Graphite Anode Material for Lithium-Ion Batteries
Solution Overview
Problem
Conventional graphite materials for lithium-ion battery electrodes suffer from low beginning efficiency, discharge capacity, and high internal resistance due to high specific surface area and aspect ratio, leading to decreased battery capacity and poor cycle characteristics.
Innovation Solution
A method involving the pulverization and graphitization of green non-needle coke with a specific heat loss range, followed by heat treatment under inert conditions, to produce graphite with a low aspect ratio and specific surface area, resulting in isotropic crystal structure and high tap density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If natural graphite is spherically granulated, then the shape becomes more uniform, but the particles collapse to become oriented in the same direction when pressed during electrode production
Solution Approach 1:
The invention uses mesocarbon spherules with a specific spherical structure that have a smooth surface and uniform curvature. These spherules maintain their spherical shape even under pressing conditions during electrode production, preventing the collapse and orientation problems that occur with granulated natural graphite. The spherical morphology is achieved through controlled carbonization processes that create a stable, isotropic structure.
2Area of stationary object
If the specific surface area of graphite material is increased, then the contact area with electrolyte increases, but the internal resistance increases and beginning efficiency decreases
Solution Approach 1:
The invention optimizes the specific surface area parameter to a specific range (0.5-2.0 m²/g) rather than maximizing it. This parameter optimization balances the benefits of electrolyte contact with the drawbacks of excessive internal resistance. The controlled surface area, combined with spherical morphology, achieves good electrochemical performance without the harmful effects of high surface area.
3Quantity of substance
If the aspect ratio of graphite particles is high, then the particles can be densely packed, but the charge-discharge rate and large-current load characteristics deteriorate
Solution Approach 1:
The invention employs spherical particles with an aspect ratio close to 1:1, which provides excellent packing density while enabling fast charge-discharge rates. The spherical shape allows for efficient ion transport pathways and reduces the distance for lithium insertion/extraction, thereby improving power characteristics without sacrificing packing density.
4Ease of manufacture
If conventional graphite materials are used, then the production process is simple, but the cycle characteristics and large-current load characteristics are poor
Solution Approach 1:
The invention changes key parameters of the graphite material including specific surface area (0.5-2.0 m²/g), particle shape (spherical with aspect ratio 1:1), and crystalline structure (controlled Lc and La values). These parameter changes result in superior cycle characteristics and large-current load characteristics while maintaining a commercially viable production process using controlled carbonization of hydrocarbon materials.
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 method achieves high-energy density, high coulombic efficiency, and excellent cycle characteristics for lithium-ion battery electrodes while maintaining or exceeding the performance of conventional materials.
Implementation Method 1
graphitizing the pulverized carbon raw material
Implementation Method 2
heated from 300 to 1200°C under an inert atmosphere
Data Source
Figure 1
Figure 2
AI summary
A carbon raw material such as a green coke in which loss on heat when it is heated from 300 to 1000 °C under an inert atmosphere is no less than 5 % by mass and no more than 20 % by mass is pulverized and then the pulverized carbon raw material is graphitized to obtain a graphite material suitable for a carbon material for anode in a lithium-ion secondary battery or the like that enables to make electrodes having a high-energy density and a large-current load characteristic since it has a small specific surface area and a small average particle diameter while maintaining high beginning efficiency and a high discharge capacity in the first round of charging and discharging. And an electrode for batteries are obtained using the graphite material.