Graphite Negative Electrode Kinetic Balance
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Solution Overview
Problem
Current negative electrode active materials in secondary batteries face challenges such as rapid degradation due to unbalanced kinetic properties between artificial and natural graphite, leading to poor life characteristics and performance, especially with increased temperature and volumetric expansion during charge/discharge.
Innovation Solution
A negative electrode active material comprising a combination of artificial graphite with a large particle diameter and natural graphite with a small particle diameter, both coated with amorphous carbon, in a specific ratio and amount, to achieve kinetic balance and improved charge transfer resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If natural graphite is used as negative electrode active material to increase capacity, then the amount of accessible lithium ions per unit area is increased, but rate characteristics are degraded and life characteristics are poor due to large volumetric expansion during charge/discharge
Solution Approach 1:
The patent changes the particle size parameter of natural graphite from large to small (average particle diameter of 3-15 μm, preferably 5-10 μm). This parameter change reduces volumetric expansion during charge/discharge while maintaining high lithium ion capacity, thereby improving both rate characteristics and life characteristics without sacrificing the quantity of accessible lithium ions
2Stability of the object's composition
If artificial graphite is used as negative electrode active material, then it is graphitized through powder graphitization, but it has no pores therein and shows poor rolling characteristics during the manufacture of an electrode
Solution Approach 1:
The patent introduces pores into specific regions of the artificial graphite structure during the graphitization process. This creates local quality differences where certain areas maintain graphitic stability while other areas contain pores that improve rolling characteristics during electrode manufacture, resolving the contradiction between structural stability and manufacturability
3Stability of the object's composition
If artificial graphite is used as negative electrode active material, then it is graphitized through powder graphitization, but it has a small surface area and increases the charge transfer resistance of lithium ions
Solution Approach 1:
The patent utilizes porous artificial graphite with controlled pore structures. The pores increase the internal surface area available for lithium ion charge transfer while maintaining the graphitized structure for stability. This resolves the contradiction by providing both graphitic stability and enhanced charge transfer characteristics through the porous architecture
4Quantity of substance
If a method for manufacturing an electrode by blending natural graphite with artificial graphite is used, then both materials are combined, but their kinetic properties are different and they provide unbalanced kinetic properties in a negative electrode of a battery
Solution Approach 1:
The patent optimizes the particle size parameter of natural graphite to 3-15 μm (preferably 5-10 μm) to match the kinetic properties of artificial graphite. This parameter adjustment creates balanced kinetic characteristics between the two materials, enabling them to work synergistically rather than creating unbalanced kinetic properties
Solution Approach 2:
The patent creates a composite negative electrode active material consisting of natural graphite and artificial graphite in specific ratios (natural graphite: 30-70 wt%, artificial graphite: 30-70 wt%). This composite structure combines the high capacity of natural graphite with the good kinetic properties of artificial graphite, achieving both high capacity and kinetic balance through proper material composition
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 enhances high-rate charging performance, reduces charge transfer and liquid diffusion resistance, and improves life characteristics by maintaining kinetic balance and inhibiting exfoliation, resulting in a secondary battery with high capacity and stability.
Implementation Method 1
each of the artificial graphite having a large particle diameter and the natural graphite having a small particle diameter is further provided with a coating layer containing amorphous carbon
Implementation Method 2
When applying graphite to design a lithium secondary battery, a degree of volumetric expansion caused by a structural change of graphite depending on a charging degree should be considered
Data Source
AI summary
Disclosed is a negative electrode active material including artificial graphite having a large particle diameter and natural graphite having a small particle diameter, wherein the average particle diameter ratio of the small particle and the large particle is 1:1.5-1:5. A secondary battery including the negative electrode active material is also disclosed.