Spherical Graphite Coating for Stable Li-Ion Anode Cycling
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Solution Overview
Problem
Existing methods for preparing spherical graphite particles for anode active materials in lithium secondary batteries face limitations in charge/discharge characteristics and cycle life-span due to unstable structures and irreversible reactions with electrolytes, particularly when using graphite byproducts from pulverization processes.
Innovation Solution
A method involving isostatic pressing and mechanochemical reaction to coat graphite byproduct particles with composite materials and amorphous carbon, forming stable spherical graphite particles with improved bonding and uniform gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If spherical graphite particles are granulated without gaps between flaky graphite fragments on the surface, then particle density is improved, but charge/discharge characteristics are reduced due to limited electrolyte contact
Solution Approach 1:
The patent introduces a porous coating layer comprising amorphous carbon and crystalline graphite on the surface of spherical graphite particles. This porous structure provides gaps and channels that enable electrolyte penetration and contact with internal flaky graphite fragments, resolving the contradiction between maintaining particle density and enabling sufficient electrolyte access for high-rate charge/discharge performance
Solution Approach 2:
The patent creates a composite structure by coating spherical graphite particles with a combination of amorphous carbon and crystalline graphite materials. This composite coating layer provides both structural integrity and controlled porosity, allowing the particle to maintain density while enabling electrolyte access through the composite structure's inherent gaps and channels
2Ease of manufacture
If conventional granulation methods are used to prepare spherical graphite particles, then particle formation is simplified, but bonding force of flaky graphite fragments is reduced leading to structural instability
Solution Approach 1:
The patent introduces an intermediary coating layer of amorphous carbon and crystalline graphite that bonds to the surface of spherical graphite particles. This intermediary layer acts as a binding agent that strengthens the bonding between flaky graphite fragments without requiring complex granulation processes, maintaining ease of manufacture while improving structural strength
Solution Approach 2:
The patent changes the physical and chemical parameters of the particle surface by applying a coating layer with different material properties (amorphous carbon and crystalline graphite). This parameter change in surface composition and structure enhances the bonding force of flaky graphite fragments while maintaining a simple manufacturing process
3Duration of action of moving object
If repeated charging and discharging occur without effective control of particle expansion and contraction, then battery cycling continues, but excessive solid-electrolyte interphase film forms and swelling occurs
Solution Approach 1:
The patent applies a protective coating layer of amorphous carbon and crystalline graphite beforehand on the spherical graphite particles. This pre-applied coating acts as a cushioning layer that accommodates expansion and contraction during charging/discharging cycles, preventing direct contact between the electrolyte and the graphite surface that would otherwise lead to excessive solid-electrolyte interphase film formation and swelling
Solution Approach 2:
The patent introduces a flexible thin film coating composed of amorphous carbon and crystalline graphite on the particle surface. This flexible shell structure can dynamically adjust during battery cycling, expanding and contracting with the graphite particles while maintaining integrity, thereby preventing harmful side reactions and swelling that would limit battery duration
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
Enhances high-rate charge/discharge characteristics and cycle life-span of secondary batteries by stabilizing flaky graphite particles and utilizing graphite byproducts, resulting in improved charge/discharge efficiency and capacity retention.
Implementation Method 1
spheroidizing the coated particles by performing an isostatic pressing process thereon
Implementation Method 2
pulverizing the coated particles and coating the surface thereof with amorphous carbon
Data Source
AI summary
The present invention relates to a method for preparing an anode active material including the steps of: obtaining graphite byproduct particles that have not been spheroidized in a step of pulverizing and spheroidizing flaky graphite particles; preparing coated particles by liquid phase mixing the graphite byproduct particles with composite particles to coat the surface of the graphite byproduct particles with the composite particles; spheroidizing the coated particles by performing an isostatic pressing process thereon; and pulverizing the coated particles and coating the surface thereof with amorphous carbon to prepare spherical graphite.