Silicon-Anode Lithium Battery Resistance Tuning for Cycle Life
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Solution Overview
Problem
Existing lithium secondary batteries face challenges in maintaining battery life and performance, particularly when using NCM-based positive electrodes with silicon-based negative electrodes, due to increased kinetic burden and depth of use of the silicon-based active material.
Innovation Solution
The battery design includes specific resistance ratios and particle size distributions for the positive and negative electrodes, utilizing a silicon-based active material with controlled discharge resistances at varying states of charge, and incorporating Mg and Li compounds to manage volume changes, along with carbon layers for improved conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used in the negative electrode to achieve high capacity, then the battery capacity is improved, but the kinetic burden and depth of use of silicon-based active material increase leading to decreased battery life
Solution Approach 1:
The patent applies parameter changes by precisely controlling the resistance ratio (R5/R20) within a specific range of 1.05-1.30 and the depth of use of silicon-based active material within 30-70%. By adjusting these parameters, the patent achieves high capacity utilization while maintaining battery life, resolving the contradiction between capacity and reliability.
Solution Approach 2:
The patent employs partial action by using a controlled depth of use (30-70%) of the silicon-based active material rather than fully utilizing it. This partial utilization approach prevents excessive kinetic burden and depth of use that would otherwise degrade battery life, while still achieving high capacity through optimized resistance ratio control.
2Quantity of substance
If the depth of use of silicon-based active material is increased to improve capacity, then the battery capacity is improved, but the charging performance and life performance deteriorate
Solution Approach 1:
The patent changes the parameter of depth of use to an optimal range of 30-70%, preventing it from being too high. Combined with controlling the resistance ratio R5/R20 within 1.05-1.30, this parameter optimization achieves high capacity while maintaining good charging performance, resolving the contradiction between capacity and productivity.
Data Source
AI summary
A lithium secondary battery includes a positive electrode, a separator, and a negative electrode, wherein the negative electrode includes a silicon-based active material and wherein a resistance ratio represented by Equation 1 is 100% to 140%.