JP6819533B2 - Negative electrode mixture for all-solid-state lithium-ion secondary batteries - Google Patents
Negative electrode mixture for all-solid-state lithium-ion secondary batteries Download PDFInfo
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- 239000000203 mixture Substances 0.000 title claims description 59
- 229910001416 lithium ion Inorganic materials 0.000 title claims description 41
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims description 31
- 239000007784 solid electrolyte Substances 0.000 claims description 53
- 239000007773 negative electrode material Substances 0.000 claims description 38
- 239000000654 additive Substances 0.000 claims description 32
- 230000000996 additive effect Effects 0.000 claims description 31
- WVLBCYQITXONBZ-UHFFFAOYSA-N trimethyl phosphate Chemical compound COP(=O)(OC)OC WVLBCYQITXONBZ-UHFFFAOYSA-N 0.000 claims description 20
- 239000002203 sulfidic glass Substances 0.000 claims description 14
- 229910003002 lithium salt Inorganic materials 0.000 claims description 8
- 159000000002 lithium salts Chemical class 0.000 claims description 8
- DQWPFSLDHJDLRL-UHFFFAOYSA-N triethyl phosphate Chemical compound CCOP(=O)(OCC)OCC DQWPFSLDHJDLRL-UHFFFAOYSA-N 0.000 claims description 6
- 230000000052 comparative effect Effects 0.000 description 18
- 239000010410 layer Substances 0.000 description 15
- 239000004020 conductor Substances 0.000 description 11
- 239000011230 binding agent Substances 0.000 description 10
- 239000002994 raw material Substances 0.000 description 9
- -1 lithium hexafluorophosphate Chemical compound 0.000 description 8
- 238000000034 method Methods 0.000 description 8
- 239000000126 substance Substances 0.000 description 8
- 229910045601 alloy Inorganic materials 0.000 description 7
- 239000000956 alloy Substances 0.000 description 7
- 238000007599 discharging Methods 0.000 description 7
- 229910003473 lithium bis(trifluoromethanesulfonyl)imide Inorganic materials 0.000 description 7
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 239000002033 PVDF binder Substances 0.000 description 6
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- 238000004519 manufacturing process Methods 0.000 description 5
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- XUPYJHCZDLZNFP-UHFFFAOYSA-N butyl butanoate Chemical compound CCCCOC(=O)CCC XUPYJHCZDLZNFP-UHFFFAOYSA-N 0.000 description 4
- 239000002612 dispersion medium Substances 0.000 description 4
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Inorganic materials [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 239000007774 positive electrode material Substances 0.000 description 4
- 229910018130 Li 2 S-P 2 S 5 Inorganic materials 0.000 description 3
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 description 3
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 3
- 239000002134 carbon nanofiber Substances 0.000 description 3
- 229910021393 carbon nanotube Inorganic materials 0.000 description 3
- 239000002041 carbon nanotube Substances 0.000 description 3
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- 238000003825 pressing Methods 0.000 description 3
- 229910018119 Li 3 PO 4 Inorganic materials 0.000 description 2
- 229910013641 LiNbO 3 Inorganic materials 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
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- 150000002500 ions Chemical class 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- HSZCZNFXUDYRKD-UHFFFAOYSA-M lithium iodide Inorganic materials [Li+].[I-] HSZCZNFXUDYRKD-UHFFFAOYSA-M 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
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- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 2
- 230000007017 scission Effects 0.000 description 2
- XZZNDPSIHUTMOC-UHFFFAOYSA-N triphenyl phosphate Chemical compound C=1C=CC=CC=1OP(OC=1C=CC=CC=1)(=O)OC1=CC=CC=C1 XZZNDPSIHUTMOC-UHFFFAOYSA-N 0.000 description 2
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910018091 Li 2 S Inorganic materials 0.000 description 1
- 229910018133 Li 2 S-SiS 2 Inorganic materials 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910010835 LiI-Li2S-P2S5 Inorganic materials 0.000 description 1
- 229910010833 LiI-Li2S-SiS2 Inorganic materials 0.000 description 1
- 229910010842 LiI—Li2S—P2O5 Inorganic materials 0.000 description 1
- 229910010840 LiI—Li2S—P2S5 Inorganic materials 0.000 description 1
- 229910010855 LiI—Li2S—SiS2 Inorganic materials 0.000 description 1
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 229910001228 Li[Ni1/3Co1/3Mn1/3]O2 (NCM 111) Inorganic materials 0.000 description 1
- NIPNSKYNPDTRPC-UHFFFAOYSA-N N-[2-oxo-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 NIPNSKYNPDTRPC-UHFFFAOYSA-N 0.000 description 1
- 229910015222 Ni1/3Mn1/3Co1/3O2 Inorganic materials 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
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- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
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- 239000003273 ketjen black Substances 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- GLNWILHOFOBOFD-UHFFFAOYSA-N lithium sulfide Chemical compound [Li+].[Li+].[S-2] GLNWILHOFOBOFD-UHFFFAOYSA-N 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- VROAXDSNYPAOBJ-UHFFFAOYSA-N lithium;oxido(oxo)nickel Chemical compound [Li+].[O-][Ni]=O VROAXDSNYPAOBJ-UHFFFAOYSA-N 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-N phosphoric acid Substances OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 1
- CYQAYERJWZKYML-UHFFFAOYSA-N phosphorus pentasulfide Chemical compound S1P(S2)(=S)SP3(=S)SP1(=S)SP2(=S)S3 CYQAYERJWZKYML-UHFFFAOYSA-N 0.000 description 1
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- 125000000383 tetramethylene group Chemical group [H]C([H])([*:1])C([H])([H])C([H])([H])C([H])([H])[*:2] 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Battery Electrode And Active Subsutance (AREA)
Description
本開示は、全固体リチウムイオン二次電池用の負極合材に関する。 The present disclosure relates to a negative electrode mixture for an all-solid-state lithium ion secondary battery.
Ｌｉと合金を形成することが可能な金属を含有する活物質（合金系活物質）は、炭素系の負極活物質と比較して体積当たりの理論容量が大きいことから、このような合金系活物質を負極に用いたリチウムイオン電池が提案されている。
中でも、特に容量が大きいことから、Ｌｉと合金を形成することが可能な金属としてＳｉ単体が注目されている。
Since the active material containing a metal capable of forming an alloy with Li (alloy-based active material) has a larger theoretical capacity per volume than the carbon-based negative electrode active material, such an alloy-based active material is used. A lithium ion battery using a substance as a negative electrode has been proposed.
