JP2001283833A - Secondary battery - Google Patents
Secondary batteryInfo
- Publication number
- JP2001283833A JP2001283833A JP2000100406A JP2000100406A JP2001283833A JP 2001283833 A JP2001283833 A JP 2001283833A JP 2000100406 A JP2000100406 A JP 2000100406A JP 2000100406 A JP2000100406 A JP 2000100406A JP 2001283833 A JP2001283833 A JP 2001283833A
- Authority
- JP
- Japan
- Prior art keywords
- active material
- material layer
- secondary battery
- negative electrode
- electrode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Links
Classifications
-
- 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
Landscapes
- Carbon And Carbon Compounds (AREA)
- Cell Electrode Carriers And Collectors (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、リチウム二次電池
等の二次電池に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery such as a lithium secondary battery.
【０００２】[0002]
【従来の技術】リチウム金属を負極として用いたリチウ
ム二次電池は、そのエネルギー密度が大きいことから、
次世代の二次電池として注目されている。しかしなが
ら、リチウム金属を負極に用いるため、充放電に伴って
リチウム金属の溶解析出が生じ、デンドライトの生成や
電極の変形が生じる。このため、サイクル性能が劣悪で
あり、実用化に耐え得るものはできていない。このよう
な問題を解決し得るものとして、Ｌｉと合金化する金属
を用いたＬｉ合金負極や、黒鉛などの炭素材料を用いた
炭素負極が提案されており、炭素負極を用いたものは一
部実用化されている。2. Description of the Related Art A lithium secondary battery using lithium metal as a negative electrode has a high energy density.
It is attracting attention as a next-generation secondary battery. However, since lithium metal is used for the negative electrode, the dissolution and deposition of lithium metal occurs with charging and discharging, which causes dendrite generation and electrode deformation. For this reason, the cycle performance is inferior, and there is no product that can withstand practical use. As a solution to such a problem, a Li alloy negative electrode using a metal alloying with Li and a carbon negative electrode using a carbon material such as graphite have been proposed. Has been put to practical use.
【０００３】しかしながら、炭素負極はその理論容量が
３７２ｍＡｈ／ｇと低いため、金属リチウムを負極に用
いた場合に比べて、大幅にエネルギー密度が低下すると
いう欠点がある。また、Ｌｉ合金負極を用いた場合に
は、充放電に伴い体積の膨張と収縮が繰り返されるた
め、充放電サイクルが進むにつれて活物質粒子が微粉化
し、サイクル性能が悪くなるという欠点があった。However, since the theoretical capacity of the carbon anode is low at 372 mAh / g, there is a disadvantage that the energy density is greatly reduced as compared with the case where lithium metal is used for the anode. In addition, when a Li alloy negative electrode is used, the volume expansion and contraction are repeated with charge / discharge, so that the active material particles become finer as the charge / discharge cycle progresses, and the cycle performance deteriorates.
【０００４】一方、リチウム二次電池を用いる応用機器
においては、より一層のエネルギー密度の向上が要求さ
れており、黒鉛負極を用いたリチウム二次電池と同等以
上のサイクル性能と、より一層の高エネルギー密度を有
するリチウム二次電池が要望されている。On the other hand, in the application equipment using a lithium secondary battery, further improvement in energy density is required, and the cycle performance is equal to or higher than that of a lithium secondary battery using a graphite negative electrode, and further higher performance is required. There is a demand for a lithium secondary battery having an energy density.
【０００５】そこで、黒鉛に比べて非常に大きな容量を
有するケイ素粉末を、黒鉛粉末と混合した負極が提案さ
れている。これは、ケイ素粉末の有する大きな容量と、
黒鉛の優れたサイクル性能を兼ね備えることを目的とす
るものである。Accordingly, a negative electrode has been proposed in which silicon powder having a much larger capacity than graphite is mixed with graphite powder. This is due to the large capacity of silicon powder and
The purpose is to combine the excellent cycle performance of graphite.
