JP7067445B2 - Sulfide solid state battery - Google Patents

Sulfide solid state battery Download PDF

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JP7067445B2
JP7067445B2 JP2018228264A JP2018228264A JP7067445B2 JP 7067445 B2 JP7067445 B2 JP 7067445B2 JP 2018228264 A JP2018228264 A JP 2018228264A JP 2018228264 A JP2018228264 A JP 2018228264A JP 7067445 B2 JP7067445 B2 JP 7067445B2
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sulfide solid
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洋平 進藤
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Toyota Motor Corp
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Description

本願は硫化物固体電池を開示するものである。 The present application discloses a sulfide solid state battery.

固体電池の分野において、活物質の表面を被覆することで、活物質と固体電解質との反応を抑制し、電池性能を高める試みが行われている。 In the field of solid-state batteries, attempts have been made to suppress the reaction between the active material and the solid electrolyte by covering the surface of the active material to improve the battery performance.

特許文献１には、ＬｉＮｂＯ３を被覆した正極活物質が開示されおり、これにより硫化物固体電解質と正極活物質との界面反応を抑制し、良好な電池特性を得ることができることが記載されている。
特許文献２には、Ｌｉ２ＷＯ４を被覆した活物質が開示されており、これにより界面抵抗の増加を抑制可能であることが記載されている。 Patent Document 1 discloses a positive electrode active material coated with LiNbO 3 , which describes that the interface reaction between the sulfide solid electrolyte and the positive electrode active material can be suppressed and good battery characteristics can be obtained. There is.
Patent Document 2 discloses an active material coated with Li 2 WO 4 , and describes that it is possible to suppress an increase in interfacial resistance.

特開２０１７－５９５３４号公報JP-A-2017-59534 特許５４７２４９２号公報Japanese Patent No. 5472492

ＬｉＮｂＯ３は４．３Ｖ以上の高電位下において硫化物固体電解質と反応し劣化する問題がある。そのため、ＬｉＮｂＯ３を被覆した活物質では、４．３Ｖ以上の高電位下において活物質の界面抵抗が増加し、容量が低下する虞がある。
特許文献２によれば、Ｌｉ２ＷＯ４で被覆した活物質を用いると、作動電位が４．１Ｖであっても耐久試験において抵抗増加率が低いことが分かっている。しかしながら、４．１Ｖ以上のさらに高電位における抵抗増加率については検討されていない。 LiNbO 3 has a problem of reacting with a sulfide solid electrolyte and deteriorating under a high potential of 4.3 V or higher. Therefore, in the active material coated with LiNbO 3 , the interfacial resistance of the active material may increase and the capacity may decrease under a high potential of 4.3 V or higher.
According to Patent Document 2, it is known that when an active material coated with Li 2 WO 4 is used, the resistance increase rate is low in the durability test even when the operating potential is 4.1 V. However, the rate of increase in resistance at higher potentials of 4.1 V or higher has not been investigated.

そこで、本願では高電位においても抵抗増加及び容量維持率の低減を抑制可能な硫化物固体電池を提供することを課題とする。 Therefore, it is an object of the present application to provide a sulfide solid-state battery capable of suppressing an increase in resistance and a decrease in capacity retention rate even at a high potential.

本願は上記課題を解決する一つの手段として、正極合材層と、負極合材層と、正極合材層及び負極合材層の間に配置された硫化物固体電解質層とを備えた硫化物固体電池において、正極合材層はＬｉ２ＷＯ４で被覆された正極活物質を備え、正極合材層の作動電位が少なくとも４．１Ｖ～４．５Ｖの間であることを特徴とする、硫化物固体電池を開示する。 In the present application, as one means for solving the above problems, a sulfide having a positive electrode mixture layer, a negative electrode mixture layer, and a sulfide solid electrolyte layer arranged between the positive electrode mixture layer and the negative electrode mixture layer is provided. In a solid-state battery, the positive electrode mixture layer comprises a positive electrode active material coated with Li 2 WO 4 , and the operating potential of the positive electrode mixture layer is at least between 4.1 V and 4.5 V. Disclose a solid-state battery.

