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EP-4742278-A1 - METHOD FOR PRODUCING SULFIDE SOLID ELECTROLYTE AND METHOD FOR REUSING SAME

EP4742278A1EP 4742278 A1EP4742278 A1EP 4742278A1EP-4742278-A1

Abstract

The purpose of the present invention is to provide a method for, by using a sulfide solid electrolyte, producing a new sulfide solid electrolyte. The present invention pertains to a method for producing a sulfide solid electrolyte, the method comprising: heating and melting a wet-ground first sulfide solid electrolyte to obtain a melt; removing carbon from the melt; and cooling the carbon-removed melt to obtain a second sulfide solid electrolyte.

Inventors

  • SEKI HIDENOBU

Assignees

  • AGC INC.

Dates

Publication Date
20260513
Application Date
20240701

Claims (8)

  1. A method for producing a sulfide solid electrolyte, comprising: heating and melting a wet-pulverized first sulfide solid electrolyte to obtain a melt, and removing carbon from the melt; and cooling the carbon-removed melt to obtain a second sulfide solid electrolyte.
  2. The method for producing a sulfide solid electrolyte according to claim 1, wherein carbon is removed from the melt by introducing a sulfur source into the melt.
  3. The method for producing a sulfide solid electrolyte according to claim 1, wherein carbon is removed from the melt by introducing a sulfur source into the wet-pulverized first sulfide solid electrolyte and heating and melting the first sulfide solid electrolyte.
  4. The method for producing a sulfide solid electrolyte according to claim 2 or 3, wherein a sulfur amount B to be introduced with respect to a carbon amount A in the wet-pulverized first sulfide solid electrolyte satisfies A/B ≤ 0.2 in weight ratio.
  5. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the wet-pulverized first sulfide solid electrolyte is heated and melted at 600°C or higher to obtain the melt.
  6. The method for producing a sulfide solid electrolyte according to claim 1 or 2, wherein the wet-pulverized first sulfide solid electrolyte is heated and melted together with a sulfide solid electrolyte raw material to obtain the melt.
  7. The method for producing a sulfide solid electrolyte according to claim 6, wherein a mixture obtained by mixing the wet-pulverized first sulfide solid electrolyte and the sulfide solid electrolyte raw material is heated and melted to obtain the melt.
  8. A method for reusing a sulfide solid electrolyte, comprising: heating and melting a wet-pulverized sulfide solid electrolyte to obtain a melt, and removing carbon from the melt; and cooling the carbon-removed melt to obtain a sulfide solid electrolyte recycled product.

Description

TECHNICAL FIELD The present invention relates to a method for producing a sulfide solid electrolyte and a method for reusing a sulfide solid electrolyte. BACKGROUND ART Lithium ion secondary batteries are widely used in portable electronic devices such as a mobile phone and a laptop computer. In the related art, a liquid electrolyte has been used in a lithium ion secondary battery. On the other hand, in recent years, an all-solid-state lithium ion secondary 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, highspeed charging and discharging, and a reduction in size of a case can be expected. Examples of the solid electrolyte used in the all-solid-state lithium ion secondary battery include a sulfide solid electrolyte. Performance of an inorganic solid electrolyte such as a sulfide solid electrolyte may greatly vary due to a slight composition deviation. When the composition deviation deviates beyond an allowable error, the solid electrolyte has to be discarded as being out of specification. Therefore, there is a demand for a method capable of preventing the composition deviation and producing a sulfide solid electrolyte without waste of raw material resources. For example, Patent Literature 1 discloses a method for eliminating a composition deviation by bringing a sulfide solid electrolyte having the composition deviation into contact with an alkali metal sulfide or the like by using a solid phase method. In addition to the case where the composition deviation occurs, there is a demand for separately producing a new sulfide solid electrolyte by reusing the once obtained sulfide solid electrolyte. CITATION LIST PATENT LITERATURE Patent Literature 1: JP2015-5372A SUMMARY OF INVENTION TECHNICAL PROBLEM However, in the case of separately producing a new sulfide solid electrolyte by reusing the sulfide solid electrolyte by using the solid phase method, there are problems that a solid phase reaction takes time and it is difficult to obtain a sulfide solid electrolyte having a uniform composition. In addition, in the case of the solid phase method, since the step is easily influenced by a particle diameter of the original electrolyte to be reused, it is difficult to control the particle diameter to be newly obtained. Therefore, although recovery of a lithium ion conductivity can be realized, it is difficult to reuse the electrolyte in the case where the particle diameter is out of specification. Further, in the case of a dry reaction, a residual solvent adheres to the electrolyte, which causes a problem of reaction inhibition. The present invention has been made in view of the above circumstances, and object thereof is to provide a method for producing a new sulfide solid electrolyte by using a sulfide solid electrolyte. SOLUTION TO PROBLEM The present inventors have focused on a method for reusing a sulfide solid electrolyte by using a melting method. According to the melting method, the reaction time can be shortened as compared with the solid phase method, and a sulfide solid electrolyte having a uniform composition is easily obtained. In addition, since the sulfide solid electrolyte is once formed into a melt, the problem of particle diameter control as in the solid phase method does not occur. On the other hand, in the case of melting the sulfide solid electrolyte obtained after wet pulverization for reuse, carbon derived from the solvent during the wet pulverization remains in the electrolyte, and thus the carbon changes to inorganic carbon (elemental carbon) during the melting. It has been found that when inorganic carbon remains in the electrolyte, electron conductivity is exhibited, and thus a separator cannot function as a battery. Based on the above findings, the present inventors have intensively studied and found that a sulfide solid electrolyte having an excellent lithium ion conductivity can be obtained through a step of removing carbon from a melt obtained by heating and melting a wet-pulverized sulfide solid electrolyte, and have completed the present invention. That is, the present invention relates to a method for producing a sulfide solid electrolyte, including: heating and melting a wet-pulverized first sulfide solid electrolyte to obtain a melt, and removing carbon from the melt; and cooling the carbon-removed melt to obtain a second sulfide solid electrolyte. ADVANTAGEOUS EFFECTS OF INVENTION According to the present invention, a sulfide solid electrolyte having an excellent lithium ion conductivity can be produced by a melting method using a sulfide solid electrolyte. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a flowchart of a method for producing a sulfide solid electrolyte according to an embodiment of the present invention.FIG. 2 is a diagram showing a result of AC impedance measurement in Examples. DESCRIPTION OF EMBODIMENTS Hereinafter, the present invention is describe