Porous Graphite Anode Structure Balancing Diffusion and Tap Density
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Solution Overview
Problem
Graphite anode materials face limitations in the diffusion of lithium ions, and the graphite anode materials have a low diffusion rate of lithium ions, leading to poor rate performance and safety issues such as lithium precipitation and thermal runaway.
Innovation Solution
An anode material with controlled pore volume, specific surface area, and tap density within the range of 2≤V*S/T≤10, created by mixing carbon-based raw materials with a pore-forming agent and binder, followed by specific heat treatments, to enhance lithium ion diffusion pathways and electrochemical reaction interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If graphite anode material uses a dense layered structure, then structural stability is improved, but lithium ion diffusion rate deteriorates
Solution Approach 1:
The patent introduces a porous structure into the graphite anode material, creating controlled pores within the layered structure. These pores serve as additional diffusion pathways for lithium ions, allowing them to penetrate deeper into the graphite particles more rapidly while the surrounding graphite layers maintain their structural stability and integrity during charge-discharge cycles.
Solution Approach 2:
The patent segments the graphite structure by creating pores that divide the dense layered structure into regions separated by void spaces. This segmentation creates multiple shorter diffusion pathways for lithium ions, reducing the overall diffusion distance and improving rate performance while maintaining the stability of the individual graphite crystal domains.
2Productivity
If pore volume is increased to enhance lithium ion diffusion, then rate performance is improved, but tap density deteriorates
Solution Approach 1:
The patent optimizes the pore volume parameter within a specific range (0.03-0.15 mL/g) to achieve the best balance between rate performance and tap density. By precisely controlling this parameter, the patent ensures sufficient pores for lithium ion diffusion while preventing excessive pore formation that would significantly reduce the tap density and energy density of the battery.
Solution Approach 2:
The patent creates pores with specific local characteristics, including controlled size distribution (0.003-0.1 μm) and strategic placement within the graphite structure. This local quality approach ensures that pores are distributed in a manner that maximizes lithium ion diffusion pathways while minimizing the overall volume occupied by pores, thereby maintaining acceptable tap density.
3Productivity
If specific surface area is increased to provide more reaction interfaces, then electrochemical performance is improved, but lithium precipitation risk increases
Solution Approach 1:
The porous structure provides a three-dimensional network of pores that distributes the electrochemical reaction interfaces throughout the volume of the graphite particles rather than concentrating them on the external surface. This distributed interface architecture reduces local current density hotspots, preventing lithium precipitation while maintaining high overall electrochemical performance.
Solution Approach 2:
The patent transitions from a two-dimensional surface-based reaction interface to a three-dimensional volume-based porous structure. This dimensional change allows lithium ions to access reaction sites throughout the particle interior, distributing the electrochemical reactions more uniformly and reducing the likelihood of lithium precipitation on the surface.
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 anode material achieves improved rate performance, processability, and cycle stability by optimizing the distribution of defects in the graphite structure, ensuring sufficient lithium ion diffusion and reducing concentration polarization.
Implementation Method 1
a special layered structure of graphite determines that Li+ can only be embedded from the end plane of the material and gradually diffused into particles, resulting in a low diffusion rate of lithium ions
Implementation Method 2
followed by specific heat treatments
Data Source
AI summary
An anode material and a battery. The anode material includes graphite, an interior and/or a surface of the graphite has pores, a pore volume of the anode material is V (cm3/kg), a specific surface area is S (m2/g), a tap density is T (g/cc), wherein, 2≤V*S/T≤10. By constructing the ratio relationship of the specific surface area of the anode material, the pore volume and the tap density of the anode material, the overall distribution condition of defects such as pore pathways, crystal lattices and micro cracks in the graphite particles can be reflected. Within the limited range, when the anode material is made into an electrode to be applied to a battery, the defect distribution in the anode material is uniform.