JP2020167146A - All-solid type secondary battery, and manufacturing method, using method and charging method thereof - Google Patents
All-solid type secondary battery, and manufacturing method, using method and charging method thereof Download PDFInfo
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- JP2020167146A JP2020167146A JP2020013978A JP2020013978A JP2020167146A JP 2020167146 A JP2020167146 A JP 2020167146A JP 2020013978 A JP2020013978 A JP 2020013978A JP 2020013978 A JP2020013978 A JP 2020013978A JP 2020167146 A JP2020167146 A JP 2020167146A
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- Prior art keywords
- electrode active
- active material
- negative electrode
- solid
- secondary battery
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- 238000000034 method Methods 0.000 title claims abstract description 42
- 239000007787 solid Substances 0.000 title claims abstract description 11
- 238000004519 manufacturing process Methods 0.000 title claims description 12
- 239000007773 negative electrode material Substances 0.000 claims abstract description 173
- 229910003481 amorphous carbon Inorganic materials 0.000 claims abstract description 79
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 66
- 239000007784 solid electrolyte Substances 0.000 claims abstract description 64
- 239000007774 positive electrode material Substances 0.000 claims abstract description 63
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 56
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 55
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 33
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 18
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 12
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 10
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- 229910052799 carbon Inorganic materials 0.000 description 10
- 210000004027 cell Anatomy 0.000 description 9
- 238000002360 preparation method Methods 0.000 description 9
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- 229910018091 Li 2 S Inorganic materials 0.000 description 4
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
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- 229910017052 cobalt Inorganic materials 0.000 description 2
- 239000010941 cobalt Substances 0.000 description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
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- 238000010030 laminating Methods 0.000 description 2
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 2
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 238000007578 melt-quenching technique Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
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- 229910052759 nickel Inorganic materials 0.000 description 2
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- 229910018068 Li 2 O Inorganic materials 0.000 description 1
- 229910018127 Li 2 S-GeS 2 Inorganic materials 0.000 description 1
- 229910018133 Li 2 S-SiS 2 Inorganic materials 0.000 description 1
- 229910009324 Li2S-SiS2-Li3PO4 Inorganic materials 0.000 description 1
- 229910009320 Li2S-SiS2-LiBr Inorganic materials 0.000 description 1
- 229910009316 Li2S-SiS2-LiCl Inorganic materials 0.000 description 1
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- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
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- NDPGDHBNXZOBJS-UHFFFAOYSA-N aluminum lithium cobalt(2+) nickel(2+) oxygen(2-) Chemical compound [Li+].[O--].[O--].[O--].[O--].[Al+3].[Co++].[Ni++] NDPGDHBNXZOBJS-UHFFFAOYSA-N 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
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- 239000000470 constituent Substances 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
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- 238000011156 evaluation Methods 0.000 description 1
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- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 150000002641 lithium Chemical class 0.000 description 1
- HSZCZNFXUDYRKD-UHFFFAOYSA-M lithium iodide Inorganic materials [Li+].[I-] HSZCZNFXUDYRKD-UHFFFAOYSA-M 0.000 description 1
- CASZBAVUIZZLOB-UHFFFAOYSA-N lithium iron(2+) oxygen(2-) Chemical compound [O-2].[Fe+2].[Li+] CASZBAVUIZZLOB-UHFFFAOYSA-N 0.000 description 1
- GLNWILHOFOBOFD-UHFFFAOYSA-N lithium sulfide Chemical compound [Li+].[Li+].[S-2] GLNWILHOFOBOFD-UHFFFAOYSA-N 0.000 description 1
- URIIGZKXFBNRAU-UHFFFAOYSA-N lithium;oxonickel Chemical compound [Li].[Ni]=O URIIGZKXFBNRAU-UHFFFAOYSA-N 0.000 description 1
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- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
- H01M10/0562—Solid materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/44—Methods for charging or discharging
- H01M10/446—Initial charging measures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/64—Carriers or collectors
- H01M4/66—Selection of materials
- H01M4/661—Metal or alloys, e.g. alloy coatings
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0065—Solid electrolytes
- H01M2300/0068—Solid electrolytes inorganic
-
- 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、全固体二次電池、その製造方法、その使用方法及びその充電方法に関するものである。 The present invention relates to an all-solid-state secondary battery, a method for manufacturing the battery, a method for using the battery, and a method for charging the battery.
近年、電解質として固体電解質を使用した全固体二次電池が注目されている。このような全固体二次電池のエネルギー密度を高めるために、負極活物質としてリチウムを使用することが提案されている。リチウムの容量密度（単位質量当りの容量）は、負極活物質として一般的に使用される黒鉛の容量密度の１０倍程度である。そのため、負極活物質としてリチウムを使用することにより、全固体二次電池を薄型化しつつも、その出力を高めることができる。 In recent years, an all-solid-state secondary battery using a solid electrolyte as an electrolyte has attracted attention. In order to increase the energy density of such an all-solid-state secondary battery, it has been proposed to use lithium as the negative electrode active material. The volume density (capacity per unit mass) of lithium is about 10 times the volume density of graphite generally used as a negative electrode active material. Therefore, by using lithium as the negative electrode active material, it is possible to increase the output of the all-solid-state secondary battery while reducing the thickness.
リチウムを負極活物質として使用する全固体二次電池として、負極活物質層を備えておらず、充電によって負極集電体と固体電解質との界面に金属リチウムを析出させ、この析出した金属リチウムを負極活物質として用いるものが提案されている。しかしながらこの種の全固体二次電池では、充放電を繰り返すと、析出した金属リチウムが固体電解質の隙間を縫うように樹枝状（デンドライト状）に成長する。樹枝状に成長した金属リチウムは、二次電池の短絡の原因となり得るだけでなく、充電容量低下の原因にもなり得るという問題がある。 As an all-solid-state secondary battery that uses lithium as the negative electrode active material, it does not have a negative electrode active material layer, and metallic lithium is precipitated at the interface between the negative electrode current collector and the solid electrolyte by charging, and the precipitated metallic lithium is deposited. Those used as a negative electrode active material have been proposed. However, in this type of all-solid-state secondary battery, when charging and discharging are repeated, the precipitated metallic lithium grows in a dendritic shape (dendrite shape) so as to sew the gaps between the solid electrolytes. There is a problem that metallic lithium grown in a dendritic shape can not only cause a short circuit of a secondary battery but also cause a decrease in charge capacity.
このような問題を解決するため、特許文献１には、リチウム又はリチウムと合金を形成する金属で構成される金属層を負極活物質層として使用し、かつ負極活物質層上に非晶質炭素からなる界面層を設けることが開示されている。これにより界面層内にリチウムイオンが分散するため、金属リチウムの析出及び成長を抑制できることが開示されている。 In order to solve such a problem, Patent Document 1 uses a metal layer composed of lithium or a metal forming an alloy with lithium as a negative electrode active material layer, and amorphous carbon on the negative electrode active material layer. It is disclosed to provide an interface layer composed of. It is disclosed that the precipitation and growth of metallic lithium can be suppressed because lithium ions are dispersed in the interface layer.
しかしながら、上記した特許文献１に記載される全固体二次電池では、依然として各種の電池特性を十分に向上することができず、近年の要求を満足するには不十分であると考えられる。 However, the all-solid-state secondary battery described in Patent Document 1 described above still cannot sufficiently improve various battery characteristics, and is considered to be insufficient to satisfy recent demands.
そこで本発明は、電池特性に優れた、とりわけサイクル特性及び放電レート特性のいずれにも優れた全固体二次電池及びその充電方法を提供することを主たる課題とするものである。 Therefore, it is a main object of the present invention to provide an all-solid-state secondary battery having excellent battery characteristics, particularly excellent in both cycle characteristics and discharge rate characteristics, and a charging method thereof.
本発明者らは、鋭意検討した結果、正極活物質層と負極活物質層のそれぞれの初期充電容量の比を所定の範囲にするとともに、負極活物質層が、ストラクチャーが大きい無定形炭素、又は粒子径が大きい無定形炭素を負極活物質として所定量以上含有することにより、サイクル特性及び放電レート特性のいずれにも優れた全固体二次電池が得られることを見出した。すなわち、負極活物質層が、このような特性の無定形炭素を所定量以上含有することにより、炭素粒子間又は炭素粒子アグリゲート間の界面の数が減少し、負極活物質層内におけるリチウムの拡散が容易になり、サイクル特性及び放電レート特性のいずれにも優れた全固体二次電池を得られることを見出し、本発明に至ったのである。 As a result of diligent studies, the present inventors set the ratio of the initial charge capacities of the positive electrode active material layer and the negative electrode active material layer to a predetermined range, and the negative electrode active material layer is formed of amorphous carbon having a large structure, or It has been found that an all-solid secondary battery having excellent both cycle characteristics and discharge rate characteristics can be obtained by containing a predetermined amount or more of amorphous carbon having a large particle size as a negative electrode active material. That is, when the negative electrode active material layer contains a predetermined amount or more of amorphous carbon having such characteristics, the number of interfaces between carbon particles or between carbon particle aggregates is reduced, and lithium in the negative electrode active material layer is reduced. We have found that an all-solid-state secondary battery that facilitates diffusion and has excellent cycle characteristics and discharge rate characteristics can be obtained, and has reached the present invention.
すなわち、本発明の態様１は、正極活物質層と、固体電解質層と、リチウムと合金又は化合物を形成する負極活物質層とをこの順に有する全固体二次電池であって、前記負極活物質層が、（ａ）窒素吸着比表面積が０ｍ２／ｇ超、１００ｍ２／ｇ以下、又は（ｂ）ＤＢＰ吸油量が１５０ｍｌ／１００ｇ以上、の少なくとも一方を満たす無定形炭素を、負極活物質総質量に対して３３質量％以上含有し、前記正極活物質層の初期充電容量と前記負極活物質層の初期充電容量との比が、以下の式（１）を満たすことを特徴とする全固体リチウム二次電池である。
０．０１＜ｂ／ａ＜０．５ （１）
（ここで、ａは前記正極活物質層の初期充電容量（ｍＡｈ）であり、ｂは前記負極活物質層の初期充電容量（ｍＡｈ）である）
That is, the first aspect of the present invention is an all-solid secondary battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer forming an alloy or compound with lithium in this order, and the negative electrode active material. The layer is composed of atypical carbon satisfying at least one of (a) a nitrogen adsorption specific surface area of more than 0 m 2 / g and 100 m 2 / g or less, or (b) a DBP oil absorption of 150 ml / 100 g or more. All solids containing 33% by mass or more with respect to the mass, and the ratio of the initial charge capacity of the positive electrode active material layer to the initial charge capacity of the negative electrode active material layer satisfies the following formula (1). It is a lithium secondary battery.
0.01 <b / a <0.5 (1)
(Here, a is the initial charge capacity (mAh) of the positive electrode active material layer, and b is the initial charge capacity (mAh) of the negative electrode active material layer).
本発明の態様２は、前記無定形炭素の窒素吸着比表面積が２０ｍ２／ｇ以上、１００ｍ２／ｇ以下である前記態様１の全固体二次電池である。 Aspect 2 of the present invention is the all-solid-state secondary battery of the aspect 1 in which the nitrogen adsorption specific surface area of the amorphous carbon is 20 m 2 / g or more and 100 m 2 / g or less.
本発明の態様３は、前記無定形炭素の窒素吸着比表面積が３０ｍ２／ｇ以上、１００ｍ２／ｇ以下である前記態様２の全固体二次電池である。 Aspect 3 of the present invention is the all-solid-state secondary battery of the aspect 2 in which the nitrogen adsorption specific surface area of the amorphous carbon is 30 m 2 / g or more and 100 m 2 / g or less.
本発明の態様４は、前記無定形炭素のＤＢＰ吸油量が１５０ｍｌ／１００ｇ以上、４００ｍｌ／１００ｇ以下である前記態様１〜３のいずれかの全固体二次電池である。 Aspect 4 of the present invention is the all-solid-state secondary battery according to any one of the above-mentioned aspects 1 to 3 in which the DBP oil absorption of the amorphous carbon is 150 ml / 100 g or more and 400 ml / 100 g or less.
本発明の態様５は、前記無定形炭素のＤＢＰ吸油量が２００ｍｌ／１００ｇ以下である前記態様４の全固体二次電池である。 Aspect 5 of the present invention is the all-solid-state secondary battery of the aspect 4 in which the DBP oil absorption of the amorphous carbon is 200 ml / 100 g or less.
本発明の態様６は、前記負極活物質層が、金、白金、パラジウム、ケイ素、銀、アルミニウム、ビスマス、錫、インジウム及び亜鉛よりなる群から選択される少なくとも１種を更に含む、前記態様１〜５のいずれかの全固体二次電池である。 Aspect 6 of the present invention further comprises at least one selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, indium and zinc in the negative electrode active material layer. It is an all-solid-state secondary battery according to any one of ~ 5.
本発明の態様７は、前記負極活物質層が、前記無定形炭素を、負極活物質総質量に対して合計で３３質量％以上９５質量％以下含有する前記態様１〜６のいずれかの全固体二次電池である。 In aspect 7 of the present invention, the negative electrode active material layer contains 33% by mass or more and 95% by mass or less in total of the amorphous carbon with respect to the total mass of the negative electrode active material. It is a solid-state secondary battery.
本発明の態様８は、前記無定形炭素が、カーボンブラックである、前記態様１〜７のいずれかの全固体二次電池である。 Aspect 8 of the present invention is an all-solid-state secondary battery according to any one of aspects 1 to 7, wherein the amorphous carbon is carbon black.
