JP6403943B2 - Lithium ion secondary battery, method for producing the same, and method for using the same - Google Patents
Lithium ion secondary battery, method for producing the same, and method for using the same Download PDFInfo
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Description
本発明は、非水電解質を備えるリチウムイオン二次電池、及び、その製造方法、並びに、その使用方法に関する。
The present invention relates to a lithium ion secondary battery including a non-aqueous electrolyte , a manufacturing method thereof, and a usage method thereof .
リチウムイオン二次電池に代表される非水電解質電池は、エネルギー密度が高いことから、携帯電話に代表されるモバイル機器用の電源として広く普及している。非水電解質電池は、今後、電力貯蔵用、電気自動車用及びハイブリッド自動車用等の用途への展開が見込まれている。 Non-aqueous electrolyte batteries typified by lithium ion secondary batteries are widely used as power supplies for mobile devices typified by mobile phones because of their high energy density. In the future, non-aqueous electrolyte batteries are expected to be used for power storage, electric vehicles, hybrid vehicles, and the like.
近年、電気自動車、ハイブリッド自動車、プラグインハイブリッド自動車といった自動車分野に非水電解質電池を適用することが検討されており、一部、実用化している。これらの自動車用電池には、高いエネルギー密度が求められると共に、優れた充放電サイクル性能が求められている。即ち、電気自動車、ハイブリッド自動車、プラグインハイブリッドといった自動車に対して充電を行った場合、一定の走行可能距離が確保されることが期待される。一般に、非水電解質二次電池は、充放電を繰り返すと放電容量が徐々に低下するが、自動車に対して充電を繰り返した場合、放電容量の低下の程度が大きいと、走行可能距離が短くなる程度が大きいことを意味するから、次に充電が必要となる時期を予測することが困難となり、充電時期を逸して走行中に自動車が停止してしまう虞がある。 In recent years, application of nonaqueous electrolyte batteries to the automobile field such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles has been studied, and some have been put into practical use. These automobile batteries are required to have high energy density and excellent charge / discharge cycle performance. That is, when a vehicle such as an electric vehicle, a hybrid vehicle, or a plug-in hybrid is charged, it is expected that a certain travelable distance is secured. In general, non-aqueous electrolyte secondary batteries gradually decrease in discharge capacity when charging and discharging are repeated. However, when charging is repeated on an automobile, if the degree of decrease in discharge capacity is large, the travelable distance becomes shorter. This means that it is difficult to predict the next time when charging is required, and there is a risk that the car will stop while traveling because the charging time is missed.
特許文献１には、フッ素化合物を含有する電解液中にホウ素化合物を含有するリチウム電池が記載され、ホウ素化合物として「例えばＢ２Ｏ３、Ｈ３ＢＯ３、（ＣＨ３Ｏ）３Ｂ、（Ｃ２Ｈ５Ｏ）３Ｂ、（ＣＨ３Ｏ）３Ｂ−Ｂ２Ｏ３等が使用できる。それらの中でも特にＢ２Ｏ３が望ましい。」（段落００３７）と記載されている。また、「実施例１」には、正極にＬｉＣｏＯ２を用いた非水電解液リチウム二次電池の非水電解液として、ＥＣ／ＰＣ／ＤＭＥ（２／２／１）−１ＭＬｉＰＦ６に０．８ｗｔ％のＢ２Ｏ３を添加したものを用いたことが具体的に記載されている。また、「上記ホウ素化合物を電解液に含有させることにより、電界液中の含有水分により生成する酸性物質を大巾に減少することができ、これは電解液の劣化、電池容器の腐蝕による容器構成金属イオンに起因する負極の活性低下を防止する結果をもたらす。」（段落００３９）、「これらの脱水剤を含ませることにより、電解質の水による分解を防止し、ひいては電解液の劣化、酸性物質の生成を抑えることが出来る。」（段落００４１）との記載がある。 Patent Document 1 describes a lithium battery containing a boron compound in an electrolyte solution containing a fluorine compound. As the boron compound, for example, “B 2 O 3 , H 3 BO 3 , (CH 3 O) 3 B, ( C 2 H 5 O) 3 B, (CH 3 O) 3 B—B 2 O 3, etc. Among them, B 2 O 3 is particularly desirable ”(paragraph 0037). Further, in “Example 1”, EC / PC / DME (2/2/1) -1MLiPF 6 is used as a non-aqueous electrolyte for a non-aqueous electrolyte lithium secondary battery using LiCoO 2 for the positive electrode. It is specifically described that 8 wt% B 2 O 3 added was used. In addition, the inclusion of the boron compound in the electrolytic solution can greatly reduce the acidic substance produced by the water contained in the electrolysis solution. This is due to the deterioration of the electrolytic solution and the container structure due to the corrosion of the battery container. This results in preventing the negative electrode activity from being reduced due to metal ions ”(paragraph 0039),“ By including these dehydrating agents, the electrolyte is prevented from being decomposed by water, and thus the electrolyte is deteriorated, and the acidic substance. Can be suppressed ”(paragraph 0041).
特許文献２には、非水電解質二次電池の内部に、温度上昇により水を生成する物質を含むこと（請求項１）、温度上昇により水を生成する物質が非水電解質に含まれること（請求項３）、温度上昇により水を生成する物質がホウ酸であること（請求項７）が記載されている。また、「実施例１」には、ＬｉＮｉＯ２とＨ３ＢＯ３を含む正極ペーストをチタンの芯材に塗布し、９５℃で乾燥、圧延して正極とした非水電解質二次電池が記載され、「実施例２」には、炭素材料とＨ３ＢＯ３を含む負極ペーストを銅の芯材に塗布し、９５℃で乾燥、圧延して負極とした非水電解質二次電池が記載されている。なお、「非水電解質には、１モル／ｌの過塩素酸リチウムを溶解したエチレンカーボネートとジメトキシエタンの等比体積混合溶液を用いた。」（段落００１３）との記載がある。 Patent Document 2 includes a substance that generates water by increasing the temperature inside the nonaqueous electrolyte secondary battery (Claim 1), and a substance that generates water by increasing temperature is included in the nonaqueous electrolyte ( (Claim 3), it is described that the substance which produces | generates water by a temperature rise is a boric acid (Claim 7). In addition, “Example 1” describes a nonaqueous electrolyte secondary battery in which a positive electrode paste containing LiNiO 2 and H 3 BO 3 is applied to a titanium core, dried at 95 ° C., and rolled to form a positive electrode. “Example 2” describes a non-aqueous electrolyte secondary battery in which a negative electrode paste containing a carbon material and H 3 BO 3 is applied to a copper core, dried at 95 ° C., and rolled to form a negative electrode. Yes. In addition, there is a description that “a non-aqueous electrolyte is an equal volume mixed solution of ethylene carbonate and dimethoxyethane in which 1 mol / l lithium perchlorate is dissolved” (paragraph 0013).
特許文献３には、「正極にリチウム含有マンガン酸化物を用いたリチウム二次電池において、前記正極は、電解液に溶解可能なホウ素化合物を含むことを特徴とするリチウム二次電池。」（請求項１）、「前記ホウ素化合物が、Ｂ２Ｏ３、Ｈ３ＢＯ３、ＨＢＯ２、Ｈ２Ｂ４Ｏ７から選ばれる少なくとも１つ以上を含むホウ素化合物であることを特徴とする請求項１記載のリチウム二次電池。」（請求項２）、「しかしながら、正極にＬｉＭｎ２Ｏ４を用い、電解液にＬｉＰＦ４等のハロゲン含有リチウム塩を用いた場合、前記リチウム塩が微量水分と反応し、フッ素化水素酸などのハロゲン化水素酸を発生する。このハロゲン化水素酸は、正極のＬｉＭｎ２Ｏ４を溶解し、負極の炭素表面にＭｎＦ２等の抵抗の高い被膜を形成し、サイクル性能を低下させる原因となっていた。」（段落０００３）、「ホウ素化合物を正極に添加する方法としては、正極活物質であるリチウム含有マンガン酸化物にＨ３ＢＯ３を混合してから電極を作成する方法が挙げられる。しかしながらＨ３ＢＯ３は、リチウムと反応する水素原子を多く含み、電池内において不可逆な副反応を起こす虞れがあるため、正極を１００℃〜１４０℃、あるいはそれ以上の温度で熱処理を施すことが好ましい。前記熱処理によって、Ｈ３ＢＯ３はＨＢＯ２やＨ２Ｂ４Ｏ７等に変化するものと考えられる。」（段落０００９）との記載がある。また、「実施例」には、スピネルマンガンとＨ３ＢＯ３を含むポリテトラフルオロエチレンシート電極を減圧下９０〜３００℃で４０時間熱処理して得た正極を用い、ＥＣ／ＤＥＣ（１／１）−１ＭＬｉＰＦ６電解液と組み合わせた電池を４．４Ｖで定電流定電圧充電した結果、ホウ素化合物無添加品と比べてサイクル寿命が優れたことが記載されている。また、減圧下９０℃４０時間熱処理により、正極中のＨ３ＢＯ３はＨ３ＢＯ４に変化していると推定されること（段落００３３〜００３４）が記載されている。 Patent Document 3 discloses “a lithium secondary battery using a lithium-containing manganese oxide as a positive electrode, wherein the positive electrode contains a boron compound that can be dissolved in an electrolytic solution” (claim). Item 1), “The boron compound is a boron compound containing at least one selected from B 2 O 3 , H 3 BO 3 , HBO 2 , and H 2 B 4 O 7. The lithium secondary battery according to claim 2 ”(Claim 2),“ However, when LiMn 2 O 4 is used for the positive electrode and a halogen-containing lithium salt such as LiPF 4 is used for the electrolyte, the lithium salt reacts with a trace amount of moisture. and, generating a hydrohalic acid such as hydrofluoric acid. the hydrohalic acid can be prepared by dissolving the LiMn 2 O 4 positive electrode, the form of the high resistance coating such as MnF 2 on the carbon surface of the negative electrode And has been a cause of reducing the cycle performance. "(Paragraph 0003), a method of adding a" boron compound cathode, a mixture of H 3 BO 3 in the lithium-containing manganese oxide as a positive electrode active material However, H 3 BO 3 contains many hydrogen atoms that react with lithium and may cause irreversible side reactions in the battery, so that the positive electrode is heated to 100 ° C. to 140 ° C. Alternatively, it is preferable to perform heat treatment at a temperature higher than that.It is considered that H 3 BO 3 is changed to HBO 2 , H 2 B 4 O 7, etc. by the heat treatment ”(paragraph 0009). . Further, in the “Example”, a positive electrode obtained by heat-treating a polytetrafluoroethylene sheet electrode containing spinel manganese and H 3 BO 3 at 90 to 300 ° C. for 40 hours under reduced pressure was used, and EC / DEC (1/1 ) As a result of charging a battery combined with -1MLiPF 6 electrolyte at a constant current and a constant voltage at 4.4 V, it is described that the cycle life is superior to that of a boron compound-free product. Further, it is described that it is estimated that H 3 BO 3 in the positive electrode is changed to H 3 BO 4 by heat treatment at 90 ° C. for 40 hours under reduced pressure (paragraphs 0033 to 0034).
