JP2007258084A - Lithium secondary battery - Google Patents
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- JP2007258084A JP2007258084A JP2006083340A JP2006083340A JP2007258084A JP 2007258084 A JP2007258084 A JP 2007258084A JP 2006083340 A JP2006083340 A JP 2006083340A JP 2006083340 A JP2006083340 A JP 2006083340A JP 2007258084 A JP2007258084 A JP 2007258084A
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 60
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 58
- 239000011255 nonaqueous electrolyte Substances 0.000 claims abstract description 16
- 239000011149 active material Substances 0.000 claims abstract description 13
- 229910000676 Si alloy Inorganic materials 0.000 claims abstract description 7
- 239000000463 material Substances 0.000 claims description 4
- 150000002641 lithium Chemical class 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 14
- 238000007599 discharging Methods 0.000 description 11
- 239000000203 mixture Substances 0.000 description 8
- 229910052710 silicon Inorganic materials 0.000 description 5
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 3
- 239000003575 carbonaceous material Substances 0.000 description 3
- 239000012046 mixed solvent Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- 229910013063 LiBF 4 Inorganic materials 0.000 description 2
- -1 LiCF 3 SO 3 Inorganic materials 0.000 description 2
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 2
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 230000008602 contraction Effects 0.000 description 2
- 150000005676 cyclic carbonates Chemical class 0.000 description 2
- 239000002612 dispersion medium Substances 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- 239000005518 polymer electrolyte Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- ZZXUZKXVROWEIF-UHFFFAOYSA-N 1,2-butylene carbonate Chemical compound CCC1COC(=O)O1 ZZXUZKXVROWEIF-UHFFFAOYSA-N 0.000 description 1
- LZDKZFUFMNSQCJ-UHFFFAOYSA-N 1,2-diethoxyethane Chemical compound CCOCCOCC LZDKZFUFMNSQCJ-UHFFFAOYSA-N 0.000 description 1
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 229910017873 Cu—Ni—Si—Mg Inorganic materials 0.000 description 1
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 1
- 229910015015 LiAsF 6 Inorganic materials 0.000 description 1
- 229910013684 LiClO 4 Inorganic materials 0.000 description 1
- 229910013595 LiCo0.5Ni0.5O2 Inorganic materials 0.000 description 1
- 229910015645 LiMn Inorganic materials 0.000 description 1
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 1
- 229910014689 LiMnO Inorganic materials 0.000 description 1
- 229910011669 LiNi0.7Co0.2Mn0.1O2 Inorganic materials 0.000 description 1
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 150000005678 chain carbonates Chemical class 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 125000004177 diethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- 230000009477 glass transition Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000005001 laminate film Substances 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- ACFSQHQYDZIPRL-UHFFFAOYSA-N lithium;bis(1,1,2,2,2-pentafluoroethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)C(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)C(F)(F)F ACFSQHQYDZIPRL-UHFFFAOYSA-N 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229920002239 polyacrylonitrile Polymers 0.000 description 1
- 229920001690 polydopamine Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000011863 silicon-based powder Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 229920006259 thermoplastic polyimide Polymers 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
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
本発明はリチウム二次電池に係り、特に、活物質にＳｉ又はＳｉ合金を含む負極を用い、正極とこの負極との間にセパレータを介在させて扁平状に巻いた扁平電極体を非水電解質と一緒に電池容器内に収容させたリチウム二次電池において、このリチウム二次電池を充放電させた場合に、上記の扁平電極体の平面部に撓みなどが生じて電池の厚みが増加するのを防止し、充放電特性に優れると共に高エネルギー密度のリチウム二次電池が得られるようにした点に特徴を有するものである。 The present invention relates to a lithium secondary battery, and in particular, a non-aqueous electrolyte comprising a flat electrode body using a negative electrode containing Si or a Si alloy as an active material and having a separator interposed between the positive electrode and the negative electrode. In a lithium secondary battery housed in a battery container together with this lithium secondary battery, when the lithium secondary battery is charged / discharged, the flat portion of the flat electrode body is bent and the thickness of the battery increases. This is characterized in that a lithium secondary battery having a high energy density and excellent charge / discharge characteristics is obtained.