本発明の態様９は、前記カーボンブラックがファーネスブラック、アセチレンブラック及びケッチェンブラックよりなる群から選択される少なくとも１種である、前記態様１〜８のいずれかの全固体二次電池である。 Aspect 9 of the present invention is an all-solid-state secondary battery according to any one of aspects 1 to 8, wherein the carbon black is at least one selected from the group consisting of furnace black, acetylene black and ketjen black.
本発明の態様１０は、前記態様１〜９のいずれか１項に記載の全固体二次電池を前記負極活物質層の初期充電容量を超えて充電することを特徴とする全固体二次電池の充電方法である。 Aspect 10 of the present invention is an all-solid-state secondary battery according to any one of aspects 1 to 9, wherein the all-solid-state secondary battery is charged in excess of the initial charge capacity of the negative electrode active material layer. It is a charging method of.
本発明の態様１１は、充電量が前記負極活物質層の初期充電容量の２倍以上、１００倍以下の間の値であること前記態様１０の全固体二次電池の充電方法である。 Aspect 11 of the present invention is the method for charging an all-solid-state secondary battery according to the aspect 10, wherein the charge amount is a value between twice or more and 100 times or less the initial charge capacity of the negative electrode active material layer.
本発明によれば、サイクル特性及び放電レート特性のいずれにも優れた全固体二次電池及びその充電方法を提供することができる。 According to the present invention, it is possible to provide an all-solid-state secondary battery having excellent both cycle characteristics and discharge rate characteristics and a charging method thereof.
以下に本発明の全固体二次電池の一実施形態について説明する。なお以下に示す実施形態は、本発明の技術思想を具体化するための全固体二次電池を例示するものであり、本発明は以下のものに限定されない。また以下の説明では、全固体二次電池の各種の特性を向上できるメカニズムについて説明している場合がある。これらは本発明者らが現時点で得ている知見により考えたメカニズムであり、本発明の技術的範囲を限定するものではない。 An embodiment of the all-solid-state secondary battery of the present invention will be described below. The embodiments shown below exemplify an all-solid-state secondary battery for embodying the technical idea of the present invention, and the present invention is not limited to the following. Further, in the following description, a mechanism capable of improving various characteristics of the all-solid-state secondary battery may be described. These are mechanisms considered based on the findings obtained by the present inventors at present, and do not limit the technical scope of the present invention.
＜１．全固体二次電池の構成＞
本実施形態の全固体二次電池１は、正極と負極との間をリチウムイオンが移動することで充放電を行う、所謂リチウム二次電池である。具体的にこの全固体二次電池１は、図１に示すように、正極層１０と、負極層２０と、正極層１０と負極層２０の間に配置された固体電解質層３０と備えている。
<1. Configuration of all-solid-state secondary battery>
The all-solid-state secondary battery 1 of the present embodiment is a so-called lithium secondary battery that charges and discharges by moving lithium ions between the positive electrode and the negative electrode. Specifically, as shown in FIG. 1, the all-solid-state secondary battery 1 includes a positive electrode layer 10, a negative electrode layer 20, and a solid electrolyte layer 30 arranged between the positive electrode layer 10 and the negative electrode layer 20. ..
（１）正極層
正極層１０は、負極層２０に向かって順に配置された正極集電体１１及び正極活物質層１２を有する。
(1) Positive Electrode Layer The positive electrode layer 10 has a positive electrode current collector 11 and a positive electrode active material layer 12 arranged in order toward the negative electrode layer 20.
正極集電体１１は板状又は箔状をなすものである。正極集電体１１は、例えば、インジウム、銅、マグネシウム、ステンレス鋼、チタン、鉄、コバルト、ニッケル、亜鉛、アルミニウム、ゲルマニウム、リチウムよりなる群から選択される１種の金属、又は２種以上の金属の合金からなるものである。 The positive electrode current collector 11 has a plate shape or a foil shape. The positive electrode current collector 11 is, for example, one kind of metal selected from the group consisting of indium, copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, and lithium, or two or more kinds of metals. It is made of a metal alloy.
正極活物質層１２はリチウムイオンを可逆的に吸蔵及び放出するものである。具体的には、正極活物質層１２は正極活物質と固体電解質とを含有する。 The positive electrode active material layer 12 reversibly occludes and releases lithium ions. Specifically, the positive electrode active material layer 12 contains a positive electrode active material and a solid electrolyte.
正極活物質の具体的な態様として、例えば、コバルト酸リチウム（以下、ＬＣＯと称する）、ニッケル酸リチウム、ニッケルコバルト酸リチウム、ニッケルコバルトアルミニウム酸リチウム（以下、ＮＣＡと称する）、ニッケルコバルトマンガン酸リチウム（以下、ＮＣＭと称する）、マンガン酸リチウム及びリン酸鉄リチウム等のリチウム塩、並びに硫化リチウム等を挙げることができる。正極活物質層１２は、正極活物質として、これらの化合物から選択される１種のみを含んでよく、また２種以上を含んでいてもよい。 Specific embodiments of the positive electrode active material include, for example, lithium cobalt oxide (hereinafter referred to as LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (hereinafter referred to as NCA), and lithium nickel cobalt manganate. (Hereinafter referred to as NCM), lithium salts such as lithium manganate and lithium iron oxide, lithium sulfide and the like can be mentioned. The positive electrode active material layer 12 may contain only one type selected from these compounds as the positive electrode active material, or may contain two or more types.
正極活物質は、上述したリチウム塩のうち、層状岩塩型構造を有する遷移金属酸化物のリチウム塩を含んで構成されることが好ましい。ここで「層状岩塩型構造」とは、立方晶岩塩型構造の＜１１１＞方向に酸素原子層と金属原子層とが交互に規則配列し、その結果それぞれの原子層が二次元平面を形成している構造である。また「立方晶岩塩型構造」とは、結晶構造の１種である塩化ナトリウム型構造のことを意味する。具体的には、陽イオン及び陰イオンの各々が形成する面心立方格子が互いに単位格子の稜の１／２だけずれて配置された構造を表す。 The positive electrode active material is preferably composed of the above-mentioned lithium salts containing a lithium salt of a transition metal oxide having a layered rock salt type structure. Here, the "layered rock salt type structure" means that oxygen atomic layers and metal atomic layers are alternately regularly arranged in the <111> direction of the cubic rock salt structure, and as a result, each atomic layer forms a two-dimensional plane. It is a structure. Further, the "cubic rock salt type structure" means a sodium chloride type structure which is one kind of crystal structure. Specifically, it represents a structure in which face-centered cubic lattices formed by each of cations and anions are arranged so as to be offset from each other by 1/2 of the ridge of the unit cell.
このような層状岩塩型構造を有する遷移金属酸化物のリチウム塩として、例えば、ＬｉＮｉｘＣｏｙＡｌｚＯ２（ＮＣＡ）、又はＬｉＮｉｘＣｏｙＭｎｚＯ２（ＮＣＭ）（ただし、０＜ｘ＜１、０＜ｙ＜１、０＜ｚ＜１、かつｘ＋ｙ＋ｚ＝１）等の三元系遷移金属酸化物のリチウム塩が挙げられる。正極活物質層１２が、このような層状岩塩型構造を有する三元系遷移金属酸化物のリチウム塩を正極活物質として含有することにより、全固体二次電池１のエネルギー密度及び熱安定性を向上させることができる。 As the lithium salt of a transition metal oxide having such a layered rock-salt structure, for example, LiNi x Co y Al z O 2 (NCA), or LiNi x Co y Mn z O 2 (NCM) ( however, 0 <x Examples thereof include lithium salts of ternary transition metal oxides such as <1, 0 <y <1, 0 <z <1, and x + y + z = 1). By containing the lithium salt of the ternary transition metal oxide having such a layered rock salt type structure as the positive electrode active material in the positive electrode active material layer 12, the energy density and thermal stability of the all-solid-state secondary battery 1 can be improved. Can be improved.
ここで、正極活物質の形状としては、例えば、真球状、楕円球状等の粒子形状を挙げることができる。また、正極活物質の粒径は特に制限されず、従来の全固体二次電池の正極活物質に適用可能な範囲であればよい。なお、正極活物質層１２における正極活物質の含有量も特に制限されず、従来の全固体二次電池の正極層に適用可能な範囲であればよい。 Here, examples of the shape of the positive electrode active material include particle shapes such as a true sphere and an elliptical sphere. The particle size of the positive electrode active material is not particularly limited as long as it is applicable to the positive electrode active material of the conventional all-solid-state secondary battery. The content of the positive electrode active material in the positive electrode active material layer 12 is not particularly limited as long as it is applicable to the positive electrode layer of the conventional all-solid-state secondary battery.
正極活物質は被覆層によって覆われていてもよい。この被覆層は全固体二次電池の正極活物質の被覆層として既知のものであってよい。被覆層の具体的な材料として、例えばＬｉ２Ｏ−ＺｒＯ２等が挙げられる。 The positive electrode active material may be covered with a coating layer. This coating layer may be known as a coating layer for the positive electrode active material of the all-solid-state secondary battery. Specific examples of the material of the coating layer include Li 2 O-ZrO 2 .
正極活物質層１２に含まれる固体電解質は、後述する固体電解質層３０に含まれる固体電解質と同種のものであってもよく、異なるものであってもよい。 The solid electrolyte contained in the positive electrode active material layer 12 may be of the same type as or different from the solid electrolyte contained in the solid electrolyte layer 30 described later.
また正極活物質層１２は、正極活物質及び固体電解質に加えて、例えば既知の導電助剤、結着剤（バインダ）、フィラー及び分散剤等を更に含有してもよい。 Further, the positive electrode active material layer 12 may further contain, for example, a known conductive auxiliary agent, a binder, a filler, a dispersant, or the like, in addition to the positive electrode active material and the solid electrolyte.
（２）負極層
負極層２０は、正極層１０に向かって順に配置された負極集電体２１及び負極活物質層２２を含む。
(2) Negative electrode layer The negative electrode layer 20 includes a negative electrode current collector 21 and a negative electrode active material layer 22 arranged in order toward the positive electrode layer 10.
負極集電体２１は板状又は箔状をなすものである。負極集電体２１は、リチウムと反応しない、すなわち合金及び化合物のいずれも形成しない材料から構成されることが好ましい。負極集電体２１を構成する材料としては、例えば、銅、ステンレス鋼、チタン、鉄、コバルト及びニッケル等を挙げることができる。負極集電体２１は、これらの金属のいずれか１種で構成されていてもよいし、２種以上の金属の合金又はクラッド材で構成されていてもよい。 The negative electrode current collector 21 has a plate shape or a foil shape. The negative electrode current collector 21 is preferably made of a material that does not react with lithium, that is, does not form either an alloy or a compound. Examples of the material constituting the negative electrode current collector 21 include copper, stainless steel, titanium, iron, cobalt, nickel and the like. The negative electrode current collector 21 may be composed of any one of these metals, or may be composed of an alloy or clad material of two or more kinds of metals.
負極活物質層２２は、リチウムと合金又は化合物を形成する負極活物質を含有する。負極活物質層２２は、リチウムと合金又は化合物を形成する負極活物質として無定形炭素を含有する。無定形炭素の具体例として、例えば、アセチレンブラック、ファーネスブラック及びケッチェンブラック等のカーボンブラック、並びにグラフェン等が挙げられる。負極活物質層２２は、これらから選択される無定形炭素を１種又は複数種含んでもよい。 The negative electrode active material layer 22 contains a negative electrode active material that forms an alloy or compound with lithium. The negative electrode active material layer 22 contains amorphous carbon as a negative electrode active material that forms an alloy or compound with lithium. Specific examples of the amorphous carbon include carbon blacks such as acetylene black, furnace black and Ketjen black, and graphene. The negative electrode active material layer 22 may contain one or more types of amorphous carbon selected from these.
本実施形態の全固体二次電池１は、負極活物質層２２が、負極活物質として以下の（ａ）又は（ｂ）の少なくとも一方を満たす無定形炭素を、負極活物質総質量に対して合計で３３質量％以上含有することを特徴とする。
（ａ）窒素吸着比表面積が０ｍ２／ｇ超、１００ｍ２／ｇ以下
（ｂ）ＤＢＰ吸油量が１５０ｍｌ／１００ｇ以上
In the all-solid-state secondary battery 1 of the present embodiment, the negative electrode active material layer 22 contains amorphous carbon satisfying at least one of the following (a) or (b) as the negative electrode active material with respect to the total negative electrode active material mass. It is characterized by containing 33% by mass or more in total.
(A) Nitrogen adsorption specific surface area is more than 0 m 2 / g, 100 m 2 / g or less (b) DBP oil absorption is 150 ml / 100 g or more
（窒素吸着比表面積が０ｍ２／ｇ超、１００ｍ２／ｇ以下）
負極活物質として含有する無定形炭素の窒素吸着比表面積を１００ｍ２／ｇ以下にすることにより、炭素の粒径が大きくなり、リチウムが炭素粒子の粒界を伝導する回数が減少する。そのため負極活物質層２２内においてリチウムの拡散が容易になる。その結果、放電中にリチウムが負極層内に孤立しにくくなり、全固体二次電池１のサイクル特性及び放電レート特性を向上させることができる。
(Nitrogen adsorption specific surface area is more than 0 m 2 / g, 100 m 2 / g or less)
By reducing the specific surface area of the amorphous carbon contained as the negative electrode active material to 100 m 2 / g or less, the particle size of carbon is increased and the number of times lithium conducts through the grain boundaries of carbon particles is reduced. Therefore, the diffusion of lithium in the negative electrode active material layer 22 becomes easy. As a result, lithium is less likely to be isolated in the negative electrode layer during discharge, and the cycle characteristics and discharge rate characteristics of the all-solid-state secondary battery 1 can be improved.
