Solid-State Battery Electrode Coating for Stable Sulfide Interfaces
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Solution Overview
Problem
Sulfide-based all-solid-state batteries experience increased resistance over time due to degradation of the sulfide-based solid electrolyte when in direct contact with positive electrode active material particles, despite the use of phosphorus-based coating films to inhibit degradation.
Innovation Solution
The electrode comprises a sulfide-based solid electrolyte with a PS4 crystalline phase ratio of 60% or more and a composite particle with a phosphorus-based coating film containing a glass network forming element and a transition element, where the lithium composition ratio in the coating film is limited to ensure optimal hardness matching and bonding strength at the interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phosphorus-based coating film is used to cover the active material particle surface, then degradation of the sulfide-based solid electrolyte is inhibited, but resistance increases over time due to poor bonding strength at the interface
Solution Approach 1:
The invention changes the chemical composition parameters of the coating film by incorporating specific elements (B, Si, Ge, Sn, Ti, Zr, or Hf) along with P and Li, optimizing the ratio CLi/(CP+CE1+CE2)≤2.5 to achieve optimal bonding strength and prevent resistance increase over time
Solution Approach 2:
The invention creates a composite coating film material combining multiple elements (Li, P, and at least one of B, Si, Ge, Sn, Ti, Zr, or Hf) to achieve both protective function and good bonding strength, resolving the contradiction between protection and interface adhesion
2Manufacturing precision
If LiNbO3 is used as the coating film material, then resistance is lower compared to Li3PO4, but high-voltage endurance is inferior to phosphorus compounds
Solution Approach 1:
The invention develops a composite phosphorus-based coating film containing Li, P, and specific elements (B, Si, Ge, Sn, Ti, Zr, or Hf) that combines the low resistance characteristics with enhanced high-voltage endurance, surpassing the performance of conventional single-material coatings like LiNbO3 and Li3PO4
Solution Approach 2:
The invention optimizes the chemical composition parameters of the coating film, specifically controlling the ratio CLi/(CP+CE1+CE2)≤2.5 and incorporating specific elements to achieve both low resistance and high voltage stability, resolving the trade-off between resistance and endurance
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
This configuration inhibits the over-time increase in resistance by enhancing the bonding strength between the coating film and the solid electrolyte, leading to improved high-voltage endurance and power output in all-solid-state batteries.
Implementation Method 1
a sulfide-based solid electrolyte... The sulfide-based solid electrolyte includes S and P, has a PS4 crystalline phase
Implementation Method 2
forming a coating film on a surface of the positive electrode active material particle... The coating film inhibits direct contact between the positive electrode active material particle and the sulfide-based solid electrolyte
Data Source
AI summary
An electrode comprises a sulfide-based solid electrolyte and a composite particle. The sulfide-based solid electrolyte includes S and P, has a PS4 crystalline phase, and has a molar ratio of the PS4 crystalline phase to a total amount of phases consisting of P and S of 60% or more. The composite particle comprises a positive electrode active material particle and a coating film covering at least part of a surface of the positive electrode active material particle. The coating film includes a phosphorus compound. The phosphorus compound includes at least one of a first element (a glass network forming element) and a second element (a transition element) as well as phosphorus. In the coating film, a relationship of “expression (1): CLi/(CP+CE1+CE2)≤2.5” is satisfied. CLi, CP, CE1, and CE2 represent element concentrations of respective elements measured by XPS.