JP2010218819A - Cathode for nonaqueous electrolyte battery and nonaqueous electrolyte battery - Google Patents
Cathode for nonaqueous electrolyte battery and nonaqueous electrolyte battery Download PDFInfo
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- 239000011255 nonaqueous electrolyte Substances 0.000 title claims abstract description 34
- 239000007784 solid electrolyte Substances 0.000 claims abstract description 64
- 239000002245 particle Substances 0.000 claims abstract description 37
- 239000013078 crystal Substances 0.000 claims abstract description 13
- 150000002642 lithium compounds Chemical class 0.000 claims abstract description 9
- 238000005498 polishing Methods 0.000 description 24
- 239000002344 surface layer Substances 0.000 description 13
- 239000010410 layer Substances 0.000 description 12
- 238000003780 insertion Methods 0.000 description 6
- 230000037431 insertion Effects 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 5
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 5
- 238000003795 desorption Methods 0.000 description 5
- 229910052744 lithium Inorganic materials 0.000 description 5
- 238000003917 TEM image Methods 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 239000007774 positive electrode material Substances 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 239000011149 active material Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 238000001771 vacuum deposition Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910018091 Li 2 S Inorganic materials 0.000 description 1
- 229910000733 Li alloy Inorganic materials 0.000 description 1
- 229910015118 LiMO Inorganic materials 0.000 description 1
- 229910013641 LiNbO 3 Inorganic materials 0.000 description 1
- 229910002995 LiNi0.8Co0.15Al0.05O2 Inorganic materials 0.000 description 1
- 229910014422 LiNi1/3Mn1/3Co1/3O2 Inorganic materials 0.000 description 1
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 239000001989 lithium alloy Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005240 physical vapour deposition Methods 0.000 description 1
- 239000004014 plasticizer Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- 238000001238 wet grinding Methods 0.000 description 1
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
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- Battery Electrode And Active Subsutance (AREA)
Abstract
Description
本発明は、固体電解質を用いた非水電解質電池用の正極および非水電解質電池であって、特に体積容量密度が高く、内部抵抗が低減された非水電解質電池用の正極および非水電解質電池に関する。 The present invention relates to a positive electrode and a non-aqueous electrolyte battery for a non-aqueous electrolyte battery using a solid electrolyte, and particularly a positive electrode and a non-aqueous electrolyte battery for a non-aqueous electrolyte battery having a high volume capacity density and a reduced internal resistance. About.
非水電解質電池に関して、体積容量密度の更なる向上を図るため、活物質充填密度の高い焼結式の正極を用いた非水電解質電池が開発されている（特許文献１）。また、安全性に優れるため、固体電解質を用いた非水電解質電池（以下、「固体電解質電池」ともいう。）が注目されている。 With respect to non-aqueous electrolyte batteries, non-aqueous electrolyte batteries using a sintered positive electrode having a high active material filling density have been developed in order to further improve the volume capacity density (Patent Document 1). In addition, since it is excellent in safety, a non-aqueous electrolyte battery using a solid electrolyte (hereinafter also referred to as “solid electrolyte battery”) has attracted attention.
しかしながら、焼結式の正極を用いた固体電解質電池の場合、電池の内部抵抗が高く、必ずしも充分に満足できる充放電性能が得られないという問題があった。 However, in the case of a solid electrolyte battery using a sintered positive electrode, there is a problem that the internal resistance of the battery is high, and a sufficiently satisfactory charge / discharge performance cannot always be obtained.
そこで本発明は、体積容量密度が高く、内部抵抗を大幅に低減させることができ、充分に満足できる充放電性能を有する固体電解質電池用の正極および固体電解質電池を提供することを課題とする。 Therefore, an object of the present invention is to provide a positive electrode and a solid electrolyte battery for a solid electrolyte battery that have a high volume capacity density, can significantly reduce internal resistance, and have sufficiently satisfactory charge / discharge performance.
本発明者らは、上記の課題に鑑み、鋭意研究の結果、前記課題を解決する方法を見出し本発明に至った。以下、各請求項の発明について説明する。 In view of the above problems, the present inventors have found a method for solving the above problems as a result of intensive studies, and have reached the present invention. Hereinafter, the invention of each claim will be described.
