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JP-2026076075-A - Novel crystalline solid electrolyte for lithium secondary batteries and method for manufacturing the same

JP2026076075AJP 2026076075 AJP2026076075 AJP 2026076075AJP-2026076075-A

Abstract

[Problem] The present invention relates to a solid electrolyte for lithium secondary batteries with a novel crystal structure and a method for producing the same. [Solution] A solid electrolyte for lithium secondary batteries containing lithium (Li), germanium (Ge), and sulfur (S), having a monoclinic crystal structure, wherein the solid electrolyte has excellent lithium ion conductivity and is chemically stable. [Selection Diagram] Figure 1

Inventors

  • ソン、インウ
  • 高瀬 浩成
  • チェ、ナムイル
  • ジャン、ヨンジュン
  • 佐々木 勇樹
  • 菅野 了次
  • 堀 智

Assignees

  • 現代自動車株式会社
  • 起亞株式会社
  • 国立大学法人東京科学大学

Dates

Publication Date
20260511
Application Date
20241023

Claims (20)

  1. A solid electrolyte for lithium secondary batteries, containing lithium (Li), germanium (Ge), and sulfur (S), and having a monoclinic crystal structure.
  2. The solid electrolyte for a lithium secondary battery according to claim 1, wherein the solid electrolyte comprises a three-component compound of lithium (Li), germanium (Ge), and sulfur (S).
  3. The solid electrolyte for a lithium secondary battery according to claim 1, wherein the unit cell of the monoclinic crystal structure has a three-dimensional structure including a Ge₂S₃ polyhedron and a GeS₄tetrahedron .
  4. The solid electrolyte for a lithium secondary battery according to claim 3, wherein the unit cell contains Ge₂S₃7 polyhedra and GeS₄tetrahedra in a molar ratio of 2:1.
  5. The solid electrolyte for a lithium secondary battery according to claim 1, wherein the solid electrolyte has a monoclinic crystal structure with a space group of P2 1 .
  6. The solid electrolyte for a lithium secondary battery according to claim 1, wherein the solid electrolyte comprises a compound represented by the following chemical formula 1. Chemical formula 1 satisfies 0.71 ≤ x ≤ 0.78, 0.22 ≤ y ≤ 0.29, and x + y = 1.
  7. The solid electrolyte for a lithium secondary battery according to claim 1, wherein the solid electrolyte comprises Li 16 Ge 5 S 18 .
  8. The solid electrolyte for a lithium secondary battery according to claim 7, further comprising at least one selected from the group consisting of Li₂GeS₃ , Li₄GeS₄ , and combinations thereof.
  9. The solid electrolyte exhibits diffraction angles 2θ = 13.1°±0.5°, 14.0°±0.5°, 14.9°±0.5°, 15.4°±0.5°, 16.3°±0.5°, 16.5°±0.5°, 16.7°±0.5°, 17.1°±0.5°, 17.4°±0.5°, and 17.8°±0.5° in its X-ray diffraction (XRD) spectrum using Cu-Kα rays. The solid electrolyte for a lithium secondary battery according to claim 1, exhibiting peaks at 18.5°±0.5°, 19.0°±0.5°, 19.4°±0.5°, 20.0°±0.5°, 21.0°±0.5°, 21.9°±0.5°, 26.3°±0.5°, 26.6°±0.5°, 28.7°±0.5°, and 30.0°±0.5°.
  10. The solid electrolyte for a lithium secondary battery according to claim 1, wherein the solid electrolyte has a lithium ion conductivity of 8.7 × 10⁻⁶ S· cm⁻¹ or higher at 25°C.
  11. A step of grinding a starting material containing lithium sulfide and germanium sulfide to obtain an amorphous intermediate material, The step includes heat treatment of the intermediate material to obtain a crystalline solid electrolyte, A method for producing a solid electrolyte for a lithium secondary battery, wherein the solid electrolyte contains lithium (Li), germanium (Ge), and sulfur (S), and has a monoclinic crystal structure.
  12. The unit cell of the monoclinic crystal structure includes a three-dimensional structure containing Ge₂S₃ polyhedra and GeS₄tetrahedra . The method for producing a solid electrolyte for a lithium secondary battery according to claim 11, wherein the solid electrolyte has a monoclinic crystal structure with a space group of P2 1 .
  13. The method for producing a solid electrolyte for a lithium secondary battery according to claim 11, wherein the solid electrolyte comprises Li 16 Ge 5 S 18 .
  14. The method for producing a solid electrolyte for a lithium secondary battery according to claim 11, wherein the step of obtaining the solid electrolyte involves heat-treating the intermediate material at 530°C to 620°C.
  15. A step of preparing a mixture containing a crystalline first raw material and a crystalline second raw material, The step of heat-treating the mixture to obtain a crystalline solid electrolyte is included, Each of the first and second raw materials comprises lithium (Li), germanium (Ge), and sulfur (S). A method for producing a solid electrolyte for a lithium secondary battery, wherein the solid electrolyte contains lithium (Li), germanium (Ge), and sulfur (S), and has a monoclinic crystal structure.
  16. The method for producing a solid electrolyte for a lithium secondary battery according to claim 15 , wherein the first raw material contains Li₂GeS₃ .
  17. The method for producing a solid electrolyte for a lithium secondary battery according to claim 15 , wherein the second raw material contains Li₄GeS₄ .
  18. The aforementioned monoclinic unit cell includes a three-dimensional structure comprising Ge₂S₃7 polyhedra and GeS₄tetrahedra . The method for producing a solid electrolyte for a lithium secondary battery according to claim 15, wherein the solid electrolyte has a monoclinic crystal structure with a space group of P2 1 .
  19. The method for producing a solid electrolyte for a lithium secondary battery according to claim 15, wherein the solid electrolyte comprises Li 16 Ge 5 S 18 .
  20. The method for producing a solid electrolyte for a lithium secondary battery according to claim 15, wherein the step of obtaining the solid electrolyte involves heat-treating the mixture at 530°C to 620°C.