【０００６】[0006]
【発明が解決しようとする課題】しかしながら、ケイ素
粉末は、上述のようにリチウムとの合金化によりリチウ
ムを吸蔵及び放出する活物質であるので、黒鉛粉末と混
合して用いた場合にも、充放電サイクルに伴い微粉化が
進行し、集電体から活物質が剥離するため、電極全体の
サイクル性能は劣ったものとなり、実用性を有するもの
ではなかった。However, since silicon powder is an active material that absorbs and releases lithium by alloying with lithium as described above, it is not charged even when used in a mixture with graphite powder. Since the pulverization progressed with the discharge cycle and the active material was separated from the current collector, the cycle performance of the entire electrode was inferior and was not practical.
【０００７】本発明の目的は、充放電時の膨張収縮によ
る集電体からの活物質の剥離を防止することができ、優
れたサイクル特性を得ることができる二次電池を提供す
ることにある。An object of the present invention is to provide a secondary battery which can prevent the active material from peeling off from the current collector due to expansion and contraction at the time of charging and discharging, and can obtain excellent cycle characteristics. .
【０００８】[0008]
【課題を解決するための手段】本発明の二次電池は、Ｌ
ｉと合金化しない材料からなる集電体の上に、炭素から
なる第１の活物質層を設け、該第１の活物質層の上にＬ
ｉと合金化する金属または半導体からなる第２の活物質
層を設けた電極を用いることを特徴としている。The secondary battery according to the present invention has an L
A first active material layer made of carbon is provided on a current collector made of a material that does not alloy with i, and L is placed on the first active material layer.
An electrode provided with a second active material layer made of a metal or a semiconductor that is alloyed with i is used.
【０００９】本発明の上記電極においては、上記第２活
物質層の上に、さらに第１の活物質層が設けられていて
もよい。すなわち、集電体の上に、第１の活物質層／第
２の活物質層／第１の活物質層の３層構造の活物質層が
設けられていてもよい。さらに、本発明の上記電極にお
いては、上記第２活物質層の上に、第１の活物質層及び
第２の活物質層がこの順序で交互に繰り返し積層されて
いてもよい。すなわち、集電体の上に、第１の活物質層
／第２の活物質層／第１の活物質層／第２の活物質層の
ように第１の活物質層と第２の活物質層からなる繰り返
しの積層構造が形成されていてもよい。In the above electrode of the present invention, a first active material layer may be further provided on the second active material layer. That is, an active material layer having a three-layer structure of first active material layer / second active material layer / first active material layer may be provided over the current collector. Further, in the electrode of the present invention, a first active material layer and a second active material layer may be alternately and repeatedly stacked in this order on the second active material layer. That is, the first active material layer and the second active material layer such as a first active material layer / a second active material layer / a first active material layer / a second active material layer are formed on the current collector. A repeated laminated structure composed of the material layers may be formed.
【００１０】本発明の第２の活物質層に用いる活物質
は、Ｌｉと合金化する金属または半導体から形成された
ものであれば特に限定されないが、大きな電極容量を得
るという観点からは、Ｓｉ、Ｇｅ、Ｓｎ、Ａｌ、及びＩ
ｎなどが好ましく用いられる。これらの中でも、Ｓｉ及
びＧｅは、特に高い容量を有しており、Ｌｉ4.4Ｓｉ及
びＬｉ4.4Ｇｅの組成までＬｉを吸蔵することが可能で
あるので、特に好ましく用いられる。また、Ｓｉ−Ｇｅ
合金も高い容量を有しており、同様に好ましく用いられ
る。The active material used for the second active material layer of the present invention is not particularly limited as long as it is formed of a metal or a semiconductor that can be alloyed with Li. , Ge, Sn, Al, and I
n and the like are preferably used. Among them, Si and Ge are particularly preferably used because they have particularly high capacities and can store Li up to the composition of Li 4.4 Si and Li 4.4 Ge. In addition, Si-Ge
Alloys also have a high capacity and are likewise preferably used.
