Solid Electrolyte Particle Size Optimization for Cathode Impedance
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Solution Overview
Problem
Current solid-state lithium batteries face performance gaps in energy density and rate capability due to high impedance caused by small solid electrolyte particles, which restrict the utilization of positive electrode active materials.
Innovation Solution
A positive electrode with a multi-modal particle size distribution for the active material and a solid electrolyte with a mean particle diameter of 0.1 to 12 micrometers is used, combined with a conductive agent, to enhance ionic conductivity and energy density, achieving improved loading and rate capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If very small solid electrolyte particles are used to achieve high packing density (λ>8), then the packing density of the composite electrode is improved, but the impedance in the cathode increases
Solution Approach 1:
The patent changes the particle size parameter of the solid electrolyte from very small particles (less than 1.5 μm) to larger particles (1.5 μm to 12 μm). This parameter change resolves the contradiction by demonstrating that larger particles can achieve adequate packing density while reducing impedance and improving ionic conductivity in the cathode.
Solution Approach 2:
The patent applies different particle size ranges to different components: solid electrolyte particles (1.5-12 μm) are optimized for low impedance and good ionic conductivity, while active material particles (3-50 μm) are optimized for capacity. This local quality differentiation resolves the contradiction by allowing each component to have optimal properties for its specific function.
2Quantity of substance
If small solid electrolyte particles (less than 1.5 μm) are used, then the packing density is improved, but the rate capacity and energy density decrease due to increased impedance
Solution Approach 1:
The patent changes the solid electrolyte particle size parameter from less than 1.5 μm to 1.5-12 μm, which resolves the contradiction by showing that this size range maintains adequate packing density while significantly improving rate capacity and energy density through reduced impedance and enhanced ionic conductivity.
Solution Approach 2:
The patent adopts a particle size range (1.5-12 μm) that has been proven effective in other solid-state battery configurations, adapting it to the specific cathode composite structure. This copying of successful parameters from related systems resolves the contradiction between packing density and rate capacity.
3Quantity of substance
If small solid electrolyte particles are used to achieve high packing density, then the loading is improved, but the ionic conductivity decreases
Solution Approach 1:
The patent changes the solid electrolyte particle size from very small particles to the 1.5-12 μm range, which resolves the contradiction by demonstrating that this size optimization maintains high loading while improving ionic conductivity through reduced grain boundary resistance and enhanced ion transport pathways.
Solution Approach 2:
The patent creates a composite cathode structure combining solid electrolyte particles (1.5-12 μm) with active material particles (3-50 μm) in specific ratios. This composite approach resolves the contradiction by allowing the larger solid electrolyte particles to provide good ionic conductivity while the composite structure maintains high loading through optimized packing.
Data Source
AI summary
A positive active material layer includes a positive active material comprising a plurality of particles having multi-modal particle size distribution, wherein the multi-modal particle size distribution comprises a first particle size distribution having a first mean particle diameter (D1) and a second particle size distribution having a second mean particle diameter (D2); a conductive agent; and a solid electrolyte comprising particles having a mean particle diameter (DSE) of 0.1 micrometers to 12 micrometers, wherein each of the first mean particle diameter and the second mean particle diameter are independently 1 micrometer to 50 micrometers.