Negative-electrode active material for non-aqueous electrolyte secondary battery, negative electrode for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery
A non-aqueous electrolyte secondary battery that contains a silicon material as a negative-electrode active material has improved cycle life. A negative-electrode active material particle ( 10 ) according to an embodiment includes a lithium silicate phase ( 11 ) represented by Li 2z SiO (2+z) {0<z<2}, silicon particles ( 12 ) dispersed in the lithium silicate phase ( 11 ), and a metallic compound ( 15 ) (other than lithium compounds and silicon oxides) dispersed in the lithium silicate phase ( 11 ). The metallic compound ( 15 ) is preferably selected from zirconium oxide, aluminum oxide, zirconium carbide, tungsten carbide, and silicon carbide.
1. A negative-electrode active material for a non-aqueous electrolyte secondary battery, comprising:
a lithium silicate phase comprising at least one selected from Li 2 SiO 3 and Li 2 Si 2 O 5 ;
silicon particles dispersed in the lithium silicate phase; and
a metallic compound dispersed in the lithium silicate phase (other than lithium compounds and silicon oxides), wherein a peak intensity of Si(111) is higher than a peak intensity of lithium silicate (111) in an XRD pattern obtained by XRD measurement, wherein the negative electrode active material contains no Li 4 SiO 4 .
2. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the metallic compound comprises at least one selected from zirconium oxide, aluminum oxide, zirconium carbide, tungsten carbide, and silicon carbide.
3. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 2 , wherein the metallic compound is composed mainly of zirconium oxide.
4. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein a ratio of the metallic compound to the lithium silicate phase and the silicon particles ranges from 0.01% to 10% by mass.
5. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the metallic compound has an average particle size of 200 nm or less.
6. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the silicon particles have an average particle size of 200 nm or less before initial charging.
7. The negative-electrode active material for a non-aqueous electrolyte secondry battery according to claim 1 , wherein the lithium silicate phase, the silicon particles, and the metallic compound constitute a base particle, and the base particle is covered with an electrically conductive layer.
8. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the lithium silicate phase is composed mainly of Li 2 SiO 3 .
9. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the lithium silicate phase is composed mainly of Li 2 Si 2 O 5 .
10. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein no SiO 2 peak is observed at 2θ=25 degrees in an XRD pattern obtained by XRD measurement.
11. A negative electrode for a non-aqueous electrolyte secondary battery, comprising:
a negative-electrode current collector; and
a negative-electrode mixture layer on the negative-electrode current collector, the negative-electrode mixture layer containing the negative-electrode active material according to claim 1 and a binder.
12. A non-aqueous electrolyte secondary battery comprising: negative electrode according to claim 11 ;
a positive electrode; and
a non-aqueous electrolyte.
13. A negative-electrode active material for a non-aqueous electrolyte secondary battery, comprising:
a lithium silicate phase represented by Li 2z SiO (2+z) {0<z <2};
silicon particles dispersed in the lithium silicate phase; and
a metallic compound dispersed in the lithium silicate phase (other than lithium compounds and silicon oxides),
wherein no peak emitted by SiO 2 is observed in the XRD pattern obtained by XRD measurement.
14. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 13 , wherein the metallic compound comprises at least one selected from zirconium oxide, aluminum oxide, zirconium carbide, tungsten carbide, and silicon carbide.
15. A negative-electrode active material for a non-aqueous electrolyte secondary battery, comprising:
a lithium silicate phase represented by Li 2z SiO (2+z) {0<z <2};
silicon particles dispersed in the lithium silicate phase; and
a metallic compound dispersed in the lithium silicate phase (other than lithium compounds and silicon oxides),
wherein the metallic compound comprises at least one selected from aluminum oxide, zirconium carbide, tungsten carbide and silicon carbide.
16. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 15 ,
wherein the metallic compound comprises aluminum oxide.
17. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 15 ,
wherein the metallic compound comprises zirconium carbide.
18. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 15 ,
wherein the metallic compound comprises tungsten carbide.
19. The negative-electrode active material for a non-aqueous electrolyte secondary battery according to claim 15 ,
wherein the metallic compound comprises silicon carbide.