負極活物質として含有する無定形炭素の窒素吸着比表面積は、２０ｍ２／ｇ以上であることが好ましく、３０ｍ２／ｇ以上であることがより好ましく、４０ｍ２／ｇ以上であることがさらに好ましい。無定形炭素の窒素吸着比表面積の下限値がこのような範囲であれば、放電レート特性をより一層向上させることができる。 The nitrogen adsorption specific surface area of the amorphous carbon contained as the negative electrode active material is preferably 20 m 2 / g or more, more preferably 30 m 2 / g or more, and further preferably 40 m 2 / g or more. .. If the lower limit of the nitrogen adsorption specific surface area of amorphous carbon is in such a range, the discharge rate characteristics can be further improved.
ここで、負極活物質層２２が負極活物質として含有する無定形炭素の「窒素吸着比表面積」とは、負極活物質層２２が含有する無定形炭素が１種である場合は、当該１種の無定形炭素の窒素吸着比表面積である。また、負極活物質層２２が含有する無定形炭素が複数種である場合は、複数種の無定形炭素のそれぞれの窒素吸着比表面積である。 Here, the "nitrogen adsorption specific surface area" of the amorphous carbon contained in the negative electrode active material layer 22 as the negative electrode active material is the type 1 when the amorphous carbon contained in the negative electrode active material layer 22 is one type. It is the specific surface area of nitrogen adsorption of amorphous carbon. When the negative electrode active material layer 22 contains a plurality of types of amorphous carbon, it is the nitrogen adsorption specific surface area of each of the plurality of types of amorphous carbon.
負極活物質層２２が含有する無定形炭素の窒素吸着比表面積は、窒素吸着法（ＪＩＳ Ｋ６２１７−２：２００１）により測定することができる。具体的には、約３００℃の高温で一度脱気した例えばカーボンブラック等の無定形炭素を、窒素雰囲気下で液体窒素温度に冷却する。そして平衡状態に達したのちのカーボン試料の質量増加（窒素吸着量）とその際の窒素雰囲気圧を測定し、ＢＥＴ（Ｂｒｕｎａｕｅｒ−Ｅｍｍｅｔｔ−Ｔｅｌｌｅｒ）の式に当てはめることにより窒素吸着比表面積の値を算出することができる。 The nitrogen adsorption specific surface area of the amorphous carbon contained in the negative electrode active material layer 22 can be measured by the nitrogen adsorption method (JIS K6217-2: 2001). Specifically, amorphous carbon such as carbon black, which has been degassed once at a high temperature of about 300 ° C., is cooled to a liquid nitrogen temperature in a nitrogen atmosphere. Then, after reaching the equilibrium state, the mass increase (nitrogen adsorption amount) of the carbon sample and the nitrogen atmospheric pressure at that time are measured, and the value of the nitrogen adsorption specific surface area is calculated by applying it to the formula of BET (Brunauer-Emmett-Teller). Can be calculated.
（ＤＢＰ吸油量が１５０ｍｌ／１００ｇ以上）
負極活物質として含有する無定形炭素のＤＢＰ吸油量を１５０ｍｌ／１００ｇ以上にすることにより、炭素粒子のアグリゲート（一次凝集体）のサイズが大きくなり、アグリゲート内部を伝ったリチウムの拡散が容易になる。そのため負極活物質層２２内においてリチウムの拡散が容易になり、放電中に負極層内にリチウムが孤立しにくくなり、全固体二次電池１のサイクル特性及び放電レート特性が向上する。
(DBP oil absorption is 150 ml / 100 g or more)
By increasing the DBP oil absorption of amorphous carbon contained as the negative electrode active material to 150 ml / 100 g or more, the size of the aggregate (primary aggregate) of the carbon particles becomes large, and the diffusion of lithium transmitted through the inside of the aggregate is easy. become. Therefore, the diffusion of lithium in the negative electrode active material layer 22 becomes easy, lithium is less likely to be isolated in the negative electrode layer during discharging, and the cycle characteristics and the discharge rate characteristics of the all-solid-state secondary battery 1 are improved.
負極活物質として含有する無定形炭素のＤＢＰ吸油量は、４００ｍｌ／１００ｇ以下であることが好ましく、２００ｍｌ／１００ｇ以下であることがより好ましい。無定形炭素のＤＢＰ吸油量の上限値がこのような範囲であれば、放電レート特性をより一層向上させることができる。 The amount of DBP oil absorbed by the amorphous carbon contained as the negative electrode active material is preferably 400 ml / 100 g or less, and more preferably 200 ml / 100 g or less. If the upper limit of the DBP oil absorption amount of amorphous carbon is in such a range, the discharge rate characteristic can be further improved.
ここで、負極活物質層２２が負極活物質として含有する無定形炭素の「ＤＢＰ吸油量」とは、負極活物質層２２が含有する無定形炭素が１種である場合は、当該１種の無定形炭素のＤＢＰ吸油量である。また、負極活物質層２２が含有する無定形炭素が複数種である場合は、複数種の無定形炭素のそれぞれのＤＢＰ吸油量である。 Here, the "DBP oil absorption amount" of the amorphous carbon contained in the negative electrode active material layer 22 as the negative electrode active material is the one type of amorphous carbon contained in the negative electrode active material layer 22. DBP oil absorption of amorphous carbon. When the negative electrode active material layer 22 contains a plurality of types of amorphous carbon, it is the DBP oil absorption amount of each of the plurality of types of amorphous carbon.
負極活物質層２２が含有する無定形炭素のＤＢＰ吸油量は、ＪＩＳ Ｋ６２１７−４：２００８に準拠するＤＢＰ吸油量の測定により算出することができる。具体的には、回転翼によってかき混ぜられている試料にフタル酸ジブチル（ＤＢＰ）を定速度ビュレットで滴定する。ＤＢＰを添加するにつれて，この混合物は自由に流動する粉体から、やや粘性をもつ塊へと変化する。粘性特性の変化によって発生するトルクが、設定値に達するか、又はトルク曲線から得られた最大トルクの一定割合に達した時点をこの測定の終点とする。終点時のＤＢＰの体積（ｍｌ）を試料質量（ｇ）で割り、１００倍することにより、ＤＢＰ吸油量（ｍｌ／１００ｇ）を求めることができる。 The DBP oil absorption amount of the amorphous carbon contained in the negative electrode active material layer 22 can be calculated by measuring the DBP oil absorption amount according to JIS K6217-4: 2008. Specifically, dibutyl phthalate (DBP) is titrated with a constant velocity burette on a sample stirred by a rotor. With the addition of DBP, the mixture changes from a freely flowing powder to a slightly viscous mass. The end point of this measurement is when the torque generated by the change in viscosity characteristics reaches a set value or a certain percentage of the maximum torque obtained from the torque curve. The DBP oil absorption amount (ml / 100 g) can be obtained by dividing the volume (ml) of DBP at the end point by the sample mass (g) and multiplying by 100.
負極活物質層２２は、リチウムと合金又は化合物を形成する負極活物質として無定形炭素のみを含有してもよく、無定形炭素に加えて、例えば金、白金、パラジウム、ケイ素、銀、アルミニウム、ビスマス、錫、インジウム及び亜鉛よりなる群から選択される少なくとも１種を更に含有していてもよい。 The negative electrode active material layer 22 may contain only amorphous carbon as the negative electrode active material forming an alloy or compound with lithium, and in addition to the amorphous carbon, for example, gold, platinum, palladium, silicon, silver, aluminum, etc. It may further contain at least one selected from the group consisting of bismuth, tin, indium and zinc.
ここで、金、白金、パラジウム、ケイ素、銀、アルミニウム、ビスマス、錫、インジウム及び亜鉛から選択される少なくとも１種を負極活物質として含有する場合、これらの負極活物質の粒径は４μｍ以下であることが好ましい。さらに１００ｎｍ以下であることがより好ましい。このような粒径であれば、全固体二次電池１の出力特性、サイクル特性が更に向上する。ここで、負極活物質の粒径は、例えばレーザー式粒度分布系を用いて測定したメジアン径（いわゆるＤ５０）を用いることができる。粒径の下限値は特に制限されないが、１０ｎｍであってもよい。当該効果は、負極活物質層２２において、金、白金、パラジウム、ケイ素、銀、アルミニウム、ビスマス、錫、インジウム及び亜鉛から選択される１種以上を、合計で５質量％以上含有することで得ることができる。 Here, when at least one selected from gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, indium and zinc is contained as the negative electrode active material, the particle size of these negative electrode active materials is 4 μm or less. It is preferable to have. Further, it is more preferably 100 nm or less. With such a particle size, the output characteristics and cycle characteristics of the all-solid-state secondary battery 1 are further improved. Here, as the particle size of the negative electrode active material, for example, the median diameter (so-called D 50 ) measured using a laser particle size distribution system can be used. The lower limit of the particle size is not particularly limited, but may be 10 nm. The effect is obtained by containing at least one selected from gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, indium and zinc in the negative electrode active material layer 22 in a total of 5% by mass or more. be able to.
（無定形炭素の含有量が合計で３３質量％以上）
負極活物質層２２における、上記した（ａ）又は（ｂ）の条件を満たす無定形炭素の含有量が合計で３３質量％未満であると、全固体二次電池１のサイクル特性及び放電レート特性を十分に向上することができない。それ故、負極活物質層２２における、上記した（ａ）又は（ｂ）の条件を満たす無定形炭素の含有量を合計で３３質量％以上とする必要がある。
(The total content of amorphous carbon is 33% by mass or more)
When the total content of amorphous carbon satisfying the above conditions (a) or (b) in the negative electrode active material layer 22 is less than 33% by mass, the cycle characteristics and discharge rate characteristics of the all-solid-state secondary battery 1 Cannot be improved sufficiently. Therefore, the content of the amorphous carbon satisfying the above conditions (a) or (b) in the negative electrode active material layer 22 needs to be 33% by mass or more in total.
一方で、上記した（ａ）又は（ｂ）の条件を満たす無定形炭素の含有量の上限は特に制限されないが、例えば９５質量％以下であることが好ましい。 On the other hand, the upper limit of the content of amorphous carbon satisfying the above-mentioned conditions (a) or (b) is not particularly limited, but is preferably 95% by mass or less, for example.
ここで、負極活物質層２２における無定形炭素の「含有量」とは、負極活物質層２２に含まれる負極活物質の総質量を１００質量％とし、これに対する上記した（ａ）又は（ｂ）の条件を満たす１種又は複数種の無定形炭素の合計質量の比を意味する。 Here, the "content" of amorphous carbon in the negative electrode active material layer 22 means that the total mass of the negative electrode active material contained in the negative electrode active material layer 22 is 100% by mass, and the above-mentioned (a) or (b) with respect to this. ) Means the ratio of the total mass of one or more types of amorphous carbon.
負極活物質層２２における上記した（ａ）又は（ｂ）の条件を満たす無定形炭素の含有量は、例えば以下の方法によりにより測定することができる。まず燃焼法により負極活物質層２２中の炭素の含有量を測定する。具体的には、負極活物質層２２のサンプルを酸素を混合したヘリウム気流下で高温に加熱し、発生する二酸化炭素を定量することにより負極活物質層２２中の炭素の含有量を測定する。さらにレーザー散乱法で粒度分布を見積もり、負極活物質層２２中に何種類の無定形炭素が含有されているかを測定する。さらに透過型電子顕微鏡（ＴＥＭ）を用いて、粒径とストラクチャーを観察する。上記の測定・観察結果を総合することにより、負極活物質層２２中に含まれる無形系炭素の種類数、各種の無定形炭素の含有率、各種の無定形炭素の粒径及びストラクチャーについての情報を得て、これにより負極活物質層２２における上記した（ａ）又は（ｂ）の条件を満たす無定形炭素の含有量を測定することができる。なお当然ながら、負極活物質層２２の製造条件（各種の無定形炭素の窒素吸着比表面積、ＤＢＰ吸油量及び含有量、その他の負極活物質の含有量等）から、完成品である全固体二次電池１における、負極活物質層２２中の上記した（ａ）又は（ｂ）の条件を満たす無定形炭素の含有量を見積もることもできる。 The content of amorphous carbon satisfying the above conditions (a) or (b) in the negative electrode active material layer 22 can be measured by, for example, the following method. First, the carbon content in the negative electrode active material layer 22 is measured by a combustion method. Specifically, the carbon content in the negative electrode active material layer 22 is measured by heating the sample of the negative electrode active material layer 22 to a high temperature under a helium stream mixed with oxygen and quantifying the generated carbon dioxide. Further, the particle size distribution is estimated by the laser scattering method, and the number of types of amorphous carbon contained in the negative electrode active material layer 22 is measured. In addition, a transmission electron microscope (TEM) is used to observe the particle size and structure. By combining the above measurement and observation results, information on the number of types of intangible carbon contained in the negative electrode active material layer 22, the content of various amorphous carbons, the particle size and structure of various amorphous carbons. With this, the content of amorphous carbon satisfying the above-mentioned conditions (a) or (b) in the negative electrode active material layer 22 can be measured. As a matter of course, from the production conditions of the negative electrode active material layer 22 (nitrogen adsorption specific surface area of various amorphous carbons, DBP oil absorption and content, content of other negative electrode active materials, etc.), the finished all-solid rechargeable battery It is also possible to estimate the content of amorphous carbon in the negative electrode active material layer 22 in the next battery 1 that satisfies the above conditions (a) or (b).