高出力，高エネルギー密度の新型二次電池として、非水電解液を用い、リチウムイオンを正極と負極との間で移動させて充放電を行うようにしたリチウム二次電池が様々な機器に利用されるようになった。 As a new secondary battery with high output and high energy density, a lithium secondary battery that uses a non-aqueous electrolyte and moves lithium ions between the positive and negative electrodes to perform charging and discharging is used in various devices. It came to be.
そして、近年においては、携帯電話、ノートパソコン、ＰＤＡなどのモバイル機器の小型化・軽量化が著しく進行すると共に、多機能化に伴って消費電力も増加している。 In recent years, mobile devices such as mobile phones, notebook personal computers, and PDAs have been remarkably reduced in size and weight, and the power consumption has increased with the increase in functionality.
このため、リチウム二次電池をこれらの電源として使用する場合、リチウム二次電池にも軽量化及び高容量化が要望されている。 For this reason, when a lithium secondary battery is used as these power supplies, the lithium secondary battery is also required to be lighter and have a higher capacity.
ここで、リチウム二次電池においては、その負極の活物質に黒鉛などの炭素材料が使用されているが、近年においては、上記のようにリチウム二次電池の軽量化及び高容量化を図るため、黒鉛などの炭素材料に比べて単位質量及び単位体積あたりの充放電容量に優れる材料として、Ｓｉ、Ｇｅ、Ｓｎ等のリチウムと合金化するものを負極の活物質に用いることが提案されており、特に、Ｓｉは活物質１ｇあたり約４０００ｍＡｈの高い理論容量を示すことから、負極の活物質にＳｉを用いた様々なリチウム二次電池が提案されている（例えば、特許文献１参照。）。 Here, in the lithium secondary battery, a carbon material such as graphite is used as the active material of the negative electrode. However, in recent years, in order to reduce the weight and increase the capacity of the lithium secondary battery as described above. It has been proposed that materials that are alloyed with lithium, such as Si, Ge, Sn, etc., be used as the active material of the negative electrode, as materials having superior unit mass and charge / discharge capacity per unit volume compared to carbon materials such as graphite. In particular, since Si exhibits a high theoretical capacity of about 4000 mAh per gram of active material, various lithium secondary batteries using Si as the negative electrode active material have been proposed (see, for example, Patent Document 1).
しかし、このように負極の活物質にＳｉを用いたリチウム二次電池の場合、充放電時におけるＳｉの膨張収縮による体積変化が大きくなり、正極と負極との間にセパレータを介在させて扁平状に巻いた扁平電極体を非水電解質と一緒に電池容器内に収容させたリチウム二次電池の場合、この扁平電極体の平面部に撓みが生じて電池の厚みが増加し、リチウム二次電池の充放電特性が低下すると共にエネルギー密度が低下するという問題があった。
本発明は、負極の活物質としてＳｉ又はＳｉ合金を用い、正極と負極との間にセパレータを介在させて扁平状に巻いた扁平電極体を非水電解質と一緒に電池容器内に収容させたリチウム二次電池における上記のような問題を解決することを課題とするものであり、充放電により扁平電極体の平面部に撓みが生じて電池の厚みが増加するのを防止し、充放電特性に優れると共に高エネルギー密度のリチウム二次電池が得られるようにすることを課題とするものである。 In the present invention, Si or Si alloy is used as an active material for a negative electrode, and a flat electrode body wound in a flat shape with a separator interposed between the positive electrode and the negative electrode is housed in a battery container together with a nonaqueous electrolyte. An object of the present invention is to solve the above-mentioned problems in a lithium secondary battery, and charging / discharging prevents the flat portion of the flat electrode body from being bent to increase the thickness of the battery, and charge / discharge characteristics. It is an object of the present invention to obtain a lithium secondary battery having excellent energy efficiency and high energy density.
