ、Ｍｎ等）を目的とする複合酸化物の組成通りに含有する原料を調製し、これを焼成することなどに得ることができる。 The lithium transition metal composite oxide can be produced by a conventionally known method. For example, for the lithium transition metal composite oxide, a raw material containing the metal elements (Li, Ni, Mn, etc.) constituting the desired composite oxide according to the composition of the desired composite oxide is prepared. Can be obtained by firing.
正極活物質には、上記リチウム遷移金属複合酸化物以外の他の正極活物質が含まれていてもよい。上記正極活物質に占める上記リチウム遷移金属複合酸化物の含有量は例えば５０質量％以上であってよいが、７０質量％超が好ましく、８０質量％以上がより好ましく、９０質量％以上がさらに好ましく、９９質量％以上がよりさらに好ましく、実質的に１００質量％であってもよい。正極活物質に占める上記リチウム遷移金属複合酸化物の含有割合を高めることで、容量維持率をより高めることができる。 The positive electrode active material may contain a positive electrode active material other than the above lithium transition metal composite oxide. The content of the lithium transition metal composite oxide in the positive electrode active material may be, for example, 50% by mass or more, preferably more than 70% by mass, more preferably 80% by mass or more, still more preferably 90% by mass or more. , 99% by mass or more is more preferable, and it may be substantially 100% by mass. By increasing the content ratio of the lithium transition metal composite oxide in the positive electrode active material, the capacity retention rate can be further increased.
上記リチウム遷移金属複合酸化物以外の他の正極活物質としては、リチウムイオン二次電池等に通常用いられる公知の正極活物質の中から適宜選択できる。上記正極活物質としては、通常、リチウムイオンを吸蔵及び放出することができる材料が用いられる。例えば、上述したＬｉＭｅＯ２型活物質、スピネル型結晶構造を有するリチウム遷移金属酸化物、ポリアニオン化合物、カルコゲン化合物、硫黄等が挙げられる。 The positive electrode active material other than the lithium transition metal composite oxide can be appropriately selected from known positive electrode active materials usually used for lithium ion secondary batteries and the like. As the positive electrode active material, a material capable of occluding and releasing lithium ions is usually used. For example, the above-mentioned LiMeO type 2 active material, lithium transition metal oxide having a spinel type crystal structure, polyanion compound, chalcogen compound, sulfur and the like can be mentioned.
正極活物質の平均粒径は、例えば、０．１μｍ以上２０μｍ以下とすることが好ましい。正極活物質の平均粒径を上記下限以上とすることで、正極活物質の製造又は取り扱いが容易になる。正極活物質の平均粒径を上記上限以下とすることで、正極活物質層の電子伝導性が向上する。ここで、「平均粒径」とは、ＪＩＳ−Ｚ−８８２５（２０１３年）に準拠し、粒子を溶媒で希釈した希釈液に対しレーザ回折・散乱法により測定した粒径分布に基づき、ＪＩＳ−Ｚ−８８１９−２（２００１年）に準拠し計算される体積基準積算分布が５０％となる値を意味する。 The average particle size of the positive electrode active material is preferably 0.1 μm or more and 20 μm or less, for example. By setting the average particle size of the positive electrode active material to the above lower limit or more, the production or handling of the positive electrode active material becomes easy. By setting the average particle size of the positive electrode active material to the above upper limit or less, the electron conductivity of the positive electrode active material layer is improved. Here, the "average particle size" is based on JIS-Z-8825 (2013), and is based on the particle size distribution measured by the laser diffraction / scattering method for a diluted solution obtained by diluting the particles with a solvent. It means a value at which the volume-based integrated distribution calculated in accordance with Z-8819-2 (2001) is 50%.
正極活物質等の粒子を所定の形状で得るためには粉砕機や分級機等が用いられる。粉砕方法として、例えば、乳鉢、ボールミル、サンドミル、振動ボールミル、遊星ボールミル、ジェットミル、カウンタージェットミル、旋回気流型ジェットミル又は篩等を用いる方法が挙げられる。粉砕時には水、あるいはヘキサン等の有機溶剤を共存させた湿式粉砕を用いることもできる。分級方法としては、篩や風力分級機等が、乾式、湿式ともに必要に応じて用いられる。 A crusher, a classifier, or the like is used to obtain particles such as a positive electrode active material in a predetermined shape. Examples of the crushing method include a method using a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling airflow type jet mill, a sieve, and the like. At the time of pulverization, wet pulverization in which water or an organic solvent such as hexane coexists can also be used. As a classification method, a sieve, a wind power classifier, or the like is used as needed for both dry and wet types.
正極活物質層（正極合剤）における正極活物質の含有量の下限としては、７０質量％が好ましく、８０質量％がより好ましく、９０質量％がさらに好ましい。正極活物質の含有量の上限としては、９８質量％が好ましく、９６質量％がより好ましい。正極活物質の含有量を上記範囲とすることで、二次電池の電気容量をより大きくすることができる。正極活物質層における正極活物質の含有量は、上記いずれかの下限以上かつ上記いずれかの上限以下とすることができる。 The lower limit of the content of the positive electrode active material in the positive electrode active material layer (positive electrode mixture) is preferably 70% by mass, more preferably 80% by mass, and even more preferably 90% by mass. The upper limit of the content of the positive electrode active material is preferably 98% by mass, more preferably 96% by mass. By setting the content of the positive electrode active material in the above range, the electric capacity of the secondary battery can be further increased. The content of the positive electrode active material in the positive electrode active material layer can be at least one of the above lower limits and below any of the above upper limits.
また、正極活物質層（正極合剤）における正極活物質の含有量が上記範囲（例えば７０質量％以上）であれば、正極合剤における正極活物質の含有量は、上記正極に対して正極合剤の質量あたり９ｍＡ／ｇの電流密度により行う２サイクルの充放電に基づく測定値（（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００）に実質的に影響を与えない。 Further, if the content of the positive electrode active material in the positive electrode active material layer (positive electrode mixture) is within the above range (for example, 70% by mass or more), the content of the positive electrode active material in the positive electrode mixture is positive with respect to the positive electrode. Substantially affects the measured values ((C 2A / C 2B ) x 100- (C 1A / C 1B ) x 100) based on two cycles of charging and discharging performed at a current density of 9 mA / g per mass of the mixture. Absent.
導電剤は、導電性を有する材料であれば特に限定されない。このような導電剤としては、例えば、黒鉛；ファーネスブラック、アセチレンブラック等のカーボンブラック；金属；導電性セラミックス等が挙げられる。導電剤の形状としては、粉状、繊維状等が挙げられる。これらの中でも、電子伝導性及び塗工性の観点よりアセチレンブラックが好ましい。 The conductive agent is not particularly limited as long as it is a conductive material. Examples of such a conductive agent include graphite; carbon black such as furnace black and acetylene black; metal; conductive ceramics and the like. Examples of the shape of the conductive agent include powder and fibrous. Among these, acetylene black is preferable from the viewpoint of electron conductivity and coatability.
正極活物質層（正極合剤）における導電剤の含有量の下限としては、１質量％が好ましく、２質量％がより好ましい。導電剤の含有量の上限としては、１０質量％が好ましく、５質量％がより好ましい。導電剤の含有量を上記範囲とすることで、二次電池の電気容量を高めることができる。また、これらの理由から、導電剤の含有量は上記いずれかの下限以上かつ上記いずれかの上限以下とすることが好ましい。 The lower limit of the content of the conductive agent in the positive electrode active material layer (positive electrode mixture) is preferably 1% by mass, more preferably 2% by mass. The upper limit of the content of the conductive agent is preferably 10% by mass, more preferably 5% by mass. By setting the content of the conductive agent in the above range, the electric capacity of the secondary battery can be increased. Further, for these reasons, it is preferable that the content of the conductive agent is at least one of the above lower limits and at least one of the above upper limits.
バインダとしては、例えば、フッ素樹脂（ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）等）、ポリエチレン、ポリプロピレン、ポリイミド等の熱可塑性樹脂；エチレン−プロピレン−ジエンゴム（ＥＰＤＭ）、スルホン化ＥＰＤＭ、スチレンブタジエンゴム（ＳＢＲ）、フッ素ゴム等のエラストマー；多糖類高分子等が挙げられる。 Examples of the binder include fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), thermoplastic resins such as polyethylene, polypropylene, and polyimide; ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, and the like. Elastomers such as styrene-butadiene rubber (SBR) and fluororubber; polysaccharide polymers and the like can be mentioned.
正極活物質層（正極合剤）におけるバインダの含有量の下限としては、１質量％が好ましく、２質量％がより好ましい。バインダの含有量の上限としては、１０質量％が好ましく、５質量％がより好ましい。バインダの含有量を上記範囲とすることで、活物質を安定して保持することができる。また、これらの理由から、バインダの含有量は上記いずれかの下限以上かつ上記いずれかの上限以下とすることが好ましい。 The lower limit of the binder content in the positive electrode active material layer (positive electrode mixture) is preferably 1% by mass, more preferably 2% by mass. The upper limit of the binder content is preferably 10% by mass, more preferably 5% by mass. By setting the binder content within the above range, the active material can be stably retained. Further, for these reasons, it is preferable that the binder content is at least one of the above lower limits and at least one of the above upper limits.
増粘剤としては、例えばカルボキシメチルセルロース（ＣＭＣ）、メチルセルロース等の多糖類高分子が挙げられる。増粘剤がリチウム等と反応する官能基を有する場合、予めメチル化等によりこの官能基を失活させてもよい。 Examples of the thickener include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. When the thickener has a functional group that reacts with lithium or the like, this functional group may be inactivated by methylation or the like in advance.
フィラーは、特に限定されない。フィラーとしては、ポリプロピレン、ポリエチレン等のポリオレフィン、シリカ、アルミナ、ゼオライト、ガラス、アルミナシリケイト等が挙げられる。 The filler is not particularly limited. Examples of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, alumina silicate and the like.
正極活物質層は、Ｂ、Ｎ、Ｐ、Ｆ、Ｃｌ、Ｂｒ、Ｉ等の典型非金属元素、Ｌｉ、Ｎａ、Ｍｇ、Ａｌ、Ｋ、Ｃａ、Ｚｎ、Ｇａ、Ｇｅ、Ｓｎ、Ｓｒ、Ｂａ等の典型金属元素、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｏ、Ｚｒ、Ｎｂ、Ｗ等の遷移金属元素を正極活物質、導電剤、バインダ、増粘剤、フィラー以外の成分として含有してもよい。 The positive electrode active material layer includes typical non-metal elements such as B, N, P, F, Cl, Br, I, Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba and the like. Typical metal elements of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, W and other transition metal elements are used as positive electrode active materials, conductive agents, binders, thickeners, fillers. It may be contained as a component other than.
（正極の充電電気量）
上記正極に対して、上記正極合剤の質量あたり９ｍＡ／ｇの電流密度により、電位が２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの放電を行った後、上記電流密度により、電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電と電位が２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの放電とからなる充放電を２サイクル行ったときの充電電気量は、下記式（１）を満たす。
（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００≧１．０ ・・・（１）
式（１）中、Ｃ１Ａは、上記充放電の１サイクル目の充電の際に、充電開始から電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ１Ｂは、上記充放電の１サイクル目の充電の際に、充電開始から電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ２Ａは、上記充放電の２サイクル目の充電の際に、充電開始から電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ２Ｂは、上記充放電の２サイクル目の充電の際に、充電開始から電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。
(Amount of electricity charged for the positive electrode)
With respect to the positive electrode, the potential was 2.00 V vs. due to the current density of 9 mA / g per mass of the positive electrode mixture. After discharging up to Li / Li + , the potential becomes 4.80 V vs. due to the above current density. Charging and potential up to Li / Li + is 2.00 V vs. The amount of electricity charged when two cycles of charge / discharge consisting of discharge up to Li / Li + is performed satisfies the following equation (1).
(C 2A / C 2B ) × 100- (C 1A / C 1B ) × 100 ≧ 1.0 ・ ・ ・ (1)
In the formula (1), C 1A has a potential of 4.45 V vs. from the start of charging at the time of charging in the first cycle of charging / discharging. It is the amount of electricity charged up to Li / Li + . C 1B has a potential of 4.80 V vs. from the start of charging at the time of charging in the first cycle of charging / discharging. It is the amount of electricity charged up to Li / Li + . The potential of C 2A is 4.45 V vs. from the start of charging at the time of charging in the second cycle of charging / discharging. It is the amount of electricity charged up to Li / Li + . The potential of C 2B is 4.80 V vs. from the start of charging at the time of charging in the second cycle of charging / discharging. It is the amount of electricity charged up to Li / Li + .
上記式（１）の左辺、すなわち「（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００」の下限は、１．５が好ましく、２．０、３．０、４．０又は５．０がより好ましいこともある。「（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００」は、上述のように、十分な高電位化成がなされていない程度を示す。従って、「（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００」が上記下限以上である場合、経時化成がより生じやすくなり、容量維持率がより高まる傾向にある。一方、「（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００」の上限は、例えば２０であり、１０が好ましく、５．０であってもよい。 The left side of the above formula (1), that is, the lower limit of "(C 2A / C 2B ) x 100- (C 1A / C 1B ) x 100" is preferably 1.5, and 2.0, 3.0, 4. 0 or 5.0 may be more preferred. "(C 2A / C 2B ) x 100- (C 1A / C 1B ) x 100" indicates the degree to which sufficient high potential formation is not performed as described above. Therefore, when "(C 2A / C 2B ) x 100- (C 1A / C 1B ) x 100" is not more than the above lower limit, aging is more likely to occur, and the capacity retention rate tends to be higher. On the other hand, the upper limit of "(C 2A / C 2B ) x 100- (C 1A / C 1B ) x 100" is, for example, 20, preferably 10, and may be 5.0.
（負極）
負極は、負極基材、及びこの負極基材に直接又は中間層を介して配される負極活物質層を有する。負極の中間層の構成は特に限定されず、正極の中間層と同様の構成とすることができる。
(Negative electrode)
The negative electrode has a negative electrode base material and a negative electrode active material layer arranged directly on the negative electrode base material or via an intermediate layer. The configuration of the intermediate layer of the negative electrode is not particularly limited, and the same configuration as that of the intermediate layer of the positive electrode can be used.
負極基材は、導電性を有する。負極基材の材質としては、銅、ニッケル、ステンレス鋼、ニッケルメッキ鋼、アルミニウム等の金属又はこれらの合金が用いられる。これらの中でも銅又は銅合金が好ましい。負極基材としては、箔、蒸着膜等が挙げられ、コストの観点から箔が好ましい。したがって、負極基材としては銅箔又は銅合金箔が好ましい。銅箔の例としては、圧延銅箔、電解銅箔等が挙げられる。 The negative electrode base material has conductivity. As the material of the negative electrode base material, metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum, or alloys thereof are used. Among these, copper or a copper alloy is preferable. Examples of the negative electrode base material include foils and vapor-deposited films, and foils are preferable from the viewpoint of cost. Therefore, a copper foil or a copper alloy foil is preferable as the negative electrode base material. Examples of the copper foil include rolled copper foil, electrolytic copper foil and the like.
