Sulfide-based solid electrolyte particles
A sulfide-based solid electrolyte particle having a crystal phase of a cubic argyrodite-type crystal structure composed of Li, P, S and a halogen (Ha. The proposed sulfide-based solid electrolyte particle has a feature such that the ratio (Z Ha2 /Z Ha1 ) of an element ratio Z Ha2 of the halogen (Ha) at the position of 5 nm in depth from the particle surface to an element ratio Z Ha1 of the halogen (Ha) at the position of 100 nm in depth from the particle surface is 0.5 or lower, as measured by XPS; and the ratio (Z O2 /Z A2 ) of an element ratio Z O2 of oxygen to the total Z A2 of element ratios of phosphorus (P), sulfur (S), oxygen (O) and the halogen (Ha) at the position of 5 nm in depth from the particle surface is 0.5 or higher, as measured by XPS.
1. A sulfide-based solid electrolyte particle, comprising a solid electrolyte particle having a crystal phase of a cubic argyrodite-type crystal structure and comprising lithium (Li), phosphorus (P), sulfur (S) and a halogen (Ha),
wherein the solid electrolyte particle has been subjected to a surface modification treatment in which the solid electrolyte particle is directly exposed to an atmosphere having a dew point of −35° C. to 10° C., the atmosphere reacts with the solid electrolyte particle, and no subsequent drying of the solid electrolyte particle is performed;
a ratio (Z Ha2 /Z Ha1 ) of an element ratio Z Ha2 of the halogen (Ha) at a position, in terms of an SiO 2 sputter rate, of 5 nm in depth from the particle surface to an element ratio Z Ha1 of the halogen (Ha) at a position, in terms of the SiO 2 sputter rate, of 100 nm in depth from the particle surface is higher than 0 and 0.5 or lower, as measured by X-ray photoelectron spectroscopy (XPS); and
a ratio (Z O2 /Z A2 ) of an element ratio Z O2 of oxygen to a total Z A2 of element ratios of phosphorus (P), sulfur (S), oxygen (O) and the halogen (Ha) at the position, in terms of the SiO 2 sputter rate, of 5 nm in depth from the particle surface is 0.5 or higher and 1.0 or lower, as measured by XPS.
2. The sulfide-based solid electrolyte particle according to claim 1 , wherein a ratio (Z Ha2 /Z A2 ) of an element ratio Z Ha2 of the halogen (Ha) to a total Z A2 of element ratios of phosphorus (P), sulfur (S), oxygen (O) and the halogen (Ha) at the position, in terms of SiO 2 sputter rate, of 5 nm in depth from the particle surface is 0.1 or lower.
3. The sulfide-based solid electrolyte particle according to claim 1 , wherein a ratio (Z Ha1 /Z A1 ) of an element ratio Z Ha1 of the halogen (Ha) to a total Z A1 of element ratios of phosphorus (P), sulfur (S), oxygen (O) and the halogen (Ha) at the position, in terms of SiO 2 sputter rate, of 100 nm in depth from the particle surface is 0.03 to 0.3.
4. An electrode material for a lithium secondary battery, comprising: a sulfide-based solid electrolyte particle according to claim 1 ; and a positive electrode active material and/or a negative electrode active material.
5. A lithium secondary battery, having a layer comprising a sulfide-based solid electrolyte particle according to claim 1 .
6. The sulfide-based solid electrolyte particle according to claim 2 , wherein a ratio (Z Ha1 /Z A1 ) of an element ratio Z Ha1 of the halogen (Ha) to a total Z A1 of element ratios of phosphorus (P), sulfur (S), oxygen (O) and the halogen (Ha) at the position, in terms of SiO 2 sputter rate, of 100 nm in depth from the particle surface is 0.03 to 0.3.
7. An electrode material for a lithium secondary battery, comprising: a sulfide-based solid electrolyte particle according to claim 2 ; and a positive electrode active material and/or a negative electrode active material.
8. An electrode material for a lithium secondary battery, comprising: a sulfide-based solid electrolyte particle according to claim 3 ; and a positive electrode active material and/or a negative electrode active material.
9. An electrode material for a lithium secondary battery, comprising: a sulfide-based solid electrolyte particle according to claim 6 ; and a positive electrode active material and/or a negative electrode active material.
10. A lithium secondary battery, having a layer comprising a sulfide-based solid electrolyte particle according to claim 2 .
11. A lithium secondary battery, having a layer comprising a sulfide-based solid electrolyte particle according to claim 3 .
12. A lithium secondary battery, having a layer comprising a sulfide-based solid electrolyte particle according to claim 6 .
13. The sulfide-based solid electrolyte particle according to claim 1 , wherein a ratio (Z Ha2 /Z Ha1 ) of an element ratio Z Ha2 of the halogen (Ha) at a position, in terms of an SiO 2 sputter rate, of 5 nm in depth from the particle surface to an element ratio Z Ha1 of the halogen (Ha) at a position, in terms of the SiO 2 sputter rate, of 100 nm in depth from the particle surface is 0.01 or higher.