特許文献４の要約書及び請求項１には、「電極の界面抵抗の増大を抑制し、電池にすぐれた負荷特性および低温特性を与え、さらに優れた寿命特性を与える非水電解液と、それを用いた寿命特性にすぐれた二次電池を提供すること」を目的として「式（１）で表わされるホウ酸エステルと、非水溶媒と電解質を含む非水電解液、及びそれを用いた二次電池」からなる発明が記載され、式（１）としてＢ（ＯＲ１）（ＯＲ２）（ＯＲ３）が記載され、「Ｒ１〜Ｒ３は、同一であっても異なっていてもよく、水素、金属または有機基を示し、互いに結合していてもよい。」と記載されている。しかしながら、ホウ酸を用いることについては記載がない。また、特許文献４の実施例の欄には、ＬｉＣｏＯ２を正極に用いた非水電解液二次電池の特性を評価するにあたって、充電条件を４．２Ｖ定電圧又は４．１Ｖ定電圧としたことが記載されている。 The abstract of patent document 4 and claim 1 include: “a non-aqueous electrolyte that suppresses an increase in electrode interface resistance, gives the battery excellent load characteristics and low-temperature characteristics, and provides excellent life characteristics; For the purpose of “providing a secondary battery having excellent life characteristics using a non-aqueous electrolytic solution containing a boric acid ester represented by the formula (1), a non-aqueous solvent and an electrolyte, and a battery using the same. The invention consisting of “secondary battery” is described, B (OR 1 ) (OR 2 ) (OR 3 ) is described as formula (1), and “R 1 to R 3 ” may be the same or different. , Represents a hydrogen, metal, or organic group, and may be bonded to each other. However, there is no description about using boric acid. Further, in the column of Examples of Patent Document 4, in order to evaluate the characteristics of the non-aqueous electrolyte secondary battery using LiCoO 2 for the positive electrode, and the charge condition and 4.2V constant voltage or 4.1V constant voltage It is described.
本発明者らは、予備試験として後述するように、非水電解質に添加する添加剤として各種ホウ酸化合物を検討したところ、ホウ酸を選択することにより、これを用いた非水電解質電池の充放電サイクル性能を顕著に向上できるとの知見を得た。本発明は、この知見に基づき、さらに電池性能を向上させることを目的とする。 As will be described later as a preliminary test, the present inventors have examined various boric acid compounds as additives to be added to the nonaqueous electrolyte, and by selecting boric acid, charging of a nonaqueous electrolyte battery using the boric acid compound is possible. The knowledge that the discharge cycle performance can be remarkably improved was obtained. The present invention aims to further improve battery performance based on this finding.
本発明の構成及び作用効果について、技術思想を交えて説明する。但し、作用機構については推定を含んでおり、その正否は、本発明を制限するものではない。なお、本発明は、その精神又は主要な特徴から逸脱することなく、他のいろいろな形で実施することができる。そのため、後述の実施の形態若しくは実験例は、あらゆる点で単なる例示に過ぎず、限定的に解釈してはならない。さらに、特許請求の範囲の均等範囲に属する変形や変更は、すべて本発明の範囲内のものである。 The configuration and operational effects of the present invention will be described with the technical idea. However, the action mechanism includes estimation, and the correctness does not limit the present invention. It should be noted that the present invention can be implemented in various other forms without departing from the spirit or main features thereof. For this reason, the following embodiments or experimental examples are merely examples in all respects and should not be interpreted in a limited manner. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.
本発明は、正極と、負極と、ホウ酸及び環状スルホン酸化合物が添加された非水電解質を備える非水電解質二次電池である。 The present invention is a nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte to which boric acid and a cyclic sulfonic acid compound are added.
このような構成によれば、充放電サイクル性能及び保存性能に優れた非水電解質二次電池を提供することができる。 According to such a configuration, a nonaqueous electrolyte secondary battery excellent in charge / discharge cycle performance and storage performance can be provided.
ホウ酸は極めて安価な材料であるため、ホウ酸を選択することにより、他のホウ素化合物よりも優れた効果を奏するだけでなく、非水電解質電池を安価に提供できる。 Since boric acid is an extremely inexpensive material, selecting boric acid not only provides an effect superior to that of other boron compounds, but can also provide a nonaqueous electrolyte battery at a low cost.
また、本発明は、正極と、負極と、ホウ酸及び環状スルホン酸化合物を含有している非水電解質と、を備える非水電解質二次電池である。 Moreover, this invention is a nonaqueous electrolyte secondary battery provided with a positive electrode, a negative electrode, and the nonaqueous electrolyte containing a boric acid and a cyclic sulfonic acid compound.
即ち、後述するように、本発明者らは、ホウ酸が添加された非水電解質が含有するホウ酸の量は、該非水電解質を調整する際に添加したホウ酸の量に比べて減少することがあるとしても、少なくとも０．５質量％以上のホウ酸が添加された非水電解質は、ホウ酸を含有していることを見出した。また、環状スルホン酸化合物及び０．５質量％以上のホウ酸が添加された非水電解質を用いた非水電解質電池は、優れた電池性能を示すことを見出した。また、環状スルホン酸化合物及び０．５質量％以上のホウ酸が添加された非水電解質を用いて非水電解質電池を作製し、充放電を伴う使用がなされた状態であっても、非水電解質電池が備える非水電解質は、環状スルホン酸化合物及びホウ酸を含有していることを見出した。 That is, as will be described later, the present inventors reduce the amount of boric acid contained in the nonaqueous electrolyte to which boric acid is added as compared with the amount of boric acid added when adjusting the nonaqueous electrolyte. In some cases, the non-aqueous electrolyte to which at least 0.5% by mass or more of boric acid was added was found to contain boric acid. Moreover, it discovered that the nonaqueous electrolyte battery using the nonaqueous electrolyte to which the cyclic sulfonic acid compound and 0.5 mass% or more of boric acid were added showed the outstanding battery performance. In addition, a non-aqueous electrolyte battery is prepared using a non-aqueous electrolyte to which a cyclic sulfonic acid compound and 0.5% by mass or more of boric acid are added. It has been found that the nonaqueous electrolyte provided in the electrolyte battery contains a cyclic sulfonic acid compound and boric acid.
また、本発明は、上記した本発明に係る非水電解質二次電池を４．４Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）以上の正極電位に至って充電を行う、非水電解質二次電池の使用方法である。本発明に係る非水電解質を適用した非水電解質二次電池に対してこのような使用方法を採用することにより、多数回にわたる充放電サイクルを繰り返しても高い放電容量を維持できる非水電解質二次電池の使用方法を提供できる。本発明は、１個又は複数個の本発明に係る非水電解質二次電池を備え、４．４Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）以上の正極電位に至って充電が制御される電池システムとして実現できる。また、本発明は、１個又は複数個の本発明に係る非水電解質電池と、４．４Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）以上の正極電位に至って充電が制御される電池システムを搭載した電気自動車、ハイブリッド自動車又はプラグインハイブリッド自動車として実現できる。 The present invention also relates to a method of using a nonaqueous electrolyte secondary battery in which the nonaqueous electrolyte secondary battery according to the present invention is charged at a positive electrode potential of 4.4 V (vs. Li / Li + ) or higher. is there. By adopting such a usage method for the non-aqueous electrolyte secondary battery to which the non-aqueous electrolyte according to the present invention is applied, the non-aqueous electrolyte can maintain a high discharge capacity even after repeated many charge / discharge cycles. A method of using the secondary battery can be provided. The present invention can be realized as a battery system that includes one or a plurality of non-aqueous electrolyte secondary batteries according to the present invention and whose charge is controlled by reaching a positive electrode potential of 4.4 V (vs. Li / Li + ) or higher. . In addition, the present invention also includes an electric battery equipped with one or a plurality of non-aqueous electrolyte batteries according to the present invention and a battery system in which charging is controlled by reaching a positive electrode potential of 4.4 V (vs. Li / Li + ) or higher. It can be realized as a car, a hybrid car or a plug-in hybrid car.
本発明によれば、充放電サイクル性能に優れた非水電解質電池を提供できる。 ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte battery excellent in charging / discharging cycling performance can be provided.
本発明に係る非水電解質を調整する方法については、何ら限定されるものではない。例えば、電解質塩としてＬｉＰＦ６を用いた一般的な電解液にホウ酸及び環状スルホン酸化合物を添加することによって得ることができる。前記ホウ酸は、化学式Ｈ３ＢＯ３又はＢ（ＯＨ）３と表記され、試薬等として入手できる。なお、上記化学式のＨの部分が炭化水素基であるホウ酸エステルは、ホウ酸に比べて効果が劣る。 The method for adjusting the non-aqueous electrolyte according to the present invention is not limited at all. For example, it can be obtained by adding boric acid and a cyclic sulfonic acid compound to a general electrolytic solution using LiPF 6 as an electrolyte salt. The boric acid is represented by the chemical formula H 3 BO 3 or B (OH) 3 and can be obtained as a reagent or the like. In addition, the boric acid ester whose H part of the above chemical formula is a hydrocarbon group is inferior to boric acid.