Among them, Si alone is attracting attention as a metal capable of forming an alloy with Li because of its particularly large capacity.
特許文献１には、負極活物質として、リチウムイオンの挿入脱離が可能な金属又は合金を用いた全固体電池であって、特定の充放電サイクル条件下で、充放電を１００サイクル行った後の放電容量維持率が５０％以上である、全固体電池が開示されている。また、特許文献１の実施例には、負極活物質としてＳｉ粉末を用いて作製した全固体電池が開示されている。 Patent Document 1 describes an all-solid-state battery using a metal or alloy capable of inserting and removing lithium ions as a negative electrode active material, after 100 cycles of charge and discharge under specific charge / discharge cycle conditions. An all-solid-state battery having a discharge capacity retention rate of 50% or more is disclosed. Further, in the examples of Patent Document 1, an all-solid-state battery manufactured by using Si powder as a negative electrode active material is disclosed.
しかしながら、本研究者らは、特許文献１に開示されているような、Ｓｉ元素を含有する負極活物質を用いた負極を備える全固体リチウムイオン二次電池では、充放電サイクルを繰り返すと内部抵抗が大きく上昇することを知見した。
本開示は、上記実情に鑑み、Ｓｉ単体を含有する負極活物質を有し、全固体リチウムイオン二次電池における内部抵抗の上昇を抑制できる、全固体リチウムイオン二次電池用の負極合材を提供することを目的とする。
However, the present researchers have found that in an all-solid-state lithium-ion secondary battery provided with a negative electrode using a negative electrode active material containing a Si element, as disclosed in Patent Document 1, the internal resistance is repeated when the charge / discharge cycle is repeated. Was found to rise significantly.
In view of the above circumstances, the present disclosure provides a negative electrode mixture for an all-solid-state lithium-ion secondary battery, which has a negative electrode active material containing Si alone and can suppress an increase in internal resistance in the all-solid-state lithium-ion secondary battery. The purpose is to provide.
本開示の全固体リチウムイオン二次電池用の負極合材は、負極活物質、固体電解質及び添加剤を含有し、前記負極活物質は、Ｓｉ単体を含み、前記固体電解質は、硫化物固体電解質であり、前記添加剤は、リン酸トリメチル及びリン酸トリエチルからなる群より選ばれる少なくとも一種、並びにリチウム塩を含むことを特徴とする。 The negative electrode mixture for an all-solid lithium ion secondary battery of the present disclosure contains a negative electrode active material, a solid electrolyte and an additive, the negative electrode active material contains Si alone, and the solid electrolyte is a sulfide solid electrolyte. The additive is characterized by containing at least one selected from the group consisting of trimethyl phosphate and triethyl phosphate, and a lithium salt.
本開示によれば、Ｓｉ単体を含有する負極活物質を有し、全固体リチウムイオン二次電池における内部抵抗の上昇を抑制できる、全固体リチウムイオン二次電池用の負極合材を提供することができる。 According to the present disclosure, there is provided a negative electrode mixture for an all-solid-state lithium ion secondary battery, which has a negative electrode active material containing Si alone and can suppress an increase in internal resistance in the all-solid-state lithium ion secondary battery. Can be done.
本開示の負極合材は、全固体リチウムイオン二次電池用の負極合材であって、前記負極合材は、負極活物質、固体電解質及び添加剤を含有し、前記負極活物質は、Ｓｉ単体を含み、前記固体電解質は、硫化物固体電解質であり、前記添加剤は、リン酸トリメチル及びリン酸トリエチルからなる群より選ばれる少なくとも一種、並びにリチウム塩を含むことを特徴とする。 The negative electrode mixture of the present disclosure is a negative electrode mixture for an all-solid lithium ion secondary battery, the negative electrode mixture contains a negative electrode active material, a solid electrolyte and an additive, and the negative electrode active material is Si. The solid electrolyte comprises a simple substance, the solid electrolyte is a sulfide solid electrolyte, and the additive comprises at least one selected from the group consisting of trimethyl phosphate and triethyl phosphate, and a lithium salt.
Ｌｉと合金を形成可能な金属自体はイオン伝導性及び電子伝導性が低いことから、通常、当該金属を負極活物質として用いる場合には、負極中に負極活物質と共に導電材と固体電解質を含有させる。 Since the metal itself capable of forming an alloy with Li has low ionic conductivity and electron conductivity, normally, when the metal is used as the negative electrode active material, the negative electrode contains a conductive material and a solid electrolyte together with the negative electrode active material. Let me.
本研究者らは、特許文献１に開示されているような全固体リチウムイオン二次電池では、充放電に伴う負極活物質の体積膨張収縮が大きいため、充放電を繰り返すと、固体電解質と負極電解質との間に空隙が発生し、空隙部分においてＬｉイオン伝導パスが切れることで、内部抵抗が大きく上昇することを知見した。
Ｓｉ単体を含有する負極活物質を用いた負極における、固体電解質と負極電解質との間の空隙発生のメカニズムは以下の通りである。まず、Ｌｉイオン挿入時（充電時）に、負極活物質が大幅に体積膨張すると共に、負極活物質周辺の固体電解質が、膨張する負極活物質により押されて変形する。その後、Ｌｉイオン脱離時（放電時）に負極活物質が体積収縮すると共に、変形後の固体電解質が、負極活物質の体積収縮に追従できないことにより、空隙が発生する。
In the all-solid-state lithium-ion secondary battery as disclosed in Patent Document 1, the present researchers have a large volume expansion and contraction of the negative electrode active material due to charging and discharging. Therefore, when charging and discharging are repeated, the solid electrolyte and the negative electrode It was found that the internal resistance greatly increases due to the generation of voids with the electrolyte and the breakage of the Li ion conduction path in the void portion.
The mechanism of void generation between the solid electrolyte and the negative electrode electrolyte in the negative electrode using the negative electrode active material containing Si alone is as follows. First, when Li ions are inserted (during charging), the negative electrode active material expands significantly in volume, and the solid electrolyte around the negative electrode active material is pushed and deformed by the expanding negative electrode active material. After that, the negative electrode active material undergoes volume shrinkage during Li ion desorption (during discharge), and the deformed solid electrolyte cannot follow the volume shrinkage of the negative electrode active material, so that voids are generated.