本発明に係る非水電解質電池用の正極は、
固体電解質を用いた非水電解質電池用の正極であって、
層状の結晶構造を有するリチウム化合物の粒子の焼結体を主体とし、
前記焼結体の表面の粒子の少なくとも一部の粒子が、多結晶構造を有することを特徴とする。
The positive electrode for a non-aqueous electrolyte battery according to the present invention is
A positive electrode for a non-aqueous electrolyte battery using a solid electrolyte,
Mainly a sintered body of lithium compound particles having a layered crystal structure,
At least some of the particles on the surface of the sintered body have a polycrystalline structure.
本発明者は、固体電解質電池に焼結式正極を適用した場合、何故内部抵抗が高く充分に
満足できる充放電性能が得られないのかについて検討した結果、以下のことが分かった。即ち、層状の結晶構造を有するリチウム化合物の場合、Ｌｉ＋の挿入脱離は結晶のａｂ軸面に対して平行な方向に起き、ｃ軸方向には起き難い。そして、従来の焼結体を構成するリチウム化合物の粒子（単一粒子）は単結晶であり、正極／固体電解質界面、即ち焼結体の表面の粒子のうちｃ軸配向している（ｃ軸が表面の方向を向いている。）粒子の場合は、正極と固体電解質との間でＬｉ＋が移動し難く界面が高抵抗層となることが、内部抵抗を増大させ、充分に満足できる充放電性能が得られない原因である。
As a result of studying why the charge / discharge performance with high internal resistance and sufficient satisfaction cannot be obtained when the sintered positive electrode is applied to the solid electrolyte battery, the present inventor has found the following. That is, in the case of a lithium compound having a layered crystal structure, insertion and removal of Li + occurs in a direction parallel to the ab axis surface of the crystal and hardly occurs in the c axis direction. The lithium compound particles (single particles) constituting the conventional sintered body are single crystals and are c-axis-oriented among the positive electrode / solid electrolyte interface, that is, the particles on the surface of the sintered body (c-axis). In the case of particles, it is difficult for Li + to move between the positive electrode and the solid electrolyte, and the interface becomes a high resistance layer, which increases the internal resistance and is sufficiently satisfactory. This is the reason why the discharge performance cannot be obtained.
そこで、本発明者は焼結体表面の粒子の少なくとも一部の粒子を、多結晶構造を有する粒子に変える、即ち焼結体の表層を多結晶化することにより、Ｌｉ＋の挿入脱離を結晶の軸の方向による影響を受けないようにすることができ、その結果Ｌｉ＋の挿入脱離のチャンネルを増大させ、界面の抵抗を大幅に低減できることを見出した。 Therefore, the present inventor changed Li + insertion / desorption by changing at least some of the particles on the surface of the sintered body to particles having a polycrystalline structure, that is, by polycrystallizing the surface layer of the sintered body. It has been found that the influence of the direction of the crystal axis can be avoided, and as a result, the number of Li + insertion and desorption channels can be increased and the interface resistance can be greatly reduced.
本発明は以上の知見に基づくものであり、本発明に係る固体電解質電池用の正極は、焼結体の表層の少なくとも一部が多結晶化されているため、正極／固体電解質界面の抵抗を低減することができ、充分に満足できる充放電性能を有する固体電解質電池を提供することができる。 The present invention is based on the above knowledge, and the positive electrode for a solid electrolyte battery according to the present invention has a resistance at the positive electrode / solid electrolyte interface because at least a part of the surface layer of the sintered body is polycrystallized. It is possible to provide a solid electrolyte battery that can be reduced and has sufficiently satisfactory charge / discharge performance.
なお、焼結体の表層の多結晶化は、従来法により焼結された焼結体の表面を水やエタノール等のアルコールを用いながら研磨する湿式研磨によって行うことができる。また、多結晶化は、焼結体が固体電解質と対向する面の表層のみに行われればよく、焼結体の全ての面の表層が多結晶化される必要はない。 Note that polycrystallization of the surface layer of the sintered body can be performed by wet polishing in which the surface of the sintered body sintered by the conventional method is polished using alcohol such as water or ethanol. Further, the polycrystallization may be performed only on the surface layer of the surface facing the solid electrolyte, and the surface layers of all surfaces of the sintered body need not be polycrystallized.