【００１１】また、第２の活物質層は、気相から堆積さ
せた薄膜であることが好ましい。これらの薄膜は、ＣＶ
Ｄ法、スパッタリング法、及び蒸着法などの気相からの
薄膜形成法により形成することができる。The second active material layer is preferably a thin film deposited from a gas phase. These thin films are CV
It can be formed by a method of forming a thin film from a gas phase such as a D method, a sputtering method, and a vapor deposition method.
【００１２】Ｓｉ薄膜は、微結晶Ｓｉ薄膜または非晶質
Ｓｉ薄膜であることが好ましい。微結晶Ｓｉ薄膜は、ラ
マン分光分析において、結晶領域に対応する５２０ｃｍ
-1近傍のピークと、非晶質領域に対応する４８０ｃｍ-1
近傍のピークの両方が実質的に検出されるＳｉ薄膜であ
る。また、非晶質Ｓｉ薄膜は、ラマン分光分析におい
て、結晶領域に対応する５２０ｃｍ-1近傍のピークは実
質的に検出されず、非晶質領域に対応する４８０ｃｍ-1
のピークが実質的に検出されるＳｉ薄膜である。また、
Ｇｅ薄膜及びＳｉ−Ｇｅ合金薄膜は、いずれも非晶質薄
膜であることが好ましい。The Si thin film is preferably a microcrystalline Si thin film or an amorphous Si thin film. The microcrystalline Si thin film has a size of 520 cm corresponding to the crystal region in Raman spectroscopy.
-1 peak and 480 cm -1 corresponding to the amorphous region.
Both of the nearby peaks are Si thin films that are substantially detected. In the amorphous Si thin film, a peak near 520 cm −1 corresponding to the crystalline region was not substantially detected in the Raman spectroscopic analysis, and 480 cm −1 corresponding to the amorphous region was not detected.
Is a Si thin film in which the peak is substantially detected. Also,
Both the Ge thin film and the Si—Ge alloy thin film are preferably amorphous thin films.
【００１３】本発明において第１の活物質層に用いる炭
素材料は、リチウム二次電池において負極として用いる
ことができる炭素材料であれば特に限定されるものでは
なく、例えば、天然黒鉛、人造黒鉛、カーボンブラッ
ク、活性炭、カーボンファイバー、コークス、有機前駆
体を不活性雰囲気中で熱処理して合成した炭素、あるい
はダイヤモンドライクカーボン（ＤＬＣ）などが挙げら
れる。黒鉛としては、層間距離ｄが３．３７Å以下、積
層方向の結晶子寸法Ｌｃが３００Å以上の黒鉛が好まし
く用いられる。In the present invention, the carbon material used for the first active material layer is not particularly limited as long as it can be used as a negative electrode in a lithium secondary battery. For example, natural graphite, artificial graphite, Examples include carbon black, activated carbon, carbon fiber, coke, carbon synthesized by heat-treating an organic precursor in an inert atmosphere, or diamond-like carbon (DLC). As the graphite, graphite having an interlayer distance d of 3.37 ° or less and a crystallite size Lc in the stacking direction of 300 ° or more is preferably used.
【００１４】本発明における集電体は、Ｌｉと合金化し
ない材料であって、高い導電性を有するものであれば特
に限定されないが、銅箔等の金属箔が好ましく用いられ
る。本発明によれば、炭素からなる第１の活物質層の上
に、Ｌｉと合金化する金属または半導体からなる第２の
活物質層が設けられる。第２の活物質層は、Ｌｉを吸蔵
・放出することにより膨張収縮するが、その下地層であ
る第１の活物質層も、同様にＬｉの吸蔵・放出により膨
張収縮するので、第２の活物質層の剥離を防止すること
ができ、サイクル性能を高めることができる。The current collector in the present invention is not particularly limited as long as it is a material that does not alloy with Li and has high conductivity, but a metal foil such as a copper foil is preferably used. According to the present invention, the second active material layer made of a metal or a semiconductor that alloys with Li is provided on the first active material layer made of carbon. The second active material layer expands and contracts by occluding and releasing Li. However, the first active material layer, which is the underlying layer, similarly expands and contracts by occluding and releasing Li. Separation of the active material layer can be prevented, and cycle performance can be improved.