本開示の負極合材を全固体リチウムイオン二次電池に用いることにより、充放電の繰り返しによって発生した空隙が、前記添加剤により埋められ、当該添加剤が、固体電解質と負極活物質との間に発生した空隙のイオン伝導を担う。具体的には、前記添加剤中のリン酸トリメチル及び／又はリン酸トリエチルにより、固体電解質と負極活物質との間に発生した空隙が埋められる。それと共に、前記添加剤中のリチウム塩により、固体電解質の内部を移動するＬｉイオンが供給される。このため、全固体リチウムイオン二次電池において充放電サイクルを繰り返したときの、Ｌｉイオン伝導パスの切断を抑制し、内部抵抗の上昇を抑制することができる。
ここでいう「空隙部分」とは、少なくとも固体電解質及び負極活物質が存在しない部分をいう。
By using the negative electrode mixture of the present disclosure in an all-solid-state lithium-ion secondary battery, voids generated by repeated charging and discharging are filled with the additive, and the additive is placed between the solid electrolyte and the negative electrode active material. It is responsible for the ion conduction of the voids generated in. Specifically, the trimethyl phosphate and / or triethyl phosphate in the additive fills the voids generated between the solid electrolyte and the negative electrode active material. At the same time, the lithium salt in the additive supplies Li ions that move inside the solid electrolyte. Therefore, it is possible to suppress the disconnection of the Li ion conduction path and the increase in the internal resistance when the charge / discharge cycle is repeated in the all-solid-state lithium ion secondary battery.
The "void portion" here means a portion where at least the solid electrolyte and the negative electrode active material do not exist.
負極合材は、負極活物質、固体電解質及び添加剤を含有する。 The negative electrode mixture contains a negative electrode active material, a solid electrolyte and an additive.
（負極活物質）
前記負極活物質は、Ｓｉ単体を含む。
負極合材中の負極活物質の割合は、特に限定されるものではないが、例えば４０質量％以上であり、５０質量％〜９０質量％の範囲内であってもよく、５０質量％〜７０質量％の範囲内であってもよい。
前記Ｌｉと合金を形成可能な金属、及び当該金属の酸化物の形状には特に制限はなく、例えば、粒子状、膜状の形状等が挙げられる。
(Negative electrode active material)
The negative electrode active material contains Si alone.
The ratio of the negative electrode active material in the negative electrode mixture is not particularly limited, but is, for example, 40% by mass or more, may be in the range of 50% by mass to 90% by mass, and 50% by mass to 70%. It may be in the range of mass%.
The shape of the metal capable of forming an alloy with Li and the shape of the oxide of the metal are not particularly limited, and examples thereof include a particle-like shape and a film-like shape.
（固体電解質）
固体電解質としては、硫化物固体電解質を用いる。前記硫化物固体電解質としては、例えば、Ｌｉ２Ｓ−ＳｉＳ２、ＬｉＩ−Ｌｉ２Ｓ−ＳｉＳ２、ＬｉＩ−Ｌｉ２Ｓ−Ｐ２Ｓ５、ＬｉＩ−Ｌｉ２Ｓ−Ｐ２Ｏ５、ＬｉＩ−Ｌｉ３ＰＯ４−Ｐ２Ｓ５、Ｌｉ２Ｓ−Ｐ２Ｓ５−ＬｉＢｒ、Ｌｉ２Ｓ−Ｐ２Ｓ５、ＬｉＩ−ＬｉＢｒ−Ｌｉ２Ｓ−Ｐ２Ｓ５等が挙げられる。また、前記硫化物固体電解質としては、Ｌｉ１０ＧｅＰ２Ｓ１２等のＬＧＰＳ系の固体電解質も挙げられる。
負極合材中の固体電解質の割合は、特に限定されるものではないが、例えば１０質量％以上であり、２０質量％〜５０質量％の範囲内であってもよく、２５質量％〜４５質量％の範囲内であってもよい。
前記固体電解質の原料は、密度が２．０〜２．５ｇ／ｃｍ３であってもよい。
(Solid electrolyte)
As the solid electrolyte, a sulfide solid electrolyte is used. Examples of the sulfide solid electrolyte include Li 2 S-SiS 2 , LiI-Li 2 S-SiS 2 , LiI-Li 2 S-P 2 S 5 , LiI-Li 2 S-P 2 O 5 , LiI-. Li 3 PO 4 -P 2 S 5 , Li 2 S-P 2 S 5 -LiBr, Li 2 S-P 2 S 5, LiI-LiBr-Li 2 S-P 2 S 5 , and the like. Further, examples of the sulfide solid electrolyte include LGPS-based solid electrolytes such as Li 10 GeP 2 S 12 .
The ratio of the solid electrolyte in the negative electrode mixture is not particularly limited, but is, for example, 10% by mass or more, may be in the range of 20% by mass to 50% by mass, and 25% by mass to 45% by mass. It may be in the range of%.
The raw material of the solid electrolyte may have a density of 2.0 to 2.5 g / cm 3 .
（添加剤）
前記添加剤は、リン酸トリメチル及びリン酸トリエチルからなる群より選ばれる少なくとも一種（以下、「リン酸トリメチル等」と称する場合がある。）、並びにリチウム塩を含む。
(Additive)
The additive contains at least one selected from the group consisting of trimethyl phosphate and triethyl phosphate (hereinafter, may be referred to as "trimethyl phosphate or the like"), and a lithium salt.
リン酸トリメチル等は、いずれも常温で液体である。したがって、リン酸トリメチル等を含む添加剤を含有する負極合材を、全固体リチウムイオン二次電池に用いることにより、充放電の繰り返しによって負極活物質と固体電解質との間に発生した空隙部分に、リン酸トリメチル等が浸入する。その結果、当該空隙部分がリン酸トリメチル等により埋まる。また、リン酸トリメチル等は、いずれも、負極活物質中のＳｉ単体及び硫化物固体電解質との反応性に乏しいため、これらの成分との反応による内部抵抗の上昇を抑制することができる。 All of trimethyl phosphate and the like are liquid at room temperature. Therefore, by using a negative electrode mixture containing an additive containing trimethyl phosphate or the like in an all-solid-state lithium-ion secondary battery, the voids generated between the negative electrode active material and the solid electrolyte due to repeated charging and discharging can be formed. , Trimethyl phosphate, etc. infiltrate. As a result, the void portion is filled with trimethyl phosphate or the like. Further, since trimethyl phosphate and the like have poor reactivity with Si alone and the sulfide solid electrolyte in the negative electrode active material, it is possible to suppress an increase in internal resistance due to the reaction with these components.