本開示の硫化物固体電池によれば、高電位であっても抵抗増加及び容量維持率の低減を抑制することができる。 According to the sulfide solid-state battery of the present disclosure, it is possible to suppress an increase in resistance and a decrease in capacity retention rate even at a high potential.

硫化物固体電池１００の概略断面図である。It is a schematic sectional drawing of a sulfide solid-state battery 100. 正極活物質１１の概略断面図である。It is the schematic sectional drawing of the positive electrode active material 11.

なお、数値Ａ及びＢについて「Ａ～Ｂ」という表記は「Ａ以上Ｂ以下」を意味するものとする。かかる表記において数値Ｂのみに単位を付した場合には、当該単位が数値Ａにも適用されるものとする。 Regarding the numerical values A and B, the notation "A to B" means "A or more and B or less". When a unit is attached only to the numerical value B in such a notation, the unit shall be applied to the numerical value A as well.

［硫化物固体電池］
本開示の硫化物固体電池について、一実施形態である硫化物固体電池１００（以下において、「硫化物固体電池１００」ということがある。）を用いて詳しく説明する。 [Sulfide solid-state battery]
The sulfide solid-state battery of the present disclosure will be described in detail with reference to the sulfide solid-state battery 100 (hereinafter, may be referred to as “sulfide solid-state battery 100”) which is an embodiment.

図１に硫化物固体電池１００の概略断面図を示した。硫化物固体電池１００は正極合材層１０と、負極合材層２０と、正極合材層１０及び負極合材層２０の間に配置された硫化物固体電解質層３０とを備えており、図１に示されているとおり、正極合材層１０、硫化物固体電解質層３０、負極合材層２０の順に積層されている。また、図１に示した通り、硫化物固体電池１００は、正極合材層１０の硫化物固体電解質層３０側とは反対側の面に正極集電体４０が積層されており、負極合材層２０の硫化物固体電解質層３０側とは反対側の面に負極集電体５０が積層されていることが好ましい。 FIG. 1 shows a schematic cross-sectional view of the sulfide solid-state battery 100. The sulfide solid-state battery 100 includes a positive electrode mixture layer 10, a negative electrode mixture layer 20, and a sulfide solid electrolyte layer 30 arranged between the positive electrode mixture layer 10 and the negative electrode mixture layer 20. As shown in 1, the positive electrode mixture layer 10, the sulfide solid electrolyte layer 30, and the negative electrode mixture layer 20 are laminated in this order. Further, as shown in FIG. 1, in the sulfide solid-state battery 100, the positive electrode current collector 40 is laminated on the surface of the positive electrode mixture layer 10 opposite to the sulfide solid electrolyte layer 30 side, and the negative electrode mixture is used. It is preferable that the negative electrode current collector 50 is laminated on the surface of the layer 20 opposite to the sulfide solid electrolyte layer 30 side.

正極合材層１０はＬｉ２ＷＯ４で被覆された正極活物質１１を備える。好ましくは、正極合材層１０は上記正極活物質１１と硫化物固体電解質とを備える。また、正極合材層１０は必要に応じて導電材やバインダーを備えていてもよい。 The positive electrode mixture layer 10 includes a positive electrode active material 11 coated with Li 2 WO 4 . Preferably, the positive electrode mixture layer 10 includes the positive electrode active material 11 and a sulfide solid electrolyte. Further, the positive electrode mixture layer 10 may be provided with a conductive material or a binder, if necessary.

正極活物質１１は正極活物質材料１１ａと該正極活物質材料を被覆する被覆層１１ｂ（Ｌｉ２ＷＯ４）とからなる。図２に正極活物質１１の概略断面図を示した。 The positive electrode active material 11 is composed of a positive electrode active material 11a and a coating layer 11b (Li 2 WO 4 ) covering the positive electrode active material. FIG. 2 shows a schematic cross-sectional view of the positive electrode active material 11.