【００１５】本発明において、さらに好ましくは、第２
の活物質層の充放電時における膨張収縮率と、第１の活
物質層の充放電時おける膨張収縮率とがほぼ同じになる
ように調整される。例えば、第１の活物質層及び第２の
活物質層のそれぞれの厚みを調整することにより、この
ような調整が可能である。In the present invention, more preferably, the second
The expansion and contraction rate of the first active material layer during charge and discharge is adjusted to be substantially the same as the expansion and contraction rate of the first active material layer during charge and discharge. For example, such adjustment is possible by adjusting the thickness of each of the first active material layer and the second active material layer.
【００１６】本発明において、上記電極は、負極として
用いてもよいし、正極として用いてもよいが、一般には
負極として用いられる。この場合の正極としては、特に
制限されるものではないが、従来からリチウム二次電池
の正極として用いられているものを用いることができ
る。このような正極活物質としては、ＬｉＣｏＯ2 、Ｌ
ｉＮｉＯ2 、ＬｉＭｎ2Ｏ4 、ＬｉＭｎＯ2 、ＬｉＣｏ
0.5Ｎｉ0.5Ｏ2 、ＬｉＮｉ0.7Ｃｏ0.2Ｍｎ0.1Ｏ2 など
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が例示される。また、
この他にも、リチウムを電気化学的に挿入・脱離する物
質であれば、制限なく用いることができる。In the present invention, the electrode is used as a negative electrode
May be used, or may be used as a positive electrode, but generally,
Used as a negative electrode. As the positive electrode in this case,
Although not limited, conventional lithium secondary batteries
Can be used as the positive electrode of
You. As such a positive electrode active material, LiCoOTwo, L
iNiOTwo, LiMnTwoOFour, LiMnOTwo , LiCo
0.5Ni0.5OTwo, LiNi0.7Co0.2Mn0.1OTwoSuch
Lithium-containing transition metal oxides and MnOTwoSuch as Richi
An example is a metal oxide containing no metal. Also,
Other materials that insert and remove lithium electrochemically
Any quality can be used without restriction.
【００１７】本発明の二次電池に用いる電解質の溶媒
は、特に限定されるものではないが、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
などの環状カーボネートと、ジメチルカーボネート、メ
チルエチルカーボネート、ジエチルカーボネートなどの
鎖状カーボネートとの混合溶媒が例示される。また、前
記環状カーボネートと１，２−ジメトキシエタン、１，
２−ジエトキシエタンなどのエーテル系溶媒との混合溶
媒も例示される。また、電解質の溶質としては、ＬｉＰ
Ｆ6 、ＬｉＢＦ4 、ＬｉＣＦ3ＳＯ3 、ＬｉＮ（ＣＦ3Ｓ
Ｏ2)2 、ＬｉＮ（Ｃ2Ｆ5ＳＯ2)2 、ＬｉＮ（ＣＦ3Ｓ
Ｏ2)(Ｃ4Ｆ9ＳＯ2)、ＬｉＣ（ＣＦ3ＳＯ2)3、ＬｉＣ
（Ｃ2Ｆ5ＳＯ2)3 など及びそれらの混合物が例示され
る。さらに電解質として、ポリエチレンオキシド、ポリ
アクリロニトリルなどのポリマー電解質に電解液を含浸
したゲル状ポリマー電解質や、ＬｉＩ、Ｌｉ3Ｎなどの
無機固体電解質が例示される。本発明の二次電池の電解
質は、イオン導電性を発現させる溶媒としてのＬｉ化合
物とこれを溶解・保持する溶媒が電池の充電時や放電時
あるいは保存時の電圧で分解しない限り、制約なく用い
ることができる。The solvent of the electrolyte used in the secondary battery of the present invention is not particularly limited, but a cyclic carbonate such as ethylene carbonate, propylene carbonate, butylene carbonate, and a solvent such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, etc. A mixed solvent with a chain carbonate is exemplified. Further, the cyclic carbonate and 1,2-dimethoxyethane,
A mixed solvent with an ether solvent such as 2-diethoxyethane is also exemplified. As a solute of the electrolyte, LiP
F 6 , LiBF 4 , LiCF 3 SO 3 , LiN (CF 3 S
O 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , LiN (CF 3 S
O 2 ) (C 4 F 9 SO 2 ), LiC (CF 3 SO 2 ) 3 , LiC
(C 2 F 5 SO 2 ) 3 and the like and mixtures thereof are exemplified. Examples of the electrolyte further include a gel polymer electrolyte obtained by impregnating an electrolyte with a polymer electrolyte such as polyethylene oxide and polyacrylonitrile, and an inorganic solid electrolyte such as LiI and Li 3 N. The electrolyte of the secondary battery of the present invention is used without limitation, as long as the Li compound as a solvent that develops ionic conductivity and the solvent that dissolves and retains the Li compound are not decomposed at the time of charging, discharging, or storing the battery. be able to.