負極基材の平均厚さの下限としては、３μｍが好ましく、５μｍがより好ましい。負極基材の平均厚さの上限としては、３０μｍが好ましく、２０μｍがより好ましい。負極基材の平均厚さを上記下限以上とすることで、負極基材の強度を高めることができる。負極基材の平均厚さを上記上限以下とすることで、二次電池の体積当たりのエネルギー密度を高めることができる。また、これらの理由から、負極基材の平均厚さは、上記いずれかの下限以上かつ上記いずれかの上限以下とすることが好ましい。 The lower limit of the average thickness of the negative electrode base material is preferably 3 μm, more preferably 5 μm. The upper limit of the average thickness of the negative electrode base material is preferably 30 μm, more preferably 20 μm. By setting the average thickness of the negative electrode base material to the above lower limit or more, the strength of the negative electrode base material can be increased. By setting the average thickness of the negative electrode base material to be equal to or less than the above upper limit, the energy density per volume of the secondary battery can be increased. Further, for these reasons, the average thickness of the negative electrode base material is preferably not less than or equal to one of the above lower limits and not more than or equal to any of the above upper limits.
負極活物質層は、負極活物質を含む負極合剤の層である。負極活物質層（負極合剤）は、負極活物質の他、必要に応じて導電剤、バインダ、増粘剤、フィラー等の任意成分を含んでいてよい。導電剤、バインダ、増粘剤、フィラー等の任意成分は、正極活物質層と同様のものを用いることができる。負極活物質層におけるこれらの各任意成分の含有量は、正極活物質層におけるこれらの含有量として記載した範囲とすることができる。 The negative electrode active material layer is a layer of a negative electrode mixture containing a negative electrode active material. The negative electrode active material layer (negative electrode mixture) may contain an optional component such as a conductive agent, a binder, a thickener, and a filler, if necessary, in addition to the negative electrode active material. As any component such as a conductive agent, a binder, a thickener, and a filler, the same one as that of the positive electrode active material layer can be used. The content of each of these optional components in the negative electrode active material layer can be in the range described as these contents in the positive electrode active material layer.
負極活物質としては、公知の負極活物質の中から適宜選択できる。リチウムイオン二次電池用の負極活物質としては、通常、リチウムイオンを吸蔵及び放出することができる材料が用いられる。負極活物質としては、例えば、金属Ｌｉ；Ｓｉ、Ｓｎ等の金属又は半金属；Ｓｉ酸化物、Ｔｉ酸化物、Ｓｎ酸化物等の金属酸化物又は半金属酸化物；Ｌｉ４Ｔｉ５Ｏ１２、ＬｉＴｉＯ２、ＴｉＮｂ２Ｏ７等のチタン含有酸化物；ポリリン酸化合物；炭化ケイ素；黒鉛（グラファイト）、非黒鉛質炭素（易黒鉛化性炭素又は難黒鉛化性炭素）等の炭素材料等が挙げられる。負極活物質層においては、これら材料の１種を単独で用いてもよく、２種以上を混合して用いてもよい。 The negative electrode active material can be appropriately selected from known negative electrode active materials. As the negative electrode active material for a lithium ion secondary battery, a material capable of occluding and releasing lithium ions is usually used. Examples of the negative electrode active material include metal Li; metal or semi-metal such as Si and Sn; metal oxide or semi-metal oxide such as Si oxide, Ti oxide and Sn oxide; Li 4 Ti 5 O 12 ; Titanium-containing oxides such as LiTIO 2 and TiNb 2 O 7 ; polyphosphate compounds; silicon carbide; carbon materials such as graphite (graphite) and non-graphitizable carbon (graphitizable carbon or non-graphitizable carbon). Be done. In the negative electrode active material layer, one of these materials may be used alone, or two or more thereof may be mixed and used.
「黒鉛」とは、充放電前又は放電状態において、Ｘ線回折法により決定される（００２）面の平均格子面間隔（ｄ００２）が０．３３ｎｍ以上０．３４ｎｍ未満の炭素材料をいう。黒鉛としては、天然黒鉛、人造黒鉛が挙げられる。安定した物性の材料を入手できるという観点で、人造黒鉛が好ましい。 “Graphite” refers to a carbon material having an average lattice spacing (d 002 ) of (002) planes determined by X-ray diffraction before charging / discharging or in a discharged state of 0.33 nm or more and less than 0.34 nm. Examples of graphite include natural graphite and artificial graphite. Artificial graphite is preferable from the viewpoint that a material having stable physical properties can be obtained.
「非黒鉛質炭素」とは、充放電前又は放電状態においてＸ線回折法により決定される（００２）面の平均格子面間隔（ｄ００２）が０．３４ｎｍ以上０．４２ｎｍ以下の炭素材料をいう。非黒鉛質炭素としては、難黒鉛化性炭素や、易黒鉛化性炭素が挙げられる。非黒鉛質炭素としては、例えば、樹脂由来の材料、石油ピッチまたは石油ピッチ由来の材料、石油コークスまたは石油コークス由来の材料、植物由来の材料、アルコール由来の材料等が挙げられる。 “Non-graphitic carbon” refers to a carbon material having an average lattice spacing (d 002 ) of (002) planes determined by X-ray diffraction before charging / discharging or in a discharged state of 0.34 nm or more and 0.42 nm or less. Say. Examples of non-graphitizable carbon include non-graphitizable carbon and easily graphitizable carbon. Examples of the non-graphitic carbon include a resin-derived material, a petroleum pitch or a petroleum pitch-derived material, a petroleum coke or a petroleum coke-derived material, a plant-derived material, an alcohol-derived material, and the like.
ここで、黒鉛及び非黒鉛質炭素を定義する「放電状態」とは、負極活物質として炭素材料を含む負極を作用極として、金属Ｌｉを対極として用いた単極電池において、開回路電圧が０．７Ｖ以上である状態をいう。開回路状態での金属Ｌｉ対極の電位は、Ｌｉの酸化還元電位とほぼ等しいため、上記単極電池における開回路電圧は、Ｌｉの酸化還元電位に対する炭素材料を含む負極の電位とほぼ同等である。つまり、上記単極電池における開回路電圧が０．７Ｖ以上であることは、負極活物質である炭素材料から、充放電に伴い吸蔵放出可能なリチウムイオンが十分に放出されていることを意味する。 Here, the “discharge state” that defines graphite and non-graphitic carbon means that the open circuit voltage is 0 in a unipolar battery in which a negative electrode containing a carbon material as a negative electrode active material is used as a working electrode and metallic Li is used as a counter electrode. It means a state where the voltage is 7V or higher. Since the potential of the metal Li counter electrode in the open circuit state is substantially equal to the oxidation-reduction potential of Li, the open circuit voltage in the single-pole battery is substantially equal to the potential of the negative electrode containing the carbon material with respect to the oxidation-reduction potential of Li. .. That is, the fact that the open circuit voltage in the single-pole battery is 0.7 V or more means that lithium ions that can be occluded and discharged are sufficiently released from the carbon material that is the negative electrode active material during charging and discharging. ..
「難黒鉛化性炭素」とは、上記ｄ００２が０．３６ｎｍ以上０．４２ｎｍ以下の炭素材料をいう。 The “non-graphitizable carbon” refers to a carbon material having d 002 of 0.36 nm or more and 0.42 nm or less.
「易黒鉛化性炭素」とは、上記ｄ００２が０．３４ｎｍ以上０．３６ｎｍ未満の炭素材料をいう。 The “graphitizable carbon” refers to a carbon material in which d 002 is 0.34 nm or more and less than 0.36 nm.
より容量維持率の高い二次電池とするためなどには、負極活物質としては、炭素材料が好ましく、黒鉛がより好ましい。負極活物質として炭素材料を用いる場合、全負極活物質に占める炭素材料の含有量としては、５０質量％以上であってよく、７０質量％以上であってもよく、９０質量％以上であってもよく、実質的に１００質量％であってよい。 As the negative electrode active material, a carbon material is preferable, and graphite is more preferable, in order to obtain a secondary battery having a higher capacity retention rate. When a carbon material is used as the negative electrode active material, the content of the carbon material in the total negative electrode active material may be 50% by mass or more, 70% by mass or more, or 90% by mass or more. It may be substantially 100% by mass.
一方、Ｓｉ、Ｓｎ及びこれらの酸化物等、リチウムの消費が特に大きい負極活物質が用いられている場合は、経時化成により正極からリチウムを補充できるという本発明の利点をより十分に享受できる。但し、通常、どのような負極活物質を用いた二次電池も、少なからずリチウムは消費されるため、負極活物質の種類によらず本発明を適用することができる。また、Ｓｉ、Ｓｎ及びこれらの酸化物等を負極活物質として用いることで、放電容量を大きくすることなどもできる。Ｓｉ、Ｓｎ及びこれらの酸化物は、炭素材料と併用してもよい。全負極活物質に占めるＳｉ、Ｓｎ及びこれらの酸化物の含有割合としては、例えば１質量％以上９０質量％以下であってよく、５質量％以上７０質量％以下であってよい。 On the other hand, when a negative electrode active material such as Si, Sn and oxides thereof, which consumes a large amount of lithium, is used, the advantage of the present invention that lithium can be replenished from the positive electrode by aging can be more fully enjoyed. However, since lithium is usually consumed in a secondary battery using any negative electrode active material, the present invention can be applied regardless of the type of the negative electrode active material. Further, by using Si, Sn, oxides thereof and the like as the negative electrode active material, the discharge capacity can be increased. Si, Sn and oxides thereof may be used in combination with a carbon material. The content ratio of Si, Sn and their oxides in the total negative electrode active material may be, for example, 1% by mass or more and 90% by mass or less, and may be 5% by mass or more and 70% by mass or less.
負極活物質は、通常、粒子（粉体）である。負極活物質の平均粒径は、例えば、１ｎｍ以上１００μｍ以下とすることができる。負極活物質の平均粒径を上記下限以上とすることで、負極活物質の製造又は取り扱いが容易になる。負極活物質の平均粒径を上記上限以下とすることで、活物質層の電子伝導性が向上する。粉体を所定の粒径で得るためには粉砕機や分級機等が用いられる。粉砕方法及び粉級方法は、例えば、上記正極で例示した方法から選択できる。 The negative electrode active material is usually particles (powder). The average particle size of the negative electrode active material can be, for example, 1 nm or more and 100 μm or less. By setting the average particle size of the negative electrode active material to the above lower limit or more, the production or handling of the negative electrode active material becomes easy. By setting the average particle size of the negative electrode active material to the above upper limit or less, the electron conductivity of the active material layer is improved. A crusher, a classifier, or the like is used to obtain a powder having a predetermined particle size. The pulverization method and the powder grade method can be selected from, for example, the methods exemplified for the positive electrode.
負極活物質層（負極合剤）における負極活物質の含有量は、６０質量％以上９９質量％以下が好ましく、９０質量％以上９８質量％以下がより好ましい。負極活物質の含有量を上記の範囲とすることで、負極活物質層の高エネルギー密度化と製造性を両立できる。 The content of the negative electrode active material in the negative electrode active material layer (negative electrode mixture) is preferably 60% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 98% by mass or less. By setting the content of the negative electrode active material within the above range, it is possible to achieve both high energy density and manufacturability of the negative electrode active material layer.
負極活物質層は、Ｂ、Ｎ、Ｐ、Ｆ、Ｃｌ、Ｂｒ、Ｉ等の典型非金属元素、Ｌｉ、Ｎａ、Ｍｇ、Ａｌ、Ｋ、Ｃａ、Ｚｎ、Ｇａ、Ｇｅ、Ｓｎ、Ｓｒ、Ｂａ等の典型金属元素、Ｓｃ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｏ、Ｚｒ、Ｔａ、Ｈｆ、Ｎｂ、Ｗ等の遷移金属元素を負極活物質、導電剤、バインダ、増粘剤、フィラー以外の成分として含有してもよい。 The negative electrode active material layer includes typical non-metal elements such as B, N, P, F, Cl, Br, I, Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba and the like. Typical metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, W and other transition metal elements are added to the negative electrode active material, conductive agent, binder, and more. It may be contained as a component other than the adhesive and the filler.
（セパレータ）
セパレータは、公知のセパレータの中から適宜選択できる。セパレータとして、例えば、基材層のみからなるセパレータ、基材層の一方の面又は双方の面に耐熱粒子とバインダとを含む耐熱層が形成されたセパレータ等を使用することができる。セパレータの基材層の材質としては、例えば、織布、不織布、多孔質樹脂フィルム等が挙げられる。これらの材質の中でも、強度の観点から多孔質樹脂フィルムが好ましく、非水電解質の保液性の観点から不織布が好ましい。セパレータの基材層の材料としては、シャットダウン機能の観点から例えばポリエチレン、ポリプロピレン等のポリオレフィンが好ましく、耐酸化分解性の観点から例えばポリイミドやアラミド等が好ましい。セパレータの基材層として、これらの樹脂を複合した材料を用いてもよい。
(Separator)
The separator can be appropriately selected from known separators. As the separator, for example, a separator composed of only a base material layer, a separator having a heat-resistant layer containing heat-resistant particles and a binder formed on one surface or both surfaces of the base material layer can be used. Examples of the material of the base material layer of the separator include woven fabrics, non-woven fabrics, and porous resin films. Among these materials, a porous resin film is preferable from the viewpoint of strength, and a non-woven fabric is preferable from the viewpoint of liquid retention of a non-aqueous electrolyte. As the material of the base material layer of the separator, polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of shutdown function, and polyimide and aramid are preferable from the viewpoint of oxidative decomposition resistance. A composite material of these resins may be used as the base material layer of the separator.
耐熱層に含まれる耐熱粒子は、大気下で５００℃にて質量減少が５％以下であるものが好ましく、大気下で８００℃にて質量減少が５％以下であるものがさらに好ましい。質量減少が所定以下である材料として無機化合物が挙げられる。無機化合物として、例えば、酸化鉄、酸化ケイ素、酸化アルミニウム、酸化チタン、チタン酸バリウム、酸化ジルコニウム、酸化カルシウム、酸化ストロンチウム、酸化バリウム、酸化マグネシウム、アルミノケイ酸塩等の酸化物；水酸化マグネシウム、水酸化カルシウム、水酸化アルミニウム等の水酸化物；窒化アルミニウム、窒化ケイ素等の窒化物；炭酸カルシウム等の炭酸塩；硫酸バリウム等の硫酸塩；フッ化カルシウム、フッ化バリウム等の難溶性のイオン結晶；シリコン、ダイヤモンド等の共有結合性結晶；タルク、モンモリロナイト、ベーマイト、ゼオライト、アパタイト、カオリン、ムライト、スピネル、オリビン、セリサイト、ベントナイト、マイカ等の鉱物資源由来物質又はこれらの人造物等が挙げられる。無機化合物として、これらの物質の単体又は複合体を単独で用いてもよく、２種以上を混合して用いてもよい。これらの無機化合物の中でも、二次電池の安全性の観点から、酸化ケイ素、酸化アルミニウム、又はアルミノケイ酸塩が好ましい。 The heat-resistant particles contained in the heat-resistant layer preferably have a mass loss of 5% or less at 500 ° C. in the atmosphere, and more preferably 5% or less in mass loss at 800 ° C. in the atmosphere. Inorganic compounds can be mentioned as materials whose mass reduction is less than or equal to a predetermined value. As inorganic compounds, for example, oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, barium titanate, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, aluminosilicate; magnesium hydroxide, water. Hydroxides such as calcium oxide and aluminum hydroxide; nitrides such as aluminum nitride and silicon nitride; carbonates such as calcium carbonate; sulfates such as barium sulfate; sparingly soluble ion crystals such as calcium fluoride and barium fluoride Covalently bonded crystals such as silicon and diamond; mineral resource-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mulite, spinel, olivine, sericite, bentonite, mica, etc. .. As the inorganic compound, a simple substance or a complex of these substances may be used alone, or two or more kinds may be mixed and used. Among these inorganic compounds, silicon oxide, aluminum oxide, or aluminosilicate is preferable from the viewpoint of safety of the secondary battery.