正極の焼結体を構成する層状の結晶構造を有するリチウム化合物からなる正極活物質としては、一般式ＬｉＭＯ２（但しＭはＣｏ、Ｍｎ、Ｎｉ、Ａｌの１種または２以上を含み、Ｍに占めるＣｏ、Ｍｎ、Ｎｉ、Ａｌの比率が５０ａｔ％以上）で表されるリチウム複合酸化物を好ましく用いることができる。このようなリチウム複合酸化物として、たとえば、ＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＮｉ０．８Ｃｏ０．１５Ａｌ０．０５Ｏ２、ＬｉＮｉ１／３Ｍｎ１／３Ｃｏ１／３Ｏ２などが挙げられる。 The positive electrode active material comprising a lithium compound having a layered crystal structure that constitutes the sintered body of the positive electrode includes a general formula LiMO 2 (where M includes one or more of Co, Mn, Ni, and Al, and M includes A lithium composite oxide represented by the ratio of Co, Mn, Ni, and Al occupied by 50 at% or more can be preferably used. Examples of such lithium composite oxide include LiCoO 2 , LiNiO 2 , LiNi 0.8 Co 0.15 Al 0.05 O 2 , and LiNi 1/3 Mn 1/3 Co 1/3 O 2. .
なお、前記焼結体の厚みは、０．３ｍｍを超えると焼結体内部におけるＬｉ＋の移動経路が長くなるため、正極としてのバルク抵抗が増大する。また、充放電に伴う体積の膨張収縮が大きくなり正極にクラックが生じる恐れがある。このため、焼結体の厚みは０．３ｍｍ以下であることが好ましい。 If the thickness of the sintered body exceeds 0.3 mm, the movement path of Li + in the sintered body becomes longer, and the bulk resistance as the positive electrode increases. In addition, the volume expansion and contraction associated with charging / discharging may increase and the positive electrode may crack. For this reason, it is preferable that the thickness of a sintered compact is 0.3 mm or less.
なお、本発明の正極には焼結体以外の構成物質を含んでいてもよい。また、焼結体には、活物質以外に、例えば、金属酸化物等の化合物や固体電解質の成分等の物質を一部含有していてもよい。 The positive electrode of the present invention may contain a constituent material other than the sintered body. In addition to the active material, the sintered body may contain, for example, a compound such as a metal oxide or a material such as a solid electrolyte component.
本発明に係る非水電解質用電池の正極は、前記の非水電解質用電池の正極であって、
前記焼結体において、前記多結晶構造を有する粒子が占める領域の厚みｔが、０．００５μｍ＜ｔ＜１μｍを満たしていることを特徴とする。
The positive electrode of the nonaqueous electrolyte battery according to the present invention is the positive electrode of the nonaqueous electrolyte battery,
In the sintered body, a thickness t of a region occupied by the particles having a polycrystalline structure satisfies 0.005 μm <t <1 μm.
本発明においては多結晶構造を有する粒子が占める領域の厚みｔが０．００５μｍを超えるため、よりＬｉが挿入脱離できる箇所が多くある。また、１μｍ未満であるため、より粒子内部のＬｉ拡散がスムーズに起こる。 In the present invention, since the thickness t of the region occupied by particles having a polycrystalline structure exceeds 0.005 μm, there are many places where Li can be inserted and desorbed. Moreover, since it is less than 1 μm, Li diffusion inside the particles occurs more smoothly.
なお、前記多結晶構造を有する粒子が占める領域の厚みｔは、研磨器の回転数と研磨時間を制御することにより０．００５μｍ＜ｔ＜１μｍを満たすように調整される。 The thickness t of the region occupied by the particles having the polycrystalline structure is adjusted so as to satisfy 0.005 μm <t <1 μm by controlling the rotation speed and polishing time of the polishing machine.