正極活物質材料１１ａとしては、特に限定されないが、酸化物活物質を挙げることができる。具体的には、ＬｉＣｏＯ２、ＬｉＭｎＯ２、ＬｉＮｉＯ２、ＬｉＶＯ２、ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２等の岩塩層状型活物質、ＬｉＭｎ２Ｏ４、Ｌｉ（Ｎｉ０．５Ｍｎ１．５）Ｏ４等のスピネル型活物質等を挙げることができる。 The positive electrode active material 11a is not particularly limited, and examples thereof include an oxide active material. Specifically, rock salt layered active materials such as LiCoO 2 , LiMnO 2 , LiNiO 2 , LiVO 2 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiMn 2 O 4 , Li (Ni 0.5 ). Mn 1.5 ) Spinel-type active substances such as O4 can be mentioned.

被覆層１１ｂは上記したとおり、Ｌｉ２ＷＯ４からなる。被覆層１１ｂにＬｉ２ＷＯ４を用いた理由は、リチウムイオン伝導性を有し、かつ、４．１Ｖ以上、好ましくは４．３Ｖ以上の高電位において長期間保存したとしても抵抗増加が抑制されるためである。
例えば、特許文献１に記載されているＬｉＮｂＯ３で被覆した正極活物質を用いた場合、４．３Ｖ以上の高電位において、ＬｉＮｂＯ３と硫化物固体電解質とが反応する確率が高くなる。具体的な反応形式は酸化還元反応であり、ＬｉＮｂＯ３が還元され、酸素が脱離すると考えられている（反対に、硫化物固体電解質は酸化され、酸素が付加すると考えられている）。このような反応が起こると、ＬｉＮｂＯ３からなる被覆層は劣化するため、長期間保存により正極活物質の表面抵抗が増加し、電池の容量維持率も低下する。
一方で、Ｌｉ２ＷＯ４はＷ－Ｏの結合がＬｉＮｂＯ３におけるＮｉ－Ｏの結合よりも強いため、酸素が脱離し難い。そのため、４．１Ｖ以上、好ましくは４．３Ｖ以上の高電位において長期間保存したとしても抵抗増加が抑制される。よって、Ｌｉ２ＷＯ４からなる被覆層１１ｂを有することにより、容量維持率の低下が抑制され、電池の耐久性が向上する。
なお、当然であるが、活物質材料１１ａを被覆層１１ｂで被覆することにより、活物質材料１１ａと硫化物固体電解質との反応を抑制することができる。 As described above, the coating layer 11b is made of Li 2 WO 4 . The reason why Li 2 WO 4 is used for the coating layer 11b is that it has lithium ion conductivity and the increase in resistance is suppressed even if it is stored at a high potential of 4.1 V or more, preferably 4.3 V or more for a long period of time. Because.
For example, when the positive electrode active material coated with LiNbO 3 described in Patent Document 1 is used, the probability that LiNbO 3 reacts with the sulfide solid electrolyte at a high potential of 4.3 V or higher is high. The specific reaction form is a redox reaction, in which LiNbO 3 is reduced and oxygen is desorbed (conversely, the sulfide solid electrolyte is considered to be oxidized and oxygen is added). When such a reaction occurs, the coating layer made of LiNbO 3 deteriorates, so that the surface resistance of the positive electrode active material increases due to long-term storage, and the capacity retention rate of the battery also decreases.
On the other hand, in Li 2 WO 4 , the W—O bond is stronger than the Ni—O bond in LiNbO 3 , so oxygen is difficult to desorb. Therefore, the increase in resistance is suppressed even when stored at a high potential of 4.1 V or higher, preferably 4.3 V or higher for a long period of time. Therefore, by having the coating layer 11b made of Li 2 WO 4 , the decrease in the capacity retention rate is suppressed, and the durability of the battery is improved.
As a matter of course, by coating the active material material 11a with the coating layer 11b, the reaction between the active material material 11a and the sulfide solid electrolyte can be suppressed.

