Carbon-Coated Natural Graphite Anode for Thickness Expansion Control
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Solution Overview
Problem
Rechargeable lithium batteries face issues with thickness expansion and cycle-life deterioration due to side reactions with electrolytes and internal pore volume expansion, particularly in negative active materials like spheroidized natural graphite, which affects their capacity and durability.
Innovation Solution
A negative active material is developed using spheroidized natural graphite with amorphous carbon coating and specific particle size ranges, combined with a method of pulverizing and heat-treating natural graphite to reduce internal pore volume and side reactions, resulting in improved cycle-life characteristics and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If spheroidized natural graphite is used as negative active material, then capacity is improved, but thickness expansion occurs due to side reactions with electrolyte
Solution Approach 1:
The patent applies parameter changes by controlling the particle size distribution (D10, D50, D90 values) and spheroidization degree of natural graphite particles to optimize capacity while minimizing thickness expansion. By adjusting these parameters, the material achieves high capacity utilization without excessive side reactions.
Solution Approach 2:
The patent creates a composite structure by spheroidizing natural graphite particles and coating them with amorphous carbon. This composite approach combines the high capacity of natural graphite with the protective and conductive properties of amorphous carbon, reducing side reactions and thickness expansion while maintaining high capacity.
2Quantity of substance
If spheroidized natural graphite is used, then capacity is improved, but cycle-life deteriorates due to internal pore volume expansion
Solution Approach 1:
The amorphous carbon coating forms a protective composite layer around the spheroidized natural graphite particles. This composite structure prevents electrolyte penetration into internal pores, reducing side reactions and volume expansion that would otherwise deteriorate cycle-life, while preserving the high capacity of the graphite core.
Solution Approach 2:
The patent optimizes the particle size parameters (D10, D50, D90) and spheroidization degree to minimize internal pore volume expansion during cycling. By controlling these parameters, the material achieves high capacity while maintaining structural integrity and long cycle-life.
3Object-generated harmful factors
If natural graphite particles are reduced in size, then side reactions are reduced, but manufacturing complexity increases
Solution Approach 1:
The patent employs spheroidization to transform flake-shaped natural graphite particles into spherical particles with controlled size distribution. This spherical morphology reduces the surface area for side reactions while the specific particle size parameters (D10, D50, D90) are optimized to balance reaction reduction with manufacturing feasibility.
Solution Approach 2:
The patent controls specific particle size parameters (D10, D50, D90) to optimize the balance between reducing side reactions and maintaining manufacturability. By defining these parameters within specific ranges, the invention achieves reduced harmful effects while keeping the manufacturing process practical and scalable.
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 effectively suppresses thickness expansion and enhances cycle-life characteristics by reducing side reactions and internal pore volume, maintaining high capacity and improving charge and discharge rate capabilities in lithium batteries.
Implementation Method 1
amorphous carbon on the surface of the primary particles; and a coating layer including amorphous carbon surrounding the secondary particles
Implementation Method 2
heat-treating the mixture
Implementation Method 3
pulverizing natural graphite raw materials into primary particles having a small particle size
Data Source
Figure 1A~1B
Figure 2
AI summary
Disclosed is a negative active material for a rechargeable battery including natural graphite including secondary particles in which a plurality of primary particles are assembled; amorphous carbon on the surface of the primary particles; and a coating layer including amorphous carbon surrounding the secondary particles, wherein the primary particles have a particle diameter of about 5 µm to about 15 µm, the secondary particles have a particle diameter of about 8 µm to about 24 µm.