セパレータの空孔率は、強度の観点から８０体積％以下が好ましく、放電性能の観点から２０体積％以上が好ましい。ここで、「空孔率」とは、体積基準の値であり、水銀ポロシメータでの測定値を意味する。 The porosity of the separator is preferably 80% by volume or less from the viewpoint of strength, and preferably 20% by volume or more from the viewpoint of discharge performance. Here, the "vacancy ratio" is a volume-based value, and means a value measured by a mercury porosimeter.
セパレータとして、ポリマーと非水電解質とで構成されるポリマーゲルを用いてもよい。ポリマーとして、例えば、ポリアクリロニトリル、ポリエチレンオキシド、ポリプロピレンオキシド、ポリメチルメタアクリレート、ポリビニルアセテート、ポリビニルピロリドン、ポリフッ化ビニリデン等が挙げられる。ポリマーゲルを用いると、漏液を抑制する効果がある。セパレータとして、上述したような多孔質樹脂フィルム又は不織布等とポリマーゲルを併用してもよい。 As the separator, a polymer gel composed of a polymer and a non-aqueous electrolyte may be used. Examples of the polymer include polyacrylonitrile, polyethylene oxide, polypropylene oxide, polymethylmethacrylate, polyvinylacetate, polyvinylpyrrolidone, polyvinylidene fluoride and the like. The use of polymer gel has the effect of suppressing liquid leakage. As the separator, a polymer gel may be used in combination with the above-mentioned porous resin film or non-woven fabric.
（非水電解質）
非水電解質としては、公知の非水電解質の中から適宜選択できる。非水電解質には、非水電解液を用いてもよい。非水電解液は、非水溶媒と、この非水溶媒に溶解されている電解質塩とを含む。
(Non-aqueous electrolyte)
The non-aqueous electrolyte can be appropriately selected from known non-aqueous electrolytes. A non-aqueous electrolyte solution may be used as the non-aqueous electrolyte. The non-aqueous electrolyte solution contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
非水溶媒としては、公知の非水溶媒の中から適宜選択できる。非水溶媒としては、環状カーボネート、鎖状カーボネート、カルボン酸エステル、リン酸エステル、スルホン酸エステル、エーテル、アミド、ニトリル等が挙げられる。非水溶媒として、これらの化合物に含まれる水素原子の一部がハロゲンに置換されたものを用いてもよい。例えば、フッ素化された化合物（フッ素化環状カーボネート、フッ素化鎖状カーボネート等）を用いることで、正極電位が高電位に至る使用条件下でも十分に使用できる。 The non-aqueous solvent can be appropriately selected from known non-aqueous solvents. Examples of the non-aqueous solvent include cyclic carbonate, chain carbonate, carboxylic acid ester, phosphoric acid ester, sulfonic acid ester, ether, amide, nitrile and the like. As the non-aqueous solvent, those in which some of the hydrogen atoms contained in these compounds are replaced with halogen may be used. For example, by using a fluorinated compound (fluorinated cyclic carbonate, fluorinated chain carbonate, etc.), it can be sufficiently used even under usage conditions where the positive electrode potential reaches a high potential.
環状カーボネートとしては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、ビニレンカーボネート（ＶＣ）、ビニルエチレンカーボネート（ＶＥＣ）、クロロエチレンカーボネート、フルオロエチレンカーボネート（ＦＥＣ）、ジフルオロエチレンカーボネート（ＤＦＥＣ）、スチレンカーボネート、１−フェニルビニレンカーボネート、１，２−ジフェニルビニレンカーボネート等が挙げられる。これらの中でもＥＣ、ＰＣ及びＦＥＣが好ましい。 Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), and difluoroethylene carbonate. (DFEC), styrene carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate and the like can be mentioned. Among these, EC, PC and FEC are preferable.
鎖状カーボネートとしては、ジエチルカーボネート（ＤＥＣ）、ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）、ジフェニルカーボネート、メチルトリフルオロエチルカーボネート（ＭＦＥＣ）、ビス（トリフルオロエチル）カーボネート等が挙げられる。これらの中でもＥＭＣ及びＭＦＥＣが好ましい。 Examples of the chain carbonate include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diphenyl carbonate, methyltrifluoroethyl carbonate (MFEC), bis (trifluoroethyl) carbonate and the like. Of these, EMC and MFEC are preferable.
非水溶媒として、環状カーボネート又は鎖状カーボネートを用いることが好ましく、環状カーボネートと鎖状カーボネートとを併用することがより好ましい。環状カーボネートを用いることで、電解質塩の解離を促進して非水電解液のイオン伝導度を向上させることができる。鎖状カーボネートを用いることで、非水電解液の粘度を低く抑えることができる。環状カーボネートと鎖状カーボネートとを併用する場合、環状カーボネートと鎖状カーボネートとの体積比率（環状カーボネート：鎖状カーボネート）としては、例えば、５：９５から５０：５０の範囲とすることが好ましい。 As the non-aqueous solvent, it is preferable to use cyclic carbonate or chain carbonate, and it is more preferable to use cyclic carbonate and chain carbonate in combination. By using the cyclic carbonate, the dissociation of the electrolyte salt can be promoted and the ionic conductivity of the non-aqueous electrolyte solution can be improved. By using the chain carbonate, the viscosity of the non-aqueous electrolytic solution can be kept low. When the cyclic carbonate and the chain carbonate are used in combination, the volume ratio of the cyclic carbonate to the chain carbonate (cyclic carbonate: chain carbonate) is preferably in the range of, for example, 5:95 to 50:50.
電解質塩としては、公知の電解質塩から適宜選択できる。電解質塩としては、リチウム塩、ナトリウム塩、カリウム塩、マグネシウム塩、オニウム塩等が挙げられる。これらの中でもリチウム塩が好ましい。 The electrolyte salt can be appropriately selected from known electrolyte salts. Examples of the electrolyte salt include lithium salt, sodium salt, potassium salt, magnesium salt, onium salt and the like. Of these, lithium salts are preferred.
リチウム塩としては、ＬｉＰＦ６、ＬｉＰＯ２Ｆ２、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＮ（ＳＯ２Ｆ）２等の無機リチウム塩、ＬｉＳＯ３ＣＦ３、ＬｉＮ（ＳＯ２ＣＦ３）２、ＬｉＮ（ＳＯ２Ｃ２Ｆ５）２、ＬｉＮ（ＳＯ２ＣＦ３）（ＳＯ２Ｃ４Ｆ９）、ＬｉＣ（ＳＯ２ＣＦ３）３、ＬｉＣ（ＳＯ２Ｃ２Ｆ５）３等のハロゲン化炭化水素基を有するリチウム塩等が挙げられる。これらの中でも、無機リチウム塩が好ましく、ＬｉＰＦ６がより好ましい。 Lithium salts include inorganic lithium salts such as LiPF 6 , LiPO 2 F 2 , LiBF 4 , LiClO 4 , LiN (SO 2 F) 2 , LiSO 3 CF 3 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2). C 2 F 5 ) 2 , LiN (SO 2 CF 3 ) (SO 2 C 4 F 9 ), LiC (SO 2 CF 3 ) 3 , LiC (SO 2 C 2 F 5 ) 3 and other halogenated hydrocarbon groups Examples thereof include lithium salts having. Among these, an inorganic lithium salt is preferable, and LiPF 6 is more preferable.
非水電解液における電解質塩の含有量は、０．１ｍｏｌ／ｄｍ３以上２．５ｍｏｌ／ｄｍ３以下であると好ましく、０．３ｍｏｌ／ｄｍ３以上２．０ｍｏｌ／ｄｍ３以下であるとより好ましく、０．５ｍｏｌ／ｄｍ３以上１．７ｍｏｌ／ｄｍ３以下であるとさらに好ましく、０．７ｍｏｌ／ｄｍ３以上１．５ｍｏｌ／ｄｍ３以下であると特に好ましい。電解質塩の含有量を上記の範囲とすることで、非水電解液のイオン伝導度を高めることができる。 The content of the electrolyte salt in the nonaqueous electrolytic solution, preferable to be 0.1 mol / dm 3 or more 2.5 mol / dm 3 or less, more preferable to be 0.3 mol / dm 3 or more 2.0 mol / dm 3 or less , more preferable to be 0.5 mol / dm 3 or more 1.7 mol / dm 3 or less, and particularly preferably 0.7 mol / dm 3 or more 1.5 mol / dm 3 or less. By setting the content of the electrolyte salt in the above range, the ionic conductivity of the non-aqueous electrolyte solution can be increased.
非水電解液は、添加剤を含んでもよい。添加剤としては、例えばビフェニル、アルキルビフェニル、ターフェニル、ターフェニルの部分水素化体、シクロヘキシルベンゼン、ｔ−ブチルベンゼン、ｔ−アミルベンゼン、ジフェニルエーテル、ジベンゾフラン等の芳香族化合物；２−フルオロビフェニル、ｏ−シクロヘキシルフルオロベンゼン、ｐ−シクロヘキシルフルオロベンゼン等の上記芳香族化合物の部分ハロゲン化物；２，４−ジフルオロアニソール、２，５−ジフルオロアニソール、２，６−ジフルオロアニソール、３，５−ジフルオロアニソール等のハロゲン化アニソール化合物；無水コハク酸、無水グルタル酸、無水マレイン酸、無水シトラコン酸、無水グルタコン酸、無水イタコン酸、シクロヘキサンジカルボン酸無水物；亜硫酸エチレン、亜硫酸プロピレン、亜硫酸ジメチル、硫酸ジメチル、硫酸エチレン、スルホラン、ジメチルスルホン、ジエチルスルホン、ジメチルスルホキシド、ジエチルスルホキシド、テトラメチレンスルホキシド、ジフェニルスルフィド、４，４’−ビス（２，２−ジオキソ−１，３，２−ジオキサチオラン）、４−メチルスルホニルオキシメチル−２，２−ジオキソ−１，３，２−ジオキサチオラン、チオアニソール、ジフェニルジスルフィド、ジピリジニウムジスルフィド、パーフルオロオクタン、ホウ酸トリストリメチルシリル、リン酸トリストリメチルシリル、チタン酸テトラキストリメチルシリル等が挙げられる。これら添加剤は、１種を単独で用いてもよく、２種以上を混合して用いてもよい。 The non-aqueous electrolyte solution may contain additives. Examples of the additive include aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, and partially hydride of terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; 2-fluorobiphenyl, o. Partial halides of the above aromatic compounds such as −cyclohexylfluorobenzene and p-cyclohexylfluorobenzene; such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole and the like. Anisole halide compounds; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic acid anhydride; ethylene sulfite, propylene sulfite, dimethyl sulfite, dimethyl sulfite, ethylene sulfate, Sulforane, dimethylsulfone, diethylsulfone, dimethylsulfoxide, diethylsulfoxide, tetramethylenesulfoxide, diphenylsulfide, 4,4'-bis (2,2-dioxo-1,3,2-dioxathiolane), 4-methylsulfonyloxymethyl- Examples thereof include 2,2-dioxo-1,3,2-dioxathiolane, thioanisole, diphenyldisulfide, dipyridinium disulfide, perfluorooctane, tristrimethylsilyl borate, tristrimethylsilyl phosphate, tetraxtrimethylsilyl titanate and the like. One of these additives may be used alone, or two or more thereof may be mixed and used.
非水電解液に含まれる添加剤の含有量は、非水電解液全体の質量に対して０．０１質量％以上１０質量％以下であると好ましく、０．１質量％以上７質量％以下であるとより好ましく、０．２質量％以上５質量％以下であるとさらに好ましく、０．３質量％以上３質量％以下であると特に好ましい。添加剤の含有量を上記の範囲とすることで、高温保存後の容量維持性能又はサイクル性能を向上させたり、安全性をより向上させたりすることができる。 The content of the additive contained in the non-aqueous electrolytic solution is preferably 0.01% by mass or more and 10% by mass or less, and 0.1% by mass or more and 7% by mass or less, based on the total mass of the non-aqueous electrolytic solution. It is more preferable to have it, more preferably 0.2% by mass or more and 5% by mass or less, and particularly preferably 0.3% by mass or more and 3% by mass or less. By setting the content of the additive in the above range, it is possible to improve the capacity maintenance performance or the cycle performance after high temperature storage, and further improve the safety.
非水電解質には、固体電解質を用いてもよく、非水電解液と固体電解質とを併用してもよい。 As the non-aqueous electrolyte, a solid electrolyte may be used, or a non-aqueous electrolyte solution and a solid electrolyte may be used in combination.
固体電解質としては、リチウム、ナトリウム、カルシウム等のイオン伝導性を有し、常温（例えば１５℃以上２５℃以下）において固体である任意の材料から選択できる。固体電解質としては、例えば、硫化物固体電解質、酸化物固体電解質、及び酸窒化物固体電解質、ポリマー固体電解質等が挙げられる。 The solid electrolyte can be selected from any material having ionic conductivity such as lithium, sodium and calcium and being solid at room temperature (for example, 15 ° C. or higher and 25 ° C. or lower). Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, oxynitride solid electrolytes, polymer solid electrolytes and the like.
硫化物固体電解質としては、リチウムイオン二次電池の場合、例えば、Ｌｉ２Ｓ−Ｐ２Ｓ５系等が挙げられる。硫化物固体電解質としては、例えば、Ｌｉ２Ｓ−Ｐ２Ｓ５、ＬｉＩ−Ｌｉ２Ｓ−Ｐ２Ｓ５、Ｌｉ１０Ｇｅ−Ｐ２Ｓ１２等が挙げられる。 Examples of the sulfide solid electrolyte include Li 2 SP 2 S 5 series in the case of a lithium ion secondary battery. Examples of the sulfide solid electrolyte include Li 2 SP 2 S 5 , Li I-Li 2 SP 2 S 5 , Li 10 Ge-P 2 S 12, and the like.
（通常使用時の充電終止電圧における正極電位）
当該二次電池（非水電解質蓄電素子）においては、通常使用時の充電終止電圧における正極電位が４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満であることが好ましく、４．５５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下がより好ましく、４．５０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋又は４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下がさらに好ましいこともある。通常使用時の充電終止電圧における正極電位を上記上限以下とすることで、多数回の充放電の繰り返しに伴って、経時化成が徐々に進行するため、容量維持率を高めることができる。
(Positive potential at the end of charging voltage during normal use)
In the secondary battery (non-aqueous electrolyte power storage element), the positive electrode potential at the end-of-charge voltage during normal use is 4.60 V vs. It is preferably less than Li / Li + , 4.55 V vs. Li / Li + or less is more preferable, and 4.50 V vs. Li / Li + or 4.45V vs. Li / Li + or less may be more preferred. By setting the positive electrode potential at the end-of-charge voltage during normal use to the above upper limit or less, aging gradually progresses with the repetition of charging and discharging a large number of times, so that the capacity retention rate can be increased.