正極活物質材料１１ａに対する被覆層１１ｂの被覆率は７０％以上１００％以下であることが好ましく、９０％以上１００％以下であることがより好ましい。被覆率が高いほど、正極活物質材料１１ａと硫化物固体電解質とが直接接する面積が減少するため、電池の耐久性が向上する。
ここで、被覆率はＸＰＳ分析を用いて算出することができる。例えば、下記式を用いて算出することができる。 The coverage of the coating layer 11b with respect to the positive electrode active material 11a is preferably 70% or more and 100% or less, and more preferably 90% or more and 100% or less. The higher the coverage, the smaller the area in which the positive electrode active material 11a and the sulfide solid electrolyte are in direct contact with each other, and thus the durability of the battery is improved.
Here, the coverage can be calculated using XPS analysis. For example, it can be calculated using the following formula.

被覆率＝（Ｗ／（Ｗ＋Ｍ））×１００
Ｗ：ＸＰＳ分析で定量したタングステンの元素量
Ｍ：ＸＰＳ分析で定量した正極活物質材料に含有される遷移金属元素の元素量 Coverage = (W / (W + M)) x 100
W: Elemental amount of tungsten quantified by XPS analysis M: Elemental amount of transition metal element contained in the positive electrode active material material quantified by XPS analysis

被覆層１１ｂの厚みは特に限定されず、正極活物質材料１１ａと硫化物固体電解質との反応を抑制できる厚さであればよい。例えば、１ｎｍ～５００ｎｍであることが好ましく、２ｎｍ～１００ｎｍであることがより好ましく、３ｎｍ～５０ｎｍであることがさらに好ましい。被覆層１１ｂの厚みが１ｎｍ未満であると、正極活物質材料１１ａと硫化物固体電解質が反応する虞がある。被覆層１１ｂの厚みが５００ｎｍを超えると、リチウムイオン伝導性が低下する虞がある。
なお、被覆層１１ｂの厚みは、透過型電子顕微鏡（ＴＥＭ）による観察で決定することができる。 The thickness of the coating layer 11b is not particularly limited as long as it can suppress the reaction between the positive electrode active material 11a and the sulfide solid electrolyte. For example, it is preferably 1 nm to 500 nm, more preferably 2 nm to 100 nm, and even more preferably 3 nm to 50 nm. If the thickness of the coating layer 11b is less than 1 nm, the positive electrode active material 11a may react with the sulfide solid electrolyte. If the thickness of the coating layer 11b exceeds 500 nm, the lithium ion conductivity may decrease.
The thickness of the coating layer 11b can be determined by observation with a transmission electron microscope (TEM).

正極活物質１１の平均粒子径は、特に限定されないが、０．１μｍ以上５０μｍ以下であることが好ましい。平均粒子径はレーザー回折・散乱法により取得した体積基準の粒度分布における積算値５０％での粒子径であるメディアン径である。 The average particle size of the positive electrode active material 11 is not particularly limited, but is preferably 0.1 μm or more and 50 μm or less. The average particle diameter is the median diameter which is the particle diameter at an integrated value of 50% in the volume-based particle size distribution acquired by the laser diffraction / scattering method.

このような正極活物質１１を作製する方法は、公知の方法によって作製することができる。例えば、スパッタリング法により正極活物質材料１１ａに被覆層１１ｂを被覆させることができる。 The method for producing such a positive electrode active material 11 can be produced by a known method. For example, the positive electrode active material 11a can be coated with the coating layer 11b by a sputtering method.

正極合材層１０に含むことができる硫化物固体電解質は、後述の硫化物固体電解質層に含むことができる硫化物固体電解質を用いることができる。正極合材層１０に含むことができる導電材としては、特に限定されないが、アセチレンブラックやケッチェンブラック、気相成長炭素繊維（ＶＧＣＦ）等の炭素材料を用いることができる。正極合材層１０に含むことができるバインダーとしては、特に限定されないが、ポリフッ化ビニリデン（ＰＶＤＦ）や、ブチレンゴム（ＢＲ）、スチレンブタジエンゴム（ＳＢＲ）等の公知のバインダーを用いることができる。 As the sulfide solid electrolyte that can be contained in the positive electrode mixture layer 10, a sulfide solid electrolyte that can be contained in the sulfide solid electrolyte layer described later can be used. The conductive material that can be contained in the positive electrode mixture layer 10 is not particularly limited, but a carbon material such as acetylene black, Ketjen black, or vapor phase grown carbon fiber (VGCF) can be used. The binder that can be contained in the positive electrode mixture layer 10 is not particularly limited, but known binders such as polyvinylidene fluoride (PVDF), butylene rubber (BR), and styrene-butadiene rubber (SBR) can be used.

