Solid Electrolyte with Amorphous Phase for Low Grain Boundary Resistance
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Solution Overview
Problem
Existing solid electrolytes with particulate form face challenges in achieving high total ion conductivity due to grain boundary resistance, which is exacerbated by high-temperature sintering processes that can alter composition and produce by-products, while lowering sintering temperatures may not ensure proper particle contact and conductivity.
Innovation Solution
A solid electrolyte comprising cubic garnet-type crystalline areas and amorphous areas with a composite oxide structure, where the amorphous phase contains metal atoms with an ionic radius of 78 pm or more, gradually increasing in abundance ratio from the crystalline to the amorphous regions, and an additional amorphous third area within voids, facilitating ion conductivity and reducing grain boundary resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature sintering is performed to reduce grain boundary resistance, then lithium ion conductivity improves, but composition changes due to lithium volatilization and side reactions occur
Solution Approach 1:
A glass-ceramic layer is introduced as an intermediary substance between solid electrolyte particles. This layer acts as a mediator that reduces grain boundary resistance without requiring high-temperature sintering, thereby preventing lithium volatilization and composition changes while still enabling efficient lithium ion conduction across particle boundaries.
Solution Approach 2:
The invention changes the processing temperature parameter from high-temperature sintering to low-temperature glass-ceramic formation. By controlling the temperature to remain below the melting point of the glass-ceramic material, the process achieves grain boundary resistance reduction without triggering lithium volatilization and compositional degradation that occur at higher temperatures.
2Reliability
If sintering temperature is raised to lower grain boundary resistance, then ion conductivity improves, but by-product formation increases
Solution Approach 1:
The processing temperature is changed from high-temperature sintering to low-temperature glass-ceramic formation. By maintaining the temperature below the melting point of the glass-ceramic material, the invention achieves effective grain boundary resistance reduction while preventing the thermal decomposition and side reactions that generate harmful by-products at higher temperatures.
3Object-generated harmful factors
If sintering temperature is lowered to reduce by-product formation, then by-products decrease, but grain boundary resistance increases
Solution Approach 1:
The glass-ceramic layer serves as an intermediary that enables effective grain boundary resistance reduction at low temperatures. This intermediary substance provides ion conduction pathways between particles without requiring the high thermal energy that would otherwise be needed to overcome grain boundary resistance, thus avoiding by-product formation.
Solution Approach 2:
The invention creates a composite structure consisting of solid electrolyte particles embedded in a glass-ceramic matrix. This composite material combines the high ionic conductivity of the solid electrolyte with the low-temperature processing and grain boundary modification capabilities of the glass-ceramic phase, achieving both low resistance and clean processing.
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 configuration enhances ion conductivity by connecting crystalline areas through an amorphous phase, reducing grain boundary resistance and increasing overall ion conductivity, while allowing for a lower forming temperature and reduced by-product formation, thus improving the performance of lithium ion batteries.
Implementation Method 1
a second area which is amorphous around the plurality of first areas, in which the plurality of first areas and the second area contain a composite oxide represented by formula (1) or (2) as the same forming material, the second area further contains metal atoms each having an ionic radius of 78 pm or more
Data Source
AI summary
A solid electrolyte which reduces grain boundary resistance and exhibits a high total ion conductivity is provided.The solid electrolyte includes a first area which has a cubic garnet type crystalline and a second area which is amorphous, around the first area, in which each of the first area and the second area contains a composite oxide represented by formula (1) or (2) as a forming material, and an abundance ratio of metal atoms each having an ionic radius of 78 pm or more gradually increases from the first area to the second area.Li7+xLa3−xZr2AxO12 (1)[In formula (1), A is at least one selected from the group consisting of Mg, Ca, Sr, and Ba. In addition, x is 0.1 or more and 0.6 or less.]Li7La3−xZr2BxO12 (2)[In formula (2), B is at least one selected from the group consisting of Sc and Y. In addition, x is 0.1 or more and 0.6 or less.]