当該二次電池においては、通常使用時の充電終止電圧における正極電位が４．３０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋超であることが好ましく、４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以上がより好ましく、４．４０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以上がさらに好ましい場合もある。通常使用時の充電終止電圧における正極電位を上記下限以上とすることで、通常の充電の際に十分に経時化成が進行するため、容量維持率を高めることができる。また、充電上限電位を高めることで、放電容量を大きくし、エネルギー密度を高めることができる。 In the secondary battery, the positive electrode potential at the end-of-charge voltage during normal use is 4.30 V vs. It is preferably Li / Li + or more, 4.35 V vs. Li / Li + or higher is more preferred, 4.40 V vs. Li / Li + or higher may be more preferred. By setting the positive electrode potential at the end-of-charge voltage during normal use to be equal to or higher than the above lower limit, aging progresses sufficiently during normal charging, so that the capacity retention rate can be increased. Further, by increasing the charging upper limit potential, the discharge capacity can be increased and the energy density can be increased.
当該二次電池における通常使用時の充電終止電圧における正極電位は、上記したいずれかの上限と上記したいずれかの下限との範囲内としてよい。 The positive electrode potential at the end-of-charge voltage during normal use of the secondary battery may be within the range of any of the above-mentioned upper limit and any of the above-mentioned lower limit.
（用途）
当該二次電池の用途は特に限定されず、従来公知の二次電池と同様の用途に用いることができる。当該二次電池は、経時化成が生じることにより容量維持率を高めることができていると推測されるため、充電するときは、通常所定の充電終止電圧（所定の充電終止電位）に至るまで充電される、すなわちＳＯＣ（充電状態）が１００％になるまで充電される用途に当該二次電池を特に好適に適用することができる。このような用途としては、例えば携帯用電子機器（携帯電話、ノート型パソコン、タブレット端末等）、電気玩具、電気シェーバー、電気自動車（ＥＶ）、プラグインハイブリッドカー（ＰＨＥＶ）等の電源用途を挙げることができる。
(Use)
The application of the secondary battery is not particularly limited, and can be used in the same application as a conventionally known secondary battery. Since it is presumed that the capacity retention rate of the secondary battery can be increased due to aging, when charging, the secondary battery is usually charged to a predetermined charge termination voltage (predetermined charge termination potential). That is, the secondary battery can be particularly preferably applied to an application in which the battery is charged until the SOC (charged state) reaches 100%. Examples of such applications include power supply applications for portable electronic devices (mobile phones, notebook computers, tablet terminals, etc.), electric toys, electric shavers, electric vehicles (EV), plug-in hybrid cars (PHEV), and the like. be able to.
＜非水電解質蓄電素子の使用方法＞
本発明の一実施形態に係る非水電解質蓄電素子の使用方法は、当該非水電解質蓄電素子を、正極電位が４．３０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋超４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満に至るまで充電することを備える。このように使用すること、すなわちこのような電位まで繰り返し充電することで、充電に伴って徐々に経時化成がなされるため、リチウム過剰型活物質を正極に用いた非水電解質蓄電素子を高い容量維持率で使用することができる。
<How to use non-aqueous electrolyte power storage element>
In the method of using the non-aqueous electrolyte storage element according to the embodiment of the present invention, the non-aqueous electrolyte storage element has a positive electrode potential of 4.30 V vs. Li / Li + Super 4.60V vs. It is provided to charge to less than Li / Li + . By using it in this way, that is, by repeatedly charging it to such a potential, aging is gradually performed with charging, so that a non-aqueous electrolyte power storage element using a lithium excess type active material as a positive electrode has a high capacity. It can be used at a maintenance rate.
この充電における正極電位（充電上限電位）の上限は、４．５５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下であってもよく、４．５０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋又は４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋であってもよい。また、この充電における正極電位（充電上限電位）の下限は、４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋であってもよく、４．４０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋であってもよい。 The upper limit of the positive electrode potential (charge upper limit potential) in this charging is 4.55 V vs. It may be Li / Li + or less, and 4.50 V vs. Li / Li + or 4.45V vs. It may be Li / Li + . Further, the lower limit of the positive electrode potential (charge upper limit potential) in this charging is 4.35 V vs. It may be Li / Li + , 4.40V vs. It may be Li / Li + .
この使用方法は、充電における正極電位（充電上限電位）を上記範囲内とすること以外は、従来公知の非水電解質蓄電素子の使用方法と同様であってよい。 This usage method may be the same as the usage method of the conventionally known non-aqueous electrolyte power storage element except that the positive electrode potential (charge upper limit potential) in charging is within the above range.
＜非水電解質蓄電素子の製造方法＞
本発明の一実施形態に係る非水電解質蓄電素子は、正極と負極と非水電解質とを備える未充放電非水電解質蓄電素子を組み立てること、及びこの未充放電非水電解質蓄電素子を初期充放電することを備える。この初期充放電において、正極の最大到達電位が４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満となるように初期の充電を行う。このような製造方法によれば、初期充放電において高電位化成がなされないため、リチウム過剰型活物質を正極に用いた非水電解質蓄電素子であって、充放電サイクルにおける容量維持率が高い非水電解質蓄電素子を製造することができる。
<Manufacturing method of non-aqueous electrolyte power storage element>
In the non-aqueous electrolyte storage element according to the embodiment of the present invention, an uncharged / discharged non-aqueous electrolyte storage element including a positive electrode, a negative electrode, and a non-aqueous electrolyte is assembled, and the uncharged / discharged non-aqueous electrolyte storage element is initially charged. Prepare to discharge. In this initial charge / discharge, the maximum potential of the positive electrode is 4.60 V vs. Initial charging is performed so that the value is less than Li / Li + . According to such a manufacturing method, high potential formation is not performed in the initial charge / discharge, so that the non-aqueous electrolyte power storage device using the lithium excess type active material for the positive electrode has a high capacity retention rate in the charge / discharge cycle. A water electrolyte power storage element can be manufactured.
なお、当該製造方法において、初期充放電は積極的にリチウム過剰型活物質の活性化を行わせるものではなく、例えば容量の確認等のためになされるものであってよい。すなわち、初期充放電とは、単に、非水電解質蓄電素子（未充放電非水電解質蓄電素子）を組み立てた後に初めて行われる充放電である。初期充放電における充放電の回数は１回又は２回であってもよく、３回以上であってもよい。 In the production method, the initial charge / discharge does not actively activate the lithium excess type active material, but may be performed, for example, for checking the capacity or the like. That is, the initial charge / discharge is simply the charge / discharge performed for the first time after assembling the non-aqueous electrolyte storage element (uncharged / discharged non-aqueous electrolyte storage element). The number of charge / discharge in the initial charge / discharge may be once or twice, or may be three or more.
初期充放電における正極の最大到達電位は、４．５５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下であってよく、４．５０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋又は４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下であってもよい。一方、初期充放電における正極の最大到達電位の下限は特に限定されず、例えば４．３０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋超であってよく、４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以上又は４．４０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以上であってもよい。 The maximum potential of the positive electrode in the initial charge / discharge is 4.55 V vs. It may be Li / Li + or less, and 4.50 V vs. Li / Li + or 4.45V vs. It may be Li / Li + or less. On the other hand, the lower limit of the maximum ultimate potential of the positive electrode in the initial charge / discharge is not particularly limited, and for example, 4.30 V vs. It may be Li / Li + or more, 4.35V vs. Li / Li + or higher or 4.40V vs. It may be Li / Li + or more.
正極と負極と非水電解質とを備える未充放電非水電解質蓄電素子を組み立てることは、例えば、電極体を準備することと、非水電解質を準備することと、電極体及び非水電解質を容器に収容することとを備える。電極体を準備することは、正極を準備することと、負極を準備することと、正極及び負極を、セパレータを介して積層又は巻回することにより電極体を形成することとを備える。 Assembling an uncharged / discharged non-aqueous electrolyte power storage element including a positive electrode, a negative electrode, and a non-aqueous electrolyte means, for example, preparing an electrode body, preparing a non-aqueous electrolyte, and containerizing the electrode body and the non-aqueous electrolyte. Provided to be housed in. Preparing the electrode body includes preparing a positive electrode body, preparing a negative electrode body, and forming an electrode body by laminating or winding the positive electrode body and the negative electrode body via a separator.
正極を準備することは、正極基材に直接又は中間層を介して、正極合剤ペーストを塗布し、乾燥させることにより行うことができる。上記正極合剤ペーストには、正極活物質等、正極活物質層（正極合剤）を構成する各成分、及び分散媒が含まれる。正極活物質には、上記リチウム遷移金属複合酸化物（リチウム過剰型活物質）が含まれる。同様に負極を準備することは、例えば負極基材に直接又は中間層を介して、負極合剤ペーストを塗布し、乾燥させることにより行うことができる。上記負極合剤ペーストには、負極活物質等、負極活物質層（負極合剤）を構成する各成分、及び分散媒が含まれる。 The positive electrode can be prepared by applying the positive electrode mixture paste directly to the positive electrode base material or via an intermediate layer and drying it. The positive electrode mixture paste contains each component constituting the positive electrode active material layer (positive electrode mixture) such as the positive electrode active material, and a dispersion medium. The positive electrode active material includes the above-mentioned lithium transition metal composite oxide (lithium excess type active material). Similarly, the negative electrode can be prepared, for example, by applying the negative electrode mixture paste directly to the negative electrode base material or via an intermediate layer and drying it. The negative electrode mixture paste contains each component constituting the negative electrode active material layer (negative electrode mixture) such as the negative electrode active material, and a dispersion medium.
＜その他の実施形態＞
本発明の蓄電素子は、上記実施形態に限定されるものではなく、本発明の要旨を逸脱しない範囲内において種々変更を加えてもよい。例えば、ある実施形態の構成に他の実施形態の構成を追加することができ、また、ある実施形態の構成の一部を他の実施形態の構成又は周知技術に置き換えることができる。さらに、ある実施形態の構成の一部を削除することができる。また、ある実施形態の構成に対して周知技術を付加することができる。
<Other Embodiments>
The power storage element of the present invention is not limited to the above embodiment, and various modifications may be made without departing from the gist of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and a part of the configuration of one embodiment can be replaced with the configuration of another embodiment or a well-known technique. In addition, some of the configurations of certain embodiments can be deleted. Further, a well-known technique can be added to the configuration of a certain embodiment.
また、上記実施の形態においては、非水電解質蓄電素子が非水電解質二次電池である形態を中心に説明したが、その他の非水電解質蓄電素子であってもよい。その他の非水電解質蓄電素子としては、キャパシタ（電気二重層キャパシタ、リチウムイオンキャパシタ）等が挙げられる。 Further, in the above-described embodiment, the non-aqueous electrolyte storage element is mainly a non-aqueous electrolyte secondary battery, but other non-aqueous electrolyte storage elements may be used. Examples of other non-aqueous electrolyte power storage elements include capacitors (electric double layer capacitors, lithium ion capacitors) and the like.
図５に、本発明に係る非水電解質蓄電素子の一実施形態である矩形状の非水電解質蓄電素子１（非水電解質二次電池）の概略図を示す。なお、同図は、容器内部を透視した図としている。図５に示す非水電解質蓄電素子１は、電極体２が容器３に収納されている。電極体２は、正極活物質を備える正極と、負極活物質を備える負極とが、セパレータを介して巻回されることにより形成されている。正極は、正極リード４１を介して正極端子４と電気的に接続され、負極は、負極リード５１を介して負極端子５と電気的に接続されている。
FIG. 5 shows a schematic view of a rectangular non-aqueous electrolyte storage element 1 (non-aqueous electrolyte secondary battery) which is an embodiment of the non-aqueous electrolyte storage element according to the present invention. The figure is a perspective view of the inside of the container. In the non-aqueous electrolyte
本発明に係る非水電解質蓄電素子の構成については特に限定されるものではなく、円筒型電池、角型電池（矩形状の電池）、扁平型電池等が一例として挙げられる。本発明は、上記の非水電解質蓄電素子を複数備える蓄電装置としても実現することができる。蓄電装置の一実施形態を図６に示す。図６において、蓄電装置３０は、複数の蓄電ユニット２０を備えている。それぞれの蓄電ユニット２０は、複数の非水電解質蓄電素子１を備えている。上記蓄電装置３０は、電気自動車（ＥＶ）、プラグインハイブリッド自動車（ＰＨＥＶ）等の自動車用電源として搭載することができる。
The configuration of the non-aqueous electrolyte power storage element according to the present invention is not particularly limited, and examples thereof include a cylindrical battery, a square battery (rectangular battery), and a flat battery. The present invention can also be realized as a power storage device including a plurality of the above-mentioned non-aqueous electrolyte power storage elements. An embodiment of the power storage device is shown in FIG. In FIG. 6, the
以下、実施例によって本発明をさらに具体的に説明するが、本発明は以下の実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.
［実施例１］正極Ａ（リチウム過剰型活物質）を有する試験電池（非水電解質蓄電素子）の作製
（正極Ａの作製）
正極活物質として、α−ＮａＦｅＯ２構造を有し、かつＬｉ１．０８（Ｎｉ０．３９Ｃｏ０．１５Ｍｎ０．４６）０．９２Ｏ２で表されるリチウム遷移金属複合酸化物（正極活物質Ａ）を準備した。
質量比で、正極活物質Ａ：アセチレンブラック（ＡＢ）：ポリフッ化ビニリデン（ＰＶＤＦ）＝９０：５：５の割合（固形物換算）で含み、Ｎ−メチルピロリドン（ＮＭＰ）を分散媒とする正極合剤ペーストを作製した。この正極合剤ペーストを正極基材としてのアルミニウム箔（厚み１５μｍ）に塗布し、乾燥させて、正極Ａを得た。
[Example 1] Fabrication of a test battery (non-aqueous electrolyte power storage element) having a positive electrode A (lithium excess type active material) (preparation of positive electrode A)
As a positive electrode active material, a lithium transition metal composite oxide (positive electrode) having an α-NaFeO 2 structure and represented by Li 1.08 (Ni 0.39 Co 0.15 Mn 0.46 ) 0.92 O 2 Active material A) was prepared.
Positive electrode Active material A: acetylene black (AB): polyvinylidene fluoride (PVDF) = 90: 5: 5 (solid matter equivalent), and N-methylpyrrolidone (NMP) as the dispersion medium. A mixture paste was prepared. This positive electrode mixture paste was applied to an aluminum foil (thickness 15 μm) as a positive electrode base material and dried to obtain a positive electrode A.