正極合材層１０における正極活物質１１の含有量は特に限定されないが、１０重量％～９９重量％であることが好ましい。正極合材層１０の厚みも特に限定されないが、０．１μｍ～１０００μｍであることが好ましい。 The content of the positive electrode active material 11 in the positive electrode mixture layer 10 is not particularly limited, but is preferably 10% by weight to 99% by weight. The thickness of the positive electrode mixture layer 10 is also not particularly limited, but is preferably 0.1 μm to 1000 μm.

負極合材層２０は、負極活物質と硫化物固体電解質とを備えており、必要に応じて導電材やバインダーを含むことができる。負極活物質としては、硫化物固体電池に用いることができる負極活物質であれば特に限定されない。例えば、金属、炭素材等が挙げられる。金属としては、Ｌｉ、Ｓｎ、Ｓｉ、Ａｌ、等の金属を用いることができる。炭素材としては、天然または人工黒鉛等を用いることができる。硫化物固体電解質としては、後述の硫化物固体電解質層に含むことができる硫化物固体電解質を用いることができる。導電材及びバインダーは正極合材層１０に用いることできる導電材及びバインダーを採用することができる。負極合材層２０における負極活物質の含有量は特に限定されないが、１０重量％～９９重量％であることが好ましい。負極合材層２０の厚みも特に限定されないが、０．１μｍ～１０００μｍであることが好ましい。 The negative electrode mixture layer 20 includes a negative electrode active material and a sulfide solid electrolyte, and may contain a conductive material and a binder, if necessary. The negative electrode active material is not particularly limited as long as it is a negative electrode active material that can be used in a sulfide solid-state battery. For example, metal, carbon material and the like can be mentioned. As the metal, a metal such as Li, Sn, Si, Al, etc. can be used. As the carbon material, natural or artificial graphite or the like can be used. As the sulfide solid electrolyte, a sulfide solid electrolyte that can be contained in the sulfide solid electrolyte layer described later can be used. As the conductive material and the binder, the conductive material and the binder that can be used for the positive electrode mixture layer 10 can be adopted. The content of the negative electrode active material in the negative electrode mixture layer 20 is not particularly limited, but is preferably 10% by weight to 99% by weight. The thickness of the negative electrode mixture layer 20 is also not particularly limited, but is preferably 0.1 μm to 1000 μm.

硫化物固体電解質層３０は、少なくとも硫化物固体電解質を備える。必要に応じてバインダーを備えていてもよい。硫化物固体電解質としては公知の硫化物固体電解質を用いることができ、例えばＬｉ２Ｓ－ＳｉＳ２、ＬｉＩ－Ｌｉ２Ｓ－ＳｉＳ２、ＬｉＩ－Ｌｉ２Ｓ－Ｐ２Ｓ５、ＬｉＩ－Ｌｉ２Ｓ－Ｐ２Ｏ５、ＬｉＩ－Ｌｉ３ＰＯ４－Ｐ２Ｏ５、Ｌｉ２Ｓ－Ｐ２Ｓ５、Ｌｉ３ＰＳ４等を挙げることができる。バインダーとしては、上記したバインダーを挙げることができる。硫化物固体電解質層３０の厚みは特に限定されないが、０．１μｍ～１０００μｍであることが好ましい。 The sulfide solid electrolyte layer 30 comprises at least a sulfide solid electrolyte. A binder may be provided if necessary. As the sulfide solid electrolyte, a known sulfide solid electrolyte can be used, for example, Li 2S-SiS 2 , LiI-Li 2 S-SiS 2 , LiI-Li 2 SP 2 S 5 , LiI -Li 2 . Examples thereof include SP 2 O 5 , LiI-Li 3 PO 4 -P 2 O 5 , Li 2 SP 2 S 5 , Li 3 PS 4 . Examples of the binder include the above-mentioned binders. The thickness of the sulfide solid electrolyte layer 30 is not particularly limited, but is preferably 0.1 μm to 1000 μm.