負極活物質層２２はバインダを更に含有していてもよい。バインダを含有することで、負極活物質層２２を負極集電体２１上で安定化させることができる。バインダを構成する材料としては、例えば、スチレンブタジエンゴム（ＳＢＲ）、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、ポリエチレン等の樹脂材料が挙げられる。バインダは、これらの樹脂材料から選択される少なくとも１種から構成されてよい。 The negative electrode active material layer 22 may further contain a binder. By containing the binder, the negative electrode active material layer 22 can be stabilized on the negative electrode current collector 21. Examples of the material constituting the binder include resin materials such as styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. The binder may be composed of at least one selected from these resin materials.
また負極活物質層２２には、従来の全固体二次電池で使用される添加剤、例えばフィラー、分散剤、イオン導電剤等が適宜配合されていてもよい。 Further, the negative electrode active material layer 22 may appropriately contain additives used in conventional all-solid-state secondary batteries, such as fillers, dispersants, and ionic conductive agents.
（３）固体電解質層
固体電解質層３０は、正極層１０と負極層２０の間（具体的には、正極活物質層１２と負極活物質層２２の間）に配置されている。固体電解質層３０は、イオンを移動させることができる固体電解質を含有する。
(3) Solid Electrolyte Layer The solid electrolyte layer 30 is arranged between the positive electrode layer 10 and the negative electrode layer 20 (specifically, between the positive electrode active material layer 12 and the negative electrode active material layer 22). The solid electrolyte layer 30 contains a solid electrolyte capable of transferring ions.
固体電解質は、例えば硫化物を主体とする固体電解質材料（以下、硫化物系固体電解質材料と称する）から構成される。硫化物系固体電解質材料としては、例えば、Ｌｉ２Ｓ−Ｐ２Ｓ５、Ｌｉ２Ｓ−Ｐ２Ｓ５−ＬｉＸ（Ｘは例えばＩ、Ｃｌ等のハロゲン元素）、Ｌｉ２Ｓ−Ｐ２Ｓ５−Ｌｉ２Ｏ、Ｌｉ２Ｓ−Ｐ２Ｓ５−Ｌｉ２Ｏ−ＬｉＩ、Ｌｉ２Ｓ−ＳｉＳ２、Ｌｉ２Ｓ−ＳｉＳ２−ＬｉＩ、Ｌｉ２Ｓ−ＳｉＳ２−ＬｉＢｒ、Ｌｉ２Ｓ−ＳｉＳ２−ＬｉＣｌ、Ｌｉ２Ｓ−ＳｉＳ２−Ｂ２Ｓ３−ＬｉＩ、Ｌｉ２Ｓ−ＳｉＳ２−Ｐ２Ｓ５−ＬｉＩ、Ｌｉ２Ｓ−Ｂ２Ｓ３、Ｌｉ２Ｓ−Ｐ２Ｓ５−ＺｍＳｎ（ｍ及びｎは正の数、ＺはＧｅ、Ｚｎ又はＧａのいずれか）、Ｌｉ２Ｓ−ＧｅＳ２、Ｌｉ２Ｓ−ＳｉＳ２−Ｌｉ３ＰＯ４、Ｌｉ２Ｓ−ＳｉＳ２−ＬｉｐＭＯｑ（ｐ及びｑは正の数、ＭはＰ、Ｓｉ、Ｇｅ、Ｂ、Ａｌ、Ｇａ又はＩｎのいずれか）等を挙げることができる。固体電解質は、これらの硫化物系固体電解質材料から選択される１種の材料により構成されてよく、２種以上の材料により構成されていてもよい。 The solid electrolyte is composed of, for example, a solid electrolyte material mainly composed of sulfide (hereinafter, referred to as a sulfide-based solid electrolyte material). The sulfide-based solid electrolyte material, for example, Li 2 S-P 2 S 5, Li 2 S-P 2 S 5 -LiX (X is for example I, a halogen element such as Cl), Li 2 S-P 2 S 5 -Li 2 O, Li 2 S -P 2 S 5 -Li 2 O-LiI, Li 2 S-SiS 2, Li 2 S-SiS 2 -LiI, Li 2 S-SiS 2 -LiBr, Li 2 S- SiS 2- LiCl, Li 2 S-SiS 2- B 2 S 3- LiI, Li 2 S-SiS 2- P 2 S 5- LiI, Li 2 SB 2 S 3 , Li 2 S-P 2 S 5 -Z m S n (m and n are positive numbers, Z is either Ge, Zn or Ga), Li 2 S-GeS 2 , Li 2 S-SiS 2 -Li 3 PO 4 , Li 2 S-SiS 2- Li p MO q (p and q are positive numbers, M is any of P, Si, Ge, B, Al, Ga or In) and the like can be mentioned. The solid electrolyte may be composed of one kind of material selected from these sulfide-based solid electrolyte materials, and may be composed of two or more kinds of materials.
固体電解質として、上記の硫化物固体電解質材料のうち、構成元素として硫黄（Ｓ）、リン（Ｐ）及びリチウム（Ｌｉ）を含むものを用いることが好ましい。具体的には、Ｌｉ２Ｓ−Ｐ２Ｓ５を含むものを用いることがより好ましい。硫化物系固体電解質材料としてＬｉ２Ｓ−Ｐ２Ｓ５を含むものを用いる場合、Ｌｉ２ＳとＰ２Ｓ５との混合モル比は、例えば、Ｌｉ２Ｓ：Ｐ２Ｓ５＝５０：５０〜９０：１０の範囲で選択されることが好ましい。 As the solid electrolyte, among the above-mentioned sulfide solid electrolyte materials, those containing sulfur (S), phosphorus (P) and lithium (Li) as constituent elements are preferably used. Specifically, it is more preferable to use one containing Li 2 SP 2 S 5 . When a material containing Li 2 SP 2 S 5 is used as the sulfide-based solid electrolyte material, the mixed molar ratio of Li 2 S and P 2 S 5 is, for example, Li 2 S: P 2 S 5 = 50 :. It is preferably selected in the range of 50 to 90:10.
なお固体電解質は、非晶質の状態であってもよく、結晶質の状態であってもよい。また、非晶質及び結晶質が混ざった状態でもよい。 The solid electrolyte may be in an amorphous state or in a crystalline state. Further, it may be in a state where amorphous and crystalline are mixed.
固体電解質層３０は、バインダを更に含有してもよい。当該バインダの材料として、例えば、スチレンブタジエンゴム（ＳＢＲ）、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、ポリエチレン、ポリアクリル酸等の樹脂を挙げることができる。当該バインダの材料は、正極活物質層１２及び負極活物質層２２内のバインダを構成する材料と同じであってもよいし、異なっていてもよい。 The solid electrolyte layer 30 may further contain a binder. Examples of the binder material include resins such as styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and polyacrylic acid. The material of the binder may be the same as or different from the material constituting the binder in the positive electrode active material layer 12 and the negative electrode active material layer 22.
（４）初期充電容量比
本実施形態の全固体二次電池１は、負極活物質層２２の初期充電容量に対して正極活物質層１２の初期充電容量が過大になるように構成されている。後述するように、本実施形態では、全固体二次電池１を、負極活物質層２２の初期充電容量を超えて充電（すなわち過充電）する。充電の初期には、負極活物質層２２内にリチウムが吸蔵される。すなわち、負極活物質は、正極層１０から移動してきたリチウムイオンと合金又は化合物を形成する。負極活物質層２２の初期充電容量を超えて充電が行われると、図２に示すように、負極活物質層２２の裏側、すなわち負極集電体２１と負極活物質層２２との間にリチウムが析出し、このリチウムによって金属層２３が形成される。金属層２３は主にリチウム（すなわち、金属リチウム）で構成される。このような現象は、負極活物質を特定の物質、すなわちリチウムと合金又は化合物を形成する物質で構成することで生じる。放電時には、負極活物質層２２及び金属層２３中のリチウムがイオン化し、正極層１０側に移動する。したがって、全固体二次電池１では、リチウムを負極活物質として使用することができる。さらに、負極活物質層２２は、金属層２３を被覆するので、金属層２３の保護層として機能するとともに、樹枝状の金属リチウムの析出及び成長を抑制することができる。これにより、全固体二次電池１の短絡及び容量低下が抑制され、ひいては、全固体二次電池１の特性が向上する。
(4) Initial Charge Capacity Ratio The all-solid-state secondary battery 1 of the present embodiment is configured such that the initial charge capacity of the positive electrode active material layer 12 becomes excessive with respect to the initial charge capacity of the negative electrode active material layer 22. .. As will be described later, in the present embodiment, the all-solid-state secondary battery 1 is charged (that is, overcharged) beyond the initial charge capacity of the negative electrode active material layer 22. At the initial stage of charging, lithium is occluded in the negative electrode active material layer 22. That is, the negative electrode active material forms an alloy or compound with the lithium ions that have moved from the positive electrode layer 10. When charging is performed in excess of the initial charge capacity of the negative electrode active material layer 22, lithium is formed on the back side of the negative electrode active material layer 22, that is, between the negative electrode current collector 21 and the negative electrode active material layer 22 as shown in FIG. Precipitates, and the metal layer 23 is formed by this lithium. The metal layer 23 is mainly composed of lithium (that is, metallic lithium). Such a phenomenon occurs when the negative electrode active material is composed of a specific substance, that is, a substance that forms an alloy or compound with lithium. At the time of discharge, lithium in the negative electrode active material layer 22 and the metal layer 23 is ionized and moves to the positive electrode layer 10. Therefore, in the all-solid-state secondary battery 1, lithium can be used as the negative electrode active material. Further, since the negative electrode active material layer 22 coats the metal layer 23, it can function as a protective layer of the metal layer 23 and suppress the precipitation and growth of dendritic metallic lithium. As a result, the short circuit and capacity decrease of the all-solid-state secondary battery 1 are suppressed, and the characteristics of the all-solid-state secondary battery 1 are improved.
具体的には、本実施形態の全固体二次電池１は、負極活物質層２２の初期充電容量に対する正極活物質層１２の初期充電容量の比、すなわち初期充電容量比は、以下の式（１）を満たす。
０．０１＜ｂ／ａ＜０．５ （１）
（ここで、ａは正極活物質層１２の初期充電容量（ｍＡｈ）であり、ｂは負極活物質層２２の初期充電容量（ｍＡｈ）である）
Specifically, in the all-solid-state secondary battery 1 of the present embodiment, the ratio of the initial charge capacity of the positive electrode active material layer 12 to the initial charge capacity of the negative electrode active material layer 22, that is, the initial charge capacity ratio is expressed by the following formula ( 1) is satisfied.
0.01 <b / a <0.5 (1)
(Here, a is the initial charge capacity (mAh) of the positive electrode active material layer 12, and b is the initial charge capacity (mAh) of the negative electrode active material layer 22).
初期充電容量比が０．０１以下である場合、全固体二次電池１の特性が低下する。この理由としては、負極活物質層２２が保護層として十分機能しなくなることが挙げられる。例えば、負極活物質層２２の厚さが非常に薄い場合、容量比が０．０１以下となりうる。この場合、充放電の繰り返しによって負極活物質層２２が崩壊し、樹枝状の金属リチウムが析出及び成長する可能性がある。この結果、全固体二次電池１の特性が低下する。そのため、初期充電容量比を０．０１超とする。
一方で、初期充電容量比が０．５以上になると、負極におけるリチウムの析出量が減少するため電池容量が減ってしまう。そのため、初期充電容量比は０．５未満とする。
When the initial charge capacity ratio is 0.01 or less, the characteristics of the all-solid-state secondary battery 1 deteriorate. The reason for this is that the negative electrode active material layer 22 does not sufficiently function as a protective layer. For example, when the thickness of the negative electrode active material layer 22 is very thin, the volume ratio can be 0.01 or less. In this case, the negative electrode active material layer 22 may collapse due to repeated charging and discharging, and dendritic metallic lithium may precipitate and grow. As a result, the characteristics of the all-solid-state secondary battery 1 are deteriorated. Therefore, the initial charge capacity ratio is set to more than 0.01.
On the other hand, when the initial charge capacity ratio is 0.5 or more, the amount of lithium deposited on the negative electrode decreases, so that the battery capacity decreases. Therefore, the initial charge capacity ratio is set to less than 0.5.
（初期充電容量の測定方法）
正極活物質層１２及び負極活物質層２２のそれぞれの初期充電容量は、以下のようにして測定することができる。
(Measurement method of initial charge capacity)
The initial charge capacity of each of the positive electrode active material layer 12 and the negative electrode active material layer 22 can be measured as follows.
正極活物質層１２の初期充電容量は、例えば、正極活物質の充電容量密度（ｍＡｈ／ｇ）に正極活物質層１２中の正極活物質の質量を乗じることで得られる。正極活物質が複数種類使用される場合、正極活物質毎に充電容量密度×質量の値を算出し、これらの値の総和を正極活物質層１２の初期充電容量とすればよい。 The initial charge capacity of the positive electrode active material layer 12 is obtained, for example, by multiplying the charge capacity density (mAh / g) of the positive electrode active material by the mass of the positive electrode active material in the positive electrode active material layer 12. When a plurality of types of positive electrode active materials are used, a value of charge capacity density × mass may be calculated for each positive electrode active material, and the sum of these values may be used as the initial charge capacity of the positive electrode active material layer 12.