（試験電池の組み立て）
上記正極Ａを作用極、金属リチウムを対極とした試験電池（非水電解質蓄電素子）を組み立てた。なお、非水電解質として、ＥＣ（エチレンカーボネート）とＥＭＣ（エチルメチルカーボネート）とを体積比３０：７０で混合した非水溶媒に、電解質塩としてヘキサフルオロリン酸リチウム（ＬｉＰＦ６）が１．０ｍｏｌ／ｄｍ３の含有量となるように溶解させた溶液を用い、セパレータとしてポリオレフィン製微多孔膜を用いた。
(Assembly of test battery)
A test battery (non-aqueous electrolyte power storage element) having the positive electrode A as the working electrode and metallic lithium as the counter electrode was assembled. As a non-aqueous electrolyte, 1.0 mol of lithium hexafluorophosphate (LiPF 6 ) as an electrolyte salt was added to a non-aqueous solvent in which EC (ethylene carbonate) and EMC (ethyl methyl carbonate) were mixed at a volume ratio of 30:70. A solution dissolved so as to have a content of / dm 3 was used, and a microporous polyolefin film was used as a separator.
（初期充放電）
得られた初期充放電前の試験電池（未充放電非水電解質蓄電素子）に対して、２５℃にて、以下の要領にて５サイクルの初期充放電を行い、非水電解質蓄電素子を得た。ここで、全ての充電後及び放電後にはそれぞれ１０分間の休止期間を設けた。下記の初期充放電における２サイクル目の放電電気量を放電容量とした。以下の試験では、作用極と対極との間で電圧制御を行ったが、対極における金属リチウムの溶解・析出反応抵抗が極めて低いことから、充放電中の端子間電圧は、金属リチウムを用いた参照極に対する作用極の電位と等しいとみなすことができる。
（１サイクル目）
充電電流０．１Ｃ（正極活物質の質量あたり１８ｍＡ／ｇ）、充電終止電圧４．３５Ｖ（正極電位４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）、トータル充電時間１５時間で定電流定電圧充電を行った。その後、放電電流０．２Ｃ、放電終止電圧２．５Ｖで定電流放電を行った。
（２から５サイクル目）
充電電流０．２Ｃ（正極活物質の質量あたり３６ｍＡ／ｇ）、充電終止電圧４．３５Ｖ（正極電位４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）、トータル充電時間８時間で定電流定電圧充電を行った。その後、放電電流０．２Ｃ、放電終止電圧２．５Ｖで定電流放電を行った。
(Initial charge / discharge)
The obtained test battery (uncharged / discharged non-aqueous electrolyte storage element) before initial charge / discharge is subjected to initial charge / discharge for 5 cycles at 25 ° C. in the following manner to obtain a non-aqueous electrolyte storage element. It was. Here, a rest period of 10 minutes was provided after all charging and discharging. The amount of electricity discharged in the second cycle in the following initial charge / discharge was defined as the discharge capacity. In the following tests, voltage control was performed between the working electrode and the counter electrode, but since the dissolution / precipitation reaction resistance of metallic lithium at the counter electrode is extremely low, metallic lithium was used as the voltage between terminals during charging and discharging. It can be regarded as equal to the potential of the working electrode with respect to the reference electrode.
(1st cycle)
Constant current constant voltage charging is performed with a charging current of 0.1 C (18 mA / g per mass of positive electrode active material), a charging termination voltage of 4.35 V (positive electrode potential of 4.35 V vs. Li / Li + ), and a total charging time of 15 hours. It was. Then, a constant current discharge was performed with a discharge current of 0.2 C and a discharge end voltage of 2.5 V.
(2nd to 5th cycle)
Constant current constant voltage charging is performed with a charging current of 0.2 C (36 mA / g per mass of positive electrode active material), a final charge voltage of 4.35 V (positive electrode potential of 4.35 V vs. Li / Li + ), and a total charging time of 8 hours. It was. Then, a constant current discharge was performed with a discharge current of 0.2 C and a discharge end voltage of 2.5 V.
（上記式（１）の値を求めるための２サイクルの充放電）
初期充放電を終えた試験電池について、２５℃の下、以下の要領で、上記式（１）の値を求めるための２サイクルの充放電を行った。なお、ここでは、金属リチウム電極を対極とした試験電池であることがわかっているので、正極を取り出して試験電池を組み立て直す操作は行わなかった。
まず、正極合剤の質量あたり９ｍＡ／ｇの電流密度で、端子間電圧が２．００Ｖ（正極電位２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）に至るまで定電流放電を行った。
次に、正極合剤の質量あたり９ｍＡ／ｇの電流密度、充電終止電圧４．８０Ｖ（正極電位４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流充電を行った。その後、正極合剤の質量あたり９ｍＡ／ｇの電流密度、放電終止電圧２．００Ｖ（正極電位２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流放電を行った。この充放電を２サイクル行った。また、充電後及び放電後にはそれぞれ３０分間の休止期間を設けた。
(Two-cycle charge / discharge to obtain the value of the above equation (1))
The test battery after the initial charge / discharge was charged / discharged at 25 ° C. for two cycles in order to obtain the value of the above formula (1) in the following manner. Since it is known that the test battery has a metallic lithium electrode as a counter electrode, the operation of taking out the positive electrode and reassembling the test battery was not performed here.
First, constant current discharge was performed at a current density of 9 mA / g per mass of the positive electrode mixture until the voltage between terminals reached 2.00 V (positive electrode potential 2.00 V vs. Li / Li + ).
Next, constant current charging was performed at a current density of 9 mA / g per mass of the positive electrode mixture and a charge termination voltage of 4.80 V (positive electrode potential 4.80 V vs. Li / Li + ). Then, a constant current discharge was performed at a current density of 9 mA / g per mass of the positive electrode mixture and a discharge termination voltage of 2.00 V (positive electrode potential 2.00 V vs. Li / Li + ). This charge / discharge was performed for 2 cycles. In addition, a rest period of 30 minutes was provided after charging and discharging.
（充電曲線の評価）
上記２サイクルの充放電サイクル試験から、
１サイクル目の充電において、充電開始から電圧が４．８０Ｖ（正極電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）に至るまでの充電電気量（Ｃ１Ｂ）に対する充電開始から電圧が４．４５Ｖ（正極電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）に至るまでの充電電気量（Ｃ１Ａ）の比の百分率（（Ｃ１Ａ／Ｃ１Ｂ）×１００）、
２サイクル目の充電において、充電開始から電圧が４．８０Ｖ（正極電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）に至るまでの充電電気量（Ｃ２Ｂ）に対する充電開始から電圧が４．４５Ｖ（正極電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）に至るまでの充電電気量（Ｃ２Ａ）の比の百分率（（Ｃ２Ａ／Ｃ２Ｂ）×１００）、及び
これらの差（（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００）を求めた。これらの値を表１に示す。
(Evaluation of charging curve)
From the above two-cycle charge / discharge cycle test,
In the first cycle of charging, the voltage from the start of charging to the voltage of 4.80V (positive electrode potential is 4.80V vs. Li / Li + ) is 4.45V (from the start of charging for the amount of charging electricity (C 1B )). Percentage of the ratio of the amount of electricity charged (C 1A ) until the positive electrode potential reaches 4.45V vs. Li / Li + ) ((C 1A / C 1B ) x 100),
In the second cycle of charging, the voltage from the start of charging to the voltage of 4.80V (positive electrode potential is 4.80V vs. Li / Li + ) is 4.45V (from the start of charging) for the amount of electricity charged (C 2B ). Percentage ((C 2A / C 2B ) x 100) of the ratio of the amount of electricity charged (C 2A ) until the positive electrode potential reaches 4.45V vs. Li / Li + ), and the difference between them ((C 2A / C) 2B ) × 100− (C 1A / C 1B ) × 100) was obtained. These values are shown in Table 1.
［実施例２から５、比較例１］
実施例１の「初期充放電」における１から３サイクル目の充電終止電圧（充電終止時の正極電位）を表１に示す通りとしたこと以外は、実施例１と同様の操作をし、充放電試験及び充電曲線の評価を行った。求めた値を表１に示す。
[Examples 2 to 5, Comparative Example 1]
The same operation as in Example 1 was performed to charge the battery, except that the charge termination voltage (positive electrode potential at the end of charging) in the first to third cycles in the “initial charge / discharge” of Example 1 was set as shown in Table 1. A discharge test and a charge curve evaluation were performed. The obtained values are shown in Table 1.
また、上記２サイクルの充放電試験における充放電曲線について、実施例１の充放電曲線を図１に、比較例１の充放電曲線を図２に示す。 Regarding the charge / discharge curves in the above two-cycle charge / discharge test, the charge / discharge curve of Example 1 is shown in FIG. 1, and the charge / discharge curve of Comparative Example 1 is shown in FIG.
表１に示されるように、初期充放電の際の充電終止電圧が４．６Ｖ未満であり、正極の最大到達電位（充電終止電圧における正極電位）が４．６Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満である実施例１から５においては、（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００の値が１．０以上である。すなわちこれらは、高電位化成が不十分であり、経時化成できる十分な能力を有していると評価できる。なお、正極電位が低いほどこの傾向は高まっている。これに対し、初期充放電の際の充電終止電圧が４．６Ｖであり、正極の最大到達電位が４．６Ｖ ｖｓ．Ｌｉ／Ｌｉ＋である比較例１においては、（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００の値が０．７である。すなわち比較例１は、十分な高電位化成がなされ、経時化成できる十分な能力を有していないと評価できる。 As shown in Table 1, the charge termination voltage at the time of initial charging / discharging is less than 4.6V, and the maximum ultimate potential of the positive electrode (positive electrode potential at the charging termination voltage) is 4.6V vs. In Examples 1 to 5 which are less than Li / Li + , the value of (C 2A / C 2B ) × 100− (C 1A / C 1B ) × 100 is 1.0 or more. That is, it can be evaluated that these have insufficient high potential chemicalization and have sufficient ability to be chemicalized over time. The lower the positive electrode potential, the higher this tendency. On the other hand, the final charge voltage at the time of initial charge / discharge is 4.6 V, and the maximum potential of the positive electrode is 4.6 V vs. In Comparative Example 1 which is Li / Li + , the value of (C 2A / C 2B ) × 100− (C 1A / C 1B ) × 100 is 0.7. That is, it can be evaluated that Comparative Example 1 has sufficiently high potential chemicalization and does not have sufficient ability to be chemicalized over time.
また、図１に示されるように、実施例１においては、１サイクル目に４．５Ｖ以上４．８Ｖ以下の電圧範囲内（４．５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以上５．０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋以下の正極電位範囲内）に、充電電気量に対して電圧変化が比較的緩やかな領域が観察される。なお、２サイクル目にはこの電圧変化が比較的穏やかな領域は観察されない。一方、図２に示されるように、比較例１においては、いずれのサイクルにおいてもこの電圧変化が比較的穏やかな領域が観察されない。これらの充放電曲線からも、比較例１では、初期充放電の際に既に十分な高電位化成がなされているのに対し、実施例１では、高電位化成が十分にはなされておらず、経時化成できる十分な能力を有しているといえる。 Further, as shown in FIG. 1, in the first cycle, in the first cycle, the voltage range is 4.5 V or more and 4.8 V or less (4.5 V vs. Li / Li + or more and 5.0 V vs. Li /. In the positive electrode potential range (within Li + or less), a region where the voltage change is relatively gradual with respect to the amount of charging electricity is observed. In the second cycle, a region where this voltage change is relatively gentle is not observed. On the other hand, as shown in FIG. 2, in Comparative Example 1, a region in which this voltage change is relatively gentle is not observed in any of the cycles. From these charge / discharge curves, in Comparative Example 1, sufficient high potential formation was already performed at the time of initial charge / discharge, whereas in Example 1, high potential formation was not sufficiently performed. It can be said that it has sufficient ability to be aged over time.
［実施例６］正極Ａ（リチウム過剰型活物質）及び負極Ａ（ＳｉＯ−Ｇｒ）を有する非水電解質蓄電素子の作製
（正極Ａの作製）
実施例１と同様の手順で、正極Ａを得た。
[Example 6] Fabrication of a non-aqueous electrolyte power storage element having a positive electrode A (lithium excess active material) and a negative electrode A (SiO-Gr) (preparation of positive electrode A)
A positive electrode A was obtained in the same procedure as in Example 1.
（負極Ａの作製）
負極活物質として、非黒鉛質炭素が被覆された酸化ケイ素（ＳｉＯ）と黒鉛（Ｇｒ）とを２：８（質量比）で混合した負極活物質Ａを用いた。
質量比で、負極活物質Ａ：スチレンブタジエンゴム（ＳＢＲ）：カルボキシメチルセルロース（ＣＭＣ）＝９４．８：４．０：１．２の割合（固形分換算）で含み、水を分散媒とする負極合剤ペーストを作製した。この負極合剤ペーストを負極基材としての帯状の銅箔（厚み２０μｍ）に塗布し、乾燥させて、負極Ａを得た。
(Preparation of negative electrode A)
As the negative electrode active material, the negative electrode active material A in which silicon oxide (SiO) coated with non-graphitic carbon and graphite (Gr) were mixed at a ratio of 2: 8 (mass ratio) was used.
Negative electrode active material A: Styrene butadiene rubber (SBR): Carboxymethyl cellulose (CMC) = 94.8: 4.0: 1.2 (in terms of solid content), and water is used as the dispersion medium. A mixture paste was prepared. This negative electrode mixture paste was applied to a strip-shaped copper foil (
（非水電解質Ａの調製）
ＥＣ（エチレンカーボネート）とＰＣ（プロピレンカーボネート）とＥＭＣ（エチルメチルカーボネート）とを体積比２５：５：７０で混合した非水溶媒に、電解質塩としてヘキサフルオロリン酸リチウム（ＬｉＰＦ６）が１．０ｍｏｌ／ｄｍ３の含有量となるように溶解させた溶液を調製し、非水電解質Ａとした。
(Preparation of non-aqueous electrolyte A)
Lithium hexafluorophosphate (LiPF 6 ) as an electrolyte salt is added to a non-aqueous solvent in which EC (ethylene carbonate), PC (propylene carbonate) and EMC (ethylmethyl carbonate) are mixed at a volume ratio of 25: 5: 70. A solution prepared so as to have a content of 0 mol / dm 3 was used as a non-aqueous electrolyte A.
（非水電解質蓄電素子の組み立て）
セパレータとして、耐熱層が塗工されたポリオレフィン製微多孔膜を用意した。このセパレータを介して、上記正極Ａと上記負極Ａとを積層することにより電極体を作製した。この電極体を金属樹脂複合フィルム製の容器に収納し、内部に上記非水電解質Ａを注入した後、熱溶着により封口した。
(Assembly of non-aqueous electrolyte power storage element)
As a separator, a microporous polyolefin membrane coated with a heat-resistant layer was prepared. An electrode body was produced by laminating the positive electrode A and the negative electrode A via the separator. The electrode body was housed in a container made of a metal resin composite film, the non-aqueous electrolyte A was injected into the container, and the electrode body was sealed by heat welding.