負極合材中の添加剤の割合は、負極合材の固形分の合計量（負極活物質、固体電解質等）を１００質量部としたとき、１〜５０質量部の範囲内であってもよい。負極合材中の添加剤の割合を、上記範囲とすることで、当該負極合材を用いた全固体リチウムイオン二次電池において、液漏れ等の不具合の発生を抑制しつつ、充放電を繰り返した時の、Ｌｉイオン伝導パスの切断を抑制し、これに伴う内部抵抗の上昇を抑制することができる。 The ratio of the additive in the negative electrode mixture may be in the range of 1 to 50 parts by mass when the total amount of solids in the negative electrode mixture (negative electrode active material, solid electrolyte, etc.) is 100 parts by mass. .. By setting the ratio of the additive in the negative electrode mixture to the above range, charging and discharging are repeated while suppressing the occurrence of problems such as liquid leakage in the all-solid-state lithium-ion secondary battery using the negative electrode mixture. At that time, it is possible to suppress the cleavage of the Li ion conduction path and suppress the increase in internal resistance accompanying this.
添加剤に含まれるリチウム塩は、固体電解質の内部を移動するＬｉイオンを供給するものであり、例えばリチウムビス（トリフルオロメタンスルホニル）イミド及びＬｉＰＦ６（ヘキサフルオロリン酸リチウム）からなる群から選ばれる少なくとも一つを用いることができる。 The lithium salt contained in the additive supplies Li ions that move inside the solid electrolyte, and is selected from the group consisting of, for example, lithium bis (trifluoromethanesulfonyl) imide and LiPF 6 (lithium hexafluorophosphate). At least one can be used.
添加剤中に含まれる、リチウム塩の含有割合は、０．１〜１０ｍｏｌ／ｌであることが好ましい。
添加剤中に含まれるリチウム塩の含有割合を上記範囲とすることで、Ｓｉ元素を含有する負極活物質を用いた負極を備える全固体リチウムイオン二次電池において、充放電サイクルを繰り返した場合でも、良好なＬｉイオン伝導性を得ることができる。
The content ratio of the lithium salt contained in the additive is preferably 0.1 to 10 mol / l.
By setting the content ratio of the lithium salt contained in the additive to the above range, even when the charge / discharge cycle is repeated in an all-solid-state lithium ion secondary battery provided with a negative electrode using a negative electrode active material containing a Si element. , Good Li ion conductivity can be obtained.
本開示の負極合材は、導電材を含んでいてもよい。
導電材は、全固体リチウムイオン二次電池の負極に使用できるものであれば、特に制限はない。
導電材の原料は、例えば、アセチレンブラック、ケッチェンブラック、ファーネスブラック等のカーボンブラック、カーボンナノチューブ、及び、カーボンナノファイバーからなる群より選ばれる少なくとも一種の炭素系素材であってもよい。
電子伝導性の観点から、カーボンナノチューブ、及び、カーボンナノファイバーからなる群より選ばれる少なくとも一種の炭素系素材であってもよく、当該カーボンナノチューブ、及び、カーボンナノファイバーはＶＧＣＦ（気相法炭素繊維）であってもよい。
負極合材中の導電材の割合は、負極合材の質量を１００質量％としたとき、１．０質量％以上であり、１．０質量％〜１２．０質量％の範囲内であってもよく、２．０質量％〜１０．０質量％の範囲内であってもよい。
The negative electrode mixture of the present disclosure may contain a conductive material.
The conductive material is not particularly limited as long as it can be used for the negative electrode of the all-solid-state lithium ion secondary battery.
The raw material of the conductive material may be, for example, at least one carbon-based material selected from the group consisting of carbon black such as acetylene black, ketjen black, furnace black, carbon nanotubes, and carbon nanofibers.
From the viewpoint of electron conductivity, it may be at least one carbon-based material selected from the group consisting of carbon nanotubes and carbon nanofibers, and the carbon nanotubes and carbon nanofibers are VGCF (gas phase carbon fibers). ) May be.
The ratio of the conductive material in the negative electrode mixture is 1.0% by mass or more and is in the range of 1.0% by mass to 12.0% by mass when the mass of the negative electrode mixture is 100% by mass. It may be in the range of 2.0% by mass to 10.0% by mass.
負極合材には上記成分以外に、結着剤などの他の成分が含まれていてもよい。
前記結着剤としては、例えば、ポリフッ化ビニリデン（ＰＶｄＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、ブチレンゴム（ＢＲ）、スチレン−ブタジエンゴム（ＳＢＲ）、ポリビニルブチラール（ＰＶＢ）、アクリル樹脂等を用いることができ、ポリフッ化ビニリデン（ＰＶｄＦ）であってもよい。
エネルギー密度が高くなることから、本開示に係る負極は、負極活物質以外の成分が少ないものであってもよい。
In addition to the above components, the negative electrode mixture may contain other components such as a binder.
As the binder, for example, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), butylene rubber (BR), styrene-butadiene rubber (SBR), polyvinyl butyral (PVB), acrylic resin and the like can be used. It can be polyvinylidene fluoride (PVdF).
Since the energy density is high, the negative electrode according to the present disclosure may have a small amount of components other than the negative electrode active material.
負極合材の形成方法としては、好適には、負極活物質、固体電解質、添加剤等を分散媒により分散させて、ペースト状の負極合材を作製し、負極集電体上に塗布、乾燥する方法等が挙げられる。
分散媒としては、特に限定されず、例えば、ヘプタン等が挙げられる。分散方法としては、特に限定されないが、例えば、ホモジナイザー、ビーズミル、シェアミキサー、ロールミル等が挙げられる。ペースト状の負極合材の塗布方法、乾燥方法等は適宜選択することができる。
As a method for forming the negative electrode mixture, preferably, a negative electrode active material, a solid electrolyte, an additive and the like are dispersed with a dispersion medium to prepare a paste-like negative electrode mixture, which is applied onto the negative electrode current collector and dried. The method of doing this can be mentioned.