負極活物質層２２の初期充電容量も同様の方法で算出される。すなわち、負極活物質層２２の初期充電容量は、例えば、負極活物質の充電容量密度（ｍＡｈ／ｇ）に負極活物質層２２中の負極活物質の質量を乗じることで得られる。負極活物質が複数種類使用される場合、負極活物質毎に充電容量密度×質量の値を算出し、これらの値の総和を負極活物質層２２の初期充電容量とすればよい。 The initial charge capacity of the negative electrode active material layer 22 is also calculated by the same method. That is, the initial charge capacity of the negative electrode active material layer 22 is obtained, for example, by multiplying the charge capacity density (mAh / g) of the negative electrode active material by the mass of the negative electrode active material in the negative electrode active material layer 22. When a plurality of types of negative electrode active materials are used, a value of charge capacity density × mass may be calculated for each negative electrode active material, and the sum of these values may be used as the initial charge capacity of the negative electrode active material layer 22.
ここで、正極活物質及び負極活物質の充電容量密度は、リチウム金属を対極に用いた全固体ハーフセルを用いて見積もられた容量である。 Here, the charge capacity densities of the positive electrode active material and the negative electrode active material are capacities estimated using an all-solid-state half cell using a lithium metal as a counter electrode.
正極活物質層１２及び負極活物質層２２の初期充電容量は、全固体ハーフセルを用いた測定により直接測定してもよい。初期充電容量を直接測定する具体的な方法としては、以下の様な方法を挙げることができる。 The initial charge capacity of the positive electrode active material layer 12 and the negative electrode active material layer 22 may be directly measured by measurement using an all-solid-state half cell. Specific methods for directly measuring the initial charge capacity include the following methods.
まず正極活物質層１２の初期充電容量は、正極活物質層１２を作用極、Ｌｉを対極として使用した全固体ハーフセルを作製し、ＯＣＶ（開放電圧）から上限充電電圧までＣＣ−ＣＶ充電を行うことで測定する。上限充電電圧とは、ＪＩＳ Ｃ ８７１２：２０１５の規格で定められたものであり、リチウムコバルト酸系の正極に対しては４．２５Ｖ、それ以外の正極についてはＪＩＳ Ｃ ８７１２：２０１５のＡ．３．２．３（異なる上限充電電圧を適用する場合の安全要求事項）の規定を適用して求められる電圧を指す。負極活物質層２２の初期充電容量については、負極活物質層２２を作用極、Ｌｉを対極として使用した全固体ハーフセルを作製し、ＯＣＶ（開放電圧）から０．０１ＶまでＣＣ−ＣＶ充電を行うことで測定する。 First, for the initial charge capacity of the positive electrode active material layer 12, an all-solid-state half cell using the positive electrode active material layer 12 as the working electrode and Li as the counter electrode is produced, and CC-CV charging is performed from OCV (open circuit voltage) to the upper limit charging voltage. To measure. The upper limit charging voltage is defined by the JIS C 8712: 2015 standard, and is 4.25 V for lithium cobalt oxide-based positive electrodes, and JIS C 8712: 2015 A. for other positive electrodes. Refers to the voltage required by applying the provisions of 3.2.3 (Safety requirements when applying different upper limit charging voltages). Regarding the initial charge capacity of the negative electrode active material layer 22, an all-solid-state half cell using the negative electrode active material layer 22 as the working electrode and Li as the counter electrode is produced, and CC-CV charging is performed from OCV (open circuit voltage) to 0.01 V. To measure.
前述した全固体ハーフセルについては、例えば、次のような方法で作製することができる。初期充電容量を測定したい正極活物質層１２又は負極活物質層２２を直径１３ｍｍの円板状に打ち抜く。全固体二次電池１に用いるものと同じ固体電解質粉末２００ｇを４０ＭＰａで固めて、直径：１３ｍｍ、厚み：約１．５ｍｍのペレット状にする。内径が１３ｍｍの筒の内部にこのペレットを入れて、その片側から円板状に打ち抜いた正極活物質層１２又は負極活物質層２２を入れ、反対側から直径１３ｍｍ厚みが０．０３ｍｍのリチウム箔を入れる。さらに両側からステンレス鋼の円板を１つずつ入れて、全体を筒の軸方向に３００ＭＰａ以上１０００ＭＰａ以下の圧力で一分間加圧して内容物を一体化させる。一体化させるときに加える圧力を３００ＭＰａ以上とすることによって、内容物を互いに密着させやすくなるので好ましい。また、この圧力は１０００ＭＰａより大きくしてもそれ以上は効果が横ばいになるので、１０００ＭＰａ以下にすることが好ましい。
これを、常時２２ＭＰａの圧力がかかるようにケース内に封入して全固体ハーフセルとすることができる。
The above-mentioned all-solid-state half cell can be produced, for example, by the following method. The positive electrode active material layer 12 or the negative electrode active material layer 22 whose initial charge capacity is to be measured is punched into a disk shape having a diameter of 13 mm. 200 g of the same solid electrolyte powder used for the all-solid-state secondary battery 1 is solidified at 40 MPa to form pellets having a diameter of 13 mm and a thickness of about 1.5 mm. This pellet is placed inside a cylinder with an inner diameter of 13 mm, and a positive electrode active material layer 12 or a negative electrode active material layer 22 punched out in a disk shape from one side thereof is placed, and a lithium foil having a diameter of 13 mm and a thickness of 0.03 mm is placed from the opposite side. Put in. Further, stainless steel disks are inserted one by one from both sides, and the whole is pressurized in the axial direction of the cylinder at a pressure of 300 MPa or more and 1000 MPa or less for one minute to integrate the contents. It is preferable that the pressure applied at the time of integration is 300 MPa or more because the contents can be easily brought into close contact with each other. Further, even if this pressure is made larger than 1000 MPa, the effect becomes flat above that, so it is preferable to make it 1000 MPa or less.
This can be sealed in a case so that a pressure of 22 MPa is constantly applied to form an all-solid-state half cell.
＜２．全固体二次電池の製造方法＞
次に、前記した全固体二次電池１の製造方法について説明する。本実施形態に係る全固体二次電池１は、正極層１０、負極層２０、及び固体電解質層３０をそれぞれ作製した後、上記の各層を積層することにより得ることができる。
<2. Manufacturing method of all-solid-state secondary battery>
Next, the method for manufacturing the all-solid-state secondary battery 1 described above will be described. The all-solid-state secondary battery 1 according to the present embodiment can be obtained by forming the positive electrode layer 10, the negative electrode layer 20, and the solid electrolyte layer 30, respectively, and then laminating each of the above layers.
（１）正極層作製工程
まず、正極活物質層１２を構成する材料（正極活物質、バインダ等）を非極性溶媒に添加して、スラリー（ペーストであってもよい）を作製する。ついで、得られたスラリーを、準備した正極集電体１１上に塗布する。これを乾燥させることにより積層体を得る。次いで得られた積層体を、例えば静水圧を用いて加圧することで、正極層１０が得られる。なお加圧工程は省略されてもよい。
(1) Positive Electrode Layer Preparation Step First, a material (positive electrode active material, binder, etc.) constituting the positive electrode active material layer 12 is added to a non-polar solvent to prepare a slurry (which may be a paste). Then, the obtained slurry is applied onto the prepared positive electrode current collector 11. A laminate is obtained by drying this. Next, the positive electrode layer 10 is obtained by pressurizing the obtained laminate using, for example, hydrostatic pressure. The pressurizing step may be omitted.
（２）負極層作製工程
まず、負極活物質層２２を構成する材料（負極活物質、バインダ等）を極性溶媒又は非極性溶媒に添加することで、スラリー（ペーストであってもよい）を作製する。ついで、得られたスラリーを準備した負極集電体２１上に塗布する。これを乾燥させることにより積層体を得る。次いで、得られた積層体を例えば静水圧を用いて加圧することで、負極層２０を作製する。なお加圧工程は省略されてもよい。
(2) Negative electrode layer manufacturing step First, a slurry (which may be a paste) is prepared by adding a material (negative electrode active material, binder, etc.) constituting the negative electrode active material layer 22 to a polar solvent or a non-polar solvent. To do. Then, the obtained slurry is applied onto the prepared negative electrode current collector 21. A laminate is obtained by drying this. Next, the negative electrode layer 20 is produced by pressurizing the obtained laminate using, for example, hydrostatic pressure. The pressurizing step may be omitted.
（３）固体電解質層作製工程
固体電解質層３０は、硫化物系固体電解質材料から形成された固体電解質により作製することができる。
(3) Solid Electrolyte Layer Preparation Step The solid electrolyte layer 30 can be made of a solid electrolyte formed from a sulfide-based solid electrolyte material.
まず、溶融急冷法やメカニカルミリング法により出発原料（例えば、Ｌｉ２Ｓ、Ｐ２Ｓ５等）を処理することで、硫化物系固体電解質材料を得る。 First, a sulfide-based solid electrolyte material is obtained by treating a starting material (for example, Li 2 S, P 2 S 5, etc.) by a melt quenching method or a mechanical milling method.
例えば、溶融急冷法を用いる場合、出発原料を所定量混合し、ペレット状にしたものを真空中で所定の反応温度で反応させた後、急冷することによって硫化物系固体電解質材料を作製することができる。なお、Ｌｉ２Ｓ及びＰ２Ｓ５の混合物の反応温度は、好ましくは４００℃〜１０００℃であり、より好ましくは８００℃〜９００℃である。また、反応時間は、好ましくは０．１時間〜１２時間であり、より好ましくは１時間〜１２時間である。さらに、反応物の急冷温度は、通常１０℃以下であり、好ましくは０℃以下であり、急冷速度は、通常１℃／ｓｅｃ〜１００００℃／ｓｅｃ程度であり、好ましくは１℃／ｓｅｃ〜１０００℃／ｓｅｃ程度である。 For example, when the melt quenching method is used, a sulfide-based solid electrolyte material is prepared by mixing a predetermined amount of starting materials, reacting the pellets in a vacuum at a predetermined reaction temperature, and then quenching. Can be done. The reaction temperature of the mixture of Li 2 S and P 2 S 5 is preferably 400 ° C. to 1000 ° C., more preferably 800 ° C. to 900 ° C. The reaction time is preferably 0.1 hour to 12 hours, and more preferably 1 hour to 12 hours. Further, the quenching temperature of the reaction product is usually 10 ° C. or lower, preferably 0 ° C. or lower, and the quenching rate is usually about 1 ° C./sec to 10000 ° C./sec, preferably 1 ° C./sec to 1000 ° C. It is about ° C./sec.
また、メカニカルミリング法を用いる場合、ボールミルなどを用いて出発原料を撹拌させて反応させることで、硫化物系固体電解質材料を作製することができる。なお、メカニカルミリング法における撹拌速度及び撹拌時間は特に限定されないが、撹拌速度が速いほど硫化物系固体電解質材料の生成速度を速くすることができ、撹拌時間が長いほど硫化物系固体電解質材料への原料の転化率を高くすることができる。 Further, when the mechanical milling method is used, a sulfide-based solid electrolyte material can be produced by stirring and reacting the starting raw materials with a ball mill or the like. The stirring speed and stirring time in the mechanical milling method are not particularly limited, but the faster the stirring speed, the faster the production rate of the sulfide-based solid electrolyte material, and the longer the stirring time, the more the sulfide-based solid electrolyte material. The conversion rate of the raw material of the above can be increased.
その後、得られた混合原料（硫化物系固体電解質材料）を所定温度で熱処理した後、これを粉砕することにより粒子状の固体電解質を作製することができる。固体電解質がガラス転移点を持つ場合は、熱処理によって非晶質から結晶質に変わる場合がある。 Then, the obtained mixed raw material (sulfide-based solid electrolyte material) is heat-treated at a predetermined temperature and then pulverized to produce a particulate solid electrolyte. If the solid electrolyte has a glass transition point, it may change from amorphous to crystalline by heat treatment.
続いて、上記の方法で得られた固体電解質を、例えば、エアロゾルデポジション法、コールドスプレー法、スパッタリング法等の既知の成膜法を用いて成膜することにより、固体電解質層３０を作製することができる。なお、固体電解質層３０は、固体電解質粒子単体を加圧することにより作製されてもよい。また、固体電解質層３０は、固体電解質と、溶媒、バインダを混合し、塗布乾燥し加圧することにより固体電解質層３０を作製してもよい。 Subsequently, the solid electrolyte layer 30 is produced by forming a solid electrolyte obtained by the above method using a known film forming method such as an aerosol deposition method, a cold spray method, or a sputtering method. be able to. The solid electrolyte layer 30 may be formed by pressurizing the solid electrolyte particles alone. Further, the solid electrolyte layer 30 may be formed by mixing the solid electrolyte with a solvent and a binder, applying, drying and pressurizing the solid electrolyte layer 30.
（４）積層工程
正極層１０と負極層２０とで固体電解質層３０を挟むように配置し、これを例えば静水圧等を用いて加圧することにより、本実施形態に係る全固体二次電池１を得ることができる。
(4) Laminating Step The all-solid-state secondary battery 1 according to the present embodiment is arranged so that the solid electrolyte layer 30 is sandwiched between the positive electrode layer 10 and the negative electrode layer 20, and is pressurized by using, for example, hydrostatic pressure. Can be obtained.
