Gradient-Coated Silicon Anodes to Prevent Conductive Path Loss
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Solution Overview
Problem
Silicon-based active materials in lithium secondary batteries experience rapid volume expansion during charging and discharging, leading to disconnection of conductive paths and degradation of battery characteristics, which existing coating methods fail to adequately address.
Innovation Solution
A coating layer with a dual concentration gradient of active and inactive material phases is applied to silicon-based active materials, where the inactive material phase decreases and the active material phase increases from the outer surface toward the inside, mitigating volume changes and minimizing coating film cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon-based compound is used as the negative electrode active material to increase capacity, then the discharge capacity is improved, but the volume expansion during charging causes disconnection of conductive paths and degradation of battery characteristics
Solution Approach 1:
A coating layer with a concentration gradient structure is applied to the silicon-based active material surface. This coating layer acts as a flexible protective shell that can accommodate volume expansion during charging while maintaining structural integrity and preventing conductive path disconnection.
Solution Approach 2:
The coating layer is designed with a concentration gradient where the inactive material phase concentration decreases from the outer surface toward the inside. This parameter change in material distribution allows the coating to be more compliant at the interface with silicon (accommodating expansion) while maintaining structural stability at the outer surface.
2Stability of the object's composition
If a coating layer is formed on the surface of the silicon-based active material to prevent volume changes, then the structural stability is improved, but cracks occur in the coating layer due to rapid volume changes at the interface, exposing the silicon-based active material and causing deterioration in cycle performance
Solution Approach 1:
The coating layer is designed with spatially varying properties through the concentration gradient structure. The inactive material phase concentration decreases from the outer surface toward the inside, creating different local mechanical properties that can accommodate volume expansion at the interface while maintaining outer surface stability.
Solution Approach 2:
The coating layer is formed as a composite structure containing both active material phase and inactive material phase. This composite structure combines the benefits of structural stability from the inactive phase with electrochemical activity from the active phase, while the concentration gradient optimizes the distribution of these properties.
3Stability of the object's composition
If the coating layer material is an insulator to suppress volume expansion, then the structural integrity is improved, but rapid decrease in resistance occurs
Solution Approach 1:
The concentration of inactive material phase is varied through the coating layer thickness, creating a gradient from high concentration at the outer surface to low concentration near the interface. This parameter change allows the coating to provide structural stability while maintaining electrical conductivity through regions with lower insulator concentration.
Solution Approach 2:
The coating layer is designed as a composite of active and inactive material phases with a concentration gradient. This composite structure balances the conflicting requirements of structural stability (provided by the inactive phase) and electrical conductivity (maintained by the active phase and its gradient distribution).
Data Source
Figure 1~2
AI summary
The present application relates to an anode active material, an anode composition, a lithium secondary battery anode comprising same, and a lithium secondary battery comprising the anode.