本発明に係る非水電解質電池用の正極は、前記の非水電解質用電池の正極であって、
前記多結晶構造を有する粒子が占める領域の前記焼結体の表面に対する面積の比率が４０〜１００％であることを特徴とする。
A positive electrode for a nonaqueous electrolyte battery according to the present invention is a positive electrode of the nonaqueous electrolyte battery,
The ratio of the area occupied by the particles having the polycrystalline structure to the surface of the sintered body is 40 to 100%.
本発明においては、多結晶構造を有する粒子が占める領域の前記焼結体の表面に対する面積の比率が４０〜１００％であるため、確実にＬｉ＋の挿入脱離のチャンネルを大幅に増やし、正極／固体電解質界面の抵抗をより確実に大幅に低減することができる。 In the present invention, since the ratio of the area occupied by the particles having a polycrystalline structure to the surface of the sintered body is 40 to 100%, the number of Li + insertion / desorption channels is surely greatly increased. / The resistance of the solid electrolyte interface can be greatly and reliably reduced.
なお、多結晶構造を有する粒子が占める領域の前記焼結体の表面に対する面積の比率は、湿式研磨された面積の比率にほぼ等しく、湿式研磨する面積の大きさを調整することにより、多結晶構造を有する粒子が占める領域の比率が４０％以上となるように調整される。 The ratio of the area occupied by the particles having a polycrystalline structure to the surface of the sintered body is substantially equal to the ratio of the area that has been wet-polished, and by adjusting the size of the area to be wet-polished, The ratio of the region occupied by the particles having a structure is adjusted to be 40% or more.
本発明に係る非水電解質電池用の正極は、
固体電解質を用いた非水電解質電池用の正極であって、
層状の結晶構造を有するリチウム化合物の粒子の焼結体を主体とし、
前記焼結体は、表面が湿式研磨されていることを特徴とする。
The positive electrode for a non-aqueous electrolyte battery according to the present invention is
A positive electrode for a non-aqueous electrolyte battery using a solid electrolyte,
Mainly a sintered body of lithium compound particles having a layered crystal structure,
The sintered body is characterized in that the surface is wet-polished.
本発明においては、層状の結晶構造を有するリチウム化合物の粒子の焼結体の表面が湿式研磨されているため、焼結体の表層が多結晶化する等によりＬｉ＋の挿入脱離のチャンネルが増大し、その結果固体電解質との界面の抵抗を大幅に低減させることができる固体電解質電池用の正極とすることができる。 In the present invention, since the surface of the sintered body of particles of the lithium compound having a layered crystal structure is wet polished, channel insertion and desorption of Li + such as by surface layer polycrystalline sintered body As a result, the resistance of the interface with the solid electrolyte can be greatly reduced, and a positive electrode for a solid electrolyte battery can be obtained.
本発明に係る非水電解質電池は、
固体電解質を用いた非水電解質電池であって、
前記のいずれかの発明に係る非水電解質電池用の正極が用いられていることを特徴とする。
The nonaqueous electrolyte battery according to the present invention is
A non-aqueous electrolyte battery using a solid electrolyte,
The positive electrode for a non-aqueous electrolyte battery according to any one of the above inventions is used.
本発明においては、前記のいずれかの発明に係る非水電解質電池用の正極が用いられているため、体積容量密度が高く、電池の内部抵抗が大幅に低減され、充分満足できる充放電性能を有する固体電解質電池を提供することができる。 In the present invention, since the positive electrode for a non-aqueous electrolyte battery according to any one of the above inventions is used, the volume capacity density is high, the internal resistance of the battery is greatly reduced, and charge / discharge performance that is sufficiently satisfactory can be achieved. A solid electrolyte battery can be provided.
本発明によれば、体積容量密度が高く、内部抵抗を大幅に低減させることができ、充分に満足できる充放電性能を有する固体電解質電池用の正極および固体電解質電池を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, the volume capacity density is high, an internal resistance can be reduced significantly, and the positive electrode and solid electrolyte battery for solid electrolyte batteries which have fully satisfying charging / discharging performance can be provided.