正極集電体４０は、硫化物固体電池に用いることができる公知の正極集電材を採用することができる。例えば、ＳＵＳ、アルミニウム、ニッケル、鉄、カーボン等である。負極集電体５０も、硫化物固体電池に用いることができる公知の負極集電材を採用することができる。例えば、ＳＵＳ、銅、ニッケル、カーボン等である。 As the positive electrode current collector 40, a known positive electrode current collector that can be used for a sulfide solid-state battery can be adopted. For example, SUS, aluminum, nickel, iron, carbon and the like. As the negative electrode current collector 50, a known negative electrode current collector that can be used for a sulfide solid-state battery can also be adopted. For example, SUS, copper, nickel, carbon and the like.

このような硫化物固体電池１００の製造方法は特に限定されず、目的の電池の構成に応じて適宜最適な方法を採用することができる。 The method for manufacturing such a sulfide solid-state battery 100 is not particularly limited, and an optimal method can be appropriately adopted according to the configuration of the target battery.

硫化物固体電池１００は、正極合材層１０の作動電位が少なくとも４．１Ｖ～４．５Ｖの間であることを特徴としている。上記したように、正極合材層１０に含まれる正極活物質１１は、Ｌｉ２ＷＯ４からなる被覆層１１ｂを備えているため、正極合材層の作動電位が４．１Ｖ～４．５Ｖ、好ましくは４．３Ｖ～４．５Ｖであっても、抵抗増加が抑制され、かつ、容量維持率の低下も抑制される。
なお、発明者によれば、正極合材層１０の作動電位が４．５Ｖを超えたとしても、上記の効果を奏するものと推測されている。 The sulfide solid-state battery 100 is characterized in that the operating potential of the positive electrode mixture layer 10 is at least between 4.1 V and 4.5 V. As described above, since the positive electrode active material 11 contained in the positive electrode mixture layer 10 includes the coating layer 11b made of Li 2 WO 4 , the operating potential of the positive electrode mixture layer is 4.1 V to 4.5 V. Even if it is preferably 4.3 V to 4.5 V, the increase in resistance is suppressed and the decrease in the capacity retention rate is also suppressed.
According to the inventor, it is presumed that the above effect is obtained even if the operating potential of the positive electrode mixture layer 10 exceeds 4.5 V.

以下、本開示の硫化物固体電池について、実施例を用いてさらに説明する。 Hereinafter, the sulfide solid-state battery of the present disclosure will be further described with reference to Examples.

［正極活物質の作製］
バレルスパッタを用いて、正極活物質材料（ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２）３０ｇの粉末に厚さ１０ｎｍの被覆層を形成させた。被覆層の材料は表１のとおりである。そして、被覆層を形成した正極活物質材料を表１の温度で焼成して、正極活物質を作製した。正極活物質における被覆層の被覆率は７０％であった。 [Preparation of positive electrode active material]
Using barrel sputtering, a coating layer having a thickness of 10 nm was formed on a powder of 30 g of the positive electrode active material (LiNi 1/3 Co 1/3 Mn 1/3 O 2 ). The material of the coating layer is as shown in Table 1. Then, the positive electrode active material on which the coating layer was formed was fired at the temperatures shown in Table 1 to prepare a positive electrode active material. The coverage of the coating layer in the positive electrode active material was 70%.