The dispersion medium is not particularly limited, and examples thereof include heptane. The dispersion method is not particularly limited, and examples thereof include a homogenizer, a bead mill, a share mixer, and a roll mill. The method of applying the paste-like negative electrode mixture, the method of drying, and the like can be appropriately selected.
二次電池として機能し、かつ負極に前記負極合材を用いるものであれば、全固体リチウムイオン二次電池の構成に特に制限はない。
図１に示すように、典型的には、正極２、負極３、並びに、当該正極２及び当該負極３の間に配置される固体電解質層１を備え、正極−固体電解質層−負極集合体１０１として構成される。この正極−固体電解質層−負極集合体１０１は、正極、固体電解質層及び負極がこの順序で配列され、直接または他の材料からなる部分を介して接合していてもよく、さらに、正極上の固体電解質層が存在する位置とは反対側（正極の外方側）、及び、負極上の固体電解質層が存在する位置とは反対側（負極の外方側）のうちの片方又は両方の側に、他の材料からなる部分が接合していてもよい配列構造を有する各部の集合体である。
The configuration of the all-solid-state lithium ion secondary battery is not particularly limited as long as it functions as a secondary battery and uses the negative electrode mixture for the negative electrode.
As shown in FIG. 1, typically, a positive electrode 2, a
前記正極は、正極合材を含む。正極合材は、通常、Ｌｉを含有する正極活物質を含み、必要に応じ、結着剤、固体電解質、及び導電材等の他の成分を含む。
正極活物質の原料としては、全固体リチウムイオン二次電池に使用できるものであれば、特に制限はない。例えば、コバルト酸リチウム（ＬｉＣｏＯ２）、ニッケル酸リチウム（ＬｉＮｉＯ２）、マンガン酸リチウム（ＬｉＭｎ２Ｏ４）、Ｌｉ１＋ｘＮｉ１／３Ｍｎ１／３Ｃｏ１／３Ｏ２（０≦ｘ＜０．３）等を挙げることができる。
前記正極活物質は、リチウムイオン伝導性を有し、かつ、活物質や固体電解質と接触しても流動せず、被覆層の形態を維持し得る物質を含有する被覆層を有していてもよい。当該物質としては、例えば、ＬｉＮｂＯ３、Ｌｉ４Ｔｉ５Ｏ１２、Ｌｉ３ＰＯ４が挙げられる。
固体電解質、導電材、結着剤の原料としては、負極で使用する材料と同様のものを用いることができる。
The positive electrode contains a positive electrode mixture. The positive electrode mixture usually contains a positive electrode active material containing Li, and if necessary, contains other components such as a binder, a solid electrolyte, and a conductive material.
The raw material for the positive electrode active material is not particularly limited as long as it can be used in an all-solid-state lithium ion secondary battery. For example, lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), lithium manganate (LiMn 2 O 4 ), Li 1 + x Ni 1/3 Mn 1/3 Co 1/3 O 2 (0 ≦ x <0) .3) etc. can be mentioned.
Even if the positive electrode active material has a coating layer having lithium ion conductivity and containing a substance that does not flow even when in contact with the active material or a solid electrolyte and can maintain the morphology of the coating layer. Good. Examples of the substance include LiNbO 3 , Li 4 Ti 5 O 12 , and Li 3 PO 4 .
As the raw materials for the solid electrolyte, the conductive material, and the binder, the same materials as those used for the negative electrode can be used.
前記固体電解質層も、全固体リチウム二次電池の固体電解質として機能するものであれば、特に制限はないが、通常、固体電解質原料を含み、必要に応じ、結着剤等の他の成分を含む。
固体電解質、結着剤の原料としては、負極で使用する材料と同様のものを用いることができる。
The solid electrolyte layer is also not particularly limited as long as it functions as a solid electrolyte of the all-solid-state lithium secondary battery, but usually contains a solid electrolyte raw material and, if necessary, other components such as a binder. Including.
As the raw materials for the solid electrolyte and the binder, the same materials as those used for the negative electrode can be used.
なお、全固体リチウム二次電池において、前記添加剤は、正極には含まれないことが好ましい。仮に、リン酸トリメチル等が、正極に存在する状態で通電すると、正極の電位により、リン酸トリメチル等が分解して、内部抵抗を上昇させる可能性がある。
上記したように、正極と負極との間には固体電解質層が存在する。したがって、負極中のリン酸トリメチル等は、固体電解質層に遮られ、正極まで移動することはない。このため、リン酸トリメチル等が正極中に混入することによる内部抵抗の上昇は抑制される。
In the all-solid-state lithium secondary battery, it is preferable that the additive is not contained in the positive electrode. If trimethyl phosphate or the like is energized while present in the positive electrode, trimethyl phosphate or the like may be decomposed by the potential of the positive electrode to increase the internal resistance.
As described above, there is a solid electrolyte layer between the positive electrode and the negative electrode. Therefore, trimethyl phosphate and the like in the negative electrode are blocked by the solid electrolyte layer and do not move to the positive electrode. Therefore, an increase in internal resistance due to mixing of trimethyl phosphate or the like in the positive electrode is suppressed.
全固体リチウムイオン二次電池の製造方法としては、例えば、固体電解質層の一方の面側に正極合材を加えてプレスし、他方の面側に負極合材を加えてプレスする方法が挙げられる。 Examples of the method for manufacturing the all-solid-state lithium ion secondary battery include a method in which a positive electrode mixture is added to one surface side of the solid electrolyte layer and pressed, and a negative electrode mixture is added to the other surface side and pressed. ..
