Graphite Anode Composition for Power and High-Temperature Storage
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Solution Overview
Problem
Lithium ion secondary batteries for EVs, HEVs, and PHEVs face a trade-off between improving input characteristics and high temperature storage characteristics, where increasing specific surface area enhances input characteristics but deteriorates high temperature storage, and reducing surface area improves storage but worsens input characteristics.
Innovation Solution
A negative electrode material with graphite particles having specific properties, including an R value less than 0.27 by Raman spectrometry, intensity ratios in X-ray diffraction patterns, and a BET specific surface area between 2 m2/g to 15 m2/g, combined with amorphous carbon coating on the surface of graphite particles, to balance input characteristics and high temperature storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the specific surface area of the negative electrode material is increased to improve input characteristics, then the high temperature storage characteristics deteriorate
Solution Approach 1:
The invention changes the structural parameters of graphite particles by controlling the intensity ratio (P1/P2) to be 5.0 or less and R value to be less than 0.27, which modifies the crystalline structure to achieve a balance between input characteristics and high temperature storage characteristics without simply increasing surface area
Solution Approach 2:
The invention creates a composite structure by coating amorphous carbon on the surface of graphite particles, combining the advantages of both crystalline graphite (high energy density) and amorphous carbon (good input characteristics and storage stability) to resolve the trade-off
2Reliability
If the specific surface area of the negative electrode material is reduced to improve high temperature storage characteristics, then the input characteristics deteriorate
Solution Approach 1:
The invention modifies the internal structure parameters of graphite particles (intensity ratio P1/P2 ≤ 5.0 and R value < 0.27) to enhance input characteristics without increasing surface area, allowing improved power delivery while maintaining good high temperature storage characteristics
Solution Approach 2:
The amorphous carbon coating on graphite particles provides a conductive network that improves input characteristics even when the specific surface area is kept low, resolving the contradiction between power delivery and storage stability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in lithium ion secondary batteries with excellent input characteristics and high temperature storage capabilities, effectively addressing the trade-off between these two performance metrics.
Implementation Method 1
an R value measured by Raman spectrometry is less than 0.27
Implementation Method 2
an intensity ratio (P1/P2) of a diffraction peak (P1) on a hexagonal structure (101) plane to a diffraction peak (P2) on a rhombohedral structure (101) plane in an X-ray diffraction pattern by CuKα ray is 5.0 or less
Data Source
AI summary
A negative electrode active material for a lithium ion secondary battery includes graphite particles for which an R value measured by Raman spectrometry is less than 0.27, and an intensity ratio (P1/P2) of a diffraction peak (P1) on a hexagonal structure (101) plane to a diffraction peak (P2) on a rhombohedral structure (101) plane in an X-ray diffraction pattern by CuKα ray is 5.0 or less.