本発明においては、上記のような課題を解決するため、活物質にＳｉ又はＳｉ合金を含む負極を用い、正極とこの負極との間にセパレータを介在させて扁平状に巻いた扁平電極体を非水電解質と一緒に電池容器内に収容させたリチウム二次電池において、少なくともこのリチウム二次電池の最初の充放電時に上記の扁平電極体における平面部に１．０×１０4Ｎ／ｍ2以上の圧力が作用するようにしたのである。 In the present invention, in order to solve the above-described problems, a flat electrode body that is wound in a flat shape using a negative electrode containing Si or a Si alloy as an active material and interposing a separator between the positive electrode and the negative electrode is provided. In a lithium secondary battery housed in a battery container together with a non-aqueous electrolyte, at least the flat portion of the flat electrode body has 1.0 × 10 4 N / m 2 at the time of the first charge / discharge of the lithium secondary battery. The above pressure is applied.
ここで、リチウム二次電池の最初の充放電時に、扁平電極体における平面部に１．０×１０4Ｎ／ｍ2以上の圧力を作用させるにあたっては、最初の充放電時にこのリチウム二次電池を押圧させるようにする他、この扁平電極体を収容させた電池容器の強度を高め、上記のように充放電時における膨張が大きいＳｉ又はＳｉ合金を含む負極を用いた扁平電極体が充放電時に膨張するのをこの電池容器により抑制して、扁平電極体の平面部に１．０×１０4Ｎ／ｍ2以上の圧力を作用させることができる。 Here, when applying a pressure of 1.0 × 10 4 N / m 2 or more to the flat portion of the flat electrode body during the first charge / discharge of the lithium secondary battery, the lithium secondary battery is used during the first charge / discharge. In addition to increasing the strength of the battery container in which the flat electrode body is housed, the flat electrode body using the negative electrode containing Si or Si alloy having a large expansion during charge / discharge as described above is charged / discharged. The battery container can be prevented from expanding at times, and a pressure of 1.0 × 10 4 N / m 2 or more can be applied to the flat portion of the flat electrode body.
また、上記のようにリチウム二次電池の最初の充放電時に扁平電極体の平面部に圧力を作用させるにあたり、充放電により扁平電極体に撓みなどを一層抑制するためには、扁平電極体の平面部に作用させる圧力を２．０×１０4Ｎ／ｍ2以上にすることが好ましい。 In addition, in order to further suppress the bending of the flat electrode body due to charge / discharge when the pressure is applied to the flat portion of the flat electrode body during the first charge / discharge of the lithium secondary battery as described above, It is preferable that the pressure applied to the flat portion is 2.0 × 10 4 N / m 2 or more.
ここで、本発明のリチウム二次電池において使用する非水電解質は特に限定されず、一般に使用されているものを用いることかでき、例えば、非水系溶媒に溶質を溶解させた非水電解液や、ポリエチレンオキシド，ポリアクリロニトリル等のポリマー電解質に上記の非水電解液を含浸させたゲル状ポリマー電解質などを用いることができる。 Here, the nonaqueous electrolyte used in the lithium secondary battery of the present invention is not particularly limited, and any commonly used one can be used. For example, a nonaqueous electrolyte obtained by dissolving a solute in a nonaqueous solvent, Further, a gel polymer electrolyte obtained by impregnating the above-described non-aqueous electrolyte into a polymer electrolyte such as polyethylene oxide or polyacrylonitrile can be used.
また、上記の非水系溶媒についても特に限定されず、一般に使用されているものを用いることかでき、例えば、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート等の環状カーボネートと、ジメチルカーボネート、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の混合溶媒や、環状カーボネートと１，２−ジメトキシエタン、１，２−ジエトキシエタン等のエーテル系溶媒との混合溶媒を使用することができる。 Further, the above non-aqueous solvent is not particularly limited, and those commonly used can be used. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl A mixed solvent of a chain carbonate such as carbonate or a mixed solvent of a cyclic carbonate and an ether solvent such as 1,2-dimethoxyethane or 1,2-diethoxyethane can be used.
