All-Solid-State Battery Cathode Layout for Crack-Resistant Cycling
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Solution Overview
Problem
All-solid-state secondary batteries with solid electrolytes face challenges in maintaining energy density and cycle characteristics due to cracking of positive active materials during charging and discharging, leading to electrical and ionic disconnection, which degrades their performance.
Innovation Solution
Incorporating a positive electrode with a large-diameter positive active material having radially arranged cracks and a small-diameter positive active material, where the small-diameter material is strategically used to improve mixture density and reduce cracking, thereby enhancing energy density and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If small-diameter positive active material is used to reduce cracking, then cycle characteristics are improved, but energy density decreases due to low mixture density
Solution Approach 1:
The positive active material is divided into two distinct size segments: large-diameter particles (first positive active material) and small-diameter particles (second positive active material). The large particles provide high energy density while the small particles fill interstitial spaces and reduce cracking, achieving both improved cycle characteristics and maintained energy density through size segmentation
Solution Approach 2:
Different regions of the positive active material layer have different particle size distributions. The small-diameter particles are strategically positioned to fill gaps between large particles and to areas prone to cracking, creating local quality variations that simultaneously improve structural integrity and energy density
2Quantity of substance
If large-diameter positive active material is used, then energy density is improved, but cracking occurs during charging and discharging leading to electrical and ionic disconnection
Solution Approach 1:
Small-diameter positive active material particles act as intermediary elements between large-diameter particles and the solid electrolyte. These small particles fill cracks and maintain contact pathways, mediating the mechanical stress and preventing complete electrical and ionic disconnection of large particles during cycling
Solution Approach 2:
The positive active material layer is designed as a composite system combining large-diameter and small-diameter particles with different functional roles. The composite structure leverages the high energy density of large particles while the small particles provide structural stability and crack mitigation, achieving synergistic performance
Data Source
AI summary
Provided is an all-solid-state secondary battery including: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer arranged between the positive electrode layer and the negative electrode layer. The positive electrode layer includes a positive current collector and a positive active material layer arranged on the positive current collector, the positive active material layer includes a first positive active material layer arranged on the center of the positive current collector and a second positive active material layer surrounding the first positive active material layer and arranged on the periphery of the positive current collector, the negative electrode layer includes a negative current collector and a first negative active material layer or a third negative active material layer arranged on the negative current collector.