１．負極合材の製造
［実施例１］
（１）硫化物固体電解質の合成工程
下記硫化物固体電解質用原料をメノウ乳鉢に加えた。
・硫化リチウム（Ｌｉ２Ｓ、フルウチ化学製、純度９９．９％）０．５５０ｇ
・五硫化二リン（Ｐ２Ｓ５、Ａｌｄｒｉｃｈ社製、純度９９％）０．８８７ｇ
・ヨウ化リチウム（ＬｉＩ、日宝化学製、純度９９％）０．２８５ｇ
・臭化リチウム（ＬｉＢｒ、高純度化学製）０．２７７ｇ
上記材料をメノウ乳鉢で５分間混合した後、遊星型ボールミルに投入し、脱水ヘプタン（関東化学工業製、４ｇ）を投入した。さらに、ＺｒＯ２ボールを投入し、容器を完全に密閉した（Ａｒ雰囲気）。この容器を遊星型ボールミル機（フリッチュ製）に取り付け、台盤回転数毎分３００回転で、４０時間のメカニカルミリング処理を行い、適宜乾燥することで、硫化物固体電解質（ＬｉＩ−ＬｉＢｒ−Ｌｉ２Ｓ−Ｐ２Ｓ５）を得た。
1. 1. Production of Negative Electrode Mixture [Example 1]
(1) Synthesis of sulfide solid electrolyte The following raw materials for sulfide solid electrolyte were added to an agate mortar.
Lithium sulfide (Li 2 S, Furuuchi Chemical Co., purity 99.9%) 0.550 g
· Phosphorus pentasulfide (P 2 S 5, Aldrich Co., purity 99%) 0.887 g
-Lithium iodide (LiI, manufactured by Nippoh Chemicals, purity 99%) 0.285 g
-Lithium bromide (LiBr, manufactured by high-purity chemicals) 0.277 g
After mixing the above materials in an agate mortar for 5 minutes, they were put into a planetary ball mill, and dehydrated heptane (manufactured by Kanto Chemical Industry, 4 g) was put into it. Further, ZrO 2 balls were put in and the container was completely sealed (Ar atmosphere). This container is attached to a planetary ball mill machine (manufactured by Fritsch), mechanically milled for 40 hours at a base rotation speed of 300 rpm, and dried as appropriate to obtain a sulfide solid electrolyte (LiI-LiBr-Li 2). SP 2 S 5 ) was obtained.
（２）負極合材の製造工程
容器に下記負極用原料を加えた。
・負極活物質：Ｓｉ粒子（高純度化学製）１．０ｇ
・固体電解質：上記硫化物固体電解質（ＬｉＩ−ＬｉＢｒ−Ｌｉ２Ｓ−Ｐ２Ｓ５）０．７７６ｇ
・導電材：ＶＧＣＦ（昭和電工社製）０．０４ｇ
・結着剤：ＰＶｄＦ（クレハ製）０．０２ｇ
・分散媒：酪酸ブチル（ナカライテスク社製）２．４ｇ
容器中の混合物を、超音波ホモジナイザー（ＳＭＴ社製、ＵＨ−５０）により６０秒間攪拌混合した後、適宜乾燥することで、負極合材用混合物を得た。
上記で作製した負極合材用混合物に、添加剤として、ＬｉＴＦＳＩ（リチウムビス（トリフルオロメタンスルホニル）イミド、キシダ化学社製）を添加したリン酸トリメチル（ナカライテスク社製、下記式（１））を、０．１８４ｇ加えた後、混合して、負極合材（実施例１）を調製した。
添加剤は、負極合材用混合物の固形分（負極活物質、導電材、固体電解質及び結着剤）の合計量１００質量部に対して、１０質量部となるように添加した。
添加剤としては、リン酸トリメチルに、ＬｉＴＦＳＩを、ＬｉＴＦＳＩ濃度が１．０ｍｏｌ／Ｌとなるように添加したものを用いた。
(2) Manufacturing process of negative electrode mixture The following raw materials for negative electrodes were added to the container.
-Negative electrode active material: Si particles (manufactured by high-purity chemicals) 1.0 g
-Solid electrolyte: 0.776 g of the above-mentioned sulfide solid electrolyte (LiI-LiBr-Li 2 SP 2 S 5 )
-Conductive material: VGCF (manufactured by Showa Denko) 0.04 g
-Binder: PVdF (manufactured by Kureha) 0.02 g
-Dispersion medium: Butyl butyrate (manufactured by Nacalai Tesque) 2.4 g
The mixture in the container was stirred and mixed with an ultrasonic homogenizer (UH-50, manufactured by SMT) for 60 seconds, and then appropriately dried to obtain a mixture for a negative electrode mixture.
Trimethyl phosphate (manufactured by Nacalai Tesque, manufactured by the following formula (1)) in which LiTFSI (lithium bis (trifluoromethanesulfonyl) imide, manufactured by Kishida Chemical Co., Ltd.) is added as an additive to the mixture for negative electrode mixture prepared above. , 0.184 g and then mixed to prepare a negative electrode mixture (Example 1).
The additive was added so as to be 10 parts by mass with respect to 100 parts by mass of the total amount of the solid content (negative electrode active material, conductive material, solid electrolyte and binder) of the mixture for the negative electrode mixture.
As an additive, one in which LiTFSI was added to trimethyl phosphate so that the LiTFSI concentration was 1.0 mol / L was used.
［実施例２］
実施例１の「（１）負極合材形成工程」に使用した添加剤中のエステル化合物を、リン酸トリメチルからリン酸トリエチル（ナカライテスク社製、下記式（２））に変更したこと以外は、実施例１と同様にして、負極合材（実施例２）を製造した。
[Example 2]
Except that the ester compound in the additive used in "(1) Negative electrode mixture forming step" of Example 1 was changed from trimethyl phosphate to triethyl phosphate (manufactured by Nacalai Tesque, Inc., formula (2) below). , A negative electrode mixture (Example 2) was produced in the same manner as in Example 1.
［比較例１］
実施例１の「（１）負極合材形成工程」において、添加剤を使用しなかったこと以外は、実施例１と同様にして、負極合材（比較例１）を製造した。
[Comparative Example 1]
A negative electrode mixture (Comparative Example 1) was produced in the same manner as in Example 1 except that no additive was used in the “(1) Negative electrode mixture forming step” of Example 1.
［比較例２］
実施例１の「（１）負極合材形成工程」に使用した添加剤中のエステル化合物を、リン酸トリメチルから炭酸プロピレン（ナカライテスク社製、下記式（３））に変更したこと以外は、実施例１と同様にして、負極合材（比較例２）を製造した。
[Comparative Example 2]
Except that the ester compound in the additive used in "(1) Negative electrode mixture forming step" of Example 1 was changed from trimethyl phosphate to propylene carbonate (manufactured by Nacalai Tesque, Inc., formula (3) below). A negative electrode mixture (Comparative Example 2) was produced in the same manner as in Example 1.