また、上記の溶質についても特に限定されず、一般に使用されているものを用いることができ、例えば、ＬｉＰＦ6，ＬｉＢＦ4，ＬｉＣＦ3ＳＯ3，ＬｉＮ（ＣＦ3ＳＯ2）2，ＬｉＮ（Ｃ2Ｆ5ＳＯ2）2，ＬｉＮ（ＣＦ3ＳＯ2）（Ｃ4Ｆ9ＳＯ2），ＬｉＣ（ＣＦ3ＳＯ2）3，ＬｉＣ（Ｃ2Ｆ5ＳＯ2）3，ＬｉＡｓＦ6，ＬｉＣｌＯ4，Ｌｉ2Ｂ10Ｃｌ10，Ｌｉ2Ｂ12Ｃｌ12や、これらの混合物等を用いることができる。 Further, the solute is not particularly limited, and those commonly used can be used. For example, LiPF 6 , LiBF 4 , 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, LiAsF 6, LiClO 4, Li 2 B 10 Cl 10 , Li 2 B 12 Cl 12 , a mixture thereof, or the like can be used.
また、正極に使用する正極活物質についても特に限定されず、一般に使用されているものを用いることができ、例えば、ＬｉＣｏＯ2，ＬｉＮｉＯ2，ＬｉＭｎ2Ｏ4，ＬｉＭｎＯ2，ＬｉＣｏ0.5Ｎｉ0.5Ｏ2，ＬｉＮｉ0.7Ｃｏ0.2Ｍｎ0.1Ｏ2等のリチウム含有遷移金属酸化物や、ＭｎＯ2などのリチウムを含有していない金属酸化物等を用いることができる。
Further, there is no particular limitation on the positive electrode active material used in the positive electrode, in general there can be used those which are used, for example, LiCoO 2, LiNiO 2, LiMn 2 O 4, LiMnO 2, LiCo 0.5 Ni 0.5
また、上記のリチウム二次電池における電池容器としては、その厚みを厚くしなくても充分な強度を有し、上記のように充放電により扁平電極体の平面部に撓みが生じて変形するのを防止すると共に、電池の体積密度が低下しないようにするため、その材質として、ヤング率が１．０×１０11Ｎ／ｍ2以上の強度を有するものを用いることが好ましく、このような材質としてはステンレス鋼などが挙げられる。 In addition, the battery container in the lithium secondary battery has sufficient strength without increasing its thickness, and the flat portion of the flat electrode body is bent and deformed by charging and discharging as described above. In addition, it is preferable to use a material having a Young's modulus having a strength of 1.0 × 10 11 N / m 2 or more, in order to prevent the volume density of the battery from decreasing. Examples include stainless steel.
本発明においては、活物質にＳｉ又はＳｉ合金を含む負極を用い、正極とこの負極との間にセパレータを介在させて扁平状に巻いた扁平電極体を非水電解質と一緒に電池容器内に収容させたリチウム二次電池に対して、少なくとも最初の充放電時に、上記の扁平電極体における平面部に１．０×１０4Ｎ／ｍ2以上の圧力を作用させるようにしたため、この最初の充放電によってＳｉの膨張収縮が生じるが、上記の圧力により扁平電極体の変形が規制されて、扁平電極体の平面部に撓みが生じるのが防止されるようになる。 In the present invention, a negative electrode containing Si or Si alloy as an active material is used, and a flat electrode body that is wound in a flat shape with a separator interposed between the positive electrode and the negative electrode is placed in a battery container together with a nonaqueous electrolyte. With respect to the accommodated lithium secondary battery, a pressure of 1.0 × 10 4 N / m 2 or more is applied to the flat portion of the flat electrode body at least during the first charge / discharge. Although charging and discharging cause expansion and contraction of Si, the deformation of the flat electrode body is restricted by the above pressure, and the flat portion of the flat electrode body is prevented from being bent.
