Curved SWCNT Anode Structure for Cycle-Stable Capacity Retention
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Solution Overview
Problem
The capacity retention of negative electrodes in non-aqueous electrolyte secondary batteries decreases during cycle testing, as existing technologies fail to effectively maintain the connection and conductivity between active material particles.
Innovation Solution
Incorporating curved single-walled carbon nanotubes (SWCNTs) with an average length of 1 μm or more and an average diameter of 0.05 μm or less into the negative electrode active material layer, along with alloy-based and carbon-based active materials, to maintain particle connection and electron conduction paths during expansion and shrinkage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional negative electrode materials are used, then the battery can operate, but capacity retention decreases during cycle testing
Solution Approach 1:
The patent uses a composite structure combining alloy-based negative electrode active material particles with carbon-based negative electrode active material particles. This composite material approach leverages the high capacity of alloy materials while using carbon materials to provide structural stability and maintain capacity retention over cycling, thus resolving the contradiction between initial capacity and cycle life.
Solution Approach 2:
The patent introduces conductive fibers as intermediary elements that connect alloy-based active material particles to carbon-based particles and to the current collector. These conductive fibers serve as mediators that maintain electrical connectivity and mechanical connection throughout cycling, preventing particle isolation and maintaining capacity retention over time.
2Quantity of substance
If alloy-based active material is used to increase capacity, then electron conduction paths are disrupted during expansion and shrinkage
Solution Approach 1:
Conductive fibers act as intermediary elements that bridge alloy-based active material particles to carbon-based particles and current collector, maintaining electrical connectivity even when alloy particles expand and shrink during cycling. The flexible conductive fibers accommodate volume changes while preserving electron conduction paths.
Solution Approach 2:
The composite structure of alloy-based particles embedded in a carbon-based matrix with conductive fibers provides both high capacity (from alloy) and stable electron conduction (from carbon and conductive fibers). The carbon matrix buffers volume expansion while conductive fibers maintain electrical pathways.
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 use of curved SWCNTs prevents particle separation and maintains electron conduction, thereby enhancing cycle retention and capacity retention in non-aqueous electrolyte secondary batteries.
Implementation Method 1
the CNTs include single-walled carbon nanotubes having a curved structure (hereinafter also called curved SWCNTs)
Implementation Method 2
maintain particle connection and electron conduction paths during expansion and shrinkage
Data Source
AI summary
The present disclosure relates to a negative electrode for a non-aqueous electrolyte secondary battery comprising a negative electrode active material layer, wherein the negative electrode active material layer includes a negative electrode active material, carbon nanotubes, and a binder, the negative electrode active material includes an alloy-based negative electrode active material and a carbon-based negative electrode active material, the carbon nanotubes include single-walled carbon nanotubes having a curved structure, the single-walled carbon nanotubes having a curved structure have an average length of 1 μm or more and an average diameter of 0.05 μm or less, and the single-walled carbon nanotube having a curved structure is in contact with a particle and another particle.