ホウ酸の添加量は、本発明の効果を十分に発揮させるため、０．２質量％以上が好ましく、０．５質量％以上がより好ましい。また、放電容量が低下する虞を低減するため、２質量％以下が好ましく、１．５質量％以下がより好ましい。 The amount of boric acid added is preferably 0.2% by mass or more, and more preferably 0.5% by mass or more in order to sufficiently exhibit the effects of the present invention. Moreover, 2 mass% or less is preferable and 1.5 mass% or less is more preferable in order to reduce the possibility that the discharge capacity will decrease.
環状スルホン酸化合物としては、下記一般式で表されるものが挙げられる。
〔一般式（２）において、Ｒ １ は一般式（４）又は、式（５）で表される基（＊の部分がＲ １ に結合）である。Ｒ ３ は、ハロゲンを含んでも良い炭素数１〜３のアルキル基である。〕
Examples of the cyclic sulfonic acid compound include those represented by the following general formula.
[In General Formula (2), R 1 is a group represented by General Formula (4) or Formula (5) (the part of * is bonded to R 1 ). R 3 is a C 1-3 alkyl group which may contain halogen. ]
一般式（２）で表される環状スルホン酸化合物の中には、２個以上の不斉炭素を有し、立体異性体（ジアステレオマー）が存在するものがある。本願明細書において、一般式（２）で表される環状スルホン酸化合物は、そのようなジアステレオマーの混合物であるものを含む。
Some cyclic sulfonic acid compounds represented by the general formula ( 2 ) have two or more asymmetric carbons and exist as stereoisomers (diastereomers). In the present specification, the cyclic sulfonic acid compound represented by the general formula ( 2 ) includes those which are a mixture of such diastereomers.
一般式（２）において、Ｒ １ が式（５）で表される基である環状スルホン酸化合物は、ジグリコールサルフェート（ＤＧＬＳＴ）に相当する。
In the general formula ( 2 ), the cyclic sulfonic acid compound in which R 1 is a group represented by the formula ( 5 ) corresponds to diglycol sulfate (DGLST).
Ｒ １ が一般式（４）で表される基である環状スルホン酸化合物は、３級アルコールを原料とし、環は１個であるが、２個のスルホン酸と化合した化合物であり、ＤＧＬＳＴと同様の効果を奏するものである。Ｒ３がメチル基の場合は、４−メチルスルホニルオキシメチル−２，２−ジオキソ−１，３，２−ジオキサチオランであり、Ｒ３がエチル基の場合は、４−エチルスルホニルオキシメチル−２，２−ジオキソ−１，３，２−ジオキサチオランである。
The cyclic sulfonic acid compound in which R 1 is a group represented by the general formula ( 4 ) is a compound in which a tertiary alcohol is used as a raw material and has one ring, but is combined with two sulfonic acids, and DGLST and The same effect is produced. When R 3 is a methyl group, it is 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane, and when R 3 is an ethyl group, 4-ethylsulfonyloxymethyl-2,2 -Dioxo-1,3,2-dioxathiolane.
これらの中でも、非水電解質への含有量が少なくて済むことから、分子量の小さいＤＧＬＳＴが好ましい。 Among these, DGLST having a small molecular weight is preferable because the content in the non-aqueous electrolyte is small.
上記環状スルホン酸化合物の作用機構はかならずしも明確ではない。以下に、ジグリコールサルフェート（ＤＧＬＳＴ）を含有する非水電解質を用いた場合の充放電サイクル性能改善の推定メカニズムを記載する。 The mechanism of action of the cyclic sulfonic acid compound is not always clear. Below, the estimation mechanism of the charge / discharge cycle performance improvement at the time of using the non-aqueous electrolyte containing diglycol sulfate (DGLST) is described.
一般に、非水電解質電池は、負極上において、電解液中の有機溶媒の継続的な還元分解がサイクル特性等の電池の寿命を低下させる原因になっていると考えられる。ここで、ＤＧＬＳＴの還元分解電位は約１．１Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）であり、他の一般的な溶媒よりも比較的高いため、非水電解質二次電池の初回充電時に他の溶媒に先駆けて、負極上にＤＧＬＳＴ由来の被膜が形成される。この被膜によって、有機溶媒の継続的な還元分解が抑制されると推測される。よって、ＤＧＬＳＴを非水電解質に含有させることにより、サイクル特性等の非水電解質二次電池の寿命が改善するものと考えられる。 Generally, in a nonaqueous electrolyte battery, it is considered that continuous reductive decomposition of an organic solvent in an electrolyte solution causes a decrease in battery life such as cycle characteristics on the negative electrode. Here, since the reductive decomposition potential of DGLST is about 1.1 V (vs. Li / Li + ), which is relatively higher than other general solvents, other solvents are not charged during the initial charge of the nonaqueous electrolyte secondary battery. Prior to this, a DGLST-derived film is formed on the negative electrode. It is estimated that the continuous reductive decomposition of the organic solvent is suppressed by this coating. Therefore, it is considered that the life of the nonaqueous electrolyte secondary battery such as cycle characteristics is improved by including DGLST in the nonaqueous electrolyte.
環状スルホン酸化合物の含有量としては、非水電解質二次電池中の非水電解質から環状スルホン酸化合物が検出される程度含まれていることが好ましい。このように、非水電解質二次電池中の非水電解質から検出される程度に環状スルホン酸化合物が含まれている場合、充放電サイクル性能を改善することが可能となる。また、非水電解質二次電池が初期活性化後（使用前、出荷時）の状態にあるときに、非水電解質から環状スルホン酸化合物が検出される程度含まれている場合、電池の使用時において、サイクル特性を十分に改善することが可能となるため、特に好ましい。 The content of the cyclic sulfonic acid compound is preferably included to the extent that the cyclic sulfonic acid compound is detected from the nonaqueous electrolyte in the nonaqueous electrolyte secondary battery. Thus, when the cyclic sulfonic acid compound is contained to the extent that it is detected from the nonaqueous electrolyte in the nonaqueous electrolyte secondary battery, the charge / discharge cycle performance can be improved. In addition, when the non-aqueous electrolyte secondary battery is in the state after initial activation (before use, at the time of shipment), when the cyclic sulfonic acid compound is detected from the non-aqueous electrolyte, the battery is used. Is particularly preferable because the cycle characteristics can be sufficiently improved.
非水電解質二次電池中の非水電解質から検出される環状スルホン酸化合物の量は、０．０１質量％以上、５質量％未満であることが好ましい。検出される環状スルホン酸化合物が０．０１質量％以上であれば、サイクル特性を十分に改善することが可能となるため好ましい。また、検出される環状スルホン酸化合物を５質量％未満とすることで、本発明の効果を維持しつつ、非水電解質二次電池のコストを抑制することができるため好ましい。特に好ましくは、０．０５質量％以上、４質量％以下である。 The amount of the cyclic sulfonic acid compound detected from the nonaqueous electrolyte in the nonaqueous electrolyte secondary battery is preferably 0.01% by mass or more and less than 5% by mass. If the detected cyclic sulfonic acid compound is 0.01% by mass or more, it is preferable because cycle characteristics can be sufficiently improved. Moreover, it is preferable to make the detected cyclic sulfonic acid compound less than 5% by mass because the cost of the non-aqueous electrolyte secondary battery can be suppressed while maintaining the effects of the present invention. Especially preferably, it is 0.05 mass% or more and 4 mass% or less.
非水電解質に含まれる環状スルホン酸化合物の検出（定性及び定量）は、ＧＣ−ＭＳ測定やＬＣ−ＭＳ測定により行うことが可能である。 Detection (qualitative and quantitative) of the cyclic sulfonic acid compound contained in the nonaqueous electrolyte can be performed by GC-MS measurement or LC-MS measurement.
環状スルホン酸化合物を含有する非水電解質を調製するに当たり、非水電解質を構成する電解質塩、非水溶媒及び環状スルホン酸化合物の混合順序は任意である。後述の実施例においては、非水溶媒に電解質塩を溶解させたのち、環状スルホン酸化合物を添加する手順により環状スルホン酸化合物を含有する非水電解質を調製しているが、この手順以外で調整した環状スルホン酸化合物を含有する非水電解質を用いたとしても、本発明の効果は発現する。また、環状スルホン酸化合物以外の化合物が非水電解質に含まれる場合も同様に混合順序は任意である。 In preparing a non-aqueous electrolyte containing a cyclic sulfonic acid compound, the mixing order of the electrolyte salt, the non-aqueous solvent and the cyclic sulfonic acid compound constituting the non-aqueous electrolyte is arbitrary. In the examples described later, after dissolving an electrolyte salt in a non-aqueous solvent, a non-aqueous electrolyte containing a cyclic sulfonic acid compound is prepared by a procedure of adding a cyclic sulfonic acid compound. Even if a non-aqueous electrolyte containing the prepared cyclic sulfonic acid compound is used, the effect of the present invention is exhibited. Similarly, when the nonaqueous electrolyte contains a compound other than the cyclic sulfonic acid compound, the mixing order is arbitrary.
前記非水溶媒が、エチレンカーボネート等の環状カーボネートと、エチルメチルカーボネート、ジエチルカーボネート等の鎖状カーボネートとを含有する場合、環状カーボネートと鎖状カーボネートとの合計体積中に占める環状カーボネートの体積比率は、１０体積％以上が好ましく、２０体積％以上がより好ましい。また、４０体積％以下が好ましく、３０体積％以下がより好ましい。 When the non-aqueous solvent contains a cyclic carbonate such as ethylene carbonate and a chain carbonate such as ethyl methyl carbonate and diethyl carbonate, the volume ratio of the cyclic carbonate in the total volume of the cyclic carbonate and the chain carbonate is 10 volume% or more is preferable and 20 volume% or more is more preferable. Moreover, 40 volume% or less is preferable and 30 volume% or less is more preferable.