そして、このように最初の充放電時に扁平電極体の変形が規制されることにより、扁平電極体がこの状態で維持されるようになり、その後、圧力を解除して充放電を行っても、扁平電極体が大きく変形することがなく、扁平電極体の平面部に撓みが生じてリチウム二次電池の厚みが増加するのが防止されるようになり、充放電特性に優れると共に高エネルギー密度のリチウム二次電池が得られるようになる。 And by controlling the deformation of the flat electrode body at the time of the first charge and discharge in this way, the flat electrode body will be maintained in this state, and after that, even if the charge is released by releasing the pressure, The flat electrode body is not greatly deformed, the flat portion of the flat electrode body is prevented from being bent and the thickness of the lithium secondary battery is prevented from increasing, and it has excellent charge / discharge characteristics and high energy density. A lithium secondary battery can be obtained.
以下、この発明に係るリチウム二次電池について実施例を挙げて具体的に説明すると共に、この実施例に係るリチウム二次電池においては、充放電によってその厚みが増加するのが防止されて、充放電特性やエネルギー密度が向上することを、比較例を挙げて明らかにする。なお、本発明のリチウム二次電池は下記の実施例に示したものに限定されるものではなく、その要旨を変更しない範囲において適宜変更して実施できるものである。 Hereinafter, the lithium secondary battery according to the present invention will be described in detail with reference to examples, and in the lithium secondary battery according to this example, the thickness is prevented from increasing due to charging / discharging. A comparative example will clarify that the discharge characteristics and energy density are improved. The lithium secondary battery of the present invention is not limited to those shown in the following examples, and can be implemented with appropriate modifications within a range that does not change the gist thereof.
（実施例１，２及び比較例１）
実施例１，２及び比較例１においては、下記のようにして作製した負極と正極と非水電解液とを用いるようにした。
(Examples 1 and 2 and Comparative Example 1)
In Examples 1 and 2 and Comparative Example 1, a negative electrode, a positive electrode, and a non-aqueous electrolyte prepared as described below were used.
［負極の作製］
負極の活物質として平均粒径が１５μｍのケイ素粉末（純度９９．９％）を用いると共に、バインダーとしてガラス転移温度が１９０℃，密度が１．１ｇ／ｃｍ3の熱可塑性ポリイミドを用い、上記の活物質とバインダーとが９０：１０の重量比になるように分散媒のＮ−メチル−２−ピロリドンに混合させて、負極合剤スラリーを調製した。
[Production of negative electrode]
A silicon powder (purity 99.9%) having an average particle diameter of 15 μm is used as the negative electrode active material, and a thermoplastic polyimide having a glass transition temperature of 190 ° C. and a density of 1.1 g / cm 3 is used as the binder. The active material and the binder were mixed with N-methyl-2-pyrrolidone as a dispersion medium so that the weight ratio was 90:10 to prepare a negative electrode mixture slurry.
次いで、この負極合剤スラリーを、表面粗さＲａが０．３μｍ，厚みが２０μｍのＣｕ−Ｎｉ−Ｓｉ−Ｍｇ（Ｎｉ：３ｗｔ％，Ｓｉ：０．６５ｗｔ％，Ｍｇ：０．１５ｗｔ％）合金箔からなる負極集電体の両面に塗布し、これを乾燥させ、負極集電体上に５．６ｍｇ／ｃｍ2の負極合剤層を形成した後、これを３８０ｍｍ×５２ｍｍの長方形状に切り抜き、圧延した後、アルゴン雰囲気中において４００℃で１０時間熱処理して負極を作製した。 Next, this negative electrode mixture slurry was made of a Cu—Ni—Si—Mg (Ni: 3 wt%, Si: 0.65 wt%, Mg: 0.15 wt%) alloy having a surface roughness Ra of 0.3 μm and a thickness of 20 μm. This was applied to both sides of a negative electrode current collector made of foil, dried, and a negative electrode mixture layer of 5.6 mg / cm 2 was formed on the negative electrode current collector. Then, this was cut into a rectangular shape of 380 mm × 52 mm After rolling, a negative electrode was produced by heat treatment at 400 ° C. for 10 hours in an argon atmosphere.