［硫化物固体電池の作製］
上記により作製した正極活物質と硫化物固体電解質（Ｌｉ２Ｓ－Ｐ２Ｓ５）とを体積比で５０：５０の割合で混合し、１ｔｏｎの力でプレスして正極合材層（２０ｍｇ）を作製した。
負極活物質（天然黒鉛）と硫化物固体電解質（Ｌｉ２Ｓ－Ｐ２Ｓ５）とを体積比で５０：５０の割合で混合し、１ｔｏｎの力でプレスして負極合材層（２０ｍｇ）を作製した。
硫化物固体電解質（Ｌｉ２Ｓ－Ｐ２Ｓ５）を１ｔｏｎの力でプレスして固体電解質層（５０ｍｇ）を作製した。 [Manufacturing of sulfide solid-state battery]
The positive electrode active material prepared as described above and the sulfide solid electrolyte (Li 2 SP 2 S 5 ) are mixed at a volume ratio of 50:50 and pressed with a force of 1 ton to form a positive electrode mixture layer (20 mg). Was produced.
Negative electrode active material (natural graphite) and sulfide solid electrolyte (Li 2 SP 2 S 5 ) are mixed at a volume ratio of 50:50 and pressed with a force of 1 ton to form a negative electrode mixture layer (20 mg). Was produced.
A sulfide solid electrolyte (Li 2 SP 2 S 5 ) was pressed with a force of 1 ton to prepare a solid electrolyte layer (50 mg).

正極集電体、正極合材層、硫化物固体電解質層、負極合材層、負極集電体の順に積層し、全体に６Ｎの拘束力を掛けて、硫化物固体電池を作製した。 A positive electrode current collector, a positive electrode mixture layer, a sulfide solid electrolyte layer, a negative electrode mixture layer, and a negative electrode current collector were laminated in this order, and a binding force of 6N was applied to the whole to prepare a sulfide solid state battery.

［耐久特性の評価］
上記により作製した硫化物固体電池を３．５Ｖ－４．１Ｖ（ｖｓＣ）、２５℃にて０．１Ｃで充放電を行った。次いで、ＳＯＣ（Ｓｔａｔｅｓ ｏｆ Ｃｈａｒｇｅ）を６０％に設定して、２ｍＡの電流を１０ｓ放電し、抵抗を見積もった。その後、表１のとおり正極合材層の電位を４．１Ｖ、４．３Ｖ、４．５Ｖ（ｖｓＬｉ）に調整し、６０℃にて２００時間の保存試験を行った。そして、保存試験後の抵抗及び容量を測定し、容量維持率及び抵抗増加率を算出した。結果を表１にまとめた。 [Evaluation of durability characteristics]
The sulfide solid-state battery produced as described above was charged and discharged at 3.5 V-4.1 V (vsC) and at 25 ° C. at 0.1 C. Next, the SOC (Systems of Charge) was set to 60%, a current of 2 mA was discharged for 10 s, and the resistance was estimated. Then, as shown in Table 1, the potential of the positive electrode mixture layer was adjusted to 4.1 V, 4.3 V, and 4.5 V (vsLi), and a storage test was conducted at 60 ° C. for 200 hours. Then, the resistance and the capacity after the storage test were measured, and the capacity retention rate and the resistance increase rate were calculated. The results are summarized in Table 1.