Description

Application for application of Article 30, Paragraph 2 of the Patent Law Publication 1 (1) Date of publication on the website: July 30, 2024 (2) Website address: https://pubs.acs.org/doi/10.1021/acs.chemator. 4c00885 (3) Publishers Yuki Sasaki Subin Song Satoshi Hori Naoki Matsui Kuniharu Nomoto Kota Suzuki Masaaki Hirayama Inwoo Song Yongjun Jang Ryoji Kanno Publication 2 (1) Date October 8, 2024 (2) Meeting name 2024 American Electrochemical Society Meeting "PRIME" "2024" Venue Hawaii Convention Center & Hilton Hawaiian Village Honolulu, Hawaii, USA (3) Presenters Yuki Sasaki Satoshi Hori Kota Suzuki Masaaki Hirayama Yongjun Jang Ryoji Kanno This invention relates to a novel solid electrolyte for lithium secondary batteries with a unique crystalline structure and a method for producing the same. The solid electrolyte exhibits excellent lithium ion conductivity and is chemically stable. Today, lithium-ion batteries are widely used in a range of applications, from large-scale equipment such as automobiles and power storage systems to small devices such as mobile phones, camcorders, and notebook PCs. As the application fields of secondary batteries expand, the demand for improved safety and higher performance in batteries is increasing. Lithium-ion batteries, a type of rechargeable battery, have the advantage of higher energy density and larger capacity per unit area compared to nickel-manganese and nickel-cadmium batteries. However, the majority of electrolytes used in conventional lithium-ion batteries were liquid electrolytes, such as organic solvent-based electrolytes. Therefore, safety concerns, including the risk of electrolyte leakage and resulting fires, have been constantly raised. Therefore, in recent years, there has been growing interest in all-solid-state batteries, which use solid electrolytes instead of liquid electrolytes, in order to improve the safety of lithium-ion secondary batteries. Solid electrolytes are non-flammable or flame-retardant, making them safer than liquid electrolytes. Solid electrolytes are classified into oxide-based and sulfide-based types. Sulfide-based solid electrolytes have higher lithium-ion conductivity and are more stable over a wider voltage range compared to oxide-based solid electrolytes. However, sulfide-based solid electrolytes have lower chemical stability than oxide-based solid electrolytes, resulting in less stable battery operation. Therefore, while various studies are being conducted to improve the chemical stability of sulfide-based solid electrolytes, there is a problem in that the more one attempts to increase the chemical stability of sulfide-based solid electrolytes, the greater the essential physical properties of the solid electrolyte, such as lithium-ion conductivity, tend to decrease. This figure shows a lithium secondary battery according to the present invention.This figure shows the composition of the solid electrolyte according to the present invention, expressed in terms of the molar ratio of a three-component system of lithium (Li), germanium (Ge), and sulfur (S).Figure 3a shows the crystal structure of the solid electrolyte according to the present invention, where Figure 3a is the crystal structure viewed from the [010] direction, and Figure 3b is the crystal structure viewed from the [111] direction.This figure shows the results of X-ray diffraction (XRD) analysis for Examples 1 to 7 and Comparative Examples 1 and 2.This figure shows the X-ray diffraction analysis results for Example 2, Example 8, Example 9, Comparative Example 3, and Comparative Example 4.This figure shows the X-ray diffraction analysis results for Example 3, Examples 10 to 12, Comparative Example 5, and Comparative Example 6.This figure shows the X-ray diffraction analysis results for Example 5, Examples 13 to 15, Comparative Example 7, and Comparative Example 8.This is the Nyquist diagram of the solid electrolyte according to Example 5.This is a diagram showing a magnified portion of Figure 8.Figure 8 shows the lithium ion conductivity of the solid electrolyte according to Example 6, calculated using the Nyquist diagram.This figure shows the CV (Cyclic Voltamogram) measurement results for an all-solid-state battery containing a solid electrolyte layer composed of Li -16- Ge- 5- S -18 .These are Nyquist diagrams of the solid electrolyte according to the present invention, before and after exposure.These are Nyquist diagrams of a solid electrolyte represented as Li₂₆PS₅Cl before and after exposure.This figure shows the concentration of hydrogen sulfide measured with respect to exposure time for the solid electrolyte according to the present invention and the solid electrolyte represented as Li6PS5Cl . The above-described objectives, other objectives, features, and advantages of the present invention will be readily apparent from the following preferred embodiments based on the accompanying drawings. However, the present invention is not limited to the embodiments descr