Spheroidized Graphite Composite for Battery Cycle Stability
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Solution Overview
Problem
Lithium secondary batteries using composite active materials with graphite and lithium-ion combining materials face rapid capacity deterioration due to insufficient adhesion and delamination issues during charge-discharge cycles, leading to poor cycle characteristics.
Innovation Solution
A method involving mixing graphite with a specific surface area of 30 m2/g or more and a lithium-ion combining material, followed by spheroidization treatment using high-speed rotary impact pulverizers, to create a composite active material with enhanced adhesion and conductivity, maintaining the battery's conductive path and suppressing deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphite and battery active material are mixed and pulverized in high-speed air stream, then charge-discharge capacity is improved, but cycle characteristics deteriorate due to delamination and loss of electron conductivity
Solution Approach 1:
The battery active material is embedded within the graphite matrix structure, creating a nested configuration where the active material particles are surrounded and protected by graphite. This nesting prevents delamination during charge-discharge cycles while maintaining electrical conductivity pathways, resolving the contradiction between achieving high capacity and maintaining cycle stability.
Solution Approach 2:
The invention creates a composite material system combining graphite and battery active material (such as silicon, tin, or aluminum) with specific surface area characteristics. This composite structure leverages the high capacity of the active material while graphite provides structural stability and conductivity, preventing the delamination issues that occur in simple mixtures and thereby improving cycle characteristics.
2Strength
If specific surface area of graphite is increased to 30 m2/g or more, then adhesion between graphite and active material is improved, but manufacturing complexity increases
Solution Approach 1:
The invention specifies a particular parameter range for graphite surface area (30 m2/g or more) to optimize adhesion between graphite and battery active material. By controlling this physical parameter within the specified range, the patent achieves improved interfacial adhesion and electron conductivity without requiring complex manufacturing processes, as the high-surface-area graphite can be obtained through conventional expansion methods.
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 approach results in lithium secondary batteries with improved charge-discharge capacity, high-speed charge and discharge characteristics, and excellent cycle stability by ensuring strong interaction between graphite and the active material, preventing delamination and maintaining conductivity.
Implementation Method 1
a spheroidization step of subjecting the mixture to a spheroidization treatment
Implementation Method 2
high-speed rotary impact pulverizers
Implementation Method 3
insufficient adhesion between the battery active material and the graphite is a problem, and have found that the problem can be solved by the following constitution
Data Source
AI summary
The purpose of the present invention is to provide: a composite active material for lithium secondary batteries, which is capable of providing a lithium secondary battery that has large charge and discharge capacity, high-rate charge and discharge characteristics and good cycle characteristics at the same time; and a method for producing the composite active material for lithium secondary batteries. A method of producing a composite active material for lithium secondary batteries of the present invention comprises: a mixing step wherein graphite having a specific surface area of 30 m2/g or more and a battery active material that is capable of combining with lithium ions are mixed with each other, thereby obtaining a mixture; and a spheroidizing step wherein the mixture is subjected to a spheroidization treatment, thereby producing a generally spherical composite active material for lithium secondary batteries, said composite active material containing graphite and the battery active material that is capable of combining with lithium ions.