All-solid-state cell amorphous electrolyte interface
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Solution Overview
Problem
All-solid-state lithium secondary cells face challenges in achieving high charge-discharge capacity due to increased interface reaction resistance between the electrode active material and solid electrolyte, leading to reduced capacity and instability of the sulfide electrolyte in the atmosphere.
Innovation Solution
The use of a combination of phosphate compounds as both electrode active and solid electrolyte materials, where the solid electrolyte is vitrified to form an amorphous network, ensuring a higher firing temperature for the electrode active material than the solid electrolyte's shrinkage initiation temperature, thereby preventing reaction and maintaining connectivity, thus lowering the interface reaction resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid electrolyte is used in an all-solid-state cell, then safety is improved by eliminating liquid electrolyte leakage and ignition risks, but interface reaction resistance increases leading to reduced charge-discharge capacity
Solution Approach 1:
The electrode active material is formed as a porous body with a specific pore structure that allows the solid electrolyte to penetrate and form extensive contact interfaces. The porous structure increases the surface area for ion transfer while maintaining structural integrity, thereby reducing interface reaction resistance without compromising safety
Solution Approach 2:
The solid electrolyte is selectively positioned within the pores of the electrode active material, creating localized high-conductivity pathways. This local concentration of electrolyte at critical interfaces optimizes ion transfer efficiency while maintaining the overall solid-state safety benefits
2Productivity
If the electrode active material is formed as a porous body, then the connection interface area with solid electrolyte increases improving charge-discharge ability, but manufacturing complexity increases
Solution Approach 1:
The porous structure of the electrode active material is pre-formed before electrolyte insertion. This preliminary structuring creates ready-made pathways for electrolyte penetration, simplifying the subsequent electrolyte impregnation process while ensuring optimal interface contact area for high charge-discharge ability
Solution Approach 2:
The electrode active material and solid electrolyte are combined into a single integrated porous structure where the electrolyte fills the pores of the active material. This merging creates a unified component that simultaneously provides both the electroactive function and the ion conduction pathway, reducing the number of separate manufacturing steps
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 approach allows for a significant increase in the connection interface area between the electrode active material and solid electrolyte, enabling efficient charge and discharge operations while maintaining the original theoretical capacity of the electrode active material, even in an all-solid-state configuration.
Implementation Method 1
The use of a combination of phosphate compounds as both electrode active and solid electrolyte materials, where the solid electrolyte is vitrified to form an amorphous network
Implementation Method 2
the one or both of the positive and negative electrode portions are formed by mixing and firing the electrode active material and an amorphous solid electrolyte material
Data Source
AI summary
An all-solid-state cell has a fired solid electrolyte body, a first electrode layer integrally formed on one surface of the fired solid electrolyte body by mixing and firing an electrode active material and a solid electrolyte, and a second electrode layer integrally formed on the other surface of the fired solid electrolyte body by mixing and firing an electrode active material and a solid electrolyte. The first and the second electrode layers are formed by mixing and firing the electrode active material and the amorphous solid electrolyte, which satisfy the relation Ty>Tz (wherein Ty is a temperature at which the capacity of the electrode active material is lowered by reaction between the electrode active material and the solid electrolyte material, and Tz is a temperature at which the solid electrolyte material is shrunk by firing).