Graphite Anode Composition for High-Density Secondary Batteries
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Solution Overview
Problem
Existing secondary batteries face challenges in achieving high energy density while maintaining electrochemical performance and cycle life, particularly at varying temperatures, due to limitations in active material composition and structure.
Innovation Solution
The secondary battery design incorporates a positive electrode with layered lithium transition metal oxides or lithium-containing phosphates, and a negative electrode with a combination of artificial and natural graphite, optimized through specific peak intensity ratios, particle sizes, and tap densities to enhance ion transmission and surface stability, thereby improving energy density and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high energy density is pursued through increased active material loading, then energy density improves, but electrochemical performance and cycle life deteriorate
Solution Approach 1:
The negative electrode uses a composite of artificial graphite and natural graphite in specific ratios (60-90 wt% artificial graphite, 10-40 wt% natural graphite). This composite structure combines the high capacity of artificial graphite with the stability and low-temperature performance of natural graphite, resolving the contradiction between energy density and cycle life
Solution Approach 2:
The patent optimizes specific parameters including the peak intensity ratio I(3R012)/I(2H100) of the negative electrode active material (0.03-0.20), particle size distribution (Dv50 of 10-20 μm), and tap density (1.8-2.2 g/cm³). These parameter optimizations enable high energy density while maintaining excellent electrochemical performance and cycle life
2Quantity of substance
If artificial graphite is used to increase capacity, then energy density improves, but low-temperature charging performance and surface stability worsen
Solution Approach 1:
The negative electrode combines artificial graphite (high capacity) with natural graphite (excellent low-temperature performance and surface stability). The natural graphite component compensates for the poor low-temperature characteristics of artificial graphite while maintaining high overall capacity
Solution Approach 2:
Different regions of the negative electrode have different compositions optimized for different functions: artificial graphite provides high capacity in the bulk, while natural graphite provides stable surface properties and low-temperature performance at the particle surfaces and interfaces
3Reliability
If high-temperature stability is improved through surface coating, then cycle life improves, but energy density and ion transmission worsen
Solution Approach 1:
The patent achieves high-temperature stability through optimized particle size (Dv50: 10-20 μm) and tap density (1.8-2.2 g/cm³) rather than thick surface coatings. This approach maintains high energy density and ion transmission while improving cycle life
Data Source
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AI summary
This application discloses a secondary battery and an apparatus containing the secondary batteries. The secondary battery includes a positive electrode plate and a negative electrode plate, the positive electrode plate comprising a positive electrode current collector and a positive electrode film disposed on at least one surface of the positive electrode current collector and comprising a positive active material; the negative electrode plate comprising a negative electrode current collector and a negative electrode film disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material, wherein the positive active material comprises one or more of layered lithium transition metal oxides and modified compounds thereof, the negative electrode active material comprises artificial graphite and natural graphite, and the negative electrode plate satisfies 0.02≤I3R(012)/I2H(100)≤0.18, alternatively the positive active material comprises one or more of lithium-containing phosphates with olivine structure and modified compounds thereof, the negative electrode active material includes artificial graphite and natural graphite, and the negative electrode plate satisfies 0.04≤I3R(012)/I2H(100)≤0.22.