なお上記の方法で作製した全固体二次電池１を動作させ充放電する際に、全固体二次電池１に圧力をかけた状態で行ってもよい。上記圧力は、０．５ＭＰａ以上、１０ＭＰａ以下であってもよい。また圧力の印加は、ステンレス、真鍮、アルミニウム、ガラスなどの２枚の硬い板の間に全固体電池１を挟み、この２枚の板の間をねじで締めるなどの方法で行ってもよい。本実施形態に係る全固体電池においては、充放電を繰り返すと、界面層と負極活物質層との間に析出した金属リチウムがイオン化して溶解することにより空隙が生じる恐れがある。そこで、前記圧力を０．５ＭＰａ以上にすることによって、前述した空隙の発生を抑えて、電池出力の低下を抑えやすくすることができる。また、前記圧力を大きくしすぎると、電池の短絡が生じやすくなる傾向になる。そのため、前記圧力は１０ＭＰａ以下にすることが好ましい。 When the all-solid-state secondary battery 1 produced by the above method is operated and charged / discharged, the all-solid-state secondary battery 1 may be under pressure. The pressure may be 0.5 MPa or more and 10 MPa or less. Further, the pressure may be applied by sandwiching the all-solid-state battery 1 between two hard plates such as stainless steel, brass, aluminum, and glass, and tightening the screws between the two plates. In the all-solid-state battery according to the present embodiment, when charging and discharging are repeated, the metallic lithium precipitated between the interface layer and the negative electrode active material layer may be ionized and dissolved to form voids. Therefore, by setting the pressure to 0.5 MPa or more, it is possible to suppress the generation of the above-mentioned voids and to easily suppress the decrease in battery output. Further, if the pressure is increased too much, a short circuit of the battery tends to occur easily. Therefore, the pressure is preferably 10 MPa or less.
＜３．全固体二次電池の充電方法＞
次に、全固体二次電池１の充電方法について説明する。
<3. How to charge all-solid-state secondary battery>
Next, a method of charging the all-solid-state secondary battery 1 will be described.
本実施形態の全固体二次電池１の充電方法は、全固体二次電池１を、負極活物質層２２の充電容量を超えて充電（すなわち過充電）することを特徴とする。 The method for charging the all-solid-state secondary battery 1 of the present embodiment is characterized in that the all-solid-state secondary battery 1 is charged (that is, overcharged) in excess of the charging capacity of the negative electrode active material layer 22.
充電の初期には、負極活物質層２２内にリチウムが吸蔵される。負極活物質層２２の充電容量を超えて充電が行われると、図２に示すように、負極活物質層２２の裏側、すなわち負極集電体２１と負極活物質層２２との間にリチウムが析出し、このリチウムによって製造時には存在していなかった金属層２３が形成される。放電時には、負極活物質層２２及び金属層２３中のリチウムがイオン化し、正極層１０側に移動する。したがって、全固体二次電池１では、リチウムを負極活物質として使用することができる。さらに、負極活物質層２２は、金属層２３を被覆するので、金属層２３の保護層として機能するとともに、樹枝状の金属リチウムの析出及び成長を抑制することができる。これにより、全固体二次電池１の短絡及び容量低下が抑制され、ひいては、全固体二次電池１の特性が向上する。なお、本実施形態では、金属層２３は予め形成されていないので、全固体二次電池１の製造コストを低減できる。 At the initial stage of charging, lithium is occluded in the negative electrode active material layer 22. When charging is performed in excess of the charging capacity of the negative electrode active material layer 22, lithium is generated on the back side of the negative electrode active material layer 22, that is, between the negative electrode current collector 21 and the negative electrode active material layer 22, as shown in FIG. It precipitates, and this lithium forms a metal layer 23 that did not exist at the time of production. At the time of discharge, lithium in the negative electrode active material layer 22 and the metal layer 23 is ionized and moves to the positive electrode layer 10. Therefore, in the all-solid-state secondary battery 1, lithium can be used as the negative electrode active material. Further, since the negative electrode active material layer 22 coats the metal layer 23, it can function as a protective layer of the metal layer 23 and suppress the precipitation and growth of dendritic metallic lithium. As a result, the short circuit and capacity decrease of the all-solid-state secondary battery 1 are suppressed, and the characteristics of the all-solid-state secondary battery 1 are improved. In this embodiment, since the metal layer 23 is not formed in advance, the manufacturing cost of the all-solid-state secondary battery 1 can be reduced.
全固体二次電池１の充電量が負極活物質層２２の初期充電容量の２倍未満であると、負極層２０におけるリチウムの析出量が減って、電池容量が減ってしまうことがある。そのため、全固体二次電池１の充電量が負極活物質層２２の初期充電容量の２倍以上が好ましい。
一方で、全固体二次電池１の充電量が負極活物質層２２の初期充電容量の１００倍超であると、負極層２０の厚さが不十分となり、充放電の繰り返しによって負極層２０が崩壊し、デンドライトが析出及び成長することがある。そのため、全固体二次電池１の充電量が負極活物質層２２の初期充電容量の１００倍以下であることが好ましい。
If the charge amount of the all-solid-state secondary battery 1 is less than twice the initial charge capacity of the negative electrode active material layer 22, the amount of lithium precipitated in the negative electrode layer 20 may decrease, and the battery capacity may decrease. Therefore, the charge amount of the all-solid-state secondary battery 1 is preferably twice or more the initial charge capacity of the negative electrode active material layer 22.
On the other hand, if the charge amount of the all-solid-state secondary battery 1 is more than 100 times the initial charge capacity of the negative electrode active material layer 22, the thickness of the negative electrode layer 20 becomes insufficient, and the negative electrode layer 20 becomes insufficient due to repeated charging and discharging. It may disintegrate and deposit and grow dendrites. Therefore, the charge amount of the all-solid-state secondary battery 1 is preferably 100 times or less the initial charge capacity of the negative electrode active material layer 22.
なお金属層２３は、図２に示すように負極集電体２１と負極活物質層２２との間に形成されるものに限らず、図３に示すように、負極活物質層２２の内部に形成されてもよい。さらに、図４に示すように、金属層２３が、負極集電体２１と負極活物質層２２との間及び負極活物質層２２の内部の両方に形成されてもよい。 The metal layer 23 is not limited to the one formed between the negative electrode current collector 21 and the negative electrode active material layer 22 as shown in FIG. 2, but is inside the negative electrode active material layer 22 as shown in FIG. It may be formed. Further, as shown in FIG. 4, the metal layer 23 may be formed both between the negative electrode current collector 21 and the negative electrode active material layer 22 and inside the negative electrode active material layer 22.
全固体二次電池１を充電することにより、負極集電体２１と負極活物質層２２との間、又は負極活物質層２２の内部にリチウムが層状に析出するので、充放電によって全固体二次電池１内部でのボイドの発生を抑えることができる。これにより、リチウムが層状に析出しない場合に比べて、充放電による全固体二次電池１の内部の圧力上昇を抑えることができる。 By charging the all-solid-state secondary battery 1, lithium is deposited in layers between the negative electrode current collector 21 and the negative electrode active material layer 22 or inside the negative electrode active material layer 22, so that the all-solid-state secondary battery is charged and discharged. It is possible to suppress the generation of voids inside the next battery 1. As a result, it is possible to suppress an increase in pressure inside the all-solid-state secondary battery 1 due to charging / discharging, as compared with the case where lithium does not precipitate in layers.
なお上記したように、負極活物質層２２が、無定形炭素と、必要に応じて金、白金、パラジウム、ケイ素、銀、アルミニウム、ビスマス、錫、インジウム及び亜鉛よりなる群から選択される１種以上とを負極活物質として含有しているので、過充電した場合に、負極活物質層２２の固体電解質層３０側の表面におけるリチウムの析出を抑制することができる。その結果、樹枝状の金属リチウムの析出及び成長を抑制することができる。これにより、全固体二次電池の短絡および容量低下が抑制され、ひいては、全固体二次電池の特性が向上する。 As described above, the negative electrode active material layer 22 is one selected from the group consisting of amorphous carbon and, if necessary, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, indium and zinc. Since the above is contained as the negative electrode active material, it is possible to suppress the precipitation of lithium on the surface of the negative electrode active material layer 22 on the solid electrolyte layer 30 side when overcharged. As a result, the precipitation and growth of dendritic metallic lithium can be suppressed. As a result, the short circuit and capacity reduction of the all-solid-state secondary battery are suppressed, and the characteristics of the all-solid-state secondary battery are improved.
以下、実施例を挙げて本発明をより具体的に説明する。本発明は以下の実施例によって制限を受けるものではなく、前記、後記の趣旨に適合し得る範囲で変更を加えて実施することも可能であり、それらはいずれも本発明の技術的範囲に包含される。 Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited by the following examples, and it is possible to carry out modifications to the extent that it can be adapted to the above-mentioned purpose, and all of them are included in the technical scope of the present invention. Will be done.
（実施例１）
＜１．サンプル作製＞
まず以下の手順により、負極活物質層として無定形炭素を含有する全固体二次電池のサンプル（Ｎｏ．１〜１２）を作製した。なお、全固体二次電池の各サンプルは、負極活物質層が含有する無定形炭素の種類がそれぞれ異なる以外は、同一の構成となるようにした。
(Example 1)
<1. Sample preparation>
First, a sample (No. 1 to 12) of an all-solid-state secondary battery containing amorphous carbon as a negative electrode active material layer was prepared by the following procedure. Each sample of the all-solid-state secondary battery had the same configuration except that the type of amorphous carbon contained in the negative electrode active material layer was different.
（１）正極層の作製
正極活物質としてＬｉＮｉ０．８Ｃｏ０．１５Ａｌ０．０５Ｏ２（ＮＣＡ）を準備した。この正極活物質に対し、非特許文献１に書かれている方法により、Ｌｉ２Ｏ−ＺｒＯ２で被覆を行った。また固体電解質として、Ａｒｇｙｒｏｄｉｔｅ型結晶であるＬｉ６ＰＳ５Ｃｌを準備した。また、バインダとして、ポリテトラフルオロエチレン（デュポン社製テフロン（登録商標）バインダ）を準備した。また、導電助剤としてカーボンナノファイバー（ＣＮＦ）を準備した。ついで、これらの材料を、正極活物質：固体電解質：導電助剤：バインダ＝８８：１２：２：１の質量比で混合した。混合物をシート状に引き伸ばして、正極活物質シートを作製した。そしてこの正極活物質シートを約１．７ｃｍ角に成形し、１８μｍ厚のアルミ箔からなる正極集電体に圧着することにより、正極層を作製した。
(1) Preparation of Positive Electrode Layer LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) was prepared as the positive electrode active material. This positive electrode active material was coated with Li 2 O-ZrO 2 by the method described in Non-Patent Document 1. Further, as a solid electrolyte, Li 6 PS 5 Cl, which is an Argyrodite type crystal, was prepared. In addition, as a binder, polytetrafluoroethylene (Teflon (registered trademark) binder manufactured by DuPont) was prepared. In addition, carbon nanofiber (CNF) was prepared as a conductive auxiliary agent. Then, these materials were mixed in a mass ratio of positive electrode active material: solid electrolyte: conductive auxiliary agent: binder = 88: 12: 2: 1. The mixture was stretched into a sheet to prepare a positive electrode active material sheet. Then, this positive electrode active material sheet was molded into a square of about 1.7 cm and pressed against a positive electrode current collector made of 18 μm thick aluminum foil to prepare a positive electrode layer.
（２）負極層の作製
負極活物質として銀粒子と無定形炭素とを含有する負極層を次のようにして作成した。
まず、無定形炭素（カーボンブラック）６ｇと銀粒子（平均粒径約６０ｎｍ、表１において“Ａｇ”と表記）２ｇとを容器に入れ、そこへバインダ（クレハ社製＃９３００）を７．７７質量％含むＮ−メチルピロリドン（ＮＭＰ）溶液を５．１ｇ加えた。ついで、この混合溶液にＮＭＰを少しずつ加えながら撹拌することで、スラリーを作製した。このスラリーを、１０μｍ厚のＳＵＳ３０４箔から成る負極集電体上に、ブレードコーターを用いて塗布した。そして、空気中で約８０℃で約２０分間乾燥させたのち、１００℃で約１２時間真空乾燥した。この積層体を約２ｃｍ角で打ち抜き、負極層とした。ただし、この負極層には、突出部があり、後述するように電池の負極用端子として用いる。このようにして、サンプルＮｏ．１〜１２に用いる負極層を作製した。
(2) Preparation of Negative Electrode Layer A negative electrode layer containing silver particles and amorphous carbon as a negative electrode active material was prepared as follows.
First, 6 g of amorphous carbon (carbon black) and 2 g of silver particles (average particle size of about 60 nm, indicated as "Ag" in Table 1) are placed in a container, and a binder (# 9300 manufactured by Kureha) is placed therein. 5.1 g of N-methylpyrrolidone (NMP) solution containing mass% was added. Then, a slurry was prepared by stirring the mixed solution while adding NMP little by little. This slurry was applied to a negative electrode current collector made of SUS304 foil having a thickness of 10 μm using a blade coater. Then, it was dried in air at about 80 ° C. for about 20 minutes and then vacuum dried at 100 ° C. for about 12 hours. This laminate was punched out at an approximately 2 cm square to form a negative electrode layer. However, this negative electrode layer has a protruding portion, and is used as a negative electrode terminal of a battery as described later. In this way, the sample No. The negative electrode layers used for 1 to 12 were prepared.
