Void-Structured Silicon Negative Electrode for Cycle Stability
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Solution Overview
Problem
Existing lithium-ion secondary batteries using silicon as a negative electrode active material face issues with capacity retention due to expansion and contraction during charging/discharging cycles, leading to electrode cracking and decreased cycling performance.
Innovation Solution
A negative electrode structure is designed with a void around the first active material, comprising silicon, silicon oxide, or silicon carbide, and a second active material, such as graphite, with an ion conductive polymer like polyethylene oxide and conductive material, to mitigate the effects of expansion and contraction, thereby improving cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the first active material to increase capacity, then the battery capacity is improved, but electrode cracking occurs due to expansion and contraction during charging/discharging cycles, leading to decreased cycling performance
Solution Approach 1:
The patent introduces a porous structure with voids around the silicon particles in the negative electrode active material layer. These voids accommodate the expansion and contraction of silicon during charging and discharging cycles, preventing electrode cracking and maintaining cycling performance while preserving high capacity.
Solution Approach 2:
The patent designs the negative electrode structure with pre-formed voids around silicon particles before cycling begins. These voids act as cushioning spaces that absorb the mechanical stress of silicon expansion and contraction, preventing structural failure and maintaining electrode integrity throughout cycling.
2Difficulty of detecting and measuring
If the negative electrode structure is made dense to improve conductivity, then electrical conductivity is improved, but expansion and contraction during charging/discharging cause electrode cracking and reduced capacity retention
Solution Approach 1:
The patent employs a controlled porous structure with voids around active material particles. This porous design maintains adequate electrical conductivity through the conductive material network while providing necessary space for volume changes, thereby preventing cracking and preserving capacity retention over cycling.
Solution Approach 2:
The patent creates a composite negative electrode structure combining silicon particles, conductive material, binder, and voids. This composite architecture balances electrical conductivity with mechanical flexibility, allowing the electrode to accommodate expansion/contraction while maintaining conductive pathways for electron transport.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The voids in the electrode structure reduce the influence of expansion and contraction, enhancing capacity retention and maintaining high cycling performance by suppressing electrode cracking.
Implementation Method 1
an ion conductive polymer, and a conductive material
Data Source
AI summary
A negative electrode includes: a negative electrode current collector; and a negative electrode active material layer, wherein the negative electrode active material layer includes a first active material, a second active material, an ion conductive polymer, and a conductive material, and the negative electrode active material layer has a structure provided with a void around the first active material.