Silicon-Coated Negative Electrode for Lithium Battery Cycle Life
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Solution Overview
Problem
Silicon-based materials used in negative active electrodes of rechargeable lithium batteries experience violent expansion and shrinkage during charge and discharge, leading to interrupted binding and conductive networks, which limits the cycle-life of the batteries.
Innovation Solution
A negative electrode structure is developed with a carbon-based first active material, a composite material of silicon or tin-based materials coated with a combined binder and fiber-shaped conductive material, and an additional binder, optimized in weight percentages to enhance binding and conductivity, improving the cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If silicon-based material is used as negative active material to improve discharge capacity, then discharge capacity is improved, but cycle-life deteriorates due to violent expansion and shrinkage interrupting binding and conductive networks
Solution Approach 1:
The negative active material layer is segmented into two distinct components: carbon-based material (first active material) and silicon-based or tin-based material (second active material). This segmentation allows each material to perform its specialized function - carbon provides structural stability while silicon/tin provides high capacity, resolving the contradiction between capacity improvement and cycle-life maintenance.
Solution Approach 2:
The patent employs composite materials by combining carbon-based material with silicon-based or tin-based material in a layered structure. The carbon-based component acts as a stable matrix that accommodates the expansion and shrinkage of the silicon/tin-based component, thereby maintaining conductive networks and binding integrity throughout charge-discharge cycles while preserving high discharge capacity.
2Productivity
If silicon-based material expands during charging and shrinks during discharging, then discharge capacity is improved, but binding and conductive networks are interrupted
Solution Approach 1:
Different regions of the negative active material layer are assigned different functional qualities: the carbon-based material (first active material) provides a stable, flexible matrix with good conductivity, while the silicon-based or tin-based material (second active material) provides high lithium insertion/extraction capacity. This local differentiation allows the carbon matrix to maintain network integrity while the silicon/tin regions undergo volume changes.
Solution Approach 2:
The carbon-based material acts as an intermediary between the silicon-based/tin-based material and the conductive network. It mediates the mechanical stress from expansion and shrinkage, absorbing volume changes while maintaining continuous conductive pathways and binding integrity throughout the electrode structure during charge-discharge cycles.
Data Source
AI summary
A negative electrode for a rechargeable lithium battery including a current collector and a negative active material layer positioned on the current collector, wherein the negative active material layer includes a first active material including a carbon-based material, a composite material including a second active material including a silicon-based material or a tin-based material, the second active material being coated with a combined binder and a fiber-shaped conductive material on the surface thereof, and a binder, a rechargeable lithium battery including the same and a method of preparing the same.