【００１８】[0018]
【発明の実施の形態】以下、本発明を実施例に基づいて
さらに詳細に説明するが、本発明は以下の実施例に何ら
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することが可能なものである。BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in more detail with reference to examples. However, the present invention is not limited to the following examples, and may be appropriately modified within the scope of the invention. It can be implemented by
【００１９】（本発明電池Ａの作製） 〔負極第１活物質層の作製〕負極の第１の活物質層の活
物質として黒鉛（ｄ＜３．３７Å、Ｌｃ＞３００Å）を
用い、結着剤としてフッ素樹脂（ＰＶｄＦ）を用いて第
１の活物質層を作製した。フッ素樹脂の濃度が黒鉛＋フ
ッ素樹脂の全体の５重量％となるように、フッ素樹脂を
溶解したＮ−メチルピロリドン溶液に黒鉛を添加し、３
０分間らいかい機でらいかいしてスラリーを作製した。
このスラリーをドクターブレード法により、電解銅箔の
上に塗布、乾燥して第１の活物質層とした。第１の活物
質層の厚みは６０μｍであった。(Preparation of Battery A of the Present Invention) [Preparation of Negative Electrode First Active Material Layer] Graphite (d <3.37 °, Lc> 300 °) was used as the active material of the first active material layer of the negative electrode and bound. A first active material layer was formed using a fluororesin (PVdF) as an agent. Graphite is added to an N-methylpyrrolidone solution in which the fluororesin is dissolved so that the concentration of the fluororesin is 5% by weight of the total of the graphite and the fluororesin, and 3
The slurry was prepared using a trimmer for 0 minutes.
This slurry was applied on an electrolytic copper foil by a doctor blade method and dried to form a first active material layer. The thickness of the first active material layer was 60 μm.
【００２０】〔負極第２活物質層の作製〕原料ガスとし
てＳｉＨ4ガスを用い、キャリアガスとしてＨ2ガスを用
い、プラズマＣＶＤ法により、上記第１の活物質層の上
に、第２の活物質層としてシリコン薄膜を形成し、負極
を作製した。薄膜形成条件は、原料ガス流量：１０ｓｃ
ｃｍ、キャリアガス流量：２００ｓｃｃｍ、基板温度：
１８０℃、反応圧力：４０Ｐａ、高周波電力５５５Ｗと
した。形成されたシリコン薄膜の膜厚は２μｍであり、
ラマン分光分析により微結晶シリコン薄膜であることを
確認した。[Preparation of Negative Electrode Second Active Material Layer] Using a SiH 4 gas as a source gas and an H 2 gas as a carrier gas, a second CVD method is performed on the first active material layer by a plasma CVD method. A silicon thin film was formed as an active material layer to produce a negative electrode. The conditions for forming the thin film were as follows: source gas flow rate: 10 sc
cm, carrier gas flow rate: 200 sccm, substrate temperature:
The reaction pressure was 180 ° C., the reaction pressure was 40 Pa, and the high frequency power was 555 W. The thickness of the formed silicon thin film is 2 μm,
Raman spectroscopic analysis confirmed that the film was a microcrystalline silicon thin film.