以下、本発明を実施の形態により説明する。なお、本発明は、以下の実施の形態に限定されるものではない。本発明と同一および均等の範囲内において、以下の実施の形態に対して種々の変更を加えることが可能である。 Hereinafter, the present invention will be described with reference to embodiments. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.
１．非水電解質電池の構成
初めに本実施の形態に係る固体電解質電池の構成について説明する。図１は本実施の形態に係る固体電解質電池の構成を模式的に示す断面図である。図１において１は、層状の結晶構造を有する正極活物質を主体とする粒子の焼結体からなる正極であり、２は固体電解質である。本実施の形態の場合、正極１の固体電解質２と対向させた側の表面の正極活物質の粒子は多結晶構造を有する。３は必要に応じて正極１と固体電解質２の間に形成されている緩衝層であり、４は固体電解質２の表面に形成された負極である。この固体電解質電池は以下の工程に従って作製される。
1. Configuration of Nonaqueous Electrolyte Battery First, the configuration of the solid electrolyte battery according to the present embodiment will be described. FIG. 1 is a cross-sectional view schematically showing the configuration of the solid electrolyte battery according to the present embodiment. In FIG. 1, 1 is a positive electrode made of a sintered body of particles mainly composed of a positive electrode active material having a layered crystal structure, and 2 is a solid electrolyte. In the case of the present embodiment, the positive electrode active material particles on the surface of the positive electrode 1 facing the solid electrolyte 2 have a polycrystalline structure. Reference numeral 3 denotes a buffer layer formed between the positive electrode 1 and the solid electrolyte 2 as required, and reference numeral 4 denotes a negative electrode formed on the surface of the solid electrolyte 2. This solid electrolyte battery is manufactured according to the following steps.
２．固体電解質電池の作製
（１）正極の作製
初めに正極の作製について説明する。
イ．焼結体の作製
焼結体は、ＬｉＣｏＯ２粒子等の正極活物質を主体とする粒子を加圧成形後、あるいはグリーンシート法等により塗膜等を形成後、所定の雰囲気中において所定の温度で焼結した後、出来上がり時点における焼結体の厚みが０．３ｍｍ以下の所望の厚さになるように加工される。
2. Production of Solid Electrolyte Battery (1) Production of Positive Electrode First, production of the positive electrode will be described.
I. Preparation of sintered body A sintered body has a predetermined temperature in a predetermined atmosphere after pressure forming particles mainly composed of a positive electrode active material such as LiCoO 2 particles, or after forming a coating film by a green sheet method or the like. After being sintered, the sintered body is processed so as to have a desired thickness of 0.3 mm or less at the time of completion.
焼結により直接薄い焼結体を作製しようとしても焼結体に波うちが生じるため、作製が困難である。このため、前記のように厚手の焼結体を作製した後、ワイヤーカットによるスライス加工や、種々の番手のＳｉＣ研磨紙およびＡｌ２Ｏ３研磨紙等を適宜使用して乾式研磨を行うことにより所望の厚みに加工される。 Even if an attempt is made to directly produce a thin sintered body by sintering, a wave is generated in the sintered body, making it difficult to produce. For this reason, after producing a thick sintered body as described above, by performing dry polishing by appropriately using slice processing by wire cut, SiC polishing paper of various counts, Al 2 O 3 polishing paper, etc. Processed to a desired thickness.
