Carbon-Coated Graphite Agglomerates for High-Rate Lithium Battery Anodes
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Solution Overview
Problem
Rechargeable lithium batteries face challenges with natural graphite's large particle size leading to unsuitable charge and discharge characteristics due to limited intercalation sites and slow lithium ion movement, which affects high-rate chargeability and cycle-life.
Innovation Solution
A negative active material comprising tertiary particles of agglomerated secondary particles with spheroidized primary particles, artificial graphite on their surfaces, and an amorphous carbon coating layer, optimizing particle sizes and coating thickness to enhance lithium ion intercalation and deintercalation, thereby improving charge and discharge rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If natural graphite with large particle size is used, then capacity is improved, but charge and discharge characteristics deteriorate due to limited intercalation sites and slow lithium ion movement
Solution Approach 1:
The natural graphite particles are segmented into primary particles (3-8 μm) that are further agglomerated into secondary particles (5-10 μm) with spheroidized morphology. This segmentation increases the number of intercalation sites while maintaining adequate capacity, resolving the contradiction between capacity and charge/discharge rate by creating multiple accessible entry points for lithium ions.
Solution Approach 2:
The primary particles are spheroidized to form secondary particles with spherical morphology. This spheroidization improves packing density and creates uniform stress distribution during lithium ion intercalation and deintercalation, enhancing both capacity retention and charge/discharge characteristics by eliminating the directional limitations of flake-shaped particles.
2Productivity
If particle size is reduced to increase intercalation sites, then chargeability is improved, but structural stability may deteriorate
Solution Approach 1:
Multiple primary particles (3-8 μm) are merged to form secondary particles (5-10 μm) with spheroidized morphology. This merging approach maintains smaller effective particle sizes for rapid lithium ion diffusion while creating a robust aggregated structure that provides structural stability, thus improving high-rate chargeability without compromising structural integrity.
Solution Approach 2:
The invention creates a composite structure where primary particles are agglomerated into secondary particles, forming a hierarchical composite material. This composite architecture combines the advantages of small particles (rapid ion diffusion) with the benefits of larger aggregated structures (structural stability), achieving both improved chargeability and maintained structural integrity.
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 significantly enhances high-rate chargeability and cycle-life characteristics by increasing intercalation sites and facilitating lithium ion movement, resulting in improved performance for rechargeable lithium batteries.
Implementation Method 1
enhancing lithium ion intercalation and deintercalation
Implementation Method 2
facilitating lithium ion movement
Data Source
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AI summary
A negative active material for a rechargeable lithium battery, including tertiary particles including graphite and an agglomerated product where secondary particles where a plurality of primary particles is agglomerated and spheroidized, are agglomerated, and an amorphous carbon coating layer surrounding the tertiary particles.