Carbon-Coated Graphite Anode Structure for High-Rate Charging
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high-rate charge and discharge characteristics due to limited intercalation sites and unsuitable particle sizes in natural graphite, which affects their performance and cycle life.
Innovation Solution
A negative active material comprising tertiary particles with agglomerated secondary particles and an amorphous carbon coating layer, where primary and secondary particles are natural graphite, enhancing lithium ion intercalation and deintercalation, and including artificial graphite to improve packing density and charge rate capability.
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-discharge rate deteriorates due to limited intercalation sites
Solution Approach 1:
The natural graphite particles are divided into smaller primary particles (4-8 μm) which are then agglomerated into secondary and tertiary particles. This segmentation increases the number of intercalation sites while maintaining adequate particle size for capacity, thereby improving charge-discharge rate without sacrificing capacity.
Solution Approach 2:
The patent employs a multi-level agglomeration structure where primary particles form secondary particles, which in turn form tertiary particles. This nested structure allows small primary particles (providing many intercalation sites) to be organized into larger aggregate structures (maintaining capacity), effectively resolving the contradiction between particle size and charge-discharge rate.
2Speed
If natural graphite is spheroidized to improve charge rate, then charge-discharge rate is improved, but particle size becomes unsuitable affecting capacity
Solution Approach 1:
The spheroidized primary particles are nested within agglomerated secondary and tertiary particle structures. This allows the particles to benefit from the spherical shape (improving charge rate) while the agglomerated structure maintains suitable overall particle size for capacity retention.
Solution Approach 2:
The patent transitions from considering only single particle size to a multi-scale particle size distribution. By creating a hierarchical structure with primary, secondary, and tertiary particles of different size ranges, it optimizes both charge-discharge rate (small primary particles) and capacity (larger agglomerated structures) simultaneously.
3Speed
If graphite particles are reduced to increase intercalation sites, then charge rate is improved, but packing density deteriorates
Solution Approach 1:
The nested agglomeration structure allows small primary particles (providing high charge rate) to be packed efficiently within larger secondary and tertiary particle frameworks. This maintains high packing density while preserving the beneficial effects of small particle size on charge rate.
Solution Approach 2:
By segmenting graphite into primary particles of 4-8 μm that are then agglomerated, the patent achieves both increased intercalation sites (from segmentation) and maintained packing density (through controlled agglomeration into tertiary particles with optimal size distribution).
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 improves high-rate chargeability, cycle-life characteristics, and initial efficiency by increasing intercalation sites and reducing side reactions, making it suitable for high-capacity rechargeable lithium batteries.
Implementation Method 1
enhancing lithium ion intercalation and deintercalation
Data Source
AI summary
A negative active material for a rechargeable lithium battery, including tertiary particles including graphite and an agglomerated product where secondary particles where g a plurality of primary particles is agglomerated and spheroidized, are agglomerated, and an amorphous carbon coating layer surrounding the tertiary particles.