そして、この負極の端部に、厚みが７０μｍ，長さが３５ｍｍ，幅が４ｍｍのニッケル平板からなる負極集電タブをぐさり法により取り付けた。 And the negative electrode current collection tab which consists of a nickel flat plate whose thickness is 70 micrometers, length is 35 mm, and width is 4 mm was attached to the edge part of this negative electrode by the spotting method.
［正極の作製］
正極の活物質として、平均粒径が１３μｍ，ＢＥＴ比表面積が０．３５ｍ2／ｇのＬｉＣｏＯ2粉末と、平均粒径が１１μｍ，ＢＥＴ比表面積が０．５０ｍ2／ｇのＬｉＭｎ1/3Ｎｉ1/3Ｃｏ1/3Ｏ2粉末とを、７０：３０の重量比になるように混合させたものを用いた。
[Production of positive electrode]
As an active material for the positive electrode, the average particle diameter of 13 .mu.m, and LiCoO 2 powder having a BET specific surface area of 0.35 m 2 / g, an average particle diameter of 11 [mu] m, LiMn 1/3 Ni of BET specific surface area of 0.50 m 2 / g a 1/3 Co 1/3 O 2 powder, 70: was used by mixing such that the 30 weight ratio of.
そして、上記の活物質粉末と、導電剤の炭素材料粉末と、バインダーのポリフッ化ビニリデンとを、９４：３：３の重量比になるようにして、分散媒のＮ−メチル−２−ピロリドンに加え、これを混練して正極合剤スラリー調製した。 Then, the active material powder, the carbon material powder of the conductive agent, and the polyvinylidene fluoride as the binder are made to have a weight ratio of 94: 3: 3 to the dispersion medium N-methyl-2-pyrrolidone. In addition, this was kneaded to prepare a positive electrode mixture slurry.
次いで、この正極合剤スラリーを、厚みが１５μｍ，長さが４０２ｍｍ，幅が５０ｍｍのアルミニウム箔からなる正極集電体の片面に、長さ３４０ｍｍ，幅５０ｍｍの範囲で塗布すると共に、この正極集電体の反対側の面に、長さ２７１ｍｍ，幅５０ｍｍの範囲で塗布し、これを乾燥させて圧延し、正極集電体上に４８ｍｇ／ｃｍ2の正極合剤層が形成された正極を作製した。 Next, this positive electrode mixture slurry was applied to one side of a positive electrode current collector made of an aluminum foil having a thickness of 15 μm, a length of 402 mm, and a width of 50 mm within a range of 340 mm in length and 50 mm in width. A positive electrode in which a positive electrode mixture layer of 48 mg / cm 2 is formed on a positive electrode current collector is coated on the opposite surface of the electric body in a range of 271 mm in length and 50 mm in width, dried and rolled. Produced.
そして、この正極において、正極合剤層が設けられていない正極集電体の部分に、厚み７０μｍ，長さ３５ｍｍ，幅４ｍｍのアルミニウム平板からなる正極集電タブを超音波溶着法により取り付けた。 And in this positive electrode, the positive electrode current collection tab which consists of an aluminum flat plate of thickness 70micrometer, length 35mm, and width 4mm was attached to the part of the positive electrode electrical power collector in which the positive mix layer was not provided by the ultrasonic welding method.
［非水電解液の作製］
非水電解液を作製するにあたっては、エチレンカーボネートとジエチルカーボネートとフルオロエチレンカーボネートとを２：８：１の体積比で混合させた混合溶媒に、溶質として、ＬｉＰＦ6とＬｉＢＦ4とをそれぞれ０．５モル／リットル溶解させて非水電解液を作製した。
[Preparation of non-aqueous electrolyte]
In preparing the non-aqueous electrolyte, LiPF 6 and LiBF 4 were each added as a solute in a mixed solvent in which ethylene carbonate, diethyl carbonate, and fluoroethylene carbonate were mixed at a volume ratio of 2: 8: 1. A non-aqueous electrolyte was prepared by dissolving 5 mol / liter.