ロ．焼結体の表層の多結晶化
所望の厚みに加工された焼結体の固体電解質と対向させる表面を湿式研磨することにより、焼結体の表面の粒子の少なくとも一部の粒子を、多結晶構造を有する粒子にする、即ち焼結体の表層を多結晶化することができる。具体的には、焼結体の表面を、純水と例えばＡｌ２Ｏ３研磨紙等の研磨紙等を用いた湿式研磨を行うことにより焼結体の表層を多結晶化することができる。図２は、ＬｉＣｏＯ２粒子の焼結体の表面近傍のＴＥＭ像であって、（ａ）が湿式研磨を行った試料のＴＥＭ像、（ｂ）が湿式研磨を行っていない試料のＴＥＭ像である。図２より、（ｂ）の試料の場合は表面（図２では「最表層」と記載）の粒子が単結晶であるのに対して、（ａ）の試料の場合は多結晶構造を有しており、焼結体の表層が多結晶化されていることが分かる。
B. Polycrystallization of the surface layer of the sintered body By wet polishing the surface of the sintered body that has been processed to a desired thickness and facing the solid electrolyte, at least some of the particles on the surface of the sintered body are polycrystallized. Particles having a structure, that is, the surface layer of the sintered body can be polycrystallized. Specifically, the surface of the sintered body can be polycrystallized by performing wet polishing using pure water and polishing paper such as Al 2 O 3 polishing paper. FIG. 2 is a TEM image near the surface of the sintered body of LiCoO 2 particles, where (a) is a TEM image of a sample that has been wet-polished, and (b) is a TEM image of a sample that has not been wet-polished. is there. From FIG. 2, in the case of the sample of (b), the particles on the surface (described as “the outermost layer” in FIG. 2) are single crystals, whereas in the case of the sample of (a), they have a polycrystalline structure. It can be seen that the surface layer of the sintered body is polycrystallized.
なお、湿式研磨の場合、ＳｉＣ研磨紙のように硬度が高く、目の粗い（番手の低い）研磨紙を用いると、焼結体の表面の粒子が脱落する恐れがある。このため、Ａｌ２Ｏ３研磨紙のように硬度が低く、目の細かい（番手の高い）研磨紙を用いて研磨することが好ましい。 In the case of wet polishing, if a polishing paper having a high hardness and coarseness (low count) is used like SiC polishing paper, particles on the surface of the sintered body may fall off. For this reason, it is preferable to polish using a polishing paper having a low hardness and fine (high count) like Al 2 O 3 polishing paper.
（２）固体電解質の形成
次に固体電解質の形成について図１を用いて説明する。正極１の多結晶化された表層の表面に、蒸着法やスパッタ法を用いて、Ｌｉ＋伝導性の固体電解質２を形成する。この場合、前記の通り正極１の表層が多結晶化されているため、正極１と固体電解質２の間のＬｉ＋の挿入脱離チャンネルが増大するため、正極１／固体電解質２界面の抵抗が低減され、その結果電池の内部抵抗が大幅に低減される。なお、必要に応じて正極１と固体電解質２の間に緩衝層３を形成する。
(2) Formation of solid electrolyte Next, formation of a solid electrolyte is demonstrated using FIG. A Li + conductive solid electrolyte 2 is formed on the surface of the polycrystallized surface layer of the positive electrode 1 by vapor deposition or sputtering. In this case, since the surface layer of the positive electrode 1 is polycrystallized as described above, the Li + insertion / desorption channel between the positive electrode 1 and the solid electrolyte 2 increases, so that the resistance of the positive electrode 1 / solid electrolyte 2 interface is reduced. And consequently the internal resistance of the battery is greatly reduced. Note that a buffer layer 3 is formed between the positive electrode 1 and the solid electrolyte 2 as necessary.
（３）負極
次に、固体電解質２の表面に、たとえば金属リチウム、リチウム合金、黒鉛、チタン酸リチウム等の負極を設ける。
(3) Negative Electrode Next, a negative electrode such as metal lithium, lithium alloy, graphite, or lithium titanate is provided on the surface of the solid electrolyte 2.
（４）電池の組立て
次に図１に示した正極１、固体電解質２、緩衝層３、負極４からなる積層体を、正負両極端子を有する密閉容器内に封入して固体電解質電池を組立てる。
(4) Assembly of Battery Next, the laminate composed of the positive electrode 1, the solid electrolyte 2, the buffer layer 3, and the negative electrode 4 shown in FIG. 1 is enclosed in a sealed container having positive and negative electrode terminals to assemble a solid electrolyte battery.
以下に実施例により、本発明を更に詳細に説明する。本実施例は、ＬｉＣｏＯ２粒子の焼結体であって、表層が多結晶化された焼結体からなる正極と固体電解質を用いた固体電解質電池の例である。 The following examples further illustrate the present invention. The present example is an example of a solid electrolyte battery using a positive electrode made of a sintered body of LiCoO 2 particles and having a polycrystallized surface layer and a solid electrolyte.
