Secondary battery
A secondary battery which comprises a positive electrode, a negative electrode, and an electrolytic solution, wherein the electrolytic solution comprises water, a lithium salt, and an additive, the additive including at least one of alkaline-earth metal salts, dicarboxylic acids, carboxylic anhydrides, and organic carbonates, and the negative electrode comprises a negative active material, the negative active material having a silane coupling agent adherent to the surface thereof.
1 . A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte solution, wherein
the electrolyte solution contains water, a lithium salt, and an additive,
the negative electrode includes a negative electrode active material, and a silane coupling agent is adhered to a surface of the negative electrode active material,
the negative electrode active material contains carbon material as a main component,
the additive includes an organic carbonate,
a content of the water in the electrolyte solution relative to a total amount of the electrolyte solution is in a range from 8.5% by mass to 21% by mass,
wherein the organic carbonate contains at least one of fluoroethylene carbonate or vinylidene carbonate,
wherein the silane coupling agent is a fluoroalkylsilane and the fluoroalkylsilane includes C 8 F 17 CH 2 CH 2 —Si(OCH 3 ) 3 ,
wherein the organic carbonate is present in a first molar ratio in a range from 1:0.05 to 1:1 relative to the lithium salt, and the water is present in a second molar ratio in a range from 1:1 to 1:2.5 relative to the lithium salt.
2 . The secondary battery according to claim 1 , wherein the carbon material is hard carbon material.
3 . The secondary battery according to claim 1 , wherein the silane coupling agent is reductively decomposed at a potential higher than a reductive decomposition potential of water.
4 . The secondary battery according to claim 3 , wherein a reductive decomposition potential of the silane coupling agent as determined with reference to Li is 2.1 V or higher.
5 . The secondary battery according to claim 1 , wherein the fluoroalkylsilane additionally includes at least one of C 5 F 11 CH 2 CH 2 —Si(OCH 3 ) 3 , and C 6 F 13 CH 2 CH 2 —Si(OCH 3 ) 3 .
6 . The secondary battery according to claim 1 , wherein a content of the silane coupling agent is in a range from 0.01% by mass to 10% by mass relative to a mass of the negative electrode active material.
7 . The secondary battery according to claim 1 , wherein the lithium salt includes a salt having a lithium ion and an imide anion.
8 . The secondary battery according to claim 1 , wherein the lithium salt includes lithium bis(trifluoromethanesulfonyl)imide.
9 . The secondary battery according to claim 1 , wherein the organic carbonate is reductively decomposed at a potential lower than a reductive decomposition potential of the silane coupling agent.
10 . The secondary battery according to claim 9 , wherein a reductive decomposition potential of the organic carbonate as determined with reference to Li is 2.2 V or lower.
11 . The secondary battery according to claim 1 , wherein the organic carbonate contains fluorine as a constituent element.
12 . The secondary battery according to claim 1 , wherein the water is present in a molar ratio in a range from 1.8:0.22 to 2.0:0.03 relative to the organic carbonate.