非水電解質に用いる電解質塩としては、例えば、ＬｉＣｌＯ４，ＬｉＢＦ４，ＬｉＡｓＦ６，ＬｉＰＦ６，ＬｉＳＣＮ，ＬｉＢｒ，ＬｉＩ，Ｌｉ２ＳＯ４，Ｌｉ２Ｂ１０Ｃｌ１０，ＮａＣｌＯ４，ＮａＩ，ＮａＳＣＮ，ＮａＢｒ，ＫＣｌＯ４，ＫＳＣＮ等のリチウム（Ｌｉ）、ナトリウム（Ｎａ）またはカリウム（Ｋ）の１種を含む無機イオン塩、ＬｉＣＦ３ＳＯ３，ＬｉＮ（ＣＦ３ＳＯ２）２，ＬｉＮ（Ｃ２Ｆ５ＳＯ２）２，ＬｉＮ（ＣＦ３ＳＯ２）（Ｃ４Ｆ９ＳＯ２），ＬｉＣ（ＣＦ３ＳＯ２）３，ＬｉＣ（Ｃ２Ｆ５ＳＯ２）３，（ＣＨ３）４ＮＢＦ４，（ＣＨ３）４ＮＢｒ，（Ｃ２Ｈ５）４ＮＣｌＯ４，（Ｃ２Ｈ５）４ＮＩ，（Ｃ３Ｈ７）４ＮＢｒ，（ｎ−Ｃ４Ｈ９）４、ＮＣｌＯ４，（ｎ−Ｃ４Ｈ９）４ＮＩ，（Ｃ２Ｈ５）４Ｎ−ｍａｌｅａｔｅ，（Ｃ２Ｈ５）４Ｎ−ｂｅｎｚｏａｔｅ，（Ｃ２Ｈ５）４Ｎ−ｐｈｔａｌａｔｅ、ステアリルスルホン酸リチウム、オクチルスルホン酸リチウム、ドデシルベンゼンスルホン酸リチウム等の有機イオン塩等が挙げられ、これらのイオン性化合物を単独、あるいは２種類以上混合して用いることが可能である。 Examples of the electrolyte salt used for the non-aqueous electrolyte include LiClO 4 , LiBF 4 , LiAsF 6 , LiPF 6 , LiSCN, LiBr, LiI, Li 2 SO 4 , Li 2 B 10 Cl 10 , NaClO 4 , NaI, NaSCN, and NaBr. , KClO 4 , KSCN, and other inorganic ion salts containing one of lithium (Li), sodium (Na), or potassium (K), LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 (SO 2 ) 2 , LiN (CF 3 SO 2 ) (C 4 F 9 SO 2 ), LiC (CF 3 SO 2 ) 3 , LiC (C 2 F 5 SO 2 ) 3 , (CH 3 ) 4 NBF 4 , ( CH 3 ) 4 NBr, (C 2 H 5 ) 4 NClO 4 , (C 2 H 5 ) 4 NI, (C 3 H 7 ) 4 NBr, (n-C 4 H 9) 4, NClO 4, ( n-C 4 H 9) 4 NI, (C 2 H 5) 4 N-maleate, (C 2 H 5) 4 N-benzoate, (C 2 H 5) 4 N-phtalate Organic ion salts such as lithium stearyl sulfonate, lithium octyl sulfonate, lithium dodecylbenzene sulfonate, and the like, and these ionic compounds can be used alone or in admixture of two or more.
また、非水電解質として常温溶融塩やイオン液体を用いてもよい。 Moreover, you may use normal temperature molten salt and an ionic liquid as a nonaqueous electrolyte.
負極材料としては、限定されるものではなく、リチウムイオンを析出あるいは吸蔵することのできる形態のものであればどれを選択してもよい。例えば、Ｌｉ［Ｌｉ１／３Ｔｉ５／３］Ｏ４に代表されるスピネル型結晶構造を有するチタン酸リチウム等のチタン系材料、ＳｉやＳｂ，Ｓｎ系などの合金系材料リチウム金属、リチウム合金（リチウム−シリコン、リチウム−アルミニウム，リチウム−鉛，リチウム−スズ，リチウム−アルミニウム−スズ，リチウム−ガリウム，及びウッド合金等のリチウム金属含有合金）、リチウム複合酸化物（リチウム−チタン）、酸化珪素の他、リチウムを吸蔵・放出可能な合金、炭素材料（例えばグラファイト、ハードカーボン、低温焼成炭素、非晶質カーボン等）等が挙げられる。 The negative electrode material is not limited, and any negative electrode material that can deposit or occlude lithium ions may be selected. For example, titanium-based materials such as lithium titanate having a spinel crystal structure represented by Li [Li 1/3 Ti 5/3 ] O 4 , alloy-based materials such as Si, Sb, and Sn-based lithium metal, lithium alloys (Lithium metal-containing alloys such as lithium-silicon, lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloys), lithium composite oxide (lithium-titanium), silicon oxide In addition, an alloy capable of inserting and extracting lithium, a carbon material (for example, graphite, hard carbon, low-temperature fired carbon, amorphous carbon, etc.) can be used.
正極活物質の粉体および負極材料の粉体は、平均粒子サイズ１００μｍ以下であることが望ましい。特に、正極活物質の粉体は、非水電解質電池の高出力特性を向上する目的で１０μｍ以下であることが望ましい。粉体を所定の形状で得るためには粉砕機や分級機が用いられる。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、カウンタージェトミル、旋回気流型ジェットミルや篩等が用いられる。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、特に限定はなく、篩や風力分級機などが、乾式、湿式ともに必要に応じて用いられる。 It is desirable that the positive electrode active material powder and the negative electrode material powder have an average particle size of 100 μm or less. In particular, the positive electrode active material powder is desirably 10 μm or less for the purpose of improving the high output characteristics of the non-aqueous electrolyte battery. In order to obtain the powder in a predetermined shape, a pulverizer or a classifier is used. For example, 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 air flow type jet mill or a sieve is used. At the time of pulverization, wet pulverization in the presence of water or an organic solvent such as hexane may be used. There is no particular limitation on the classification method, and a sieve, an air classifier, or the like is used as needed for both dry and wet methods.
以上、正極及び負極の主要構成成分である正極活物質及び負極材料について詳述したが、前記正極及び負極には、前記主要構成成分の他に、導電剤、結着剤、増粘剤、フィラー等が、他の構成成分として含有されてもよい。 The positive electrode active material and the negative electrode material, which are the main components of the positive electrode and the negative electrode, have been described in detail above. In addition to the main components, the positive electrode and the negative electrode include a conductive agent, a binder, a thickener, and a filler. Etc. may be contained as other constituents.
導電剤としては、電池性能に悪影響を及ぼさない電子伝導性材料であれば限定されないが、通常、天然黒鉛（鱗状黒鉛，鱗片状黒鉛，土状黒鉛等）、人造黒鉛、カーボンブラック、アセチレンブラック、ケッチェンブラック、カーボンウイスカー、炭素繊維、金属（銅，ニッケル，アルミニウム，銀，金等）粉、金属繊維、導電性セラミックス材料等の導電性材料を１種またはそれらの混合物として含ませることができる。 The conductive agent is not limited as long as it is an electron conductive material that does not adversely affect the battery performance. Usually, natural graphite (such as scaly graphite, scaly graphite, earthy graphite), artificial graphite, carbon black, acetylene black, Conductive materials such as ketjen black, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fiber, and conductive ceramic material can be included as one kind or a mixture thereof. .
これらの中で、導電剤としては、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望ましい。導電剤の添加量は、正極または負極の総重量に対して０．１重量％〜５０重量％が好ましく、特に０．５重量％〜３０重量％が好ましい。特にアセチレンブラックを０．１〜０．５μｍの超微粒子に粉砕して用いると必要炭素量を削減できるため望ましい。これらの混合方法は、物理的な混合であり、その理想とするところは均一混合である。そのため、Ｖ型混合機、Ｓ型混合機、擂かい機、ボールミル、遊星ボールミルといったような粉体混合機を乾式、あるいは湿式で混合することが可能である。 Among these, as the conductive agent, acetylene black is desirable from the viewpoints of electron conductivity and coatability. The addition amount of the conductive agent is preferably 0.1% by weight to 50% by weight, and particularly preferably 0.5% by weight to 30% by weight with respect to the total weight of the positive electrode or the negative electrode. In particular, it is desirable to use acetylene black by pulverizing into ultrafine particles of 0.1 to 0.5 μm because the required carbon amount can be reduced. These mixing methods are physical mixing, and the ideal is uniform mixing. Therefore, powder mixers such as V-type mixers, S-type mixers, crackers, ball mills, and planetary ball mills can be mixed dry or wet.
前記結着剤としては、通常、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），ポリエチレン，ポリプロピレン等の熱可塑性樹脂、エチレン−プロピレン−ジエンターポリマー（ＥＰＤＭ），スルホン化ＥＰＤＭ，スチレンブタジエンゴム（ＳＢＲ）、フッ素ゴム等のゴム弾性を有するポリマーを１種または２種以上の混合物として用いることができる。結着剤の添加量は、正極または負極の総重量に対して１〜５０重量％が好ましく、特に２〜３０重量％が好ましい。 Examples of the binder include thermoplastic resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethylene, and polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, and styrene butadiene. Polymers having rubber elasticity such as rubber (SBR) and fluororubber can be used as one kind or a mixture of two or more kinds. The addition amount of the binder is preferably 1 to 50% by weight, particularly preferably 2 to 30% by weight, based on the total weight of the positive electrode or the negative electrode.
フィラーとしては、電池性能に悪影響を及ぼさない材料であれば何でも良い。通常、ポリプロピレン，ポリエチレン等のオレフィン系ポリマー、無定形シリカ、アルミナ、ゼオライト、ガラス、炭素等が用いられる。フィラーの添加量は、正極または負極の総重量に対して添加量は３０重量％以下が好ましい。 As the filler, any material that does not adversely affect the battery performance may be used. Usually, olefin polymers such as polypropylene and polyethylene, amorphous silica, alumina, zeolite, glass, carbon and the like are used. The addition amount of the filler is preferably 30% by weight or less with respect to the total weight of the positive electrode or the negative electrode.
正極及び負極は、前記主要構成成分（正極においては正極活物質、負極においては負極材料）、およびその他の材料を混練し合剤とし、Ｎ−メチルピロリドン，トルエン等の有機溶媒又は水に混合させた後、得られた混合液を下記に詳述する集電体の上に塗布し、または圧着して５０℃〜２５０℃程度の温度で、２時間程度加熱処理することにより好適に作製される。前記塗布方法については、例えば、アプリケーターロールなどのローラーコーティング、スクリーンコーティング、ドクターブレード方式、スピンコーティング、バーコータ等の手段を用いて任意の厚さ及び任意の形状に塗布することが望ましいが、これらに限定されるものではない。 The positive electrode and the negative electrode are prepared by mixing the main constituents (positive electrode active material in the positive electrode, negative electrode material in the negative electrode) and other materials into a mixture and mixing with an organic solvent such as N-methylpyrrolidone or toluene or water. After that, the obtained liquid mixture is applied on a current collector described in detail below, or pressed and heat-treated at a temperature of about 50 ° C. to 250 ° C. for about 2 hours. . About the application method, for example, it is desirable to apply to any thickness and any shape using means such as roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater, etc. It is not limited.