（初期充放電）
得られた初期充放電前の非水電解質蓄電素子（未充放電非水電解質蓄電素子）に対して、２５℃の下、以下の要領にて初期充放電を行った。上記非水電解質蓄電素子の設計定格容量を基準として、充電電流０．１Ｃ、トータル充電時間３時間で定電流充電を行い、その後、１２時間の休止期間を設けた。その後、充電電流０．１Ｃ、充電終止電圧４．１５Ｖ（正極電位４．２５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）、トータル充電時間１３時間で定電流定電圧充電を行い、その後１０分間の休止期間を設けた。その後、放電電流０．２Ｃ、放電終止電圧２．５Ｖで定電流放電を行った。以上の手順により、非水電解質蓄電素子を完成した。
(Initial charge / discharge)
The obtained non-aqueous electrolyte storage element (uncharged / discharged non-aqueous electrolyte storage element) before the initial charge / discharge was initially charged / discharged at 25 ° C. in the following manner. Based on the design rated capacity of the non-aqueous electrolyte power storage element, constant current charging was performed with a charging current of 0.1 C and a total charging time of 3 hours, and then a rest period of 12 hours was provided. After that, constant current constant voltage charging is performed with a charging current of 0.1 C, a charge termination voltage of 4.15 V (positive electrode potential of 4.25 V vs. Li / Li + ), and a total charging time of 13 hours, and then a rest period of 10 minutes is provided. It was. Then, a constant current discharge was performed with a discharge current of 0.2 C and a discharge end voltage of 2.5 V. Through the above procedure, the non-aqueous electrolyte power storage element was completed.
（初期の放電容量の測定）
次いで、完成した非水電解質蓄電素子に対して、２５℃の下、以下の要領にて初期の放電容量を確認した。
（１サイクル目）
充電電流０．２Ｃ、充電終止電圧４．１５Ｖ（正極電位４．２５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）、トータル充電時間８時間で定電流定電圧充電を行った。その後、放電電流０．２Ｃ、放電終止電圧２．５Ｖで定電流放電を行った。
（２サイクル目）
その後、充電電流０．２Ｃ、充電終止電圧４．１５Ｖ（正極電位４．２５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）、トータル充電時間８時間で定電流定電圧充電を行った。その後、放電電流１．０Ｃ、放電終止電圧２．５Ｖで定電流放電を行った。その後、残放電として、放電電流０．２Ｃ、放電終止電圧２．５Ｖで定電流放電を行った。
充電後及び放電後にはそれぞれ１０分間の休止期間を設けた。１サイクル目の放電（放電電流０．２Ｃでの放電）における放電電気量を初期の放電容量とした。
(Measurement of initial discharge capacity)
Next, the initial discharge capacity of the completed non-aqueous electrolyte power storage element was confirmed at 25 ° C. in the following manner.
(1st cycle)
Constant current constant voltage charging was performed with a charging current of 0.2 C, a charge termination voltage of 4.15 V (positive electrode potential of 4.25 V vs. Li / Li + ), and a total charging time of 8 hours. Then, a constant current discharge was performed with a discharge current of 0.2 C and a discharge end voltage of 2.5 V.
(2nd cycle)
After that, constant current constant voltage charging was performed with a charging current of 0.2 C, a charge termination voltage of 4.15 V (positive electrode potential of 4.25 V vs. Li / Li + ), and a total charging time of 8 hours. Then, a constant current discharge was performed with a discharge current of 1.0 C and a discharge end voltage of 2.5 V. Then, as a residual discharge, a constant current discharge was performed with a discharge current of 0.2 C and a discharge end voltage of 2.5 V.
After charging and discharging, a rest period of 10 minutes was provided. The amount of electricity discharged in the first cycle of discharge (discharge at a discharge current of 0.2 C) was taken as the initial discharge capacity.
（充放電サイクル試験）
初期の放電容量を確認した非水電解質蓄電素子について、４５℃の下、以下の要領で充放電サイクル試験を行った。充電電流１．０Ｃ、充電終止電圧４．１５Ｖ（正極電位４．２５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流定電圧充電を行った。充電終止条件は、電流値が０．０５Ｃに減衰した時点とした。その後、放電電流１．０Ｃ、放電終止電圧をＳＯＣ１０％に対応する電圧値とした定電流放電を行った。充電後及び放電後にはそれぞれ１０分間の休止期間を設けた。この充放電を１００サイクル実施した。
(Charge / discharge cycle test)
The charge / discharge cycle test of the non-aqueous electrolyte power storage device whose initial discharge capacity was confirmed was carried out at 45 ° C. in the following manner. Constant current and constant voltage charging was performed with a charging current of 1.0 C and a charging termination voltage of 4.15 V (positive electrode potential of 4.25 V vs. Li / Li + ). The charging termination condition was the time when the current value was attenuated to 0.05C. After that, constant current discharge was performed with a discharge current of 1.0 C and a discharge end voltage set to a voltage value corresponding to SOC 10%. After charging and discharging, a rest period of 10 minutes was provided. This charge / discharge was carried out for 100 cycles.
（充放電サイクル試験後の放電容量の測定）
充放電サイクル試験後、２５℃の下、残放電として、放電電流０．２Ｃ、放電終止電圧２．５Ｖで定電流放電を行った。その後、「初期の放電容量の測定」と同じ手順にて、充放電サイクル試験後の放電容量を測定した。初期の放電容量に対する充放電サイクル試験後の放電容量を容量維持率として求めた。得られた容量維持率を表２に示す。
(Measurement of discharge capacity after charge / discharge cycle test)
After the charge / discharge cycle test, constant current discharge was performed at 25 ° C. as a residual discharge at a discharge current of 0.2 C and a discharge end voltage of 2.5 V. Then, the discharge capacity after the charge / discharge cycle test was measured by the same procedure as in "Measurement of initial discharge capacity". The discharge capacity after the charge / discharge cycle test with respect to the initial discharge capacity was determined as the capacity retention rate. The obtained capacity retention rate is shown in Table 2.
［実施例７から１０］
実施例６の「初期充放電」、「初期の放電容量の測定」、「充放電サイクル試験」及び「充放電サイクル試験後の放電容量の測定」における全ての充電終止電圧を表２に示す値としたこと以外は実施例６と同様の操作を行い、各非水電解質蓄電素子を得て、容量維持率を測定した。得られた容量維持率を表２に示す。
[Examples 7 to 10]
Table 2 shows all the charge termination voltages in "initial charge / discharge", "measurement of initial discharge capacity", "charge / discharge cycle test", and "measurement of discharge capacity after charge / discharge cycle test" in Example 6. The same operation as in Example 6 was carried out except for the above, and each non-aqueous electrolyte power storage element was obtained and the capacity retention rate was measured. The obtained capacity retention rate is shown in Table 2.
［実施例１１から１３、比較例３］
実施例６の非水電解質Ａに代えて、以下の要領で調製した非水電解質Ｂを用いたこと、並びに「初期充放電」、「初期の放電容量の測定」、「充放電サイクル試験」及び「充放電サイクル試験後の放電容量の測定」における全ての充電終止電圧を表２に示す値としたこと以外は実施例６と同様の操作を行い、各非水電解質蓄電素子を得て、容量維持率を測定した。得られた容量維持率を表２に示す。
[Examples 11 to 13, Comparative Example 3]
Instead of the non-aqueous electrolyte A of Example 6, the non-aqueous electrolyte B prepared in the following manner was used, and "initial charge / discharge", "measurement of initial discharge capacity", "charge / discharge cycle test" and The same operation as in Example 6 was performed except that all the charge termination voltages in "Measurement of discharge capacity after charge / discharge cycle test" were set to the values shown in Table 2, and each non-aqueous electrolyte power storage element was obtained to obtain the capacity. The maintenance rate was measured. The obtained capacity retention rate is shown in Table 2.
（非水電解質Ｂの調製）
ＦＥＣ（フルオロエチレンカーボネート）とＭＦＥＣ（メチルトリフルオロエチルカーボネート）とを体積比３０：７０で混合した非水溶媒に、電解質塩としてヘキサフルオロリン酸リチウム（ＬｉＰＦ６）が１．０ｍｏｌ／ｄｍ３の含有量となるように溶解させた溶液を調製し、非水電解質Ｂとした。
(Preparation of non-aqueous electrolyte B)
Lithium hexafluorophosphate (LiPF 6 ) as an electrolyte salt was 1.0 mol / dm 3 in a non-aqueous solvent in which FEC (fluoroethylene carbonate) and MFEC (methyltrifluoroethyl carbonate) were mixed at a volume ratio of 30:70. A solution dissolved so as to have a content was prepared and used as a non-aqueous electrolyte B.
［比較例２］正極Ｘ（ＬｉＭｅＯ２型活物質）及び負極Ａ（ＳｉＯ−Ｇｒ）を有する非水電解質蓄電素子の作製
実施例６の正極Ａに代えて、以下の要領で作製した正極Ｘを用いたこと、並びに「初期充放電」、「初期の放電容量の測定」、「充放電サイクル試験」及び「充放電サイクル試験後の放電容量の測定」における全ての充電終止電圧を表２に示す値としたこと以外は実施例６と同様の操作を行い、各非水電解質蓄電素子を得て、容量維持率を測定した。得られた容量維持率を表２に示す。
[Comparative Example 2] Fabrication of a non-aqueous electrolyte power storage element having a positive electrode X (LiMeO type 2 active material) and a negative electrode A (SiO-Gr) Instead of the positive electrode A of Example 6, a positive electrode X produced in the following manner is used. Table 2 shows all the charge termination voltages used and in "initial charge / discharge", "measurement of initial discharge capacity", "charge / discharge cycle test", and "measurement of discharge capacity after charge / discharge cycle test". The same operation as in Example 6 was performed except that the value was set, and each non-aqueous electrolyte power storage element was obtained, and the capacity retention rate was measured. The obtained capacity retention rate is shown in Table 2.
（正極Ｘの作製）
正極活物質として、α−ＮａＦｅＯ２構造を有し、かつＬｉ１．０Ｎｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２で表されるリチウム遷移金属複合酸化物（正極活物質Ｘ）を準備した。
質量比で、正極活物質Ｘ：アセチレンブラック（ＡＢ）：ポリフッ化ビニリデン（ＰＶＤＦ）＝９３：４：３の割合（固形物換算）で含み、Ｎ−メチルピロリドン（ＮＭＰ）を分散媒とする正極合剤ペーストを作製した。この正極合剤ペーストを正極基材としてのアルミニウム箔（厚み１５μｍ）に塗布し、乾燥させて、正極Ｘを得た。
(Preparation of positive electrode X)
As the positive electrode active material, a lithium transition metal composite oxide (positive electrode active material X) having an α-NaFeO 2 structure and represented by Li 1.0 Ni 0.5 Co 0.2 Mn 0.3 O 2 is used. Got ready.
Positive electrode Active material X: acetylene black (AB): polyvinylidene fluoride (PVDF) = 93: 4: 3 (solid matter equivalent), and N-methylpyrrolidone (NMP) as the dispersion medium. A mixture paste was prepared. This positive electrode mixture paste was applied to an aluminum foil (thickness 15 μm) as a positive electrode base material and dried to obtain a positive electrode X.
表２に示されるように、リチウム過剰型活物質（正極活物質Ａ）を用い、初期充放電から使用時（充放電サイクル試験時）において、充電終止電圧が４．５０Ｖ未満であり、充電終止電圧における正極電位が４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満である実施例６から１３の非水電解質蓄電素子は、容量維持率が９７．０％以上であり、優れた容量維持率を有する。中でも、充電終止電圧が４．２０Ｖ超４．５０Ｖ未満であり、充電終止電圧における正極電位が４．３０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋超４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満の範囲で使用した実施例８から１３は、容量維持率が９８．０％以上であり、容量維持率が特に優れている。正極を所定の範囲の電位まで充電して使用することで、経時化成が進行し、容量維持率が高まっているものと推測される。 As shown in Table 2, the lithium excess type active material (positive electrode active material A) is used, and the charge termination voltage is less than 4.50 V from the initial charge / discharge to the use (during the charge / discharge cycle test), and the charge is terminated. The positive electrode potential in voltage is 4.60 V vs. The non-aqueous electrolyte power storage elements of Examples 6 to 13 having less than Li / Li + have a capacity retention rate of 97.0% or more and have an excellent capacity retention rate. Above all, the final charge voltage is more than 4.20 V and less than 4.50 V, and the positive electrode potential at the final charge voltage is 4.30 V vs. Li / Li + Super 4.60V vs. In Examples 8 to 13 used in the range of less than Li / Li + , the capacity retention rate is 98.0% or more, and the capacity retention rate is particularly excellent. It is presumed that by charging the positive electrode to a potential within a predetermined range and using it, aging progresses and the capacity retention rate increases.
［実施例１４］正極Ｂ（リチウム過剰型活物質）を有する単極電池（試験電池）の作製
実施例１の正極活物質Ａに代えて、α−ＮａＦｅＯ２構造を有し、かつＬｉ１．１４（Ｎｉ０．３３Ｍｎ０．６７）０．８６Ｏ２で表されるリチウム遷移金属複合酸化物（正極活物質Ｂ）を用いたこと、質量比で、正極活物質Ｂ：アセチレンブラック（ＡＢ）：ポリフッ化ビニリデン（ＰＶＤＦ）＝９４：４．５：１．５の割合（固形物換算）で含む正極合剤ペーストを用いたこと以外は実施例１と同様にして、正極Ｂを得た。また、実施例１の正極Ａに代えて、正極Ｂを用いたこと以外は実施例１と同様にして、上記「試験電池の組み立て」及び「初期充放電」を行った。
[Example 14] Preparation of a unipolar battery (test battery) having a positive electrode B (lithium excess type active material) Instead of the positive electrode active material A of Example 1, it has an α-NaFeO 2 structure and Li 1. 14 (Ni 0.33 Mn 0.67 ) Using a lithium transition metal composite oxide (positive electrode active material B) represented by 0.86 O 2 , positive electrode active material B: acetylene black (AB) in terms of mass ratio. ): A positive electrode B was obtained in the same manner as in Example 1 except that a positive electrode mixture paste containing a ratio of polyvinylidene fluoride (PVDF) = 94: 4.5: 1.5 (solid matter equivalent) was used. .. Further, the above-mentioned "assembly of the test battery" and "initial charge / discharge" were performed in the same manner as in Example 1 except that the positive electrode B was used instead of the positive electrode A of Example 1.
［実施例１５から１８、比較例４］
実施例１の「初期充放電」における１から３サイクル目の充電終止電圧（充電終止時の正極電位）を表３に示す通りとしたこと以外は、実施例１４と同様の操作をした。
[Examples 15 to 18, Comparative Example 4]
The same operation as in Example 14 was performed except that the charge termination voltage (positive electrode potential at the end of charging) in the first to third cycles in the “initial charge / discharge” of Example 1 was set as shown in Table 3.
実施例１から５、１４から１８及び比較例１、４の「初期充放電」における２サイクル目の放電に基づき、放電容量、平均放電電位及びエネルギー密度を求めた。結果を表３に示す。また、実施例１から５、１４から１８及び比較例１、４のエネルギー密度を表すグラフを図４に示す。 The discharge capacity, average discharge potential, and energy density were determined based on the discharge in the second cycle in the "initial charge / discharge" of Examples 1 to 5, 14 to 18 and Comparative Examples 1 and 4. The results are shown in Table 3. Further, a graph showing the energy densities of Examples 1 to 5, 14 to 18 and Comparative Examples 1 and 4 is shown in FIG.
