Sulfide Solid Electrolyte Composition for Conductivity and Contact
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Solution Overview
Problem
Solid electrolytes with high volume fractions of crystals exhibit poor contact between electrolytes and between the electrolyte and active materials, leading to variations in quality due to strict heat treatment conditions.
Innovation Solution
A sulfide solid electrolyte containing a sulfide glass phase, primarily composed of PS4 and P2S7 units, with a specific composition including Li, P, S, and Ha, achieved by melting and quenching raw materials to ensure high lithium ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte with high crystal volume fraction is used, then lithium ion conductivity is improved, but contact between electrolytes and between electrolyte and active material deteriorates
Solution Approach 1:
The invention uses a composite material system consisting of Li-P-S-based sulfide glass phase and crystal phase. The glass phase acts as a matrix that ensures good contact between electrolytes and between electrolyte and active material, while the crystal phase provides high lithium ion conductivity. This composite structure resolves the contradiction by combining the advantages of both phases.
Solution Approach 2:
The invention changes the compositional parameters of the solid electrolyte by controlling the ratio of glass phase to crystal phase. By adjusting this ratio and the specific composition within the Li-P-S system, the invention optimizes both contact quality and lithium ion conductivity simultaneously.
2Reliability
If heat treatment conditions for crystallization are made strict to improve crystal quality, then lithium ion conductivity is improved, but manufacturing precision deteriorates due to large quality variation
Solution Approach 1:
The invention changes the approach by controlling compositional parameters rather than relying on strict heat treatment conditions. By defining specific composition ranges for Li, P, S and controlling the glass-to-crystal phase ratio, the invention achieves consistent quality without requiring extremely precise heat treatment control.
Solution Approach 2:
The invention allows different regions of the solid electrolyte to have different phases (glass and crystal) with different properties. The glass phase regions provide good contact and compositional homogeneity, while the crystal phase regions provide high conductivity, and this local differentiation resolves the manufacturing precision issue.
3Ease of manufacture
If a Li-P-S-based sulfide glass is used, then contact between electrolytes and between electrolyte and active material is improved, but lithium ion conductivity deteriorates
Solution Approach 1:
The invention creates a composite material where Li-P-S-based sulfide glass phase is combined with crystal phase. The glass phase ensures excellent contact properties, while the crystal phase contributes high lithium ion conductivity. This composite approach resolves the contradiction by leveraging the strengths of both phases.
Solution Approach 2:
The invention merges the Li-P-S-based sulfide glass phase with the crystal phase into a single solid electrolyte material. This merging allows the material to simultaneously exhibit good contact properties from the glass phase and high conductivity from the crystal phase.
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 sulfide solid electrolyte achieves high lithium ion conductivity, even with a sulfide glass phase, enhancing the performance and stability of lithium-ion secondary batteries.
Implementation Method 1
Sulfide ions constituting the sulfide solid electrolytes have polarizability and lithium ion conductivity higher than those of oxide ions constituting the oxide solid electrolytes
Implementation Method 2
by melting a raw material to produce a solid electrolyte containing a glass phase
Implementation Method 3
a production method in which a raw material is melted and quenched
Data Source
AI summary
A sulfide solid electrolyte includes a sulfide glass phase. The sulfide solid electrolyte includes a PS4 unit and a P2S7 unit, a ratio of a peak intensity I(PS4) of the PS4 unit and a peak intensity I(P2S7) of the P2S7 unit in a Raman spectrum satisfies a relationship of 0.05<{I(P(P2S7)/I(PS4)}<1.00, the sulfide solid electrolyte includes Li, P, S, and Ha as constituent elements, the Ha is a halogen element, and contents of the constituent elements in terms of at % are as follows: Li: 30% to 50%, P: 5% to 15%, and S: 30% to 60%.