Silicon Negative Electrode Composition for Conductive Path Stability
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Solution Overview
Problem
Lithium secondary batteries using silicon-based active materials face challenges with volume expansion during charging/discharging, which damages the conductive path and deteriorates battery performance, limiting the commercialization of high-capacity batteries.
Innovation Solution
A negative electrode comprising a conductive material with three different types of conductive materials having specific surface areas and an aqueous binder with a copolymer, ensuring high dispersibility and stability to prevent conductive path disconnection during silicon-based active material expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon-based compound is used as a negative electrode active material to increase capacity, then the battery capacity is improved, but the volume expansion during charging/discharging blocks the conductive path and deteriorates battery properties
Solution Approach 1:
The patent uses a composite conductive material comprising carbon nanotubes and carbon black. The carbon nanotubes form a three-dimensional conductive network that maintains electrical connectivity even when silicon particles expand, while carbon black fills gaps and provides additional conductive pathways. This composite structure resolves the contradiction by enabling high silicon content (improving capacity) while maintaining conductive path stability (maintaining reliability).
Solution Approach 2:
The patent applies different conductive materials to different locations and functions within the electrode structure. Carbon nanotubes are used to form the primary conductive network framework that accommodates volume expansion, while carbon black is used to fill interstitial spaces and provide secondary conductive pathways. This local differentiation of conductive material properties allows the system to handle both high capacity requirements and conductive path stability simultaneously.
2Productivity
If the content of silicon-based compound in the negative electrode is increased to improve capacity performance, then the energy density is improved, but the volume expansion damages the conductive path and limits commercialization
Solution Approach 1:
The composite conductive material system (carbon nanotubes + carbon black) enables high silicon content electrodes to be manufactured with maintained performance. The robust three-dimensional conductive network tolerates the volume expansion of high silicon content materials, making high energy density electrodes manufacturable and commercially viable without suffering from conductive path degradation.
Solution Approach 2:
The patent changes the physical and chemical parameters of the conductive material system by using carbon nanotubes with their unique tubular structure and high aspect ratio, combined with carbon black particles. This parameter change creates a conductive network that is tolerant to volume expansion, enabling the manufacturing of high silicon content electrodes with maintained electrical conductivity and commercial feasibility.
3Device complexity
If conventional conductive materials are used with silicon-based active material, then the manufacturing process is simple, but the conductive path is disconnected due to volume expansion and performance deteriorates
Solution Approach 1:
The patent employs a composite conductive material system combining carbon nanotubes and carbon black that can be integrated into existing electrode manufacturing processes. This composite provides superior conductive path continuity under volume expansion conditions compared to conventional single-material systems, while maintaining reasonable manufacturing complexity through standard slurry preparation and coating methods.
Data Source
AI summary
A negative electrode includes a conductive material for negative electrode, a silicon-based active material, and an aqueous binder, wherein the conductive material for negative electrode includes a first conductive material having a specific surface area of 250 m2/g to 1000 m2/g, a second conductive material having a specific surface area of 55 m2/g to 70 m2/g, and a third conductive material having a specific surface area of 15 m2/g to 20 m2/g. A lithium secondary battery including the negative electrode is also provided.