【００２１】第１の活物質層中の黒鉛と第２の活物質層
であるシリコン薄膜との重量比は、８４：４．６であっ
た。なお、上記の実施例では、ＣＶＤ法によりシリコン
薄膜を形成しているが、スパッタリング法及び蒸着法な
どの他の薄膜形成法で形成してもよい。また、シリコン
粉末を結着剤を用いて塗布することによって第２の活物
質層を形成してもよい。The weight ratio of the graphite in the first active material layer to the silicon thin film as the second active material layer was 84: 4.6. In the above embodiment, the silicon thin film is formed by the CVD method, but may be formed by another thin film forming method such as a sputtering method and an evaporation method. Alternatively, the second active material layer may be formed by applying silicon powder using a binder.
【００２２】〔正極の作製〕正極活物質としてＬｉＣｏ
Ｏ2 を用い、結着剤としてフッ素樹脂（ＰＶｄＦ）を用
いて正極を作製した。具体的には、ＬｉＣｏＯ2粉末１
００ｇを、フッ素樹脂が５重量％となるように溶解した
Ｎ−メチルピロリドン溶液に混合し、３０分間らいかい
機でらいかいしてスラリーを作製した。このスラリーを
ドクターブレード法によって、厚み２０μｍのアルミニ
ウム箔上に塗布し、乾燥して正極を得た。[Preparation of positive electrode] LiCo as a positive electrode active material
A positive electrode was produced using O 2 and a fluororesin (PVdF) as a binder. Specifically, LiCoO 2 powder 1
00 g was mixed with a solution of N-methylpyrrolidone in which the fluororesin was dissolved at 5% by weight, and the mixture was stirred for 30 minutes using a mill to prepare a slurry. This slurry was applied on a 20 μm-thick aluminum foil by a doctor blade method, and dried to obtain a positive electrode.
【００２３】〔電池の作製〕上記負極と上記正極を、ポ
リプロピレン製セパレータを介して積層した後、巻き取
ることによって、電極群を作製した。この電極群を電池
缶に挿入した後、電解液を注入し、封口して電池を作製
した。なお、電解液としては、エチレンカーボネートと
ジエチルカーボネートとの等体積混合溶媒に、ＬｉＰＦ
6 を１モル／リットル溶解したものを用いた。[Preparation of Battery] The above-mentioned negative electrode and the above-mentioned positive electrode were laminated via a polypropylene separator, and then wound up to prepare an electrode group. After inserting this electrode group into a battery can, an electrolytic solution was injected and sealed, to prepare a battery. In addition, as an electrolytic solution, LiPF was mixed with an equal volume mixed solvent of ethylene carbonate and diethyl carbonate.
6 dissolved at 1 mol / liter was used.
【００２４】（本発明電池Ｂの作製） 〔下層の負極第１活物質層の作製〕第１の活物質層の厚
みを３０μｍとする以外は、上記本発明電池Ａにおける
負極第１活物質層と同様にして、下層の負極第１活物質
層を作製した。(Preparation of Battery B of the Present Invention) [Preparation of Lower Electrode First Active Material Layer] Negative electrode first active material layer of Battery A of the present invention except that the thickness of the first active material layer was 30 μm. In the same manner as in the above, a lower negative electrode first active material layer was produced.
【００２５】〔負極第２活物質層の作製〕上記本発明電
池Ａにおける負極第２活物質層と同様にして、上記の下
層の負極第１活物質層の上にシリコン薄膜を形成した。
シリコン薄膜の膜厚は２μｍとした。[Preparation of Negative Electrode Second Active Material Layer] A silicon thin film was formed on the lower negative electrode first active material layer in the same manner as the negative electrode second active material layer in Battery A of the present invention.