１．正極の作製
イ．焼結体の作製
ａ．焼結
所定量のＬｉＣｏＯ２粒子、トルエン（溶媒）、ＰＶＤ（バインダー）、ＤＰＢ（可塑剤）を混練して得られた混合物を塗工後、乾燥して塗膜を作製した。前記塗膜を大気雰囲気中において昇温速度０．５℃／分で４００℃まで昇温し１２時間保持した。引き続き前記昇温速度で７００℃まで昇温して３時間保持した後、さらに昇温速度１０℃／分で９５０℃まで昇温し６時間保持した後冷却して焼結体を得た。
1. Production of positive electrode a. Production of sintered body a. Sintering A coating obtained by kneading a predetermined amount of LiCoO 2 particles, toluene (solvent), PVD (binder), and DPB (plasticizer) was applied and dried to prepare a coating film. The coating film was heated to 400 ° C. at a heating rate of 0.5 ° C./min in an air atmosphere and held for 12 hours. Subsequently, the temperature was raised to 700 ° C. at the rate of temperature rise and held for 3 hours, further heated to 950 ° C. at a rate of temperature rise of 10 ° C./min, held for 6 hours, and then cooled to obtain a sintered body.
ｂ．乾式研磨
次に、得られた焼結体をＳｉＣの研磨紙２種（＃４００、＃８００）を用いて２段階の研磨を行った後、更にＡｌ２Ｏ３の研磨紙（＃１０００）を用いて研磨（乾式研磨）を行い、焼結体の厚みを０．０６ｍｍとした。
b. Dry polishing Next, the obtained sintered body was polished in two stages using two types of SiC abrasive paper (# 400, # 800), and then further polished with Al 2 O 3 abrasive paper (# 1000). Polishing (dry polishing) was performed, and the thickness of the sintered body was set to 0.06 mm.
ｃ．湿式研磨
次に、純水を用いながらＡｌ２Ｏ３の研磨紙（＃１０００）を用いて焼結体の固体電解質と対向させる表面の全面を研磨（湿式研磨）した。なお、湿式研磨を行う際の研磨器の回転数を２０ｒｐｍとし、６０秒間研磨した。そして、湿式研磨後の焼結体の多結晶構造を有する粒子が占める領域の厚みｔをＴＥＭ分析により測定した結果、ｔの値は０．１μｍであることが確認された。
c. Wet Polishing Next, the entire surface of the sintered body facing the solid electrolyte was polished (wet polishing) using Al 2 O 3 polishing paper (# 1000) while using pure water. In addition, it grind | polished for 60 second by setting the rotation speed of the polisher at the time of performing wet grinding | polishing to 20 rpm. And as a result of measuring the thickness t of the area | region which the particle | grains which have the polycrystalline structure of the sintered compact after wet polishing occupy by TEM analysis, it was confirmed that the value of t is 0.1 micrometer.
２．緩衝層および固体電解質の形成
次に、作製した正極の研磨された表面に緩衝層を形成し、緩衝層の表面に固体電解質を形成した。具体的には、１ＰａのＯ２雰囲気下１０Ｈｚ、２００ｍＪの条件で、ＰＬＤ法によりＬｉＮｂＯ３からなる厚さ２０ｎｍの緩衝層を形成し、次に緩衝層の表面に真空蒸着法によりＰ２Ｓ５とＬｉ２Ｓのアモルファスの混合物からなる厚さ１０μｍの固体電解質を形成した。
2. Formation of Buffer Layer and Solid Electrolyte Next, a buffer layer was formed on the polished surface of the produced positive electrode, and a solid electrolyte was formed on the surface of the buffer layer. Specifically, a buffer layer having a thickness of 20 nm made of LiNbO 3 is formed by PLD under conditions of 10 Hz and 200 mJ in a 1 Pa O 2 atmosphere, and then P 2 S 5 is formed on the surface of the buffer layer by vacuum deposition. A solid electrolyte having a thickness of 10 μm made of an amorphous mixture of Li 2 S was formed.