セパレータとしては、優れた高率放電性能を示す多孔膜や不織布等を、単独あるいは併用することが好ましい。非水電解質電池用セパレータを構成する材料としては、例えばポリエチレン，ポリプロピレン等に代表されるポリオレフィン系樹脂、ポリエチレンテレフタレート，ポリブチレンテレフタレート等に代表されるポリエステル系樹脂、ポリフッ化ビニリデン、フッ化ビニリデン−ヘキサフルオロプロピレン共重合体、フッ化ビニリデン−パーフルオロビニルエーテル共重合体、フッ化ビニリデン−テトラフルオロエチレン共重合体、フッ化ビニリデン−トリフルオロエチレン共重合体、フッ化ビニリデン−フルオロエチレン共重合体、フッ化ビニリデン−ヘキサフルオロアセトン共重合体、フッ化ビニリデン−エチレン共重合体、フッ化ビニリデン−プロピレン共重合体、フッ化ビニリデン−トリフルオロプロピレン共重合体、フッ化ビニリデン−テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体、フッ化ビニリデン−エチレン−テトラフルオロエチレン共重合体等を挙げることができる。 As the separator, it is preferable to use a porous film or a non-woven fabric exhibiting excellent high rate discharge performance alone or in combination. Examples of the material constituting the separator for a nonaqueous electrolyte battery include polyolefin resins typified by polyethylene and polypropylene, polyester resins typified by polyethylene terephthalate and polybutylene terephthalate, polyvinylidene fluoride, and vinylidene fluoride-hexa. Fluoropropylene copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, fluorine Vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride - tetrafluoroethylene - hexafluoropropylene copolymer, vinylidene fluoride - ethylene - can be mentioned tetrafluoroethylene copolymer.
セパレータの空孔率は強度の観点から９８体積％以下が好ましい。また、充放電特性の観点から空孔率は２０体積％以上が好ましい。 The porosity of the separator is preferably 98% by volume or less from the viewpoint of strength. Further, the porosity is preferably 20% by volume or more from the viewpoint of charge / discharge characteristics.
また、セパレータは、例えばアクリロニトリル、エチレンオキシド、プロピレンオキシド、メチルメタアクリレート、ビニルアセテート、ビニルピロリドン、ポリフッ化ビニリデン等のポリマーと電解質とで構成されるポリマーゲルを用いてもよい。非水電解質を上記のようにゲル状態で用いると、漏液を防止する効果がある点で好ましい。 The separator may be a polymer gel composed of a polymer such as acrylonitrile, ethylene oxide, propylene oxide, methyl methacrylate, vinyl acetate, vinyl pyrrolidone, polyvinylidene fluoride, and an electrolyte. Use of the non-aqueous electrolyte in the gel state as described above is preferable in that it has an effect of preventing leakage.
さらに、セパレータは、上述したような多孔膜や不織布等とポリマーゲルを併用して用いると、電解質の保液性が向上するため望ましい。即ち、ポリエチレン微孔膜の表面及び微孔壁面に厚さ数μｍ以下の親溶媒性ポリマーを被覆したフィルムを形成し、前記フィルムの微孔内に電解質を保持させることで、前記親溶媒性ポリマーがゲル化する。 Furthermore, it is desirable that the separator be used in combination with the above-described porous film, non-woven fabric, or the like and a polymer gel because the liquid retention of the electrolyte is improved. That is, by forming a film in which the surface of the polyethylene microporous membrane and the microporous wall are coated with a solvophilic polymer having a thickness of several μm or less, and holding the electrolyte in the micropores of the film, Gels.
前記親溶媒性ポリマーとしては、ポリフッ化ビニリデンの他、エチレンオキシド基やエステル基等を有するアクリレートモノマー、エポキシモノマー、イソシアナート基を有するモノマー等が架橋したポリマー等が挙げられる。該モノマーは、ラジカル開始剤を併用して加熱や紫外線（ＵＶ）を用いたり、電子線（ＥＢ）等の活性光線等を用いて架橋反応を行わせることが可能である。 Examples of the solvophilic polymer include polyvinylidene fluoride, an acrylate monomer having an ethylene oxide group or an ester group, an epoxy monomer, a polymer having a monomer having an isocyanate group, and the like crosslinked. The monomer can be subjected to a crosslinking reaction using a radical initiator in combination with heating or ultraviolet rays (UV), or using an actinic ray such as an electron beam (EB).
非水電解質二次電池の構成については特に限定されるものではなく、正極、負極及びロール状のセパレータを有する円筒型電池、角型電池、扁平型電池等が一例として挙げられる。 The configuration of the nonaqueous electrolyte secondary battery is not particularly limited, and examples thereof include a cylindrical battery having a positive electrode, a negative electrode, and a roll separator, a square battery, and a flat battery.
（予備試験）
本発明者らが行った予備試験の内容を次に示す。
(Preliminary test)
The contents of the preliminary test conducted by the present inventors are as follows.
（正極活物質の作製）
硝酸コバルト、硝酸ニッケル及び硝酸マンガンを、Ｃｏ：Ｎｉ：Ｍｎの原子比が１：１：１の割合で含む水溶液に水酸化ナトリウム水溶液を加えて共沈させ、大気中１１０℃で加熱、乾燥して、Ｃｏ、Ｎｉ及びＭｎを含む共沈前駆体を作製した。前記共沈前駆体に水酸化リチウムを加え、瑪瑙製自動乳鉢を用いてよく混合し、Ｌｉ：（Ｃｏ，Ｎｉ，Ｍｎ）のモル比が１０２：１００である混合粉体を調製した。これをアルミナ製匣鉢に充填し、電気炉を用いて１００℃／ｈで１０００℃まで昇温し、１０００℃にて、５時間、大気雰囲気下で焼成することにより、組成式ＬｉＣｏ１／３Ｎｉ１／３Ｍｎ１／３Ｏ２で表されるリチウム遷移金属複合酸化物を作製し、これを正極活物質として用いた。窒素吸着法により測定したＢＥＴ比表面積は１．０ｍ２／ｇであり、レーザ回折散乱法粒子径分布測定装置を用いたＤ５０の値は１２．１μｍであった。このようにして、正極活物質を作製した。
(Preparation of positive electrode active material)
A sodium hydroxide aqueous solution is added to an aqueous solution containing cobalt nitrate, nickel nitrate and manganese nitrate at a Co: Ni: Mn atomic ratio of 1: 1: 1 and coprecipitated, and heated and dried at 110 ° C. in the air. Thus, a coprecipitation precursor containing Co, Ni and Mn was prepared. Lithium hydroxide was added to the coprecipitation precursor and mixed well using a smoked automatic mortar to prepare a mixed powder having a Li: (Co, Ni, Mn) molar ratio of 102: 100. This is filled in an alumina sagger, heated to 1000 ° C. at 100 ° C./h using an electric furnace, and calcined at 1000 ° C. for 5 hours in the air atmosphere, whereby the composition formula LiCo 1/3 A lithium transition metal composite oxide represented by Ni 1/3 Mn 1/3 O 2 was produced and used as a positive electrode active material. The BET specific surface area measured by the nitrogen adsorption method was 1.0 m 2 / g, and the value of D50 using a laser diffraction scattering method particle size distribution measuring device was 12.1 μm. In this way, a positive electrode active material was produced.
（正極板の作製）
前記正極活物質、アセチレンブラック（ＡＢ）及びポリフッ化ビニリデン（ＰＶｄＦ）を質量比９３：３：４の割合（固形分換算）で含有し、Ｎ−メチルピロリドン（ＮＭＰ）を溶剤とする正極ペーストを作製し、厚さ１５μｍの帯状のアルミニウム箔集電体の両面に塗布した。該正極をローラープレス機により加圧成型して正極活物質層を成型した後、１５０℃で１４時間減圧乾燥して、極板中の水分を除去した。このようにして正極板を作製した。
(Preparation of positive electrode plate)
A positive electrode paste containing the positive electrode active material, acetylene black (AB) and polyvinylidene fluoride (PVdF) in a mass ratio of 93: 3: 4 (in terms of solid content) and N-methylpyrrolidone (NMP) as a solvent. It produced and apply | coated on both surfaces of the 15-micrometer-thick strip | belt-shaped aluminum foil electrical power collector. The positive electrode was pressure-molded with a roller press to form a positive electrode active material layer, and then dried under reduced pressure at 150 ° C. for 14 hours to remove moisture in the electrode plate. In this way, a positive electrode plate was produced.
（負極板の作製）
黒鉛、スチレン−ブタジエン・ゴム（ＳＢＲ）及びカルボキシメチルセルロース（ＣＭＣ）を質量比９７：２：１の割合（固形分換算）で含有し、水を溶剤とする負極ペーストを作製し、厚さ１０μｍの帯状の銅箔集電体の両面に塗布した。該負極をローラープレス機により加圧成型して負極活物質層を成型した後、２５℃（室温）で１４時間減圧乾燥して、極板中の水分を除去した。このようにして負極板を作製した。
(Preparation of negative electrode plate)
A negative electrode paste containing graphite, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) in a mass ratio of 97: 2: 1 (in terms of solid content) and using water as a solvent was prepared, and the thickness was 10 μm. It apply | coated to both surfaces of a strip | belt-shaped copper foil collector. The negative electrode was pressure-molded with a roller press to form a negative electrode active material layer, and then dried under reduced pressure at 25 ° C. (room temperature) for 14 hours to remove moisture in the electrode plate. In this way, a negative electrode plate was produced.
（非水電解質１）
エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒に、ＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させた電解液を非水電解質１とする。
(Nonaqueous electrolyte 1)
An electrolyte solution in which LiPF 6 is dissolved at a concentration of 1.0 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3: 7 is referred to as nonaqueous electrolyte 1.
