Non-Aqueous Battery Electrolyte for Si-CNT Anode Cycle Stability
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Solution Overview
Problem
Existing non-aqueous electrolyte secondary batteries face challenges in achieving both high capacity and excellent cycle characteristics due to the volume change of Si-containing materials, which leads to increased internal resistance and deteriorated cycle characteristics when carbon nanotubes are added as a conductive agent.
Innovation Solution
Incorporating graphite, a Si-containing material, and carbon nanotubes in the negative electrode, along with specific compounds in the non-aqueous electrolyte, such as dimethyl malonate, diethyl malonate, or diethyl fluoromalonate, to form a protective coating on the positive electrode surface, inhibiting the isolation of Si-containing material and reducing side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon nanotube is added to the negative electrode to inhibit isolation of Si-containing material, then cycle characteristics are improved, but surface area of negative electrode increases leading to increased side reactions and increased internal resistance
Solution Approach 1:
A protective coating layer is introduced as an intermediary between the negative electrode (containing carbon nanotubes and Si-containing material) and the non-aqueous electrolyte. This coating layer mediates the interaction by preventing direct contact between the electrolyte and the negative electrode surface, thereby suppressing side reactions while allowing the carbon nanotubes to maintain their function of preventing Si-containing material isolation.
Solution Approach 2:
A thin protective coating film is formed on the negative electrode surface. This film acts as a barrier that reduces harmful side reactions between the electrolyte and the negative electrode materials, while being thin enough to allow lithium ion transport. The coating effectively isolates the electrolyte from the high-surface-area carbon nanotube structure.
2Quantity of substance
If Si-containing material is used in the negative electrode to achieve high capacity, then capacity is improved, but volume change with charge and discharge causes particles to run off conductive path and become isolated
Solution Approach 1:
The Si-containing material particles are embedded within a matrix of conductive carbon nanotubes in the negative electrode. This nested structure provides a stable conductive network that accommodates the volume expansion and contraction of Si-containing material during charge-discharge cycles, preventing particle isolation while maintaining electrical conductivity.
Solution Approach 2:
A composite negative electrode structure is created combining Si-containing material with carbon nanotubes and graphite. The carbon nanotubes form a flexible conductive framework that maintains structural integrity during volume changes of Si-containing material, while graphite provides additional stability. This composite approach allows high capacity from Si-containing material while maintaining conductive path stability.
Data Source
AI summary
A non-aqueous electrolyte secondary battery according to one embodiment of the present invention comprises a positive electrode 11, a negative electrode 12, and a non-aqueous electrolyte. The negative electrode 12 contains graphite, a Si-containing material, and carbon nanotubes. The non-aqueous electrolyte includes at least one compound selected from the group consisting of first compounds represent by formula 1 and second compounds represented by formula 2.