そして、リチウム二次電池を作製するにあたっては、厚みが２２μｍ，長さが４３０ｍｍ，幅が５４．５ｍｍのポリエチレン多孔質体からなるセパレータを２枚使用し、図１（Ａ），（Ｂ）に示すように、上記の正極１と負極２とが上記のセパレータ３を介して対向するようにして、これらを所定の折り曲げ位置において折り曲げ、正極１に設けられた正極集電タブ１ａ及び負極２に設けられた負極集電タブ２ａがそれぞれ最外周に位置するように捲回して扁平電極体１０を作製した。なお、この扁平電極体１０においては、その厚みＹが２．５ｍｍ、幅Ｚが５４．５ｍｍになっており、また平面部の長さＸは３０ｍｍ、平面部の実質的な幅は、正極１と負極２とが対向する部分の幅で、実質的には正極１の幅である５０ｍｍになっている。
In producing a lithium secondary battery, two separators made of a polyethylene porous body having a thickness of 22 μm, a length of 430 mm, and a width of 54.5 mm were used, as shown in FIGS. 1 (A) and 1 (B). As shown in the figure, the
次いで、図２に示すように、上記の扁平電極体１０をアルミニウムラミネートフィルムで構成された電池容器２０内に収容させると共に、この電池容器２０内に上記の非水電解液を加え、その後、上記の正極集電タブ１ａと負極集電タブ２ａとを外部に取り出すようにして、上記の電池容器２０の開口部を封口させて、リチウム二次電池を作製した。
Next, as shown in FIG. 2, the
そして、実施例１，２及び比較例１においては、上記のように作製したリチウム二次電池を充放電させるにあたり、上記の扁平電極体１０の実質的な平面部である３０ｍｍ×５０ｍｍの大きさの部分に対して、実施例１では６．７×１０4Ｎ／ｍ2の圧力を、実施例２では２．４×１０4Ｎ／ｍ2の圧力を、比較例１では２．４×１０Ｎ／ｍ2の圧力を作用させた状態で、それぞれ２５℃において、電流値２００ｍＡで４．３Ｖまで充電させ、さらに４．３Ｖに保持したまま電流値が５０ｍＡになるまで充電させた後、電流値２００ｍＡで２．７５Ｖまで放電させて、１サイクルの充放電を行った。
In Examples 1 and 2 and Comparative Example 1, when charging and discharging the lithium secondary battery produced as described above, a size of 30 mm × 50 mm, which is a substantially flat portion of the
そして、上記のように１サイクルの充放電を行った後、実施例１，２及び比較例１の各リチウム二次電池の厚みを測定し、充放電を行う前の上記のリチウム二次電池の厚みを基準の１００として、１サイクル後における実施例１，２及び比較例１の各リチウム二次電池の厚みを算出し、その結果を下記の表１に示した。 And after charging / discharging 1 cycle as mentioned above, the thickness of each lithium secondary battery of Examples 1, 2 and Comparative Example 1 is measured, and the lithium secondary battery before charging / discharging is performed. The thickness of each of the lithium secondary batteries of Examples 1 and 2 and Comparative Example 1 after one cycle was calculated with the thickness as 100, and the results are shown in Table 1 below.
また、上記の１サイクルの充放電を行った後、実施例１のものにおいては、上記の場合と同様に、扁平電極体１０の実質的な平面部である３０ｍｍ×５０ｍｍの大きさの部分に対して６．７×１０4Ｎ／ｍ2の圧力を作用させる一方、実施例２及び比較例１のものにおいては、上記の圧力を作用させないようにして、上記の充放電を１００サイクル行い、実施例１，２及び比較例１の各リチウム二次電池の１００サイクル後の厚みを測定し、充放電を行う前の上記のリチウム二次電池の厚みを基準の１００として、実施例１，２及び比較例１の各リチウム二次電池の１００サイクル後の厚みを算出し、その結果を下記の表１に示した。
In addition, after charging and discharging for one cycle as described above, in the case of Example 1, as in the above case, the portion of the
また、実施例１，２及び比較例１の各リチウム二次電池について、上記のように１００サイクルの充放電を行った時点おける放電容量維持率を算出し、その結果を下記の表１に示した。 Further, for each of the lithium secondary batteries of Examples 1 and 2 and Comparative Example 1, the discharge capacity retention rate at the time when 100 cycles of charge and discharge were performed as described above was calculated, and the results are shown in Table 1 below It was.