（非水電解質２）
エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒に、ＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させた電解液を作製し、前記電解液に対して、さらに０．５質量％のホウ酸を添加して溶解させた。これを非水電解質２とする。
(Nonaqueous electrolyte 2)
An electrolytic solution in which LiPF 6 was dissolved at a concentration of 1.0 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was prepared. .5% by weight boric acid was added and dissolved. This is designated as non-aqueous electrolyte 2.
（非水電解質３）
エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒に、ＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させた電解液を作製し、前記電解液に対して、さらに０．５質量％のリチウムビスオキサレートボラート（ＬｉＢＯＢ）を添加して溶解させた。これを非水電解質３とする。
(Nonaqueous electrolyte 3)
An electrolytic solution in which LiPF 6 was dissolved at a concentration of 1.0 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was prepared. .5 mass% lithium bisoxalate borate (LiBOB) was added and dissolved. This is designated as non-aqueous electrolyte 3.
（非水電解質４）
エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒に、ＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させた電解液を作製し、前記電解液に対して、さらに０．５質量％の（化２）で示されるボロキシン環化合物（ＴｉＰＢｘ）を添加して溶解させた。これを非水電解質４とする。
An electrolytic solution in which LiPF 6 was dissolved at a concentration of 1.0 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was prepared. 5% by mass of a boroxine ring compound (TiPBx) represented by (Chemical Formula 2) was added and dissolved. This is designated as non-aqueous electrolyte 4.
（非水電解質５）
エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒に、ＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させた電解液を作製し、前記電解液に対して、さらに０．５質量％のホウ酸トリブチル（ＴＢＢ）を添加して溶解させた。これを非水電解質５とする。
(Nonaqueous electrolyte 5)
An electrolytic solution in which LiPF 6 was dissolved at a concentration of 1.0 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was prepared. .5% by weight tributyl borate (TBB) was added and dissolved. This is designated as non-aqueous electrolyte 5.
（非水電解質６）
エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒に、ＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させた電解液を作製し、前記電解液に対して、さらに０．５質量％のホウ酸トリプロピル（ＴＰＢ）を添加して溶解させた。これを非水電解質６とする。
(Nonaqueous electrolyte 6)
An electrolytic solution in which LiPF 6 was dissolved at a concentration of 1.0 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was prepared. 5% by mass of tripropyl borate (TPB) was added and dissolved. This is designated as non-aqueous electrolyte 6.
（非水電解質７）
エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒に、ＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させた電解液を作製し、前記電解液に対して、さらに０．５質量％のホウ酸トリス（トリメチルシリル）（ＴＭＳＢ）を添加して溶解させた。これを非水電解質７とする。
(Nonaqueous electrolyte 7)
An electrolytic solution in which LiPF 6 was dissolved at a concentration of 1.0 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was prepared. 5% by weight of tris (trimethylsilyl) borate (TMSB) was added and dissolved. This is designated as non-aqueous electrolyte 7.
上記非水電解質１〜７をそれぞれ用いて、次の手順にて非水電解質二次電池を作製した。 Using each of the nonaqueous electrolytes 1 to 7, a nonaqueous electrolyte secondary battery was produced by the following procedure.
（非水電解質二次電池の作製）
＜組立工程＞
ポリエチレン製微多孔膜からなるセパレータを介して前記正極板と前記負極板を積層し、扁平形状に巻回して発電要素を作製し、アルミニウム製の角型電槽缶に収納し、正負極端子を取り付けた。この容器内部に非水電解質を注入したのちに封口した。電槽缶の外形寸法は、４９．３ｍｍ（高さ）×３３．７ｍｍ（幅）×５．１７ｍｍ（厚さ）である。このようにして非水電解質電池を組み立てた。
(Preparation of non-aqueous electrolyte secondary battery)
<Assembly process>
The positive electrode plate and the negative electrode plate are laminated through a separator made of a polyethylene microporous membrane, wound in a flat shape to produce a power generation element, housed in an aluminum square battery case, and positive and negative electrode terminals Attached. The container was sealed after injecting a nonaqueous electrolyte into the container. The outer dimensions of the battery case can are 49.3 mm (height) × 33.7 mm (width) × 5.17 mm (thickness). In this way, a non-aqueous electrolyte battery was assembled.
＜初期充放電工程＞
次に、２５℃にて、２サイクルの初期充放電工程に供した。電圧制御は、全て、正負極端子間電圧に対して行った。１サイクル目の充電は、電流０．２ＣｍＡ、電圧４．３５Ｖ、８時間の定電流定電圧充電とし、放電は、電流０．２ＣｍＡ、終止電圧２．７５Ｖの定電流放電とした。２サイクル目の充電は、電流１．０ＣｍＡ、電圧４．３５Ｖ、３時間の定電流定電圧充電とし、放電は、電流１．０ＣｍＡ、終止電圧２．７５Ｖの定電流放電とした。全てのサイクルにおいて、充電後及び放電後に、１０分の休止時間を設定した。このようにして、非水電解質電池を作製した。
<Initial charge / discharge process>
Next, it was subjected to an initial charge / discharge process of 2 cycles at 25 ° C. All voltage control was performed on the voltage between the positive and negative terminals. Charging in the first cycle was constant current constant voltage charging with a current of 0.2 CmA and a voltage of 4.35 V for 8 hours, and discharging was constant current discharging with a current of 0.2 CmA and a final voltage of 2.75 V. The second cycle charge was a constant current constant voltage charge with a current of 1.0 CmA and a voltage of 4.35 V for 3 hours, and the discharge was a constant current discharge with a current of 1.0 CmA and a final voltage of 2.75 V. In all cycles, a 10 minute rest period was set after charging and discharging. In this way, a nonaqueous electrolyte battery was produced.
＜充放電サイクル試験（条件１）＞
作製した非水電解質二次電池について、充放電サイクル試験を行い、放電容量の推移を調べた。電圧制御は、全て、正負極端子間電圧に対して行った。充電は、電流１．０ＣｍＡ、電圧４．２０Ｖ、３時間の定電流定電圧充電とし、放電は、電流１．０ＣｍＡ、終止電圧２．７５Ｖの定電流放電とした。全てのサイクルにおいて、充電後及び放電後に、１０分の休止時間を設定した。ここで、正負極端子間電圧が４．２０Ｖであるとき、正極電位は４．３０Ｖ（ｖｓ.Ｌｉ／Ｌｉ＋）であることがわかっている。この結果を図１に示
す。
<Charge / discharge cycle test (condition 1)>
About the produced nonaqueous electrolyte secondary battery, the charging / discharging cycle test was done and the transition of discharge capacity was investigated. All voltage control was performed on the voltage between the positive and negative terminals. Charging was performed at a constant current and constant voltage with a current of 1.0 CmA and a voltage of 4.20 V for 3 hours, and discharging was performed at a constant current of 1.0 CmA and a final voltage of 2.75 V. In all cycles, a 10 minute rest period was set after charging and discharging. Here, it is known that when the voltage between the positive and negative terminals is 4.20 V, the positive electrode potential is 4.30 V (vs. Li / Li + ). The result is shown in FIG.
上記「条件１」を採用した充放電サイクル試験の結果からわかるように、各種ホウ素化合物を添加した非水電解質を用いた非水電解質二次電池のうち、ホウ酸を添加した「非水電解質２」を用いた場合、及び、ＴｉＰＢｘを添加した「非水電解質４」を用いた場合において、特に優れる結果が得られた。このうち、ホウ酸は、ＴｉＰＢｘに比べて極めて安価な材料であるので、ホウ酸を用いることで、充放電サイクル性能に優れる非水電解質電池を低コストで提供できることがわかる。 As can be seen from the results of the charge / discharge cycle test employing the above “Condition 1”, among the non-aqueous electrolyte secondary batteries using non-aqueous electrolytes to which various boron compounds are added, “non-aqueous electrolyte 2 to which boric acid is added” is shown. ”And when“ Nonaqueous Electrolyte 4 ”added with TiPBx was used, particularly excellent results were obtained. Of these, boric acid is an extremely inexpensive material compared to TiPBx, and therefore it can be seen that by using boric acid, a nonaqueous electrolyte battery excellent in charge / discharge cycle performance can be provided at low cost.
＜充放電サイクル試験（条件２）＞
作製した非水電解質二次電池について、条件を変更して充放電サイクル試験を行い、放電容量の推移を調べた。電圧制御は、全て、正負極端子間電圧に対して行った。充電は、電流１．０ＣｍＡ、電圧４．３５Ｖ、３時間の定電流定電圧充電とし、放電は、電流１．０ＣｍＡ、終止電圧２．７５Ｖの定電流放電とした。全てのサイクルにおいて、充電後及び放電後に、１０分の休止時間を設定した。ここで、正負極端子間電圧が４．３５Ｖであるとき、正極電位は４．４５Ｖ（ｖｓ.Ｌｉ／Ｌｉ＋）であることがわかっている。この
結果を表１に示す。表中、「×」印は、充放電サイクル経過に伴う放電容量の低下が著しいため、１５０サイクルに達する前に試験を終了させたことを示す。
<Charge / discharge cycle test (Condition 2)>
About the produced nonaqueous electrolyte secondary battery, the conditions were changed and the charging / discharging cycle test was done, and transition of the discharge capacity was investigated. All voltage control was performed on the voltage between the positive and negative terminals. Charging was performed at a constant current and constant voltage with a current of 1.0 CmA and a voltage of 4.35 V for 3 hours, and discharging was performed at a constant current of 1.0 CmA and a final voltage of 2.75 V. In all cycles, a 10 minute rest period was set after charging and discharging. Here, it is known that when the voltage between the positive and negative terminals is 4.35 V, the positive electrode potential is 4.45 V (vs. Li / Li + ). The results are shown in Table 1. In the table, “x” marks indicate that the test was terminated before reaching 150 cycles because the discharge capacity significantly decreased with the progress of the charge / discharge cycles.
上記「条件２」を採用した充放電サイクル試験の結果からわかるように、各種ホウ素化合物を添加した非水電解質を用いた非水電解質二次電池のうち、ホウ酸を添加した「非水電解質２」を用いた場合のみ、際立って優れる結果が得られた。 As can be seen from the results of the charge / discharge cycle test employing the above “Condition 2”, among the nonaqueous electrolyte secondary batteries using the nonaqueous electrolyte to which various boron compounds are added, “nonaqueous electrolyte 2 to which boric acid is added” is shown. Only when "" was used, outstanding results were obtained.
