Segmented Current Collector for Silicon Anode Cycle Life
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving high capacity and cycle life due to stress between the anode current collector and active material layer, which is exacerbated by the expansion and shrinkage of silicon anodes during charge and discharge, leading to pulverization and reduced contact characteristics.
Innovation Solution
The electrode design incorporates a current collector with a combination of a roughened active-material-layer-formation region for improved contact with the anode active material layer and a flat, smooth region for connecting the electrode lead, reducing contact resistance and enhancing cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the surface roughness of the anode current collector is excessively increased to improve the contact characteristics between the anode active material layer and the anode current collector, then the contact characteristics are improved, but the impedance is increased in the interface with the electrode lead
Solution Approach 1:
The current collector surface is divided into two distinct regions: a first region with increased surface roughness for improved contact with the anode active material layer, and a second region with reduced surface roughness for low-impedance connection to the electrode lead. This spatial segmentation allows each region to optimize its function independently, resolving the contradiction between contact characteristics and impedance.
Solution Approach 2:
Different surface qualities are applied to different locations on the current collector. The first region (where the anode active material layer contacts) has high surface roughness to enhance mechanical interlocking and electrical contact, while the second region (where the electrode lead connects) has low surface roughness to minimize impedance. This local differentiation of surface properties directly addresses the technical contradiction.
2Reliability
If vapor-phase deposition method is used to integrate the anode current collector and anode active material layer, then pulverization is prevented and electron conductivity is improved, but the anode active material layer is intensely expanded and shrunk during charge and discharge, applying stress and causing the anode active material layer to drop
Solution Approach 1:
The current collector is segmented into a first region that provides mechanical support and stress distribution, and a second region that ensures electrical conductivity. By separating these functions spatially and applying different surface treatments to each region, the patent prevents the anode active material layer from dropping during expansion and shrinkage while maintaining electron conductivity.
Solution Approach 2:
The surface roughness parameter is changed differently in different regions of the current collector. The first region has increased surface roughness to enhance mechanical adhesion and distribute stress during volume changes, preventing the anode active material layer from detaching. The second region maintains low roughness for optimal electrical contact with the electrode lead.
Data Source
AI summary
A battery realizing the superior cycle characteristics is provided. An electrode includes a current collector including an active-material-layer-formation region and a flat and smooth region having a surface roughness smaller than that of the active-material-layer-formation region, and an active material layer provided in the active-material-layer-formation region of the current collector. An electrode lead is connected to the flat and smooth region.