The thickness of the silicon thin film was 2 μm.
【００２６】〔上層の負極第１活物質層の作製〕上記シ
リコン薄膜の上に、下層の負極第１活物質層と同様にし
て、上層の負極第１活物質層を作製した。[Preparation of Upper Negative Electrode First Active Material Layer] An upper negative electrode first active material layer was prepared on the silicon thin film in the same manner as the lower negative electrode first active material layer.
【００２７】以上のようにして、集電体である電解銅箔
の上に、第１の活物質層／第２の活物質層／第１の活物
質層の３層を積層し、負極を得た。上層及び下層の第１
の活物質層中の合計の黒鉛と、第２の活物質層であるシ
リコン薄膜との重量比は、８４：４．６であった。As described above, three layers of a first active material layer / a second active material layer / a first active material layer are laminated on an electrolytic copper foil as a current collector, and a negative electrode is formed. Obtained. First of upper layer and lower layer
The weight ratio of the total graphite in the active material layer to the silicon thin film as the second active material layer was 84: 4.6.
【００２８】〔正極の作製〕上記本発明電池Ａと同様に
して正極を作製した。 〔電池の作製〕上記負極及び上記正極を用い、上記本発
明電池Ａと同様にして電池を作製した。[Preparation of Positive Electrode] A positive electrode was prepared in the same manner as in Battery A of the present invention. [Preparation of Battery] A battery was prepared in the same manner as the battery A of the present invention using the negative electrode and the positive electrode.
【００２９】（比較電池の作製）黒鉛粉末とケイ素粉末
を重量比８４：４．６となるように混合し、結着剤とし
て上記と同様のフッ素樹脂を用いてスラリー化した後、
電解銅箔上に塗布して負極を作製した。この負極を用い
る以外は上記本発明電池と同様にして、比較電池を作製
した。(Preparation of Comparative Battery) Graphite powder and silicon powder were mixed in a weight ratio of 84: 4.6, and slurried using the same fluororesin as a binder,
A negative electrode was prepared by coating on an electrolytic copper foil. A comparative battery was produced in the same manner as the battery of the present invention except that this negative electrode was used.
【００３０】（充放電サイクル試験）本発明電池Ａ及び
Ｂ並びに比較電池について、充放電サイクル試験を行っ
た。充電は電池電圧４．２Ｖまでとし、放電は電池電圧
２．７５Ｖまでとし、充放電電流は１００ｍＡとして、
充放電を行い、１サイクル目、２サイクル目、５サイク
ル目、及び１０サイクル目の放電容量及び充放電効率を
測定した。測定結果を表１に示す。(Charge / Discharge Cycle Test) The batteries A and B of the present invention and the comparative battery were subjected to a charge / discharge cycle test. The charging is performed up to a battery voltage of 4.2 V, the discharging is performed up to a battery voltage of 2.75 V, and the charging and discharging current is 100 mA.
Charge / discharge was performed, and the discharge capacity and charge / discharge efficiency at the first cycle, the second cycle, the fifth cycle, and the tenth cycle were measured. Table 1 shows the measurement results.
【００３１】[0031]
【表１】 [Table 1]
【００３２】表１に示すように、本発明電池Ａ及びＢ
は、比較電池に比べ、高い放電容量及び充放電効率を示
している。１０サイクル後に各電池を分解したところ、
本発明電池Ａ及びＢの負極活物質は、集電体である銅箔
から剥離している部分が認められず、負極活物質自体は
その形状を保っていた。一方、比較電池においては、ほ
とんどの負極活物質が集電体から剥離、ケイ素粉末と思
われる銀白色の微粉が電解液中に分散していることが確
認された。As shown in Table 1, the batteries A and B of the present invention were
Indicates higher discharge capacity and higher charge / discharge efficiency than the comparative battery. When each battery was disassembled after 10 cycles,
In the negative electrode active materials of the batteries A and B of the present invention, no portion peeled off from the copper foil as the current collector was observed, and the negative electrode active materials themselves maintained their shapes. On the other hand, in the comparative battery, it was confirmed that most of the negative electrode active material was peeled off from the current collector, and silver white fine powder considered to be silicon powder was dispersed in the electrolytic solution.