［比較例３］
実施例１の「（１）負極合材形成工程」に使用した添加剤中のエステル化合物を、リン酸トリメチルからリン酸トリフェニル（ナカライテスク社製、下記式（４））に変更したこと以外は、実施例１と同様にして、負極合材（比較例３）を製造した。
[Comparative Example 3]
Except that the ester compound in the additive used in "(1) Negative electrode mixture forming step" of Example 1 was changed from trimethyl phosphate to triphenyl phosphate (manufactured by Nacalai Tesque, Inc., formula (4) below). Produced a negative electrode mixture (Comparative Example 3) in the same manner as in Example 1.
添加剤は、実施例２及び比較例２〜３においても、実施例１と同様に、負極合材用混合物の固形分（活物質、導電材、固体電解質及び結着剤）の合計量１００質量部に対して、１０質量部となるように添加した。
添加剤としては、実施例２及び比較例２〜３においても、実施例１と同様に、上記した各化合物に対して、それぞれ、ＬｉＴＦＳＩ濃度が１．０ｍｏｌ／ＬとなるようにＬｉＴＦＳＩを添加して調製した。
In Examples 2 and Comparative Examples 2 and 3, the additive is a total amount of 100 mass of the solid content (active material, conductive material, solid electrolyte and binder) of the mixture for the negative electrode mixture, as in Example 1. It was added so as to be 10 parts by mass with respect to the part.
As additives, in Examples 2 and Comparative Examples 2 and 3, LiTFSI was added to each of the above-mentioned compounds so that the LiTFSI concentration was 1.0 mol / L, as in Example 1. Prepared.
２．全固体リチウムイオン二次電池の製造
（１）正極合材製造工程
容器に下記正極用原料を加えた。
・正極活物質：ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２粒子、（日亜化学工業社製、ＬｉＮｂＯ３による表面処理粒子）１．５ｇ
・固体電解質：上記硫化物固体電解質（ＬｉＩ−ＬｉＢｒ−Ｌｉ２Ｓ−Ｐ２Ｓ５）０．２３９ｇ
・導電材：ＶＧＣＦ（昭和電工社製）０．０２３ｇ
・結着剤：ＰＶｄＦ（クレハ製）０．０１１ｇ
・分散媒：酪酸ブチル（ナカライテスク社製）０．８ｇ
容器中の混合物を、超音波ホモジナイザー（ＳＭＴ社製、ＵＨ−５０）により６０秒間攪拌混合した後、適宜乾燥して、正極合材を得た。
2. 2. Manufacture of all-solid-state lithium-ion secondary battery (1) Positive electrode mixture manufacturing process The following positive electrode raw materials were added to the container.
-Positive electrode active material: LiNi 1/3 Co 1/3 Mn 1/3 O 2 particles, (manufactured by Nichia Corporation, surface-treated particles with LiNbO 3 ) 1.5 g
-Solid electrolyte: 0.239 g of the above-mentioned sulfide solid electrolyte (LiI-LiBr-Li 2 SP 2 S 5 )
-Conductive material: VGCF (manufactured by Showa Denko) 0.023 g
-Binder: PVdF (manufactured by Kureha) 0.011 g
-Dispersion medium: Butyl butyrate (manufactured by Nacalai Tesque) 0.8 g
The mixture in the container was stirred and mixed with an ultrasonic homogenizer (UH-50, manufactured by SMT) for 60 seconds, and then appropriately dried to obtain a positive electrode mixture.
（２）電池の組み立て工程
上記硫化物固体電解質（ＬｉＩ−ＬｉＢｒ−Ｌｉ２Ｓ−Ｐ２Ｓ５）を０．０６５ｇ秤量し、底面積１ｃｍ２のセラミックス製の型に入れ、１ｔｏｎ／ｃｍ２のプレス圧でプレスして、固体電解質層（セパレート層）を作製した。
次いで、前記正極合材０．０１８ｇを秤量し、上記にて作製した固体電解質層（セパレート層）の一方の面側に加え、１ｔｏｎ／ｃｍ２のプレス圧でプレスして、正極を作製した。
次いで、実施例１−実施例２及び比較例１−比較例３のうちいずれか１つの負極合材０．００５４ｇを秤量し、固体電解質層（セパレート層）の他方の面側に加え、４ｔｏｎ／ｃｍ２のプレス圧でプレスして負極を作製した。
次いで、上記で作製した正極上に、アルミ箔を積層し、正極集電体を形成した。また、上記で作製した負極上に、銅箔を積層して、負極集電体を形成し、全固体リチウムイオン二次電池を得た。
このように、実施例１−実施例２及び比較例１−比較例３の各負極合材について、全固体リチウムイオン二次電池を製造した。
(2) Battery assembly process 0.065 g of the above sulfide solid electrolyte (LiI-LiBr-Li 2 SP 2 S 5 ) is weighed and placed in a ceramic mold having a bottom area of 1 cm 2 and 1 ton / cm 2 . A solid electrolyte layer (separate layer) was prepared by pressing with a pressing pressure.
Next, 0.018 g of the positive electrode mixture was weighed, added to one surface side of the solid electrolyte layer (separate layer) prepared above, and pressed with a press pressure of 1 ton / cm 2 to prepare a positive electrode.
Next, 0.0054 g of the negative electrode mixture of any one of Example 1-Example 2 and Comparative Example 1-Comparative Example 3 was weighed and added to the other surface side of the solid electrolyte layer (separate layer), and 4 ton / A negative electrode was prepared by pressing with a press pressure of cm 2 .
Next, an aluminum foil was laminated on the positive electrode produced above to form a positive electrode current collector. Further, a copper foil was laminated on the negative electrode produced above to form a negative electrode current collector to obtain an all-solid-state lithium ion secondary battery.
As described above, an all-solid-state lithium ion secondary battery was manufactured for each negative electrode mixture of Example 1-Example 2 and Comparative Example 1-Comparative Example 3.