ここで、サンプルＮｏ．１〜１２のそれぞれに用いる負極層は、窒素吸着比表面積及びＤＢＰ吸油量が表１に示す値となる１種類の無定形炭素を用いて作製した。サンプルＮｏ．１〜Ｎｏ．１０の負極層の作製において使用した無定形炭素はファーネスブラック（表１において“ＦＢ”と表記）である。Ｎｏ．１１とＮｏ．１２の負極層の作成において使用した無定形炭素は、それぞれアセチレンブラックとケッチェンブラック（表１においてそれぞれ、“ＡＢ”、“ＫＢ”と表記）である。負極活物質が含有する無定形炭素の窒素吸着比表面積、ＤＢＰ吸油量及び負極活物質層における無定形炭素の含有量が、表１に示す値になるようにそれぞれ作製した。製造した全固体二次電池のサンプルにおいても、負極活物質層に含まれる無定形炭素の窒素吸着比表面積及びＤＢＰ吸油量が表１に示す値になることを、前記した測定方法によって確認した。また、サンプルＮｏ．１〜１２のそれぞれに用いる負極層は、負極活物質層における無定形炭素の含有量が表１に示す値になるように作製した。 Here, the sample No. The negative electrode layer used for each of 1 to 12 was prepared using one type of amorphous carbon having a nitrogen adsorption specific surface area and DBP oil absorption as shown in Table 1. Sample No. 1-No. The amorphous carbon used in the preparation of the negative electrode layer of No. 10 is furnace black (denoted as “FB” in Table 1). No. 11 and No. The amorphous carbons used in the preparation of the negative electrode layer of 12 are acetylene black and Ketjen black (denoted as “AB” and “KB”, respectively in Table 1). The nitrogen adsorption specific surface area of the amorphous carbon contained in the negative electrode active material, the DBP oil absorption amount, and the content of the amorphous carbon in the negative electrode active material layer were prepared so as to be the values shown in Table 1, respectively. It was confirmed by the above-mentioned measuring method that the nitrogen adsorption specific surface area and the DBP oil absorption amount of the amorphous carbon contained in the negative electrode active material layer also became the values shown in Table 1 in the produced sample of the all-solid-state secondary battery. In addition, sample No. The negative electrode layers used for each of 1 to 12 were prepared so that the content of amorphous carbon in the negative electrode active material layer had the values shown in Table 1.
（３）固体電解質層の作製
前記したＬｉ６ＰＳ５Ｃｌ固体電解質に、当該固体電解質の質量に対して１質量％のゴム系バインダ（ＺＥＯＮ社製Ａ３３４）を加えた。この混合物にキシレンとジエチルベンゼンを加えながら撹拌することで、スラリーを作製した。このスラリーを不織布の上にブレードコーターを用いて塗布し、空気中で４０℃で乾燥させた。これにより得られた積層体を４０℃で１２時間真空乾燥した。この積層体を約２．２ｃｍ角で打ち抜き、固体電解質層を作製した。
(3) Preparation of Solid Electrolyte Layer To the above-mentioned Li 6 PS 5 Cl solid electrolyte, 1% by mass of a rubber binder (A334 manufactured by ZEON) was added to the mass of the solid electrolyte. A slurry was prepared by stirring while adding xylene and diethylbenzene to this mixture. This slurry was applied onto the non-woven fabric using a blade coater and dried in air at 40 ° C. The resulting laminate was vacuum dried at 40 ° C. for 12 hours. This laminate was punched out at a square of about 2.2 cm to prepare a solid electrolyte layer.
（４）全固体二次電池の作製
作製した正極層、固体電解質層及び負極層をこの順で重ねて、真空中でラミネートフィルムに封じることにより全固体二次電池のサンプルＮｏ．１〜１２を作製した。ここで、正極集電体と負極集電体のそれぞれ一部を、電池の真空を破らないようにラミネートフィルムから外に突出させた。これらの突出部を正極層及び負極層の端子とした。さらに、この全固体二次電池を４９０ＭＰａで３０分間静水圧処理した。さらにこの全固体二次電池を、その積層方向の両側から厚さ約１ｃｍの２枚のステンレス板で挟んだ。２枚のステンレス板にはそれぞれ同じ箇所に４つの穴が開いており、全固体二次電池はその４つの穴が作る四角形の内側に収まるようになっている。この状態で、前記２枚のステンレス板の外側から前記２枚のステンレス板を貫通するように、前記４つの穴にそれぞれ一本ずつボルトを通した。その後、２枚のステンレス板を外側から押さえ込むように、前記４つのボルトをそれぞれナットで締めこむことによって、全固体二次電池に約４ＭＰａの圧力を印加した。
(4) Preparation of All-Solid-State Secondary Battery The prepared positive electrode layer, solid electrolyte layer, and negative electrode layer are stacked in this order and sealed in a laminated film in a vacuum to obtain a sample No. of the all-solid-state secondary battery. 1 to 12 were prepared. Here, each part of the positive electrode current collector and the negative electrode current collector was projected outward from the laminated film so as not to break the vacuum of the battery. These protrusions were used as terminals for the positive electrode layer and the negative electrode layer. Further, this all-solid-state secondary battery was hydrostatically treated at 490 MPa for 30 minutes. Further, this all-solid-state secondary battery was sandwiched between two stainless steel plates having a thickness of about 1 cm from both sides in the stacking direction. Each of the two stainless steel plates has four holes in the same place, and the all-solid-state secondary battery fits inside the square formed by the four holes. In this state, one bolt was passed through each of the four holes so as to penetrate the two stainless steel plates from the outside of the two stainless steel plates. After that, a pressure of about 4 MPa was applied to the all-solid-state secondary battery by tightening the four bolts with nuts so as to press the two stainless steel plates from the outside.
＜２．初期充電容量＞
作製した全固体二次電池のサンプルＮｏ．１〜１２に対して、正極活物質層の初期充電容量（ｍＡｈ）及び負極活物質層の初期充電容量（ｍＡｈ）を次のようにして測定した。
具体的には、前記した段落［００６７］〜［００６８］の方法により全固体ハーフセルを作製する。そして、正極活物質層を作用極、Ｌｉを対極として、ＯＣＶ（開放電圧）から上限充電電圧（具体的には４．２５Ｖ）までＣＣ−ＣＶ充電を行うことで、正極活物質層の初期充電容量を測定した。また、負極活物質層を作用極、Ｌｉを対極として使用した全固体ハーフセルを作製し、ＯＣＶ（開放電圧）から０．０１ＶまでＣＣ−ＣＶ充電を行うことで、負極活物質層を測定した。測定により得られた各サンプルにおける正極活物質層及び負極活物質層の初期充電容量（ｍＡｈ）、並びに初期充電容量比を表１に示す。
<2. Initial charge capacity>
Sample No. of the prepared all-solid-state secondary battery. The initial charge capacity (mAh) of the positive electrode active material layer and the initial charge capacity (mAh) of the negative electrode active material layer were measured with respect to 1 to 12 as follows.
Specifically, an all-solid-state half cell is produced by the methods described in paragraphs [0067] to [0068] above. Then, by performing CC-CV charging from OCV (open circuit voltage) to the upper limit charging voltage (specifically, 4.25V) with the positive electrode active material layer as the working electrode and Li as the counter electrode, the initial charging of the positive electrode active material layer is performed. The capacity was measured. Further, an all-solid-state half cell using the negative electrode active material layer as the working electrode and Li as the counter electrode was prepared, and the negative electrode active material layer was measured by performing CC-CV charging from OCV (open circuit voltage) to 0.01 V. Table 1 shows the initial charge capacity (mAh) of the positive electrode active material layer and the negative electrode active material layer, and the initial charge capacity ratio in each sample obtained by the measurement.
＜３．特性評価＞
作製したサンプルＮｏ．１〜１２の全固体二次電池に対して、以下のように充放電サイクル試験を行い、その電池特性を評価した。
<3. Characterization>
Prepared sample No. The charge / discharge cycle test was performed on all solid-state secondary batteries 1 to 12 as follows, and the battery characteristics were evaluated.
（１）充放電サイクル試験
全固体二次電池を６０℃の恒温槽に入れて、充放電サイクル試験を行った。第１サイクルでは、電池電圧が４．２５Ｖになるまで０．５ｍＡ／ｃｍ２の定電流で充電を行い、電流が０．２ｍＡになるまで４．２５Ｖの定電圧で充電を行った。その後電池電圧が２．５Ｖになるまで０．５ｍＡ／ｃｍ２の定電流で放電を行った。第２、第３サイクルでは、第１サイクルと同条件で充電を行い、それぞれ１．６７ｍＡ／ｃｍ２、５．０ｍＡ／ｃｍ２の定電流で、電池電圧が２．５Ｖになるまで放電した。第４サイクル以降では、０．５ｍＡ／ｃｍ２の定電流で充放電を行い、これを１０５サイクル以上繰り返し、各サンプルの電池特性を評価した。
(1) Charge / discharge cycle test An all-solid-state secondary battery was placed in a constant temperature bath at 60 ° C. to perform a charge / discharge cycle test. In the first cycle, charging was performed at a constant current of 0.5 mA / cm 2 until the battery voltage reached 4.25 V, and charging was performed at a constant voltage of 4.25 V until the current reached 0.2 mA. After that, the battery was discharged at a constant current of 0.5 mA / cm 2 until the battery voltage reached 2.5 V. Second, third cycle, the charging is performed for the first cycle and the same conditions, respectively 1.67mA / cm 2, at a constant current of 5.0 mA / cm 2, and then discharged until the battery voltage reached 2.5V. From the 4th cycle onward, charging and discharging were performed with a constant current of 0.5 mA / cm 2 , and this was repeated for 105 cycles or more to evaluate the battery characteristics of each sample.
（２）サイクル特性
全固体二次電池のサイクル特性を、充放電サイクル試験における容量維持率により評価した。具体的には、充放電サイクル試験における、第５サイクルでの放電容量（ｍＡｈ）に対する第１０５サイクルでの放電容量（ｍＡｈ）の比を「容量維持率（％）」とした。容量維持率が８８％以上のサンプルを、“サイクル特性に優れる”と評価した。各サンプルにおける容量維持率の測定結果を表１に示す。
(2) Cycle characteristics The cycle characteristics of the all-solid-state secondary battery were evaluated by the capacity retention rate in the charge / discharge cycle test. Specifically, in the charge / discharge cycle test, the ratio of the discharge capacity (mAh) in the 105th cycle to the discharge capacity (mAh) in the 5th cycle was defined as the “capacity retention rate (%)”. Samples with a capacity retention rate of 88% or more were evaluated as having "excellent cycle characteristics". Table 1 shows the measurement results of the volume retention rate in each sample.
（３）放電レート特性
全固体二次電池の放電レート特性を、充放電サイクル試験における放電容量比により評価した。具体的には、充放電サイクル試験における、第２サイクルでの放電容量（ｍＡｈ）に対する第３サイクルでの放電容量（ｍＡｈ）の比（％）を「放電容量比（％）」とした。放電容量比が９２％以上のサンプルを、“放電レート特性に優れる”と評価した。各サンプルにおける放電容量比の測定結果を表１に示す。
(3) Discharge rate characteristics The discharge rate characteristics of the all-solid-state secondary battery were evaluated by the discharge capacity ratio in the charge / discharge cycle test. Specifically, in the charge / discharge cycle test, the ratio (%) of the discharge capacity (mAh) in the third cycle to the discharge capacity (mAh) in the second cycle was defined as the “discharge capacity ratio (%)”. Samples with a discharge capacity ratio of 92% or more were evaluated as having "excellent discharge rate characteristics". Table 1 shows the measurement results of the discharge capacity ratio in each sample.
＜４．評価＞
表１に示すように、サンプルＮｏ．１、２、４〜７及び１０〜１２は、いずれも本発明で規定する要件（（ａ）窒素吸着比表面積が０ｍ２／ｇ超、１００ｍ２／ｇ以下、又は（ｂ）ＤＢＰ吸油量が１５０ｍｌ／１００ｇ以上、の少なくとも一方を満たす無定形炭素を、負極活物質総質量に対して３３質量％以上含有する）を満たす実施例たる全固体二次電池である。これらの全固体二次電池のサンプルはいずれも容量維持率が８８％以上、かつ放電容量比が９２％以上であり、サイクル特性及び放電レート特性のいずれにも優れていることを確認できた。窒素吸着比表面積が３０ｍ２／ｇ以上であって、且つ１００ｍ２／ｇ以下である無定形炭素を、負極活物質総質量に対して３３質量％以上含むサンプルＮｏ．１、４、５、７及び１１は、窒素吸着比表面積が３０ｍ２／ｇ未満であるサンプルＮｏ．１０に比べて、放電容量比が高くなっており、放電レート特性がより一層向上していることがわかった。また、ＤＢＰ吸油量が１５０ｍｌ／１００ｇ以上、２００ｍｌ／１００ｇ以下であるサンプルＮｏ．１、２及び６は、ＤＢＰ吸油量が２００ｍｌ／１００ｇ超であるサンプルＮｏ．４に比べて、容量維持率及び放電容量比がいずれも高くなっていた。これにより、含有する無定形炭素の種類が同じであれば、ＤＢＰ吸油量を２００ｍｌ／１００ｇ以下にすることにより、サイクル特性及び放電レート特性をより一層向上できることがわかった。
<4. Evaluation ＞
As shown in Table 1, sample No. All of 1, 2, 4 to 7 and 10 to 12 are requirements specified in the present invention ((a) nitrogen adsorption specific surface area is more than 0 m 2 / g, 100 m 2 / g or less, or (b) DBP oil absorption is It is an all-solid-state secondary battery as an example that satisfies (containing 33% by mass or more of amorphous carbon satisfying at least one of 150 ml / 100 g or more with respect to the total mass of the negative electrode active material). It was confirmed that all of these samples of the all-solid-state secondary battery had a capacity retention rate of 88% or more and a discharge capacity ratio of 92% or more, and were excellent in both cycle characteristics and discharge rate characteristics. Sample No. containing 33% by mass or more of amorphous carbon having a nitrogen adsorption specific surface area of 30 m 2 / g or more and 100 m 2 / g or less with respect to the total mass of the negative electrode active material. Sample Nos. 1, 4, 5, 7 and 11 have a nitrogen adsorption specific surface area of less than 30 m 2 / g. It was found that the discharge capacity ratio was higher than that of 10, and the discharge rate characteristics were further improved. Further, the sample No. having a DBP oil absorption amount of 150 ml / 100 g or more and 200 ml / 100 g or less. Sample Nos. 1, 2 and 6 have a DBP oil absorption of more than 200 ml / 100 g. Compared with No. 4, both the capacity retention rate and the discharge capacity ratio were higher. From this, it was found that if the types of amorphous carbon contained are the same, the cycle characteristics and the discharge rate characteristics can be further improved by reducing the DBP oil absorption amount to 200 ml / 100 g or less.
