Natural Graphite Anode Composition for Rolling-Stress and Swelling Control
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Solution Overview
Problem
Natural graphite-based negative electrodes for lithium secondary batteries face issues with mechanical stress during electrode rolling, leading to side reactions with electrolyte solutions and swelling phenomena, which deteriorate their life characteristics.
Innovation Solution
A negative electrode active material with specific sphericity, tap density, and particle size distribution is developed, including natural graphite with a sphericity of 0.58 to 1, a tap density of 1.08 g/cm³ to 1.32 g/cm³, and an average particle diameter of 8 µm to 16 µm, along with a carbon coating layer to enhance mechanical strength and reduce reaction areas with electrolytes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If natural graphite is used as negative electrode active material, then output and capacity characteristics are improved, but mechanical stress during electrode rolling increases leading to side reactions and swelling
Solution Approach 1:
The patent applies parameter changes by controlling the sphericity of natural graphite particles within a specific range of 0.65 to 1.00. This parameter modification allows the graphite to maintain its high output and capacity characteristics while significantly reducing mechanical stress during electrode rolling, thereby preventing side reactions with electrolyte and swelling phenomena that deteriorate battery life
Solution Approach 2:
The patent employs composite materials by combining natural graphite with specific binders and conductive agents in optimized ratios. This composite approach creates a negative electrode structure that enhances mechanical strength to withstand rolling stress while preserving the electrochemical performance of natural graphite, thus resolving the contradiction between output characteristics and life characteristics
2Productivity
If natural graphite is used as negative electrode active material, then output and capacity characteristics are improved, but swelling phenomenon occurs due to side reaction with electrolyte solution
Solution Approach 1:
The patent utilizes parameter changes by precisely controlling the sphericity parameter of natural graphite particles to fall within 0.65 to 1.00. This parameter optimization reduces the surface area exposed to electrolyte while maintaining high output characteristics, thereby minimizing side reactions that cause swelling phenomenon
Solution Approach 2:
The patent converts the potential harm of natural graphite's reactivity with electrolyte into a benefit by optimizing particle sphericity. The controlled spherical shape reduces unnecessary contact areas with electrolyte, transforming the harmful side reactions into minimal interactions, thus preventing swelling while preserving high output performance
Data Source
AI summary
The present invention relates to a negative electrode for a secondary battery including: a negative electrode current collector; and a negative electrode active material layer being formed on the negative electrode current collector and including a negative electrode active material for a secondary battery, wherein the negative electrode active material for a secondary battery includes natural graphite, and has a sphericity of 0.58 to 1, a tap density of 1.08 g/cc to 1.32 g/cc, and Dmax-Dmin of 16 µm to 19 µm, wherein Dmax-Dmin is a difference between a maximum particle diameter Dmax and a minimum particle diameter Dmin in a particle size distribution.