【００３３】[0033]
【発明の効果】本発明によれば、充放電時の膨張収縮に
よる集電体からの活物質の剥離を防止することができ、
良好なサイクル特性を得ることができる。According to the present invention, peeling of the active material from the current collector due to expansion and contraction during charging and discharging can be prevented,
Good cycle characteristics can be obtained.
フロントページの続き (72)発明者 藤谷 伸 大阪府守口市京阪本通２丁目５番５号 三 洋電機株式会社内 Ｆターム(参考） 5H017 AA03 AS10 CC01 EE01 5H029 AJ05 AK03 AL01 AL06 AL11 AM00 AM03 AM04 AM05 AM07 AM16 BJ12 HJ13 5H050 AA07 BA17 CA08 CA09 CB01 CB07 CB11 FA02 FA18 FA19 HA13 Continuation of the front page (72) Inventor Shin Fujitani 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 5H017 AA03 AS10 CC01 EE01 5H029 AJ05 AK03 AL01 AL06 AL11 AM00 AM03 AM04 AM05 AM07 AM16 BJ12 HJ13 5H050 AA07 BA17 CA08 CA09 CB01 CB07 CB11 FA02 FA18 FA19 HA13
Claims (8)
の上に、炭素からなる第１の活物質層を設け、該第１の
活物質層の上にＬｉと合金化する金属または半導体から
なる第２の活物質層を設けた電極を用いることを特徴と
する二次電池。1. A first active material layer made of carbon is provided on a current collector made of a material that is not alloyed with Li, and a metal or semiconductor that is alloyed with Li is formed on the first active material layer. A secondary battery using an electrode provided with a second active material layer made of
の上にさらに前記第１の活物質層が設けられていること
を特徴とする請求項１に記載の二次電池。2. The secondary battery according to claim 1, wherein, in the electrode, the first active material layer is further provided on the second active material layer.
の上に前記第１の活物質層及び前記第２の活物質層がこ
の順序で交互に繰り返し積層されていることを特徴とす
る請求項１に記載の二次電池。3. The electrode according to claim 1, wherein the first active material layer and the second active material layer are alternately and repeatedly laminated on the second active material layer in this order. The secondary battery according to claim 1.
質層の充放電時における膨張収縮率が実質的に互いに同
程度となるように調整されていることを特徴とする請求
項１〜３のいずれか１項に記載の二次電池。4. The method according to claim 1, wherein the expansion and contraction rates of the first active material layer and the second active material layer during charge and discharge are adjusted to be substantially equal to each other. The secondary battery according to any one of claims 1 to 3.
たはＳｉ−Ｇｅ合金からなることを特徴とする請求項１
〜４のいずれか１項に記載の二次電池。5. The method according to claim 1, wherein the second active material layer is made of Si, Ge, or a Si—Ge alloy.
The secondary battery according to any one of claims 4 to 4.
せた薄膜であることを特徴とする請求項１〜５のいずれ
か１項に記載の二次電池。6. The secondary battery according to claim 1, wherein the second active material layer is a thin film deposited from a gas phase.
の結晶子寸法Ｌｃが３００Å以上の黒鉛を、前記第１の
活物質層の炭素として用いることを特徴とする請求項１
〜６のいずれか１項に記載の二次電池。7. The graphite of the first active material layer, wherein graphite having an interlayer distance d of 3.37 ° or less and a crystallite size Lc in the stacking direction of 300 ° or more is used.
The secondary battery according to any one of claims 1 to 6.
る請求項１〜７のいずれか１項に記載の二次電池。8. The secondary battery according to claim 1, wherein the current collector is a copper foil.
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| JP2000100406A JP3913438B2 (en) | 2000-04-03 | 2000-04-03 | Lithium secondary battery |
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