３．評価
（１）充放電サイクル時の内部抵抗測定
（ｉ）初期充放電
０．２４５ｍＡの電流値（充電レート）で、定電圧−定電流の条件下で通電して、４．３５Ｖまで充電を行った。その後、０．２４５ｍＡの電流値（放電レート）で、定電圧−定電流の条件下で通電して、３．００Ｖまで放電を行った。
3. 3. Evaluation (1) Measurement of internal resistance during charge / discharge cycle (i) Initial charge / discharge With a current value (charging rate) of 0.245 mA, energize under constant voltage-constant current conditions and charge to 4.35 V. It was. After that, the current value (discharge rate) of 0.245 mA was energized under the condition of constant voltage-constant current, and the battery was discharged to 3.00 V.
（ｉｉ）初期内部抵抗測定
次に、電流値０．２４５ｍＡにて通電して、３．７Ｖまで充電を行った後、７．３５ｍＡで５秒間放電し、放電中の電圧値を充放電装置（東洋システム社製）により測定し、その電圧値の変化から、内部抵抗を算出した。
(Ii) Initial internal resistance measurement Next, energize at a current value of 0.245 mA, charge to 3.7 V, discharge at 7.35 mA for 5 seconds, and charge / discharge the voltage value during discharge (ii). It was measured by Toyo System Co., Ltd.), and the internal resistance was calculated from the change in the voltage value.
（ｉｉｉ）充放電サイクル
（ｉｉ）にて初期内部抵抗測定を行った後のリチウムイオン二次電池を、恒温槽内に入れて６０℃に温度設定した状態で、電圧範囲３．２〜４．２Ｖで、電流値４．９ｍＡの定電流の条件下で、充放電を３００サイクル行った。
(Iii) The lithium ion secondary battery after the initial internal resistance measurement in the charge / discharge cycle (ii) was placed in a constant temperature bath and the temperature was set to 60 ° C., and the voltage range was 3.2-4. Charging and discharging were performed for 300 cycles under the condition of a constant current of 2 V and a current value of 4.9 mA.
（ｉｖ）充放電サイクル後の内部抵抗測定
次いで、（ｉｉｉ）の３００サイクルの充放電を行った後のリチウムイオン二次電池に対して、更に（ｉ）の初期充放電を行った後、（ｉｉ）で説明したのと同様にして、内部抵抗測定を行った。
(Iv) Measurement of internal resistance after charge / discharge cycle Next, after performing the initial charge / discharge of (i) on the lithium ion secondary battery after performing charge / discharge of (iii) for 300 cycles, (iv) The internal resistance was measured in the same manner as described in ii).
（ｉｖ）にて得られた内部抵抗測定値から、（ｉｉ）にて得られた初期内部抵抗の測定値を減じた値を、内部抵抗増加量として算出した。
表１に、実施例１−２及び比較例２−３について、比較例１の内部抵抗増加量を１００％としたときの、比内部抵抗増加量を示す。
下記表１には、実施例１−２及び比較例１−３の比内部抵抗増加量を、添加剤中のエステル化合物の種類及び融点と併せて示している。
The value obtained by subtracting the measured value of the initial internal resistance obtained in (ii) from the measured value of the internal resistance obtained in (iv) was calculated as the amount of increase in the internal resistance.
Table 1 shows the specific internal resistance increase amount of Example 1-2 and Comparative Example 2-3 when the internal resistance increase amount of Comparative Example 1 is 100%.
Table 1 below shows the amount of increase in the specific internal resistance of Examples 1-2 and Comparative Example 1-3 together with the type and melting point of the ester compound in the additive.
４．考察
上記表１に示すように、実施例１−２の内部抵抗増加量は、添加剤を用いない比較例１の場合よりも、いずれも大きく下回る。これは、実施例１−２の全固体リチウムイオン二次電池では、負極合材中のリン酸トリエステルにより、負極活物質と固体電解質との間に生じた空隙が埋められ、Ｌｉイオンのイオン伝導パスの切断が抑制されたためであると考えられる。
一方、比較例２における内部抵抗増加量は、比較例１における内部抵抗増加量を上回る。これは、炭酸プロピレンが硫化物固体電解質と反応したためと考えられる。
また、比較例３における内部抵抗増加量も、比較例１における内部抵抗増加量を上回る。これは、リン酸トリフェニルの融点が高く、常温で固体であるため、充放電に伴い発生した負極活物質と固体電解質との間の空隙が埋まらない結果、Ｌｉイオン伝導パスの切断が生じたためと考えられる。
4. Discussion As shown in Table 1 above, the amount of increase in internal resistance of Example 1-2 is much lower than that of Comparative Example 1 in which no additive is used. This is because, in the all-solid-state lithium-ion secondary battery of Example 1-2, the void formed between the negative electrode active material and the solid electrolyte is filled with the phosphoric acid triester in the negative electrode mixture, and Li ion ions are formed. It is considered that this is because the cutting of the conduction path was suppressed.
On the other hand, the amount of increase in internal resistance in Comparative Example 2 exceeds the amount of increase in internal resistance in Comparative Example 1. It is considered that this is because propylene carbonate reacted with the sulfide solid electrolyte.
Further, the amount of increase in internal resistance in Comparative Example 3 also exceeds the amount of increase in internal resistance in Comparative Example 1. This is because triphenyl phosphate has a high melting point and is solid at room temperature, so that the voids between the negative electrode active material and the solid electrolyte generated during charging and discharging are not filled, resulting in the cleavage of the Li ion conduction path. it is conceivable that.
１ 固体電解質層
２ 正極
３ 負極
１０１ 正極−固体電解質層−負極集合体
1 Solid electrolyte layer 2
Claims (1)
前記負極合材は、負極活物質、固体電解質及び添加剤を含有し、
前記負極活物質は、Ｓｉ単体を含み、
前記固体電解質は、硫化物固体電解質であり、
前記添加剤は、リン酸トリメチル及びリン酸トリエチルからなる群より選ばれる少なくとも一種、並びにリチウム塩を含むことを特徴とする、全固体リチウムイオン二次電池用の負極合材。 Negative electrode mixture for all-solid-state lithium-ion secondary batteries
The negative electrode mixture contains a negative electrode active material, a solid electrolyte, and an additive.
The negative electrode active material contains Si alone.
The solid electrolyte is a sulfide solid electrolyte.
The additive is a negative electrode mixture for an all-solid-state lithium ion secondary battery, which comprises at least one selected from the group consisting of trimethyl phosphate and triethyl phosphate, and a lithium salt.
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