Natural Graphite Anode Material for Low-Expansion Lithium Batteries
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Solution Overview
Problem
Natural graphite-based negative electrodes in lithium secondary batteries face significant cycle expansion issues due to electrolyte side reactions, limiting their capacity and lifespan despite their high output and capacity potential.
Innovation Solution
A negative electrode active material is developed using natural graphite with a D90/D10 ratio of 2.20 or less, a D50 of 6 μm to 11 μm, and a BET specific surface area of 2.2 m2/g or less, prepared through a Cold Isostatic Press method to reduce particle pores and enhance packing, combined with a carbon coating layer to prevent electrolyte side reactions and improve structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If natural graphite is used as negative electrode active material, then output and capacity are improved, but cycle expansion problem occurs due to electrolyte side reaction
Solution Approach 1:
The patent applies parameter changes by controlling the particle size distribution parameters (D90/D10 ratio ≤ 2.20, D50 between 6-11 μm, BET specific surface area ≤ 2.2 m2/g) of natural graphite to resolve the contradiction between high output/capacity and cycle expansion prevention
Solution Approach 2:
The patent uses composite materials by combining natural graphite with artificial graphite in specific ratios to create a negative electrode active material that maintains the high output and capacity of natural graphite while reducing cycle expansion through the structural stability of artificial graphite
2Quantity of substance
If natural graphite is used to achieve high capacity, then battery energy density is improved, but thickness expansion occurs during charging and discharging
Solution Approach 1:
The patent controls the particle size distribution parameters (D90/D10 ratio ≤ 2.20, D50 between 6-11 μm) to optimize packing density and minimize volume expansion during lithium ion intercalation and deintercalation cycles
Solution Approach 2:
The patent applies different particle size ranges to different portions of the electrode structure, using a controlled distribution where smaller particles fill voids between larger particles, optimizing both capacity and volume stability
3Productivity
If natural graphite particles are reduced in size to improve packing, then capacity is improved, but specific surface area increases causing more electrolyte side reactions
Solution Approach 1:
The patent optimizes the BET specific surface area parameter to ≤ 2.2 m2/g while maintaining high capacity through controlled particle size distribution (D50: 6-11 μm), balancing the trade-off between packing density and side reaction prevention
Solution Approach 2:
The patent utilizes the natural porous structure of graphite particles with controlled surface area to enable efficient lithium ion transport while minimizing electrolyte contact and side reactions
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
This approach effectively prevents cycle expansion and thickness growth, maintaining high output and capacity properties while enhancing the lifespan of the battery by optimizing particle size distribution and surface area, thereby improving the battery's charging performance and structural integrity.
Implementation Method 1
a method for preparing a negative electrode active material, the method including a process of pressurizing natural graphite by a Cold Isostatic Press method
Implementation Method 2
a BET specific surface area is 2.2 m2/g or less
Data Source
AI summary
A negative electrode active material including natural graphite, wherein a D90/D10, which is the ratio of D90 to D10, is 2.20 or less, a D50 is 6 μm to 11 μm, and a BET specific surface area is 2.2 m2/g or less.