３．負極の形成
次に、前記固体電解質の表面に、真空蒸着法により厚さ１０μｍの金属リチウムからなる負極を形成した。
3. Formation of Negative Electrode Next, a negative electrode made of metallic lithium having a thickness of 10 μm was formed on the surface of the solid electrolyte by a vacuum deposition method.
４．コイン型セルの組立て
前記の方法で作製した正極、緩衝層、固体電解質、負極からなる積層体をコイン型セルの容器内に組込み、固体電解質電池とした。
4). Assembling the coin-type cell The laminate made of the positive electrode, the buffer layer, the solid electrolyte, and the negative electrode produced by the above-described method was incorporated into a container of the coin-type cell to obtain a solid electrolyte battery.
５．充放電試験
次に、組立てた固体電解質電池の充放電試験を行った。充放電試験は、室温、電流密度０．０５ｍＡ／ｃｍ２、カットオフ電圧３Ｖ−４．２Ｖにて行った。そして、１サイクル目の放電開始後６０秒間の電圧降下に基づいて電池の内部抵抗値を算出し、内部抵抗が１００Ωｃｍ２であり、充分に低いことを確認した。
5). Charge / Discharge Test Next, a charge / discharge test of the assembled solid electrolyte battery was performed. The charge / discharge test was performed at room temperature, a current density of 0.05 mA / cm 2 , and a cut-off voltage of 3 V to 4.2 V. Then, the internal resistance value of the battery was calculated based on the voltage drop for 60 seconds after the start of the first cycle discharge, and it was confirmed that the internal resistance was 100 Ωcm 2 and was sufficiently low.
（比較例）
実施例の正極の作製において、湿式研磨を行わなかったこと以外は、全て実施例と同様にして固体電解質電池を作製し、同様にして内部抵抗を算出した。その結果は、内部抵抗が１００００Ωｃｍ２と高い値であった。なお、比較例の場合、正極に用いた焼結体の表層は多結晶化されていないことを確認した。
(Comparative example)
In the production of the positive electrode of the example, a solid electrolyte battery was produced in the same manner as in the example except that wet polishing was not performed, and the internal resistance was calculated in the same manner. As a result, the internal resistance was as high as 10,000 Ωcm 2 . In the case of the comparative example, it was confirmed that the surface layer of the sintered body used for the positive electrode was not polycrystallized.
以上、詳述したように、本発明によれば、焼結式の正極を用いた固体電解質電池の内部抵抗が大幅に低減され、充分に満足できる充放電性能を有する固体電解質電池を提供することができる。 As described above in detail, according to the present invention, there is provided a solid electrolyte battery having sufficiently satisfactory charge / discharge performance in which the internal resistance of a solid electrolyte battery using a sintered positive electrode is greatly reduced. Can do.
１ 正極
２ 固体電解質
３ 緩衝層
４ 負極
DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Solid electrolyte 3 Buffer layer 4 Negative electrode
Claims (5)
層状の結晶構造を有するリチウム化合物の粒子の焼結体を主体とし、
前記焼結体の表面の粒子の少なくとも一部の粒子が、多結晶構造を有することを特徴とする非水電解質電池用の正極。 A positive electrode for a non-aqueous electrolyte battery using a solid electrolyte,
Mainly a sintered body of lithium compound particles having a layered crystal structure,
A positive electrode for a nonaqueous electrolyte battery, wherein at least some of the particles on the surface of the sintered body have a polycrystalline structure.
層状の結晶構造を有するリチウム化合物の粒子の焼結体を主体とし、
前記焼結体は、表面が湿式研磨されていることを特徴とする非水電解質電池用の正極。 A positive electrode for a non-aqueous electrolyte battery using a solid electrolyte,
Mainly a sintered body of lithium compound particles having a layered crystal structure,
The sintered body is a positive electrode for a non-aqueous electrolyte battery, the surface of which is wet-polished.
請求項１ないし請求項４のいずれか１項に記載の非水電解質電池用の正極が用いられていることを特徴とする非水電解質電池。 A non-aqueous electrolyte battery using a solid electrolyte,
A nonaqueous electrolyte battery, wherein the positive electrode for a nonaqueous electrolyte battery according to any one of claims 1 to 4 is used.
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