この結果、少なくとも１サイクルの充放電時において、扁平電極体の実質的な平面部に対して１．０Ｎ×１０4Ｎ／ｍ2以上の圧力を作用させるようにした実施例１，２の各リチウム二次電池においては、扁平電極体の実質的な平面部に対して作用させる圧力が１．０Ｎ×１０4Ｎ／ｍ2未満になった比較例１のリチウム二次電池に比べて、１サイクル後及び１００サイクル後における厚みの増加が大幅に少なくなっていると共に、１００サイクル後における放電容量維持率も大きく向上しており、充放電特性及びエネルギー密度が大幅に改善された。 As a result, each of Examples 1 and 2 in which a pressure of 1.0 N × 10 4 N / m 2 or more was applied to a substantially flat portion of the flat electrode body at the time of charge / discharge of at least one cycle. Compared to the lithium secondary battery of Comparative Example 1 in which the pressure applied to the substantially flat portion of the flat electrode body is less than 1.0 N × 10 4 N / m 2 in the lithium secondary battery, The increase in thickness after the cycle and after the 100th cycle was significantly reduced, and the discharge capacity retention rate after the 100th cycle was also greatly improved, and the charge / discharge characteristics and energy density were greatly improved.
また、実施例１，２のリチウム二次電池を比較した場合、扁平電極体の実質的な平面部に対して６．７Ｎ×１０4Ｎ／ｍ2の強い圧力を各充放電サイクル時に作用させた実施例１のリチウム二次電池においては、１サイクル後及び１００サイクル後における厚みの増加がさらに少なくなると共に、１００サイクル後における放電容量維持率も大きくなっていたが、実施例２のリチウム二次電池のように、１サイクル目の充放電時にだけ、扁平電極体の実質的な平面部に対して２．４Ｎ×１０4Ｎ／ｍ2の圧力を作用させた場合においても、１００サイクル後における厚みの増加が少なくなっていると共に、１００サイクル後における放電容量維持率も大きくなっていた。これは、１サイクル目の充放電時に扁平電極体の変形が規制されることにより、その後、圧力を解除して充放電を行っても、扁平電極体がこの状態で維持されるようになるためであると考えられる。 Further, when comparing the lithium secondary batteries of Examples 1 and 2, a strong pressure of 6.7 N × 10 4 N / m 2 was applied to each substantially flat portion of the flat electrode body during each charge / discharge cycle. In the lithium secondary battery of Example 1, the increase in thickness after 1 cycle and after 100 cycles was further reduced, and the discharge capacity retention rate after 100 cycles was also increased. Even when a pressure of 2.4 N × 10 4 N / m 2 is applied to the substantially flat portion of the flat electrode body only at the time of charge / discharge at the first cycle as in the secondary battery, after 100 cycles In addition, the increase in the thickness was reduced, and the discharge capacity retention rate after 100 cycles was also increased. This is because the deformation of the flat electrode body is restricted at the time of charge / discharge in the first cycle, so that the flat electrode body is maintained in this state even after the pressure is released and the charge / discharge is performed. It is thought that.
１ 正極
１ａ 正極集電タブ
２ 負極
２ａ 負極集電タブ
３ セパレータ
１０ 扁平電極体
２０ 電池容器
Ｘ 扁平電極体の平面部の長さ
Ｙ 扁平電極体の厚み
Ｚ 扁平電極体の幅
DESCRIPTION OF
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| CN110249473A (en) * | 2017-02-24 | 2019-09-17 | 三洋电机株式会社 | Non-aqueous electrolyte secondary battery |
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| JP2009266761A (en) * | 2008-04-30 | 2009-11-12 | Panasonic Corp | Nonaqueous electrolyte secondary battery and its manufacturing method |
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