All-Solid-State Electrode Coating for High-Voltage, Low-Resistance Interfaces
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Solution Overview
Problem
In sulfide-based all-solid-state batteries, the degradation of sulfide-based solid electrolytes due to direct contact with positive electrode active materials leads to increased battery resistance, and the use of phosphorus-based coating films with high crystallinity can result in poor contact and high resistance due to mismatched hardness.
Innovation Solution
An electrode comprising a sulfide-based solid electrolyte with a high PS4 crystalline phase, an electrolyte microparticle, and a composite particle with a phosphorus-based coating film, where the coating film includes a glass network forming element and a transition element, optimizing the Li composition ratio to reduce resistance by increasing the contact area and packing density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phosphorus-based coating film is used to prevent sulfide-based solid electrolyte degradation, then high-voltage endurance is improved, but resistance increases due to poor contact at the interface caused by hardness mismatch
Solution Approach 1:
The patent changes the chemical composition parameters of the coating film by incorporating both phosphorus compounds and lithium compounds, creating a composite coating that modifies the interface properties between the active material and solid electrolyte, thereby reducing resistance while maintaining protective functions
Solution Approach 2:
The patent uses a composite coating film made of phosphorus compound and lithium compound, combining the high-voltage endurance benefits of phosphorus-based materials with the contact-improving properties of lithium compounds, thus resolving the hardness mismatch issue while maintaining protection
2Reliability
If a phosphorus-based coating film is used to protect the sulfide-based solid electrolyte, then degradation is reduced, but contact area at the interface decreases leading to high resistance
Solution Approach 1:
The patent modifies the coating film composition by adding lithium compounds to phosphorus compounds, changing the physical and chemical parameters of the coating to improve wettability and contact area with the solid electrolyte while maintaining protective functions
3Object-affected harmful factors
If LiNbO3 is used as the coating film material, then resistance is reduced compared to Li3PO4, but high-voltage endurance is inferior to phosphorus compounds
Solution Approach 1:
The patent creates a composite coating film combining phosphorus compounds (for high-voltage endurance) with lithium compounds (for low resistance), achieving a synergistic effect that surpasses the performance of individual materials like LiNbO3 or Li3PO4
Solution Approach 2:
The patent applies different material compositions to different functional requirements: phosphorus compounds provide high-voltage stability while lithium compounds provide low resistance, with each component optimized for its specific function within the composite coating structure
Data Source
AI summary
An electrode comprises a sulfide-based solid electrolyte, an electrolyte microparticle, 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. A ratio of a D50 of the electrolyte microparticle to a D50 of the sulfide-based solid electrolyte is 0.5 or less. The composite particle comprises a positive electrode active material particle and a coating film. 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.