次に、ホウ酸の好適な添加量について検討した。上記非水電解質２に準じ、エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒にＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させた電解液に対するホウ酸の添加量を０質量％、０．１質量％、０．２質量％、０．５質量％、１．０質量％、１．５質量％とした非水電解質をそれぞれ準備し、同様の手順で非水電解質電池を作製し、上記「条件２」を採用した充放電サイクル試験を最大２５０サイクルまで行った。この結果、初期充放電効率はホウ酸の添加量が０質量％では８８．９％、０．１質量％では９０．８％、０．２質量％では９２．４％、０．５質量％では９１．５％、１．０質量％では８８．８％、１．５質量％では８２．７％であった。充放電サイクル性能は、図２に示すように、ホウ酸の添加量が０質量％、０．１質量％、０．２質量％、０．５質量％と増えるにしたがって向上し、０．５〜１．０質量％のとき最も良好であり、１．５質量％では再び低下した。以上の結果から、ホウ酸の添加量は、０．１質量％以上が好ましく、０．２質量％以上がより好ましく、０．５質量％以上が最も好ましい。また、１．５質量％以下が好ましく、１．０質量％以下がより好ましい。 Next, the suitable addition amount of boric acid was examined. The amount of boric acid added to the electrolytic solution obtained by dissolving LiPF 6 at a concentration of 1.0 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 according to the nonaqueous electrolyte 2 described above. Prepared non-aqueous electrolytes with 0% by mass, 0.1% by mass, 0.2% by mass, 0.5% by mass, 1.0% by mass, and 1.5% by mass, respectively. An electrolyte battery was prepared, and a charge / discharge cycle test employing the above “condition 2” was performed up to 250 cycles. As a result, the initial charge / discharge efficiency was 88.9% when the addition amount of boric acid was 0% by mass, 90.8% at 0.1% by mass, 92.4% at 0.2% by mass, and 0.5% by mass. Was 91.5%, 1.0% by mass was 88.8%, and 1.5% by mass was 82.7%. As shown in FIG. 2, the charge / discharge cycle performance is improved as the amount of boric acid added increases to 0 mass%, 0.1 mass%, 0.2 mass%, and 0.5 mass%. It was the best when it was -1.0% by mass, and decreased again at 1.5% by mass. From the above results, the amount of boric acid added is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and most preferably 0.5% by mass or more. Moreover, 1.5 mass% or less is preferable and 1.0 mass% or less is more preferable.
（非水電解質の分析）
上記の、エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒にＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させた電解液に対してホウ酸を０．２質量％添加した非水電解質（試料１）、同じく０．５質量％添加した非水電解質（試料２）及びこれを用いて作製し上記初期充放電を終了した段階の非水電解質電池を解体して発電要素から遠心分離により取り出した非水電解質（試料３）、並びに、同じく１．５質量％添加した非水電解質（試料４）及びこれを用いて作製し上記初期充放電を終了した段階の非水電解質電池を解体して発電要素から遠心分離により取り出した非水電解質（試料５）について、イオンクロマトグラフィー分析を行った。その結果、ＰＦ６ −の濃度は、試料２及び試料３では０．９ｍｏｌ／ｌ、試料４及び試料５では０．６ｍｏｌ／ｌであった。また、ホウ酸の濃度は、試料２及び試料３では０．０１ｍｏｌ／ｌ（０．０５質量％）、試料４では０．０５ｍｏｌ／ｌ（０．２５質量％）、試料５では０．０３ｍｏｌ／ｌ（０．１５質量％）であった。試料１からはホウ酸は検出されなかった。
(Analysis of non-aqueous electrolyte)
The boric acid is 0.2% by mass with respect to the electrolytic solution in which LiPF 6 is dissolved at a concentration of 1.0 mol / l in the above mixed solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3: 7. Electric power is generated by disassembling the added nonaqueous electrolyte (sample 1), the nonaqueous electrolyte added with 0.5% by mass (sample 2), and the nonaqueous electrolyte battery at the stage where the initial charge / discharge is completed. The non-aqueous electrolyte (sample 3) taken out from the element by centrifugation, the non-aqueous electrolyte added with 1.5% by mass (sample 4), and the non-aqueous electrolyte at the stage where the initial charge / discharge was completed using this An ion chromatography analysis was performed on the nonaqueous electrolyte (sample 5) that was disassembled from the electrolyte battery and removed from the power generation element by centrifugation. As a result, the concentration of PF 6 − was 0.9 mol / l for sample 2 and sample 3, and 0.6 mol / l for sample 4 and sample 5. The concentrations of boric acid were 0.01 mol / l (0.05 mass%) for sample 2 and sample 3, 0.05 mol / l (0.25 mass%) for sample 4, and 0.03 mol / l for sample 5. l (0.15% by mass). No boric acid was detected from Sample 1.
上記イオンクロマトグラフィー分析において、ＰＦ６ −の定量に用いたカラム及び検出器は次の通りである。
日本ダイオネクス社製ＩｏｎＰａｃ ＡＳ１６（４×２５０ｍｍ）＋プレカラムＡＧ１６
溶離液：３５ｍｍｏｌ／ｌＫＯＨ水溶液
液量：１．０ｍｌ／ｍｌ
検出器:電気伝導度
In the ion chromatography analysis, the columns and detectors used for the determination of PF 6 − are as follows.
IonPac AS16 (4x250mm) + Precolumn AG16 manufactured by Nippon Dionex
Eluent: 35 mmol / l KOH aqueous solution Volume: 1.0 ml / ml
Detector: Electrical conductivity
上記イオンクロマトグラフィー分析において、ホウ酸の定量に用いたカラム及び検出器は次の通りであり、検出限界値は０．００１ｍｏｌ／ｌである。なお、分析にあたっては、試料を水で希釈して測定に供しているから、カラムが検出するイオン種はＢＯ３ ３−である。
日本ダイオネクス社製ＩｏｎＰａｃ ＩＣＥ−ＡＳ１（９×２５０ｍｍ）
溶離液：１．０ｍｏｌ／ｌオクタンスルホン酸＋２％２−プロパノール水溶液
液量：０．８ｍｌ／ｍｌ
検出器:電気伝導度
In the ion chromatography analysis, the columns and detectors used for boric acid quantification are as follows, and the detection limit is 0.001 mol / l. In the analysis, since the sample is diluted with water for measurement, the ion species detected by the column is BO 3 3- .
IonPac ICE-AS1 (9x250mm) manufactured by Nippon Dionex
Eluent: 1.0 mol / l octanesulfonic acid + 2% 2-propanol aqueous solution Volume: 0.8 ml / ml
Detector: Electrical conductivity
以上の結果から、電解液に添加したホウ酸は一部が他の化合物に変化していることが示唆される。また、非水溶媒に１．０ｍｏｌ／ｌのＬｉＰＦ６を溶解させた電解液に対してホウ酸を０．５質量％以上添加された非水電解質は、０．０１ｍｏｌ／ｌ以上のホウ酸と、０．９ｍｏｌ／ｌ以下のＬｉＰＦ６を含有していることがわかる。また、これを用いて作製した非水電解質電池が備える非水電解質についても同様に含有していることがわかる。 From the above results, it is suggested that a part of boric acid added to the electrolytic solution is changed to another compound. Further, a non-aqueous electrolyte in which 0.5% by mass or more of boric acid is added to an electrolytic solution in which 1.0 mol / l LiPF 6 is dissolved in a non-aqueous solvent is 0.01 mol / l or more boric acid. It can be seen that it contains 0.9 mol / l or less of LiPF 6 . Moreover, it turns out that it contains similarly about the nonaqueous electrolyte with which the nonaqueous electrolyte battery produced using this is equipped.
前記正極ペーストに、正極活物質に対して１質量％のホウ酸を添加した。この正極ペーストを用い、ホウ酸を添加していない「非水電解質１」を用いたことを除いては上記予備試験と同様の処方により非水電解質電池を作製し、上記「条件１」を採用した充放電サイクル試験を実施した。その結果、ホウ酸を添加した全ての参考例に比べて、種々の温度条件下における放電容量の低下及び内部抵抗の増加がみられ、有利な効果は何ら認められなかった。また、ホウ酸を添加した正極ペーストは、混練後、ほんの数時間放置するだけで活物質が凝集してしまい、生じた凝集体により塗工時に塗りむらが生じ、生産性が大きく劣るものであった。また、評価試験実施後の電池を解体して非水電解質を取り出してイオンクロマトグラフィー分析を行ったところ、ホウ酸は検出されなかった。上記処方によって正極ペーストから電池内に取り込まれたホウ酸の量は、仮に同量が非水電解質に添加されて注液されるとすると、１．２質量％のホウ酸を添加した電解液を用いた場合に相当する。このことから、ホウ酸を正極ペーストに添加した場合は、非水電解質の製造工程中に別の化合物に変化し、非水電解質中にホウ酸として含有されることはなく、また、本発明の効果も奏さないことがわかった。 1% by mass of boric acid was added to the positive electrode paste with respect to the positive electrode active material. Using this positive electrode paste, a non-aqueous electrolyte battery was prepared according to the same formulation as the preliminary test except that “non-aqueous electrolyte 1” to which boric acid was not added was used, and “condition 1” was adopted. The charge / discharge cycle test was performed. As a result, compared with all the reference examples to which boric acid was added, the discharge capacity decreased and the internal resistance increased under various temperature conditions, and no advantageous effect was observed. In addition, the positive electrode paste to which boric acid has been added causes the active material to agglomerate after being kneaded for only a few hours, and the resulting agglomerate causes uneven coating during coating, resulting in a greatly inferior productivity. It was. Further, when the battery after the evaluation test was disassembled and the nonaqueous electrolyte was taken out and subjected to ion chromatography analysis, boric acid was not detected. Assuming that the amount of boric acid taken into the battery from the positive electrode paste by the above formulation is added to the non-aqueous electrolyte and injected, the electrolyte containing 1.2% by mass of boric acid is added. It corresponds to the case of using. From this, when boric acid is added to the positive electrode paste, it is changed to another compound during the manufacturing process of the nonaqueous electrolyte, and is not contained as boric acid in the nonaqueous electrolyte. It turns out that there is no effect either.