表３及び図４に示されるように、０．０２≦（Ｍｎ／Ｍｅ−Ｎｉ／Ｍｅ）≦０．２を満たす正極活物質Ａを用いた実施例１から５の非水電解質蓄電素子においては、特に充電上限電位（充電終止電圧における正極電位）が比較的低い場合であっても、十分な放電容量を有し、エネルギー密度が高いことがわかる。 As shown in Table 3 and FIG. 4, in the non-aqueous electrolyte power storage elements of Examples 1 to 5 using the positive electrode active material A satisfying 0.02 ≦ (Mn / Me—Ni / Me) ≦ 0.2. It can be seen that even when the upper limit charging potential (positive electrode potential at the end of charging voltage) is relatively low, the battery has a sufficient discharge capacity and a high energy density.
（放置試験）
［実施例１９］正極Ａ（リチウム過剰型活物質）及び負極Ａ（ＳｉＯ−Ｇｒ）を有する非水電解質蓄電素子の作製
実施例６と同様の手順で、正極活物質Ａ（Ｌｉ１．０８（Ｎｉ０．３９Ｃｏγ０．１５Ｍｎ０．４６）０．９２Ｏ２）及び負極活物質Ａ（ＳｉＯ−Ｇｒ）を用いた未充放電非水電解質蓄電素子を組み立てた。その後、充電終止電圧を４．２５Ｖ（正極電位４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）としたこと以外は、実施例６と同様に「初期充放電」及び「初期の放電容量の測定」を行った。
(Leaving test)
[Example 19] Fabrication of non-aqueous electrolyte power storage element having positive electrode A (lithium excess type active material) and negative electrode A (SiO-Gr) Positive electrode active material A (Li 1.08 (Li 1.08 ) (Li 1.08 ) in the same procedure as in Example 6. An uncharged / discharged non-aqueous electrolyte power storage element using Ni 0.39 Co γ 0.15 Mn 0.46 ) 0.92 O 2 ) and the negative electrode active material A (SiO-Gr) was assembled. After that, "initial charge / discharge" and "measurement of initial discharge capacity" were performed in the same manner as in Example 6 except that the charge termination voltage was set to 4.25 V (positive electrode potential 4.35 V vs. Li / Li + ). It was.
［比較例５］正極Ｘ（ＬｉＭｅＯ２型活物質）及び負極Ａ（ＳｉＯ−Ｇｒ）を有する非水電解質蓄電素子の作製
比較例２と同様の手順で、正極活物質Ｘ（Ｌｉ１．０Ｎｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２）及び負極活物質Ａ（ＳｉＯ−Ｇｒ）を用いた未充放電非水電解質蓄電素子を組み立てたこと以外は、実施例１９と同様の操作を行った。
[Comparative Example 5] Fabrication of a non-aqueous electrolyte power storage element having a positive electrode X (LiMeO type 2 active material) and a negative electrode A (SiO-Gr) Positive electrode active material X (Li 1.0 Ni) in the same procedure as in Comparative Example 2. The same operation as in Example 19 was performed except that the uncharged / discharged non-aqueous electrolyte power storage element using 0.5 Co 0.2 Mn 0.3 O 2 ) and the negative electrode active material A (SiO-Gr) was assembled. went.
実施例１９及び比較例５で得られた各非水電解質蓄電素子について、充電電流０．２Ｃ、充電終止電圧４．２５Ｖ（正極電位４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）、トータル充電時間８時間の定電流定電圧充電を行った。このようにして充電状態とした非水電解質蓄電素子を４５℃の恒温槽内に１５日及び３３日放置した。その後、２５℃にて、残放電として、放電電流０．２Ｃ、放電終止電圧２．５Ｖで定電流放電を行った。続いて、上記実施例６の「初期の放電容量の測定」と同じ手順にて、放置後の放電容量を測定した。初期の放電容量に対する放置後の放電容量を容量維持率として求めた。得られた結果（容量維持率）を表４に示す。 For each non-aqueous electrolyte power storage element obtained in Example 19 and Comparative Example 5, the charging current is 0.2C, the final charging voltage is 4.25V (positive electrode potential 4.35V vs. Li / Li + ), and the total charging time is 8 hours. Constant current and constant voltage charging was performed. The non-aqueous electrolyte power storage element charged in this way was left in a constant temperature bath at 45 ° C. for 15 days and 33 days. Then, at 25 ° C., a constant current discharge was performed as a residual discharge at a discharge current of 0.2 C and a discharge end voltage of 2.5 V. Subsequently, the discharge capacity after being left to stand was measured by the same procedure as in "Measurement of initial discharge capacity" of Example 6 above. The discharge capacity after being left unattended with respect to the initial discharge capacity was determined as the capacity retention rate. The obtained results (capacity retention rate) are shown in Table 4.
表４に示されるように、リチウム過剰型活物質（正極活物質Ａ）を用い、初期充放電において十分な高電位化成がなされていない実施例１９の非水電解質蓄電素子は、ＬｉＭｅＯ２型活物質（正極活物質Ｘ）を用いた比較例５の非水電解質蓄電素子と比べて高温放置後の容量維持率が高い。これは、実施例１９の非水電解質蓄電素子においては、充電状態で高温下に放置されることによって経時化成が徐々に進行したことによると推測される。 As shown in Table 4, the non-aqueous electrolyte power storage element of Example 19 using the lithium excess type active material (positive electrode active material A) and having not been sufficiently high-potentialized in the initial charge / discharge is LiMeO type 2 active material. Compared with the non-aqueous electrolyte power storage element of Comparative Example 5 using the material (positive electrode active material X), the capacity retention rate after being left at a high temperature is high. It is presumed that this is because the non-aqueous electrolyte power storage element of Example 19 was gradually aged by being left in a charged state at a high temperature.
［実施例２０］正極Ａ（リチウム過剰型活物質）及び負極Ｂ（Ｇｒ）を有する非水電解質蓄電素子の作製
（正極Ａの作製）
実施例１と同様の手順で、正極Ａを得た。
[Example 20] Fabrication of a non-aqueous electrolyte power storage element having a positive electrode A (lithium excess active material) and a negative electrode B (Gr) (preparation of positive electrode A)
A positive electrode A was obtained in the same procedure as in Example 1.
（負極Ｂの作製）
負極活物質として、黒鉛（Ｇｒ：負極活物質Ｂ）を用いた。質量比で、負極活物質Ｂ：スチレンブタジエンゴム（ＳＢＲ）：カルボキシメチルセルロース（ＣＭＣ）＝９７．３：１．５：１．２の割合（固形分換算）で含み、水を分散媒とする負極合剤ペーストを作製した。この負極合剤ペーストを負極基材としての帯状の銅箔（厚み１０μｍ）に塗布し、乾燥させて、負極Ｂを得た。
(Preparation of negative electrode B)
Graphite (Gr: negative electrode active material B) was used as the negative electrode active material. Negative electrode active material B: Styrene butadiene rubber (SBR): Carboxymethyl cellulose (CMC) = 97.3: 1.5: 1.2 (in terms of solid content), and water is used as the dispersion medium. A mixture paste was prepared. This negative electrode mixture paste was applied to a strip-shaped copper foil (thickness 10 μm) as a negative electrode base material and dried to obtain a negative electrode B.
（非水電解質Ｃの調製）
ＦＥＣとＥＭＣとを体積比５：９５で混合した非水溶媒に、電解質塩としてヘキサフルオロリン酸リチウム（ＬｉＰＦ６）が１．０ｍｏｌ／ｄｍ３の含有量となるように溶解させた溶液を調製し、非水電解質Ｃとした。
(Preparation of non-aqueous electrolyte C)
A solution was prepared by dissolving FEC and EMC in a non-aqueous solvent mixed at a volume ratio of 5:95 so that lithium hexafluorophosphate (LiPF 6 ) as an electrolyte salt had a content of 1.0 mol / dm 3. Then, it was designated as non-aqueous electrolyte C.
（非水電解質蓄電素子の組み立て）
セパレータとして、耐熱層が塗工されたポリオレフィン製微多孔膜を用意した。このセパレータを介して、上記正極Ａと上記負極Ｂとを巻回することにより電極体を作製した。この電極体を金属樹脂複合フィルム製の容器に収納し、内部に上記非水電解質Ｃを注入した後、熱溶着により封口した。
(Assembly of non-aqueous electrolyte power storage element)
As a separator, a microporous polyolefin membrane coated with a heat-resistant layer was prepared. An electrode body was produced by winding the positive electrode A and the negative electrode B through the separator. The electrode body was housed in a container made of a metal resin composite film, the non-aqueous electrolyte C was injected into the container, and the electrode body was sealed by heat welding.
（初期充放電）
得られた初期充放電前の非水電解質蓄電素子（未充放電非水電解質蓄電素子）に対して、２５℃の下、以下の要領にて初期充放電を行った。充電電流０．１Ｃ、充電終止電圧４．２５Ｖ（正極電位４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流定電圧充電を行った。充電終止条件は、電流値が０．０５Ｃに減衰した時点とした。その後、放電電流０．１Ｃ、放電終止電圧２．５Ｖとした定電流放電を行った。
(Initial charge / discharge)
The obtained non-aqueous electrolyte storage element (uncharged / discharged non-aqueous electrolyte storage element) before the initial charge / discharge was initially charged / discharged at 25 ° C. in the following manner. Constant current and constant voltage charging was performed with a charging current of 0.1 C and a charging termination voltage of 4.25 V (positive electrode potential of 4.35 V vs. Li / Li + ). The charging termination condition was the time when the current value was attenuated to 0.05C. Then, a constant current discharge was performed with a discharge current of 0.1 C and a discharge end voltage of 2.5 V.
（放電容量の測定）
次いで、２５℃の下、以下の３サイクルの充放電を行い、初期の放電容量を確認した。２サイクル目の放電電気量を初期の放電容量とした。
（１サイクル目）
充電電流０．１Ｃ、充電終止電圧４．２５Ｖ（正極電位４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流定電圧充電を行った。充電終止条件は、電流値が０．０５Ｃに減衰した時点とした。その後、放電電流０．１Ｃ、放電終止電圧２．５Ｖとした定電流放電を行った。
（２サイクル目）
充電電流０．２Ｃ、充電終止電圧４．２５Ｖ（正極電位４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流定電圧充電を行った。充電終止条件は、電流値が０．０５Ｃに減衰した時点とした。その後、放電電流０．２Ｃ、放電終止電圧２．５Ｖとした定電流放電を行った。
（３サイクル目）
充電電流１．０Ｃ、充電終止電圧４．２５Ｖ（正極電位４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流定電圧充電を行った。充電終止条件は、電流値が０．０５Ｃに減衰した時点とした。その後、放電電流１．０Ｃ、放電終止電圧２．５Ｖとした定電流放電を行った。
(Measurement of discharge capacity)
Then, at 25 ° C., the following three cycles of charging and discharging were performed, and the initial discharge capacity was confirmed. The amount of electricity discharged in the second cycle was taken as the initial discharge capacity.
(1st cycle)
Constant current and constant voltage charging was performed with a charging current of 0.1 C and a charging termination voltage of 4.25 V (positive electrode potential of 4.35 V vs. Li / Li + ). The charging termination condition was the time when the current value was attenuated to 0.05C. Then, a constant current discharge was performed with a discharge current of 0.1 C and a discharge end voltage of 2.5 V.
(2nd cycle)
Constant current and constant voltage charging was performed with a charging current of 0.2 C and a charging termination voltage of 4.25 V (positive electrode potential of 4.35 V vs. Li / Li + ). The charging termination condition was the time when the current value was attenuated to 0.05C. Then, a constant current discharge was performed with a discharge current of 0.2 C and a discharge end voltage of 2.5 V.
(3rd cycle)
Constant current and constant voltage charging was performed with a charging current of 1.0 C and a charging termination voltage of 4.25 V (positive electrode potential of 4.35 V vs. Li / Li + ). The charging termination condition was the time when the current value was attenuated to 0.05C. Then, a constant current discharge was performed with a discharge current of 1.0 C and a discharge end voltage of 2.5 V.
（充放電サイクル試験）
初期の放電容量を確認した非水電解質蓄電素子について、４５℃の下、以下の要領で充放電サイクル試験を行った。充電電流１．０Ｃ、充電終止電圧４．２５Ｖ（正極電位４．３５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流定電圧充電を行った。充電終止条件は、電流値が０．０５Ｃに減衰した時点とした。その後、放電電流１．０Ｃ、放電終止電圧２．５Ｖとした定電流放電を行った。充電後及び放電後にはそれぞれ１０分間の休止期間を設けた。この充放電を７００サイクル実施した。
(Charge / discharge cycle test)
The charge / discharge cycle test of the non-aqueous electrolyte power storage device whose initial discharge capacity was confirmed was carried out at 45 ° C. in the following manner. Constant current and constant voltage charging was performed with a charging current of 1.0 C and a charging termination voltage of 4.25 V (positive electrode potential of 4.35 V vs. Li / Li + ). The charging termination condition was the time when the current value was attenuated to 0.05C. Then, a constant current discharge was performed with a discharge current of 1.0 C and a discharge end voltage of 2.5 V. After charging and discharging, a rest period of 10 minutes was provided. This charge / discharge was carried out for 700 cycles.
（充放電サイクル試験後の放電容量の測定）
充放電サイクル試験における４００サイクル後、６００サイクル後及び７００サイクル後のそれぞれの非水電解質蓄電素子において、上記「放電容量の測定」と同様の３サイクルの充放電を行い、放電容量を確認した。２サイクル目の放電電気量をそれぞれのサイクル後の放電容量とした。初期の放電容量に対する各サイクル後の放電容量を容量維持率として求めた。得られた容量維持率を表５に示す。
(Measurement of discharge capacity after charge / discharge cycle test)
In each of the non-aqueous electrolyte power storage elements after 400 cycles, 600 cycles, and 700 cycles in the charge / discharge cycle test, charging / discharging was performed for 3 cycles similar to the above-mentioned "Measurement of discharge capacity", and the discharge capacity was confirmed. The amount of electricity discharged in the second cycle was defined as the discharge capacity after each cycle. The discharge capacity after each cycle with respect to the initial discharge capacity was calculated as the capacity retention rate. The obtained capacity retention rate is shown in Table 5.
［実施例２１］
実施例２０の「初期充放電」、「放電容量の測定」、及び「充放電サイクル試験」における充電終止電圧を４．３０Ｖ（正極電位４．４０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）としたこと以外は実施例２０と同様の操作を行い、非水電解質蓄電素子を得て、容量維持率を測定した。得られた容量維持率を表５に示す。
[Example 21]
Except that the charge termination voltage in the "initial charge / discharge", "measurement of discharge capacity", and "charge / discharge cycle test" of Example 20 was set to 4.30 V (positive electrode potential 4.40 V vs. Li / Li + ). The same operation as in Example 20 was performed to obtain a non-aqueous electrolyte power storage element, and the capacity retention rate was measured. The obtained capacity retention rate is shown in Table 5.
