Graphite Negative Electrode Material for Lithium-Ion Batteries
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Solution Overview
Problem
Existing negative electrode materials for nonaqueous secondary batteries, particularly graphite, face issues with lithium deposition, high-rate charging/discharging characteristics, and cycle performance due to inadequate electrode orientation and particle size distribution, leading to irreversible capacity and durability concerns.
Innovation Solution
A negative electrode material composed of graphite particles with specific size, tapping density, and orientation characteristics, combined with a binder and graphitization process, to enhance electrode structure and performance, including a median diameter of 5-40 μm, tapping density of 0.7 g/cm3 or more, and a graphite crystal orientation ratio of 0.08 or more, achieved through a method involving mixing, kneading, molding, graphitization, and classification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite particles are used as negative electrode material, then lithium metal deposition is prevented, but high-rate charging/discharging characteristics and cycle performance deteriorate due to electrode orientation and expansion
Solution Approach 1:
The patent applies parameter changes by controlling the particle size distribution of graphite particles within a specific range (d50: 3-15 μm, d90/d10 ratio: 1.05-1.30) and adjusting the orientation ratio parameter (I002/I100) to 0.05 or less. These parameter optimizations resolve the contradiction by enabling both prevention of lithium deposition and maintenance of high-rate charging/discharging characteristics through precise control of particle morphology and orientation in the electrode structure
2Reliability
If graphite particles are used as negative electrode material, then lithium metal deposition is prevented, but cycle performance deteriorates due to significant electrode expansion in charging/discharging cycle
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the particle size distribution parameters (d50 between 3-15 μm, d90/d10 ratio between 1.05-1.30) and controlling the orientation ratio (I002/I100 ≤ 0.05). These parameter optimizations reduce electrode expansion during charging/discharging cycles while maintaining the ability to prevent lithium metal deposition, thereby improving cycle performance
Solution Approach 2:
The patent employs composite materials by combining graphite particles with specific size distribution and orientation characteristics with a binder and conductive agent to form a composite electrode material. This composite structure mitigates electrode expansion issues while maintaining the lithium deposition prevention capability of graphite, thus improving cycle performance
3Productivity
If graphite granulated particles with bonded particles are used, then electrode orientation is improved and high-rate charging/discharging characteristics are improved, but irreversible capacity and cycle performance remain inadequate
Solution Approach 1:
The patent resolves this contradiction through precise parameter changes by optimizing the particle size distribution (d50: 3-15 μm, d90/d10: 1.05-1.30) and controlling the orientation ratio (I002/I100 ≤ 0.05). These parameter optimizations simultaneously improve high-rate charging/discharging characteristics while reducing irreversible capacity and enhancing cycle performance, achieving a balanced solution that prior art failed to accomplish
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 a negative electrode with improved high-rate charging/discharging characteristics and cycle performance, reducing initial irreversible capacity and maintaining capacity over multiple cycles, thus enhancing the overall efficiency and stability of nonaqueous secondary batteries.
Implementation Method 1
graphite particles having a median diameter of 5 μm or more, and 40 μm or less in the volume-basis particle size distribution... the graphite crystal orientation ratio I110/I004 on the electrode is 0.08 or more
Data Source
AI summary
A negative electrode material for a nonaqueous secondary battery capable of realizing a nonaqueous secondary battery having a small charging/discharging irreversible capacity at an initial cycle and exhibiting an excellent high-rate charging/discharging characteristics and an excellent cycle performances is provided. The main component of the material is graphite particles. The median diameter is 5 μm or more, and 40 μm or less in the volume-basis particle size distribution based on the laser diffraction/scattering particle size distribution measurement. The tapping density is 0.7 g/cm3 or more. The specific surface area measured by a BET method is 0.2 m2/g or more, and 8 m2/g or less. The average circularity is 0.83 or more, and 1.00 or less. When an electrode is produced by a predetermined method for manufacturing an electrode and, the resulting electrode is subjected to X-ray diffraction, the graphite crystal orientation ratio I110/I004 on the electrode is 0.08 or more, where I110 represents the wide angle X-ray diffraction peak area of the (110) peak peak in the region of 2θ=76.5 to 78.5 degrees of the graphite particles on the electrode and I004 represents the wide angle X-ray diffraction peak area of the (004) peak peak in the region of 2θ=53.5 to 56 degrees.