（実施例１）
エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒に、ＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させた電解液を作製し、前記電解液に対して、さらに０．５質量％のホウ酸（ナカライテスク社製、純度９９．５％以上）及び２質量％のジグリコールサルフェート（ＤＧＬＳＴ）を添加し、撹拌混合した。これを実施例１に係る非水電解質とした。
Example 1
An electrolytic solution in which LiPF 6 was dissolved at a concentration of 1.0 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was prepared. 0.5% by mass of boric acid (manufactured by Nacalai Tesque, purity 99.5% or more) and 2% by mass of diglycol sulfate (DGLST) were added and mixed with stirring. This was designated as the nonaqueous electrolyte according to Example 1.
（比較例１）
上記「非水電解質１」を比較例１に係る非水電解質とした。
(Comparative Example 1)
The “non-aqueous electrolyte 1” was a non-aqueous electrolyte according to Comparative Example 1.
（比較例２）
上記「非水電解質２」を比較例２に係る非水電解質とした。
(Comparative Example 2)
The “nonaqueous electrolyte 2” was used as the nonaqueous electrolyte according to Comparative Example 2.
（比較例３）
エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒に、ＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度で溶解させた電解液を作製し、前記電解液に対して、さらに２質量％のジグリコールサルフェート（ＤＧＬＳＴ）を添加し、撹拌混合した。これを比較例３に係る非水電解質とした。
(Comparative Example 3)
An electrolytic solution in which LiPF 6 was dissolved at a concentration of 1.0 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 was prepared. Mass% of diglycol sulfate (DGLST) was added and stirred and mixed. This was used as the nonaqueous electrolyte according to Comparative Example 3.
実施例１及び比較例１〜３に係る非水電解質をそれぞれ用いたことを除いては、上記予備試験と同様にして、非水電解質電池を組み立てた。 A nonaqueous electrolyte battery was assembled in the same manner as in the preliminary test except that the nonaqueous electrolytes according to Example 1 and Comparative Examples 1 to 3 were used.
＜初期充放電工程＞
実施例１及び比較例１〜３に係る非水電解質をそれぞれ用いて組み立てたこれらの非水電解質電池は、２５℃にて、２サイクルの初期充放電工程に供した。電圧制御は、全て、正負極端子間電圧に対して行った。１サイクル目の充電は、電流０．２ＣｍＡ、電圧４．３５Ｖ、８時間の定電流定電圧充電とし、放電は、電流０．２ＣｍＡ、終止電圧２．７５Ｖの定電流放電とした。２サイクル目の充電は、電流１．０ＣｍＡ、電圧４．３５Ｖ、３時間の定電流定電圧充電とし、放電は、電流１．０ＣｍＡ、終止電圧２．７５Ｖの定電流放電とした。全てのサイクルにおいて、充電後及び放電後に、１０分の休止時間を設定した。なお、予備試験の場合と同様、正負極端子間電圧が４．３５Ｖであるとき、正極電位は４．４５Ｖ（ｖｓ.Ｌｉ／Ｌｉ＋）であることがわかっている。上記の初期充放電工程を経て非水電解質電池を作製した。
<Initial charge / discharge process>
These nonaqueous electrolyte batteries assembled using the nonaqueous electrolytes according to Example 1 and Comparative Examples 1 to 3 were each subjected to a two-cycle initial charge / discharge process at 25 ° C. All voltage control was performed on the voltage between the positive and negative terminals. Charging in the first cycle was constant current constant voltage charging with a current of 0.2 CmA and a voltage of 4.35 V for 8 hours, and discharging was constant current discharging with a current of 0.2 CmA and a final voltage of 2.75 V. The second cycle charge was a constant current constant voltage charge with a current of 1.0 CmA and a voltage of 4.35 V for 3 hours, and the discharge was a constant current discharge with a current of 1.0 CmA and a final voltage of 2.75 V. In all cycles, a 10 minute rest period was set after charging and discharging. As in the case of the preliminary test, it is known that when the voltage between the positive and negative terminals is 4.35 V, the positive electrode potential is 4.45 V (vs. Li / Li + ). A nonaqueous electrolyte battery was fabricated through the initial charge / discharge process.
このようにして作製した非水電解質電池を用いて充放電サイクル試験を行った。また、同一の処方及び手順で作製した非水電解質電池を用いて４５℃反復放置試験を行った。 A charge / discharge cycle test was conducted using the non-aqueous electrolyte battery thus produced. Moreover, the 45 degreeC repeated leaving test was done using the nonaqueous electrolyte battery produced with the same prescription and procedure.
＜充放電サイクル試験＞
充放電サイクル試験の条件は、上記「条件２」を採用した。放電容量が、上記初期充放電工程における２サイクル目の放電容量に対して６０％以上を維持したサイクル数をカウントし、表２に示した。
<Charge / discharge cycle test>
The above-mentioned “Condition 2” was adopted as the condition for the charge / discharge cycle test. The number of cycles in which the discharge capacity was maintained at 60% or more with respect to the discharge capacity of the second cycle in the initial charge / discharge step was counted and shown in Table 2.
＜４５℃反復保存試験＞
４５℃反復放置試験の条件及び手順は次のとおりである。電流１．０ＣｍＡ、電圧４．３５Ｖ、３時間の定電流定電圧充電を行った。次に、電池を開回路状態とし、４５℃の恒温槽中に１５日間保存した。次に、２５℃にて、電流１．０ＣｍＡ、終止電圧２．７５Ｖの定電流放電と、電流１．０ＣｍＡ、電圧４．３５Ｖ、３時間の定電流定電圧充電を行った後、４５℃の恒温槽中にさらに１５日間保存した。このようにして、４５℃の恒温槽中に合計３０日間放置した後、２５℃にて、電流１．０ＣｍＡ、終止電圧２．７５Ｖの定電流放電を行い、放電容量を測定し、上記初期充放電工程における２サイクル目の放電容量に対する百分率を求め、それぞれの電池の「容量保持率（％）」とした。結果を表３に示す。
<45 ° C repeated storage test>
The conditions and procedure of the 45 ° C. repeated standing test are as follows. Constant current and constant voltage charging was performed at a current of 1.0 CmA, a voltage of 4.35 V, and 3 hours. Next, the battery was placed in an open circuit state and stored in a 45 ° C. constant temperature bath for 15 days. Next, at 25 ° C., a constant current discharge with a current of 1.0 CmA and a final voltage of 2.75 V, a current of 1.0 CmA, a voltage of 4.35 V, and a constant current and constant voltage charge for 3 hours were performed. It was further stored for 15 days in a thermostatic bath. In this way, after being left in a 45 ° C. constant temperature bath for a total of 30 days, at 25 ° C., a constant current discharge with a current of 1.0 CmA and a final voltage of 2.75 V was performed, and the discharge capacity was measured. The percentage with respect to the discharge capacity at the second cycle in the discharge step was determined and used as the “capacity holding ratio (%)” of each battery. The results are shown in Table 3.
表３からわかるように、ホウ酸のみを添加した比較例２に係る電池や、環状スルホン酸化合物のみを添加した比較例３に係る電池では、ホウ酸も環状スルホン酸化合物も添加していない比較例１に係る電池よりも保存性能が悪化した。これに対して、ホウ酸及び環状スルホン酸化合物を添加した実施例１に係る非水電解質を用いた非水電解質電池は、保存性能が向上した。 As can be seen from Table 3, in the battery according to Comparative Example 2 to which only boric acid was added and the battery according to Comparative Example 3 to which only the cyclic sulfonic acid compound was added, a comparison in which neither boric acid nor cyclic sulfonic acid compound was added. The storage performance was worse than that of the battery according to Example 1. On the other hand, the storage performance of the nonaqueous electrolyte battery using the nonaqueous electrolyte according to Example 1 to which boric acid and a cyclic sulfonic acid compound were added was improved.
Claims (3)
非水溶媒に、ＬｉＰＦ ６ 、２質量％以下のホウ酸、及び、５質量％未満の下記一般式（２）で表される環状スルホン酸化合物を添加して前記非水電解質を調製することを特徴とするリチウムイオン二次電池の製造方法。
〔一般式（２）において、Ｒ １ は一般式（４）又は、式（５）で表される基（＊の部分がＲ １ に結合）である。Ｒ ３ は、ハロゲンを含んでも良い炭素数１〜３のアルキル基である。〕 A positive electrode, a negative electrode, PF 6 - anion, boric acid, and the following general formula (2) a non-aqueous electrolyte cyclic sulfonic acid compound is added is represented by a method for producing a lithium ion secondary battery having a Because
The nonaqueous electrolyte is prepared by adding LiPF 6 , 2% by mass or less of boric acid, and less than 5% by mass of the cyclic sulfonic acid compound represented by the following general formula (2) to a nonaqueous solvent. A method for producing a lithium ion secondary battery .
[In General Formula (2), R 1 is a group represented by General Formula (4) or Formula (5) (the part of * is bonded to R 1 ). R 3 is a C 1-3 alkyl group which may contain halogen. ]
ホウ酸の含有量が０．１５質量％以下であり、下記一般式（２）で表される環状スルホン酸化合物の含有量が５質量％未満であるリチウムイオン二次電池。
〔一般式（２）において、Ｒ １ は一般式（４）又は、式（５）で表される基（＊の部分がＲ １ に結合）である。Ｒ ３ は、ハロゲンを含んでも良い炭素数１〜３のアルキル基である。〕 Comprising anionic, a non-aqueous electrolyte contains a cyclic acid compound represented by the boric acid and the following general formula (2), a, - a positive electrode, a negative electrode, PF 6
The content of boric acid is not more than 0.15 wt%, a lithium ion secondary battery containing organic content is less than 5 wt% of the cyclic acid compound represented by the following general formula (2).
[In General Formula (2), R 1 is a group represented by General Formula (4) or Formula (5) (the part of * is bonded to R 1 ). R 3 is a C 1-3 alkyl group which may contain halogen. ]
The lithium ion secondary battery manufactured by the manufacturing method according to claim 1 or the lithium ion secondary battery according to claim 2 is charged to a positive electrode potential of 4.4 V (vs. Li / Li + ) or higher. How to use a lithium ion secondary battery .
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