Solid Electrolyte Grain Boundary Resistance Reduction
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Solution Overview
Problem
Existing methods for producing solid electrolytes, such as those using lithium lanthanum titanate, face challenges in reducing grain boundary resistance due to difficulties in coating particles with SiO2 and high temperature processing, which can lead to lithium evaporation and formation of unwanted phases, resulting in decreased ionic conductivity and unstable physical properties.
Innovation Solution
A solid electrolyte configuration featuring particles coated with an amorphous matrix containing lithium and elements like boron, silicon, or phosphorus, which promotes ion conduction and reduces grain boundary resistance, combined with a production method involving surface modification, dispersion in a lithium compound solution, gelling, and heat treatment to form a high-conductivity oxide matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If solid electrolyte particles are compression-molded without sintering, then the composition is maintained, but the grain boundary resistance remains high and lithium ionic conductivity is decreased
Solution Approach 1:
The invention changes the temperature parameter from high temperature (1000°C or higher) to low temperature (900°C or lower, preferably 800-950°C). This parameter change allows the solid electrolyte particles to be sintered at a lower temperature that prevents composition change due to lithium evaporation or reaction with electrode materials, while still achieving sufficient grain boundary sintering to reduce grain boundary resistance and increase lithium ionic conductivity
Solution Approach 2:
The invention uses a composite material approach by coating the surface of solid electrolyte particles (e.g., lithium lanthanum titanate) with a specific oxide layer (such as SiO2, TiO2, or other metal oxides). This composite structure allows the core particles to maintain their high lithium ionic conductivity while the coating layer facilitates grain boundary sintering at lower temperatures, resolving the contradiction between maintaining composition stability and achieving low grain boundary resistance
2Reliability
If the surface of solid electrolyte particles is coated with SiO2 and sintered at high temperature, then grain boundary resistance is decreased, but lithium evaporates and reacts with electrode materials changing composition
Solution Approach 1:
The invention changes the sintering temperature parameter from high temperature (1000°C or higher) to low temperature (900°C or lower). This parameter change resolves the contradiction by enabling grain boundary sintering to proceed effectively at a temperature that prevents lithium evaporation and unwanted reactions with electrode materials, thus maintaining composition stability while still achieving the desired reduction in grain boundary resistance
3Stability of the object's composition
If firing temperature is decreased to prevent different phase formation, then composition stability is improved, but grain boundary sintering is insufficient and grain boundary resistance cannot be decreased
Solution Approach 1:
The invention applies a composite material strategy by coating solid electrolyte particles with specific oxide materials (such as SiO2, TiO2, Al2O3, or other metal oxides). This coating layer acts as a sintering aid that enables effective grain boundary sintering at lower temperatures (900°C or lower), resolving the contradiction by allowing sufficient grain boundary bonding to reduce resistance while maintaining composition stability through lower firing temperature
4Stability of the object's composition
If sol-gel method is used to form solid electrolyte, then uniform layer is formed, but it is difficult to control particle structure and desired physical properties are hardly obtained
Solution Approach 1:
The invention uses segmentation by starting with discrete solid electrolyte particles (such as lithium lanthanum titanate particles) rather than forming a uniform continuous layer via sol-gel. This segmentation approach allows better control over particle structure, size, and distribution, enabling the achievement of desired physical properties like high lithium ionic conductivity while maintaining compositional uniformity through the particle-based architecture
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 proposed solution achieves a solid electrolyte with high total ionic conductivity and improved physical properties by reducing grain boundary resistance and maintaining desired structural integrity, enabling the formation of high-performance lithium-ion batteries.
Implementation Method 1
a solid electrolyte which includes a plurality of particles having lithium ionic conductivity and a matrix which is interposed among the particles so as to be in contact with each of the particles and is formed from an amorphous material... exhibiting a high total ionic conductivity by decreasing the grain boundary resistance
Implementation Method 2
the matrix is formed from an amorphous material... a production method involving surface modification, dispersion in a lithium compound solution, gelling, and heat treatment to form a high-conductivity oxide matrix
Data Source
AI summary
A solid electrolyte includes a plurality of particles having lithium ionic conductivity and a matrix which is interposed among the particles so as to be in contact with each of the particles and is formed from an amorphous material containing the following (a) and (b): (a) lithium atoms; and (b) an oxide of at least one element selected from the group consisting of boron, a Group 14 element in period 3 or lower, and a Group 15 element in period 3 or lower.