Silicon-Carbon Fiber Negative Electrode Mesh for Low-Swelling Batteries
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Solution Overview
Problem
Secondary batteries, particularly lithium-ion batteries, face challenges in achieving superior initial capacity, swelling, load, and cyclability characteristics due to insufficient porosity and structural integrity of their negative electrodes.
Innovation Solution
A negative electrode configuration comprising large-diameter and small-diameter carbon fiber parts with silicon particle parts, forming a three-dimensional mesh structure without a metal current collector, optimizing fiber diameters and void rates to enhance electrical conductivity and reactant accessibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a conventional negative electrode structure with metal current collector is used, then structural integrity is maintained, but weight increases and energy density decreases
Solution Approach 1:
The patent removes the metal current collector from the negative electrode structure, extracting the unnecessary component that adds weight without contributing to electrochemical function. The carbon fiber mesh itself serves as the structural backbone, eliminating the need for separate current collector layers.
Solution Approach 2:
The carbon fiber mesh performs multiple functions simultaneously: it provides structural integrity, serves as the current collector, and acts as part of the electrode active material. This multi-functionality eliminates the need for separate metal current collector components.
2Productivity
If porosity of negative electrode is increased to improve reactant accessibility, then initial capacity improves, but structural integrity deteriorates
Solution Approach 1:
The patent employs a three-dimensional carbon fiber mesh structure with controlled porosity (42-73 vol%). This porous structure allows efficient electrolyte penetration and lithium ion transport while maintaining structural integrity through the interconnected fiber network.
Solution Approach 2:
The negative electrode uses a composite structure combining carbon fiber mesh with silicon-based active materials. The carbon fiber provides structural strength while the silicon particles provide high capacity, creating a composite that balances structural integrity and electrochemical performance.
3Reliability
If fiber diameter is reduced to increase surface area, then electrical conductivity improves, but mechanical strength decreases
Solution Approach 1:
The patent uses a bimodal fiber diameter distribution with two distinct carbon fiber components: larger diameter fibers (50-7000 nm) providing structural strength and smaller diameter fibers (1-200 nm) providing high surface area and electrical conductivity. Each fiber size optimizes for its specific function.
Solution Approach 2:
The patent transitions from traditional planar electrode structures to a three-dimensional carbon fiber mesh architecture. This 3D structure provides enhanced surface area and electrical conductivity pathways while maintaining mechanical strength through the spatial network of fibers.
Data Source
AI summary
A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The negative electrode includes first fiber parts, particle parts, and second fiber parts, and has voids. The first fiber parts are coupled to each other to thereby form a three-dimensional mesh structure having the voids. The first fiber parts each include carbon as a constituent element. The particle parts cover surfaces of the first fiber parts. Some of the particle parts are coupled to each other. The particle parts each include silicon as a constituent element. At least some of the second fiber parts are coupled to surfaces of the particle parts. The second fiber parts each include carbon as a constituent element. The first fiber parts have an average fiber diameter that is greater than or equal to 50 nm and less than or equal to 7000 nm. The second fiber parts have an average fiber diameter that is greater than or equal to 1 nm and less than or equal to 200 nm. The negative electrode has a void rate that is greater than or equal to 42 vol % and less than or equal to 73 vol %.