Solid-State Sulfur Composite Cathode With Cast-Annealing Interface Relief
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Solution Overview
Problem
Current sodium-sulfur batteries face challenges with high interfacial resistance and stress due to the volume change of S/Na2S during charge/discharge cycles, limiting their practical application in grid-scale energy storage, and existing solid-state batteries suffer from poor cycling stability and safety issues.
Innovation Solution
A composite cathode comprising ordered mesoporous carbon, Na2S or Li2S, and Na3PS4 or Li3PS4, fabricated using a melting-casting process followed by stress-release annealing-precipitation, which reduces interfacial resistance and eliminates stress, enhancing electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cold-pressing process is used to fabricate solid electrolyte ASSBs, then high residential stress is achieved, but interface resistance increases and cycling stability deteriorates due to volume change stress
Solution Approach 1:
The patent changes the fabrication parameters from cold-pressing to a low-temperature sintering process (900-1100°C for 1-12 hours), fundamentally altering the physical and chemical properties of the solid electrolyte to reduce interface resistance while maintaining structural integrity during cycling
Solution Approach 2:
The patent creates a composite solid electrolyte system combining sulfide-based solid electrolyte with active materials (sulfur, Na2S, Li2S) and conductive agents, forming an integrated structure that accommodates volume changes and maintains stable interfaces during charge-discharge cycles
2Stability of the object's composition
If sulfur/Na2S volume change during charge/discharge is accommodated, then electrochemical reversibility is maintained, but interface contact deteriorates and resistance increases
Solution Approach 1:
The patent employs a flexible binder matrix that can accommodate the volume expansion and contraction of sulfur/Na2S during cycling, maintaining continuous interface contact between active materials, solid electrolyte, and conductive agents without generating excessive stress
Solution Approach 2:
The patent pre-forms the solid electrolyte and conductive agent matrix before introducing the active materials, creating a stable structural framework that can accommodate subsequent volume changes while maintaining interface integrity
3Reliability
If high temperature operation (>300°C) is used for Na-S batteries, then interface resistance decreases and ion conductivity increases, but safety issues arise and material stability deteriorates
Solution Approach 1:
The patent fundamentally changes the operating temperature parameter from high temperature (>300°C) to room temperature or near-room temperature, enabling the use of sulfide solid electrolytes that provide both high ion conductivity and intrinsic safety without requiring thermal management systems
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 composite cathode achieves stable and reversible capacity of 810 mAh/g at 50 cycles at 60°C, significantly improving the cycling stability and energy density compared to traditional methods, while maintaining safety and reducing operational costs.
Implementation Method 1
The cast-annealing process is a mature method for fabricating structural materials with high mechanical and physical properties. This method possesses several merits: (1) the tension/stress will be eliminated during the precipitation process of heat treatment
Implementation Method 2
a method of preparing a composite cathode comprising: (a) admixing X2S, P2S5, and an ordered mesoporous carbon; (b) raising the temperature of the admixture to between about 600° C. and about 1000° C.; (c) lowering the temperature of the admixture in (b)
Data Source
AI summary
The present invention is directed to solid-state composite cathodes that comprise Na2S or Li2S, Na3PS4, or Li3PS4, and mesoporous carbon. The present invention is also directed to methods of making the solid-state composite cathodes and methods of using the solid-state composite cathodes in batteries and other electrochemical technologies.