Composite Active Material Particle With Oxygen-Rich Surface Layer
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Solution Overview
Problem
The charging efficiency of batteries made with composite active material particles decreases due to the exposure of numerous silicon particles on the outer surface of the negative electrode active material, leading to poor interfacial contact with the solid electrolyte and separation during high-rate charging.
Innovation Solution
A composite active material particle is designed with an oxide phase and multiple active material domains dispersed within, where the surface layer region has a higher oxygen abundance than the inner region, reducing the exposed active material and maintaining better interfacial contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If numerous silicon particles are dispersed in the lithium silicate phase, then high capacity is achieved, but poor interfacial contact with solid electrolyte occurs and separation happens during high-rate charging
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of silicon particles within the lithium silicate phase. The outer surface region has a lower concentration of silicon particles compared to the inner region, ensuring that the surface maintains good interfacial contact with the solid electrolyte while the interior provides high capacity through abundant silicon particles.
Solution Approach 2:
The patent uses a composite material structure consisting of silicon particles dispersed in a lithium silicate phase. This composite structure combines the high capacity of silicon with the stable interfacial properties of lithium silicate, creating a material that maintains both high capacity and good contact with the solid electrolyte.
2Quantity of substance
If silicon particles are exposed on the outer surface, then high capacity is achieved, but charging efficiency decreases due to separation during high-rate charging
Solution Approach 1:
The patent creates a gradient structure where the outer surface layer has reduced silicon particle exposure compared to the interior. This local variation in particle distribution prevents surface separation during high-rate charging while preserving the high capacity provided by the silicon-rich interior, thereby maintaining high charging efficiency.
Solution Approach 2:
The lithium silicate phase acts as a cushioning matrix that prevents direct exposure and separation of silicon particles from the solid electrolyte. This protective structure is designed in advance to accommodate volume changes of silicon particles during charging and discharging, preventing interfacial separation and maintaining charging efficiency.
Data Source
AI summary
A composite active material particle includes an oxide phase containing an oxide and multiple active material domains containing an active material and dispersed in the oxide phase. When a region occupying a surface layer portion of the composite active material particle is defined as a first region, and a region located more inward than the first region is defined as a second region, the first region includes the oxide phase, the second region includes the oxide phase and the multiple active material domains, and the abundance of oxygen in the first region is higher than the abundance of oxygen in the second region.