［比較例６］正極Ｘ（Ｌｉ２ＭｅＯ２型活物質）及び負極Ｂ（Ｇｒ）を有する非水電解質蓄電素子の作製
実施例２０の正極Ａに代えて、正極Ｘを用いたこと以外は実施例２０と同様の操作を行い、非水電解質蓄電素子を得て、容量維持率を測定した。得られた容量維持率を表５に示す。
[Comparative Example 6] Fabrication of a non-aqueous electrolyte power storage element having a positive electrode X (Li 2 MeO type 2 active material) and a negative electrode B (Gr) Except that the positive electrode X was used instead of the positive electrode A of Example 20. The same operation as in Example 20 was performed to obtain a non-aqueous electrolyte power storage element, and the capacity retention rate was measured. The obtained capacity retention rate is shown in Table 5.
［比較例７］正極Ａ（リチウム過剰型活物質）及び負極Ｂ（Ｇｒ）を有する非水電解質蓄電素子の作製
実施例２０の「初期充放電」における充電終止電圧を４．５０Ｖ（正極電位４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）とし、「放電容量の測定」及び「充放電サイクル試験」における充電終止電圧を４．３５Ｖ（正極電位４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）としたこと以外は実施例２０と同様の操作を行い、非水電解質蓄電素子を得て、容量維持率を測定した。得られた容量維持率を表５に示す。
[Comparative Example 7] Fabrication of a non-aqueous electrolyte power storage element having a positive electrode A (lithium excess active material) and a negative electrode B (Gr) The charge termination voltage in the "initial charge / discharge" of Example 20 is 4.50 V (positive electrode potential 4). .60V vs.Li/Li +) and then, except that the end-of-charge voltage in the "measurement of discharge capacity" and "charge-discharge cycle test" 4.35V (positive electrode potential 4.45V vs.Li/Li +) is The same operation as in Example 20 was performed to obtain a non-aqueous electrolyte power storage element, and the capacity retention rate was measured. The obtained capacity retention rate is shown in Table 5.
表５に示されるように、正極活物質にリチウム過剰型活物質（正極活物質Ａ）、負極活物質に黒鉛（負極活物質Ｂ）を用い、初期充放電から使用時（充放電サイクル試験時）において、充電終止電圧が４．５０Ｖ未満であり、充電終止電圧における正極電位が４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満である実施例２０、２１の非水電解質蓄電素子は、長期に亘る充放電サイクルにおいても高い容量維持率を有することがわかる。 As shown in Table 5, lithium excess type active material (positive electrode active material A) is used as the positive electrode active material, and graphite (negative electrode active material B) is used as the negative electrode active material, from initial charge / discharge to use (during charge / discharge cycle test). ), The end-of-charge voltage is less than 4.50 V, and the positive electrode potential at the end-of-charge voltage is 4.60 V vs. It can be seen that the non-aqueous electrolyte power storage elements of Examples 20 and 21 having less than Li / Li + have a high capacity retention rate even in a long-term charge / discharge cycle.
［実施例２２］正極Ｂ（リチウム過剰型活物質）及び負極Ｂ（Ｇｒ）を有する非水電解質蓄電素子の作製
（正極Ｂの作製）
実施例１４と同様の手順で、正極Ｂを得た。
[Example 22] Fabrication of a non-aqueous electrolyte power storage element having a positive electrode B (lithium excess active material) and a negative electrode B (Gr) (preparation of positive electrode B)
A positive electrode B was obtained in the same procedure as in Example 14.
（負極Ｂの作製）
実施例２０と同様の手順で、負極Ｂを得た。
(Preparation of negative electrode B)
A negative electrode B was obtained in the same procedure as in Example 20.
（非水電解質Ｄの調製）
ＥＣとＥＭＣとを体積比３０：７０で混合した非水溶媒に、電解質塩としてヘキサフルオロリン酸リチウム（ＬｉＰＦ６）が１．０ｍｏｌ／ｄｍ３の含有量となるように溶解させた溶液を調製し、非水電解質Ｄとした。
(Preparation of non-aqueous electrolyte D)
A solution was prepared in which EC and EMC were dissolved in a non-aqueous solvent mixed at a volume ratio of 30:70 so that lithium hexafluorophosphate (LiPF 6 ) as an electrolyte salt had a content of 1.0 mol / dm 3. The non-aqueous electrolyte D was used.
（非水電解質蓄電素子の組み立て）
セパレータとして、耐熱層が塗工されたポリオレフィン製微多孔膜を用意した。このセパレータを介して、上記正極Ｂと上記負極Ｂとを巻回することにより電極体を作製した。この電極体を金属製の容器に収納し、内部に上記非水電解質Ｄを注入した後、封口した。
(Assembly of non-aqueous electrolyte power storage element)
As a separator, a microporous polyolefin membrane coated with a heat-resistant layer was prepared. An electrode body was produced by winding the positive electrode B and the negative electrode B through the separator. The electrode body was housed in a metal container, the non-aqueous electrolyte D was injected into the container, and then the electrode body was sealed.
（初期充放電）
得られた初期充放電前の非水電解質蓄電素子（未充放電非水電解質蓄電素子）に対して、２５℃の下、以下の要領にて初期充放電を行った。充電電流０．１Ｃ、充電終止電圧４．４５Ｖ（正極電位４．５５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流定電圧充電を行った。充電終止条件は、電流値が０．０５Ｃに減衰した時点とした。その後、放電電流０．１Ｃ、放電終止電圧２．０Ｖとした定電流放電を行った。
(Initial charge / discharge)
The obtained non-aqueous electrolyte storage element (uncharged / discharged non-aqueous electrolyte storage element) before the initial charge / discharge was initially charged / discharged at 25 ° C. in the following manner. Constant current and constant voltage charging was performed with a charging current of 0.1 C and a charging termination voltage of 4.45 V (positive electrode potential of 4.55 V vs. Li / Li + ). The charging termination condition was the time when the current value was attenuated to 0.05C. Then, a constant current discharge was performed with a discharge current of 0.1 C and a discharge end voltage of 2.0 V.
（放電容量の測定）
次いで、２５℃の下、以下の３サイクルの充放電を行い、初期の放電容量を確認した。２サイクル目の放電電気量を初期の放電容量とした。
（１サイクル目）
充電電流０．１Ｃ、充電終止電圧４．４５Ｖ（正極電位４．５５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流定電圧充電を行った。充電終止条件は、電流値が０．０５Ｃに減衰した時点とした。その後、放電電流０．１Ｃ、放電終止電圧２．０Ｖとした定電流放電を行った。
（２サイクル目）
充電電流０．２Ｃ、充電終止電圧４．４５Ｖ（正極電位４．５５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流定電圧充電を行った。充電終止条件は、電流値が０．０５Ｃに減衰した時点とした。その後、放電電流０．２Ｃ、放電終止電圧２．０Ｖとした定電流放電を行った。
（３サイクル目）
充電電流１．０Ｃ、充電終止電圧４．４５Ｖ（正極電位４．５５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流定電圧充電を行った。充電終止条件は、電流値が０．０５Ｃに減衰した時点とした。その後、放電電流１．０Ｃ、放電終止電圧２．０Ｖとした定電流放電を行った。
(Measurement of discharge capacity)
Then, at 25 ° C., the following three cycles of charging and discharging were performed, and the initial discharge capacity was confirmed. The amount of electricity discharged in the second cycle was taken as the initial discharge capacity.
(1st cycle)
Constant current and constant voltage charging was performed with a charging current of 0.1 C and a charging termination voltage of 4.45 V (positive electrode potential of 4.55 V vs. Li / Li + ). The charging termination condition was the time when the current value was attenuated to 0.05C. Then, a constant current discharge was performed with a discharge current of 0.1 C and a discharge end voltage of 2.0 V.
(2nd cycle)
Constant current and constant voltage charging was performed with a charging current of 0.2 C and a charge termination voltage of 4.45 V (positive electrode potential of 4.55 V vs. Li / Li + ). The charging termination condition was the time when the current value was attenuated to 0.05C. Then, a constant current discharge was performed with a discharge current of 0.2 C and a discharge end voltage of 2.0 V.
(3rd cycle)
Constant current and constant voltage charging was performed with a charging current of 1.0 C and a charging termination voltage of 4.45 V (positive electrode potential of 4.55 V vs. Li / Li + ). The charging termination condition was the time when the current value was attenuated to 0.05C. Then, a constant current discharge was performed with a discharge current of 1.0 C and a discharge end voltage of 2.0 V.
（充放電サイクル試験）
初期の放電容量を確認した非水電解質蓄電素子について、４５℃の下、以下の要領で充放電サイクル試験を行った。充電電流１．０Ｃ、充電終止電圧４．４５Ｖ（正極電位４．５５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）で定電流充電を行った。その後、放電電流１．０Ｃ、放電終止電圧２．０Ｖとした定電流放電を行った。充電後及び放電後にはそれぞれ１０分間の休止期間を設けた。この充放電を４００サイクル実施した。
(Charge / discharge cycle test)
The charge / discharge cycle test of the non-aqueous electrolyte power storage device whose initial discharge capacity was confirmed was carried out at 45 ° C. in the following manner. Constant current charging was performed with a charging current of 1.0 C and a charge termination voltage of 4.45 V (positive electrode potential of 4.55 V vs. Li / Li + ). Then, a constant current discharge was performed with a discharge current of 1.0 C and a discharge end voltage of 2.0 V. After charging and discharging, a rest period of 10 minutes was provided. This charge / discharge was carried out for 400 cycles.
（充放電サイクル試験後の放電容量の測定）
充放電サイクル試験における４００サイクル後の非水電解質蓄電素子において、上記「放電容量の測定」と同様の３サイクルの充放電を行い、放電容量を確認した。２サイクル目の放電電気量をそれぞれのサイクル後の放電容量とした。初期の放電容量に対する各サイクル後の放電容量を容量維持率として求めた。得られた容量維持率を表６に示す。
(Measurement of discharge capacity after charge / discharge cycle test)
In the non-aqueous electrolyte power storage element after 400 cycles in the charge / discharge cycle test, charging / discharging was performed for 3 cycles in the same manner as in the above "measurement of discharge capacity", and the discharge capacity was confirmed. The amount of electricity discharged in the second cycle was defined as the discharge capacity after each cycle. The discharge capacity after each cycle with respect to the initial discharge capacity was calculated as the capacity retention rate. The obtained capacity retention rate is shown in Table 6.
［比較例８］
実施例２２の「初期充放電」、「放電容量の測定」、及び「充放電サイクル試験」における充電終止電圧を４．５０Ｖ（正極電位４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋）としたこと以外は実施例２２と同様の操作を行い、非水電解質蓄電素子を得て、容量維持率を測定した。得られた容量維持率を表６に示す。
[Comparative Example 8]
Except that the charge termination voltage in "initial charge / discharge", "measurement of discharge capacity", and "charge / discharge cycle test" of Example 22 was set to 4.50 V (positive electrode potential 4.60 V vs. Li / Li + ). The same operation as in Example 22 was performed to obtain a non-aqueous electrolyte power storage element, and the capacity retention rate was measured. The obtained capacity retention rate is shown in Table 6.
表６に示されるように、正極活物質にリチウム過剰型活物質（正極活物質Ｂ）、負極活物質に黒鉛（負極活物質Ｂ）を用い、初期充放電から使用時（充放電サイクル試験時）において充電終止電圧が４．５０Ｖ未満であり、充電終止電圧における正極電位が４．６０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋未満である実施例２２の非水電解質蓄電素子も、充放電サイクルにおいて高い容量維持率を有することがわかる。 As shown in Table 6, lithium excess type active material (positive electrode active material B) is used as the positive electrode active material, and graphite (negative electrode active material B) is used as the negative electrode active material, from initial charge / discharge to use (during charge / discharge cycle test). ), The end-of-charge voltage is less than 4.50 V, and the positive electrode potential at the end-of-charge voltage is 4.60 V vs. It can be seen that the non-aqueous electrolyte power storage device of Example 22 having less than Li / Li + also has a high capacity retention rate in the charge / discharge cycle.
本発明は、パーソナルコンピュータ、通信端末等の電子機器、自動車、産業用等の電源として使用される非水電解質蓄電素子等に適用できる。 The present invention can be applied to electronic devices such as personal computers and communication terminals, non-aqueous electrolyte power storage elements used as power sources for automobiles, industrial use, and the like.
１ 非水電解質蓄電素子
２ 電極体
３ 容器
４ 正極端子
４１ 正極リード
５ 負極端子
５１ 負極リード
２０ 蓄電ユニット
３０ 蓄電装置
1 Non-aqueous electrolyte
Claims (14)
上記正極活物質が、α−ＮａＦｅＯ２構造を有し、かつＬｉ１＋αＭｅ１−αＯ２（０＜α＜１；ＭｅはＮｉ及びＭｎを含む遷移金属である。）で表されるリチウム遷移金属複合酸化物を含み、
上記正極に対して、上記正極合剤の質量あたり９ｍＡ／ｇの電流密度により、電位が２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの放電を行った後、上記電流密度により、電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電と電位が２．００Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの放電とからなる充放電を２サイクル行ったときの充電電気量が、下記式（１）を満たす、非水電解質蓄電素子。
（Ｃ２Ａ／Ｃ２Ｂ）×１００−（Ｃ１Ａ／Ｃ１Ｂ）×１００≧１．０ ・・・（１）
（式（１）中、Ｃ１Ａは、上記充放電の１サイクル目の充電の際に、充電開始から電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ１Ｂは、上記充放電の１サイクル目の充電の際に、充電開始から電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ２Ａは、上記充放電の２サイクル目の充電の際に、充電開始から電位が４．４５Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。Ｃ２Ｂは、上記充放電の２サイクル目の充電の際に、充電開始から電位が４．８０Ｖ ｖｓ．Ｌｉ／Ｌｉ＋に至るまでの充電電気量である。） With a positive electrode having a positive electrode mixture containing a positive electrode active material,
The positive electrode active material has an α-NaFeO 2 structure and is represented by Li 1 + α Me 1-α O 2 (0 <α <1; Me is a transition metal containing Ni and Mn). Contains metal composite oxides
With respect to the positive electrode, the potential was 2.00 V vs. due to the current density of 9 mA / g per mass of the positive electrode mixture. After discharging up to Li / Li + , the potential becomes 4.80 V vs. due to the above current density. Charging and potential up to Li / Li + is 2.00 V vs. A non-aqueous electrolyte power storage element in which the amount of electricity charged when two cycles of charge / discharge consisting of discharge up to Li / Li + is performed satisfies the following formula (1).
(C 2A / C 2B ) × 100- (C 1A / C 1B ) × 100 ≧ 1.0 ・ ・ ・ (1)
(In the formula (1), C 1A is the amount of electricity charged from the start of charging to the potential of 4.45 V vs. Li / Li + during the first cycle of charging / discharging. C 1B. Is the amount of electricity charged from the start of charging to the potential of 4.80 V vs. Li / Li + during the first cycle of charging / discharging. C 2A is the second cycle of charging / discharging. C 2B is the amount of electricity charged from the start of charging to the potential of 4.45 V vs. Li / Li + at the time of charging. C 2B is the amount of electricity charged from the start of charging during the second cycle of charging / discharging. The amount of electricity charged until the potential reaches 4.80 V vs. Li / Li + .)
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| JP2015084303A (en) * | 2013-10-25 | 2015-04-30 | 三星エスディアイ株式会社Ｓａｍｓｕｎｇ ＳＤＩ Ｃｏ．，Ｌｔｄ． | Rechargeable lithium ion battery |
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