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EP-4741338-A1 - SULFIDE SOLID ELECTROLYTE POWDER, SOLID ELECTROLYTE LAYER, AND LITHIUM ION SECONDARY BATTERY

EP4741338A1EP 4741338 A1EP4741338 A1EP 4741338A1EP-4741338-A1

Abstract

The present invention relates to sulfide solid electrolyte powder in which the content of Al on a mass basis is less than 50 ppm; the content of Zr on a mass basis is less than 50 ppm; and the particle diameter D50 is less than 1 µm.

Inventors

  • KUNISA, YASUHIRO

Assignees

  • AGC INC.

Dates

Publication Date
20260513
Application Date
20231102

Claims (6)

  1. A sulfide solid electrolyte powder comprising, in content in a mass basis: less than 50 ppm of Al; and less than 50 ppm of Zr, wherein a particle diameter D50 is less than 1 µm.
  2. The sulfide solid electrolyte powder according to claim 1, wherein a BET diameter calculated based on a BET specific surface area is 0.10 µm to 0.30 µm.
  3. The sulfide solid electrolyte powder according to claim 1, wherein a sulfide solid electrolyte constituting the sulfide solid electrolyte powder comprises a crystal phase, and the crystal phase comprises an argyrodite crystal structure.
  4. The sulfide solid electrolyte powder according to claim 1, wherein a sulfide solid electrolyte constituting the sulfide solid electrolyte powder has a composition represented by Li α PS β (5.5 ≤ α ≤ 5.6 and 4.3 ≤ β ≤ 4.4).
  5. A solid electrolyte layer comprising the sulfide solid electrolyte powder according to any one of claims 1 to 4.
  6. A lithium ion secondary battery comprising the sulfide solid electrolyte powder according to any one of claims 1 to 4.

Description

TECHNICAL FIELD The present invention relates to a sulfide solid electrolyte powder, a solid electrolyte layer, and a lithium ion secondary battery. BACKGROUND ART Lithium ion secondary batteries are widely used in portable electronic devices such as a mobile phone and a notebook computer. In the related art, a liquid electrolyte has been used in a lithium ion secondary battery, but a lithium ion all-solid-state battery (hereinafter, also referred to as a solid battery) in which a solid electrolyte is used as an electrolyte of the lithium ion secondary battery has attracted attention from the viewpoint that improvement of safety and high-speed charging and discharging can be expected. The solid electrolytes are roughly classified into a sulfide solid electrolyte and an oxide solid electrolyte. Among them, the sulfide solid electrolyte exhibits high ion conductivity since the sulfide solid electrolyte contains sulfide ions having high polarizability. As the sulfide solid electrolyte, there has been known LGPS crystals such as Li10GeP2S12, argyrodite crystals such as Li6PS5Cl, LPS crystallized glasses such as a Li7P3S11 crystallized glass, and the like. The solid electrolyte is inferior to a liquid electrolyte in terms of permeability into a positive electrode or a negative electrode. Therefore, for the purpose of improving performance of the battery, a solid electrolyte powder having a small particle diameter or having no coarse particles which has a large particle diameter is used to form more interfaces with the active material. As a technique of reducing the particle diameter of the solid electrolyte powder, for example, there is a method of pulverizing the obtained solid electrolyte or a coarsely pulverized product thereof by a wet bead mill using hard beads having a diameter of about 0.1 mm to 1 mm. Examples of the kind of beads include zirconia beads and alumina beads, and since the zirconia beads have a large specific gravity, excessive pulverization is likely to occur, and a decrease in lithium ion conductivity is likely to occur. In contrast, since the alumina beads have a smaller specific gravity than the zirconia beads, they are characterized in that the particle size of the pulverized solid electrolyte powder is easily maintained. Actually, Patent Literature 1 discloses a solid electrolyte obtained by a wet bead mill using alumina beads. CITATION LIST PATENT LITERATURE Patent Literature 1: WO2020/105604 SUMMARY OF INVENTION TECHNICAL PROBLEM With respect to this, a sulfide solid electrolyte powder obtained by pulverizing a sulfide solid electrolyte is required to have a further improved lithium ion conductivity. Therefore, an object of the present invention is to provide a sulfide solid electrolyte powder exhibiting a good lithium ion conductivity while maintaining a particle size of the powder, and a solid electrolyte layer and a lithium ion secondary battery containing the sulfide solid electrolyte powder. SOLUTION TO PROBLEM As a result of intensive studies, the present inventors have found that when the sulfide solid electrolyte powder is pulverized using a bead mill in order to maintain the particle size thereof, contamination caused by alumina (Al2O3) or zirconia (ZrO2) is present in the obtained sulfide solid electrolyte powder. As a result of further studies, the present inventors have found that the contamination is a cause of a decrease in lithium ion conductivity. That is, it is considered that the contamination inhibits continuity of the sulfide solid electrolyte powder and breaks a lithium ion conduction path, which is a factor of the decrease in lithium ion conductivity. With respect to this, the present inventors have found that the above problems can be solved by setting a content of Al (aluminum) and a content of Zr (zirconium) contained in the sulfide solid electrolyte powder to a certain amount or less, and have completed the present invention. That is, the present invention relates to the following. [1] A sulfide solid electrolyte powder including, in content in a mass basis: less than 50 ppm of Al; andless than 50 ppm of Zr,in which a particle diameter D50 is less than 1 µm.[2] The sulfide solid electrolyte powder according to [1], in which a BET diameter calculated based on a BET specific surface area is 0.10 µm to 0.30 µm.[3] The sulfide solid electrolyte powder according to [1] or [2], in which a sulfide solid electrolyte constituting the sulfide solid electrolyte powder includes a crystal phase, andthe crystal phase includes an argyrodite crystal structure.[4] The sulfide solid electrolyte powder according to [1] or [2], in which a sulfide solid electrolyte constituting the sulfide solid electrolyte powder has a composition represented by LiαPSβ (5.5 ≤ α ≤ 5.6 and 4.3 ≤ β ≤ 4.4).[5] A solid electrolyte layer comprising the sulfide solid electrolyte powder according to any one of [1] to [4].[6] A lithium ion secondary battery comprising the sulfide solid electrolyte powder