Figure 0007067445000001
Figure 0007067445000001

表１より、Ｌｉ２ＷＯ４で被覆されている正極活物質を用いた実施例１～３では、保存試験時の正極合材層の電位が４．１～４．５Ｖであっても、抵抗増加率の上昇が抑えられており、容量維持率の低減も抑制されていた。
一方で、ＬｉＮｂＯ３で被覆されている正極活物質を用いた比較例１～３に関し、保存時の正極合材層の電位が４．１Ｖの比較例３では抵抗増加率の上昇及び容量維持率の低下が抑制されているが、４．３Ｖの比較例２では実施例２に比べて抵抗増加率が高く、４．５Ｖの比較例３では実施例１に比べて抵抗増加率が高く、また容量維持率が低い結果であった。比較例３では特に抵抗増加率の上昇が顕著であった。
また、Ｌｉ３ＰＯ４で被覆されている正極活物質を用いた比較例４～６に関し、保存時の正極合材層の電位が４．１Ｖの比較例６では抵抗増加率の上昇及び容量維持率の低下が抑制されているが、４．３Ｖの比較例５では実施例２に比べて容量維持率が低下しており、４．５Ｖの比較例３では実施例１に比べて容量維持率が大きく低下していた。
以上のことから、Ｌｉ２ＷＯ４で被覆されている正極活物質を用いることにより、４．１Ｖ～４．５Ｖの高電位であっても、抵抗増加率の上昇及び容量維持率の低下が抑制されることが分かった。また、電位が４．３Ｖ～４．５Ｖである場合は、Ｌｉ２ＷＯ４で正極材料を被覆することにより、その他の被覆材料を用いた場合に比べて、抵抗増加率の上昇及び容量維持率の低下の両方が抑制されることも分かった。 From Table 1, in Examples 1 to 3 using the positive electrode active material coated with Li 2 WO 4 , even if the potential of the positive electrode mixture layer at the time of the storage test is 4.1 to 4.5 V, the resistance The increase in the rate of increase was suppressed, and the decrease in the capacity retention rate was also suppressed.
On the other hand, with respect to Comparative Examples 1 to 3 using the positive electrode active material coated with LiNbO 3 , in Comparative Example 3 in which the potential of the positive electrode mixture layer at the time of storage was 4.1 V, the resistance increase rate and the capacity retention rate increased. However, in Comparative Example 2 of 4.3 V, the resistance increase rate is higher than that of Example 2, and in Comparative Example 3 of 4.5 V, the resistance increase rate is higher than that of Example 1. The result was that the capacity retention rate was low. In Comparative Example 3, the increase in the resistance increase rate was particularly remarkable.
Further, with respect to Comparative Examples 4 to 6 using the positive electrode active material coated with Li 3 PO 4 , in Comparative Example 6 in which the potential of the positive electrode mixture layer at the time of storage was 4.1 V, the resistance increase rate was increased and the capacity was maintained. Although the decrease in the rate is suppressed, the capacity retention rate is lower in Comparative Example 5 of 4.3 V than in Example 2, and in Comparative Example 3 of 4.5 V, the capacity retention rate is higher than that of Example 1. Was greatly reduced.
From the above, by using the positive electrode active material coated with Li 2 WO 4 , the increase in resistance increase rate and the decrease in capacity retention rate are suppressed even at a high potential of 4.1 V to 4.5 V. It turned out to be done. When the potential is 4.3V to 4.5V, by coating the positive electrode material with Li 2 WO 4 , the resistance increase rate increases and the capacity retention rate increases as compared with the case where other coating materials are used. It was also found that both of the declines were suppressed.

１０ 正極合材層
１１ 正極活物質
１１ａ 正極活物質材料
１１ｂ 被覆層
２０ 負極合材層
３０ 硫化物固体電解質層
４０ 正極集電体
５０ 負極集電体
１００ 硫化物固体電池 10 Positive electrode mixture layer 11 Positive electrode active material 11a Positive electrode active material 11b Coating layer 20 Negative electrode mixture layer 30 Sulfurized solid electrolyte layer 40 Positive electrode current collector 50 Negative electrode current collector 100 Sulfurized solid battery

Claims (1)

正極合材層と、負極合材層と、前記正極合材層及び前記負極合材層の間に配置された硫化物固体電解質層とを備えた硫化物固体電池において、
前記正極合材層はＬｉ２ＷＯ４で被覆された正極活物質を備え、
前記正極合材層の電位が少なくとも４．３Ｖ～４．５Ｖの間であることを特徴とする、
硫化物固体電池。 In a sulfide solid-state battery including a positive electrode mixture layer, a negative electrode mixture layer, and a sulfide solid electrolyte layer arranged between the positive electrode mixture layer and the negative electrode mixture layer.
The positive electrode mixture layer comprises a positive electrode active material coated with Li 2 WO 4 .
The potential of the positive electrode mixture layer is at least between 4.3V and 4.5V.
Sulfide solid state battery.
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