Carbon-Coated Graphite Anode for High-Rate Lithium-Ion Discharge
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Solution Overview
Problem
Existing lithium-ion batteries for power tools face challenges in achieving rapid intercalation and deintercalation of lithium ions, necessitating improved anode materials to enhance discharge performance.
Innovation Solution
The anode material is designed with specific particle size and surface area relationships (Dv50 and BET) and controlled coating thickness to optimize lithium ion transmission paths and electrolyte infiltration, using graphite with an amorphous carbon layer and conductive coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the anode material uses larger particle size to increase capacity, then the energy storage capacity improves, but the lithium ion transmission speed decreases
Solution Approach 1:
The anode material uses a composite structure with graphite particles of different sizes (Dv10, Dv50, Dv90 parameters) segmented into specific ranges. Smaller particles provide short transmission paths for high-speed lithium ion insertion/extraction, while larger particles contribute to overall capacity. The segmentation of particle size distribution resolves the contradiction by having different size segments fulfill different functions.
Solution Approach 2:
The invention applies local quality control by specifying different particle size ranges for different portions of the particle distribution (Dv10, Dv50, Dv90). The surface area to volume ratio is optimized locally at the particle surface through controlled particle morphology, creating regions with high lithium ion conductivity while maintaining overall large particle capacity benefits.
2Quantity of substance
If the anode active material layer thickness is increased to increase capacity, then the energy storage improves, but the lithium ion diffusion path length increases reducing rate performance
Solution Approach 1:
The anode active material layer is segmented into a composite structure with binders and conductive agents distributed throughout. The layer is not uniform but composed of discrete functional components that create multiple pathways for lithium ion transport, effectively reducing the diffusion path length while maintaining high active material content for capacity.
Solution Approach 2:
The anode structure incorporates porous characteristics through the composite layer design with binders and conductive agents creating interstitial spaces. This porosity allows electrolyte penetration and creates multiple access paths for lithium ions, reducing the effective diffusion distance from the electrolyte to active material particles throughout the layer thickness.
3Speed
If the specific surface area is increased to improve lithium ion transmission speed, then the rate performance improves, but the side reactions with electrolyte increase
Solution Approach 1:
The invention applies local quality by coating only specific portions of the graphite particle surfaces with amorphous carbon or other protective layers. This selective coating reduces the reactive surface area exposed to electrolyte while maintaining sufficient surface area for lithium ion transmission. The coating is applied locally rather than uniformly across all surfaces, optimizing the balance between transmission speed and side reaction suppression.
Solution Approach 2:
The anode material is a composite combining graphite particles with amorphous carbon coatings and binder materials. This composite structure provides the benefits of high surface area for fast lithium ion transmission while the carbon coating and binder components suppress side reactions with the electrolyte, creating a multi-functional material system.
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 design accelerates lithium ion migration and improves high-rate discharge performance and cycling stability of lithium-ion batteries.
Implementation Method 1
the lithium-ion batteries can achieve rapid intercalation and deintercalation of the lithium ions during the charge and discharge process
Implementation Method 2
at least a part of the surface of the anode material includes an amorphous carbon layer
Implementation Method 3
the anode further includes a conductive coating between the anode active material layer and the current collector
Data Source
AI summary
An anode material having 0.8≤0.06×(Dv50)2−2.5×Dv50+Dv99≤12 (1); and 1.2≤0.2×Dv50−0.006×(Dv50)2+BET≤5 (2), where Dv50 represents a value in the volume-based particle size distribution of the anode material that is greater than the particle size of 50% of the particles, Dv99 represents a value in the volume-based particle size distribution of the anode material that is greater than the particle size of 99% of the particles, and BET is a specific surface area of the anode material, wherein Dv50 and Dv99 are expressed in μm and BET is expressed in m2/g. The anode material is capable of significantly improving the rate performance of electrochemical devices.