Solid Electrolyte Crystal Phase Control for Stable Li-Ion Conduction
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Solution Overview
Problem
Existing solid electrolyte materials for batteries struggle to achieve high lithium ion conductivity while maintaining stability across a wide temperature range, and they often generate hydrogen sulfide, compromising safety.
Innovation Solution
A solid electrolyte material represented by the compositional formula Li6-3zYzX6, where 0<z<2 and X represents Cl or Br, is developed. This material includes specific crystal phases and structural features that enhance lithium ion conductivity and stability, avoiding phase transitions within the battery's operation temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional solid electrolyte materials are used, then lithium ion conductivity can be improved, but stability across temperature range deteriorates and hydrogen sulfide generation occurs
Solution Approach 1:
The patent changes the chemical composition parameters by using halide ions (Cl⁻, Br⁻, I⁻) instead of sulfide ions (S²⁻), and by controlling the ratio of lithium to other metal ions within specific ranges (0.75≤x<1.5, 0<y≤2.0, x+y=6). This compositional parameter change eliminates hydrogen sulfide generation while maintaining high lithium ion conductivity through optimized crystal structure
Solution Approach 2:
The patent creates composite solid electrolyte materials with general formula LiₓM₁M₂M₃X₆ where M1-M3 are different metal ions (including Y, Er, Tm, Lu, Ho, Dy, Gd, Sm, Nd, Pr, La) and X is halide. This multi-element composite approach achieves both high conductivity and thermal stability while avoiding the harmful effects of sulfide-based materials
2Reliability
If solid electrolyte material composition is optimized for high conductivity, then lithium ion conductivity improves, but phase transition stability worsens
Solution Approach 1:
The patent optimizes compositional parameters (x, y, z ratios of metal ions and halides) to achieve a balance where the crystal structure remains stable across temperature ranges. Specific compositional ranges (0.75≤x<1.5, 0<y≤2.0) prevent phase transitions while maintaining high lithium ion conductivity through controlled atomic arrangements in the crystal lattice
Solution Approach 2:
The patent introduces local structural variations through different metal ion combinations (Y, Er, Tm, Lu, Ho, Dy, Gd, Sm, Nd, Pr, La) and halide selections (Cl, Br, I) that create localized regions with different properties. These local compositional variations stabilize the overall crystal structure against phase transitions while preserving conductive pathways for lithium ions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solid electrolyte material achieves high lithium ion conductivity and maintains stability across a wide temperature range, enabling the development of all-solid-state secondary batteries with excellent charge and discharge characteristics and improved safety by avoiding hydrogen sulfide generation.
Implementation Method 1
a solid electrolyte material having a high lithium ion conductivity
Data Source
AI summary
A solid electrolyte material according to an aspect of the present disclosure is represented by the following Compositional Formula (1):Li6-3zYzX6 where 0<z<2 is satisfied; andX represents Cl, wherein the solid electrolyte material includes at least one second crystal phase; and in the second crystal phase, the arrangement of halogen X is the same as that of Cl in Li3ErCl6 having a crystal structure belonging to space group P-3m1, wherein with ILEC(301) denoting an X-ray diffraction intensity of a plane of the second crystal phase corresponding to a (301) plane of the Li3ErCl6 crystal structure and ILEC(110) denoting an X-ray diffraction intensity of a plane of the second crystal phase corresponding to a (110) plane of the Li3ErCl6 crystal structure, ILEC(110)/ILEC(301)<0.3.