Natural Graphite Anode Material for Swelling-Resistant Li-Ion Cells
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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 ranges (0.58 to 1, 1.08 g/cc to 1.32 g/cc, and 16 μm to 19 μm respectively) is developed, along with a carbon coating layer, to minimize mechanical stress and reaction area with the electrolyte, enhancing rolling characteristics and cycle stability.
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 with electrolyte and swelling phenomenon
Solution Approach 1:
The patent applies parameter changes by precisely controlling the sphericity (0.58 to 1.00), tap density (1.08 to 1.32 g/cc), and particle size distribution (Dmax-Dmin of 16 to 19 μm) of natural graphite particles. These parameter optimizations reduce mechanical stress during electrode rolling while maintaining high output and capacity characteristics, thereby improving both productivity and reliability
Solution Approach 2:
The patent creates a composite structure by forming a carbon coating layer on the natural graphite particles. This composite material approach enhances the mechanical strength of the graphite particles, reducing breakage and swelling during electrode rolling and cycling, thus improving reliability while preserving the high capacity characteristics of natural graphite
2Quantity of substance
If natural graphite particles are used with low mechanical strength, then capacity characteristics are improved, but electrode rolling causes particle breakage and swelling phenomenon
Solution Approach 1:
The patent forms a carbon coating layer on natural graphite particles, creating a composite material that combines the high capacity characteristics of natural graphite with enhanced mechanical strength. This composite structure prevents particle breakage and swelling during electrode rolling while maintaining lithium ion insertion/extraction performance
Solution Approach 2:
The carbon coating layer acts as a protective cushion applied beforehand to the natural graphite particles. This pre-protection mechanism absorbs mechanical stress during electrode rolling and prevents direct damage to the graphite crystal structure, thereby preventing swelling and maintaining capacity characteristics
Data Source
AI summary
A negative electrode for a secondary battery including: a negative electrode current collector; and a negative electrode active material layer present on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, 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.