これに対して、サンプルＮｏ．３、８及び９は、本発明で規定するいずれかの要件（窒素吸着比表面積、ＤＢＰ吸油量）を満たしていない比較例たる全固体二次電池である。これらのサンプルでは、サイクル特性又は放電レート特性との少なくともいずれかが劣っていた。 On the other hand, sample No. Reference numerals 3, 8 and 9 are all-solid-state secondary batteries as comparative examples that do not meet any of the requirements (nitrogen adsorption specific surface area, DBP oil absorption amount) specified in the present invention. These samples were inferior in at least either the cycle characteristics or the discharge rate characteristics.
具体的には、サンプルＮｏ．３、８及び９はいずれも、窒素吸着比表面積が１００ｍ２／ｇ超であるとともに、ＤＢＰ吸油量が１５０ｍｌ／１００ｇ未満であり、サイクル特性が劣っていた。サイクル特性が劣る理由としては、粒径が小さく、またアグリゲートも小さいため、リチウムが負極層を拡散するために多数の粒界やアグリゲートの界面を超えて拡散する必要があるためであると考えられる。すなわち、放電中に活物質と固体電解質との界面までリチウムが到達することが難しくなり、負極層内に孤立するリチウムが多くなるためであると考えられる。 Specifically, sample No. All of 3, 8 and 9 had a nitrogen adsorption specific surface area of more than 100 m 2 / g and a DBP oil absorption of less than 150 ml / 100 g, and were inferior in cycle characteristics. The reason for the poor cycle characteristics is that the particle size is small and the aggregate is also small, so lithium needs to diffuse beyond a large number of grain boundaries and the interface of the aggregate in order to diffuse the negative electrode layer. Conceivable. That is, it is considered that it becomes difficult for lithium to reach the interface between the active material and the solid electrolyte during discharge, and the amount of lithium isolated in the negative electrode layer increases.
（実施例２）
実施例２では、以下の手順により、負極活物質層が含有する無定形炭素の含有量を変化させた全固体二次電池のサンプル（Ｎｏ．１３〜１６）を作製した。
(Example 2)
In Example 2, a sample (No. 13 to 16) of an all-solid-state secondary battery in which the content of amorphous carbon contained in the negative electrode active material layer was changed was prepared by the following procedure.
具体的には、窒素吸着比表面積及びＤＢＰ吸油量が表２に示す値となる１種類の無定形炭素（ファーネスブラック）と、銀粒子（平均粒径約６０ｎｍ）とを負極活物質として準備した。そして、負極活物質層における負極活物質の全質量に対する無定形炭素の含有量が表２に示す値となるように無定形炭素と銀粒子を混合し、実施例１と同じ方法で負極層を作製した。 Specifically, one type of amorphous carbon (furness black) having a nitrogen adsorption specific surface area and DBP oil absorption as shown in Table 2 and silver particles (average particle size of about 60 nm) were prepared as negative electrode active materials. .. Then, the amorphous carbon and the silver particles are mixed so that the content of the amorphous carbon with respect to the total mass of the negative electrode active material in the negative electrode active material layer becomes the value shown in Table 2, and the negative electrode layer is formed by the same method as in Example 1. Made.
また実施例１と同じ方法で、正極層及び固体電解質層を作製し、これらと負極層とを積層して、全固体二次電池のサンプルＮｏ．１３〜１６を作製した。そして、作製したサンプルに対して、実施例１と同じ方法で、各種の電池特性の評価を行った。その結果を表２に示す。 Further, a positive electrode layer and a solid electrolyte layer were prepared by the same method as in Example 1, and these and a negative electrode layer were laminated to obtain a sample No. 1 of an all-solid secondary battery. 13 to 16 were prepared. Then, various battery characteristics were evaluated for the prepared sample by the same method as in Example 1. The results are shown in Table 2.
表２に示すように、サンプルＮｏ．１３〜１８は、いずれも本発明で規定する要件（（ａ）窒素吸着比表面積が０ｍ２／ｇ超、１００ｍ２／ｇ以下、又は（ｂ）ＤＢＰ吸油量が１５０ｍｌ／１００ｇ以上、の少なくとも一方を満たす無定形炭素を、負極活物質総質量に対して３３質量％以上含有する）を満たす実施例たる全固体二次電池である。これらの全固体二次電池のサンプルは、いずれも容量維持率が８８％以上、かつ放電容量比が９２％以上であり、サイクル特性及び放電レート特性のいずれにも優れていることを確認できた。なお、サンプル１３については、１０５サイクルを待たずに短絡がおこってしまったが、短絡が起こらない限りは、サイクル特性及び放電レート特性がともに高く、十分使用に耐えうるものであった。
これらサンプルＮｏ．１３〜１８の結果から、負極活物質総量に対しての無定形炭素の含有量は３３質量％以上９５質量％以下とすることが好ましく、は、負極活物質総質量に対して３３質量％以上、８７．５質量％以下とすることがより好ましいと考えられる。
As shown in Table 2, sample No. 13 to 18 are at least one of the requirements specified in the present invention ((a) nitrogen adsorption specific surface area of more than 0 m 2 / g, 100 m 2 / g or less, or (b) DBP oil absorption of 150 ml / 100 g or more. It is an all-solid-state secondary battery which is an example of satisfying (containing 33% by mass or more of amorphous carbon with respect to the total mass of the negative electrode active material). It was confirmed that all of these samples of the all-solid-state secondary battery had a capacity retention rate of 88% or more and a discharge capacity ratio of 92% or more, and were excellent in both cycle characteristics and discharge rate characteristics. .. The sample 13 was short-circuited without waiting for 105 cycles, but as long as the short-circuit did not occur, both the cycle characteristics and the discharge rate characteristics were high, and it was sufficiently usable.
These sample Nos. From the results of 13 to 18, the content of amorphous carbon with respect to the total amount of the negative electrode active material is preferably 33% by mass or more and 95% by mass or less, and is 33% by mass or more with respect to the total amount of the negative electrode active material. , 87.5% by mass or less is considered to be more preferable.
（実施例３）
実施例３では、以下の手順により、負極活物質層として無定形炭素を含有する全固体二次電池のサンプル（Ｎｏ．１９〜２０）を作製した。
(Example 3)
In Example 3, a sample (No. 19 to 20) of an all-solid-state secondary battery containing amorphous carbon as the negative electrode active material layer was prepared by the following procedure.
具体的には、窒素吸着比表面積及びＤＢＰ吸油量が表３に示す値となる１種類の無定形炭素（ケッチェンブラック）と、白金粒子（平均粒径約１μｍ）とを負極活物質として準備した。そして、負極活物質層における負極活物質の全質量に対する無定形炭素の含有量が表３に示す値となるように無定形炭素と白金粒子を混合し、実施例１と同じ方法で負極層を作製した。 Specifically, one type of amorphous carbon (Ketjen black) having a nitrogen adsorption specific surface area and DBP oil absorption as shown in Table 3 and platinum particles (average particle size of about 1 μm) are prepared as negative electrode active materials. did. Then, the amorphous carbon and the platinum particles are mixed so that the content of the amorphous carbon with respect to the total mass of the negative electrode active material in the negative electrode active material layer becomes the value shown in Table 3, and the negative electrode layer is formed by the same method as in Example 1. Made.
また実施例１と同じ方法で、正極層及び固体電解質層を作製し、これらと負極層とを積層して、全固体二次電池のサンプルＮｏ．１９及び２０を作製した。そして、作製したサンプルに対して、実施例１と同じ方法で、各種の電池特性の評価を行った。その結果を表３に示す。 Further, a positive electrode layer and a solid electrolyte layer were prepared by the same method as in Example 1, and these and a negative electrode layer were laminated to obtain a sample No. 1 of an all-solid secondary battery. 19 and 20 were made. Then, various battery characteristics were evaluated for the prepared sample by the same method as in Example 1. The results are shown in Table 3.
表３に示すように、サンプルＮｏ．１９及び２０は、いずれも本発明で規定する要件（（ａ）窒素吸着比表面積が０ｍ２／ｇ超、１００ｍ２／ｇ以下、又は（ｂ）ＤＢＰ吸油量が１５０ｍｌ／１００ｇ以上、の少なくとも一方を満たす無定形炭素を、負極活物質総質量に対して３３質量％以上含有する）を満たす実施例たる全固体二次電池である。これらの全固体二次電池のサンプルは、いずれも容量維持率が８８％以上、かつ放電容量比が９２％以上であり、サイクル特性及び放電レート特性のいずれにも優れていることを確認できた。この結果から、負極活物質として無定形炭素と白金との混合物を用いることによっても、本発明の効果が得られることを確認できた。 As shown in Table 3, sample No. 19 and 20 are at least one of the requirements specified in the present invention ((a) nitrogen adsorption specific surface area of more than 0 m 2 / g, 100 m 2 / g or less, or (b) DBP oil absorption of 150 ml / 100 g or more. It is an all-solid-state secondary battery as an example that satisfies the above condition (containing 33% by mass or more of amorphous carbon with respect to the total mass of the negative electrode active material). It was confirmed that all of these samples of the all-solid-state secondary battery had a capacity retention rate of 88% or more and a discharge capacity ratio of 92% or more, and were excellent in both cycle characteristics and discharge rate characteristics. .. From this result, it was confirmed that the effect of the present invention can be obtained even by using a mixture of amorphous carbon and platinum as the negative electrode active material.
１ 全固体二次電池
１０ 正極層
１１ 正極集電体
１２ 正極活物質層
２０ 負極層
２１ 負極集電体
２２ 負極活物質層
２３ 金属層
３０ 固体電解質層
1 All-solid secondary battery 10 Positive electrode layer 11 Positive electrode current collector 12 Positive electrode active material layer 20 Negative electrode layer 21 Negative electrode current collector 22 Negative electrode active material layer 23 Metal layer 30 Solid electrolyte layer
Claims (17)
前記負極活物質層が、
（ａ）窒素吸着比表面積が０ｍ２／ｇ超、１００ｍ２／ｇ以下、又は
（ｂ）ＤＢＰ吸油量が１５０ｍｌ／１００ｇ以上、
の少なくとも一方を満たす無定形炭素を、負極活物質総質量に対して３３質量％以上含有し、
前記正極活物質層の初期充電容量と前記負極活物質層の初期充電容量との比が、以下の式（１）を満たすことを特徴とする全固体二次電池。
０．０１＜ｂ／ａ＜０．５ （１）
（ここで、ａは前記正極活物質層の初期充電容量（ｍＡｈ）であり、ｂは前記負極活物質層の初期充電容量（ｍＡｈ）である） An all-solid-state secondary battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer forming an alloy or compound with lithium in this order.
The negative electrode active material layer
(A) Nitrogen adsorption specific surface area is more than 0 m 2 / g, 100 m 2 / g or less, or (b) DBP oil absorption is 150 ml / 100 g or more.
Amorphous carbon satisfying at least one of the above is contained in an amount of 33% by mass or more based on the total mass of the negative electrode active material.
An all-solid-state secondary battery characterized in that the ratio of the initial charge capacity of the positive electrode active material layer to the initial charge capacity of the negative electrode active material layer satisfies the following formula (1).
0.01 <b / a <0.5 (1)
(Here, a is the initial charge capacity (mAh) of the positive electrode active material layer, and b is the initial charge capacity (mAh) of the negative electrode active material layer).
正極活物質層と固体電解質層と負極活部層をこの順で積層した状態で、静水圧を用いて加圧することを特徴とする全固体二次電池の製造方法。 The method for manufacturing an all-solid-state secondary battery according to any one of claims 1 to 11.
A method for manufacturing an all-solid-state secondary battery, characterized in that a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active part layer are laminated in this order and then pressurized using hydrostatic pressure.
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| CN202010228583.9A CN111755741A (en) | 2019-03-29 | 2020-03-27 | All-solid-state lithium secondary battery, method for producing same, method for using same, and method for charging same |
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