Spherical Graphite Anode Coating for Stable High-Rate 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 controlling particle expansion and contraction during charging and discharging, leading to unstable structures and reduced charge/discharge characteristics due to irreversible reactions with the electrolyte.

Innovation Solution

A mechanochemical reaction is employed to coat graphite byproduct particles with composite materials like silicon, tin, antimony, aluminum, or germanium, followed by spheroidization and amorphous carbon coating to form gaps and improve stability, utilizing a dry preparation method.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If spherical graphite particles are granulated without gaps between flaky graphite fragments on the surface, then particle structure is formed, but charge/discharge characteristics are reduced due to limited electrolyte contact

Engineering Contradiction:

Improvecharge/discharge characteristicsVSAvoidparticle structure stability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The flaky graphite particles are segmented into smaller fragments during the high-energy ball milling process, creating gaps between the fragments on the particle surface. This segmentation allows electrolyte penetration while maintaining overall particle integrity, resolving the contradiction between structure stability and charge/discharge characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An amorphous carbon coating layer is applied as an intermediary between the flaky graphite fragments and the electrolyte. This coating layer facilitates controlled electrolyte contact and lithium ion transport while protecting the internal fragment structure, thereby improving charge/discharge characteristics without compromising structural stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Shape

If conventional granulation process is used to form spherical particles, then particle formation is achieved, but bonding force of flaky graphite fragments decreases leading to unstable structure

Engineering Contradiction:

Improvespherical particle formationVSAvoidbonding force of fragments

Core Design Contradiction:

ShapeVSStrength

Solution Approach 1:

The conventional mechanical granulation process is replaced with a mechanochemical approach using high-energy ball milling. This process not only forms spherical shapes but also creates strong bonding between fragments through mechanical activation and potential chemical interactions, thereby improving both shape formation and fragment bonding strength simultaneously.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The spherical graphite particles are designed as composite structures with flaky graphite fragments embedded in a matrix. The amorphous carbon coating acts as a binding matrix that holds the fragments together, providing both the desired spherical shape and enhanced bonding strength between fragments.

Inventive Principle:

Principle #40Composite materials

3Reliability

If gaps are formed between spherical particles to improve properties, then charge/discharge characteristics improve, but process complexity increases

Engineering Contradiction:

Improvehigh-rate charge/discharge characteristicsVSAvoidpreparation process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The particle formation process and gap creation process are merged into a single high-energy ball milling step. This mechanochemical process simultaneously forms spherical particles, creates gaps between fragments, and prepares the surface for subsequent coating, thereby improving charge/discharge characteristics without significantly increasing process complexity.

Inventive Principle:

Principle #5Merging (Combining)

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

This approach enhances high-rate charge/discharge characteristics and cycle life-span of secondary batteries by forming stable gaps between flaky graphite particles, improving the anode active material's performance.

Implementation Method 1

preparing coated particles by mixing the graphite byproduct particles with composite particles and performing a mechanochemical reaction thereon to coat the surface of the graphite byproduct particles with the composite particles

Methodology Applied

Scientific EffectMechanochemical reaction:

Implementation Method 2

spheroidizing the coated particles and coating the surface thereof with amorphous carbon to prepare spherical graphite

Methodology Applied

Scientific EffectSpheroidization:

Implementation Method 3

coating the surface thereof with amorphous carbon to prepare spherical graphite

Methodology Applied

Scientific EffectCoating with amorphous carbon: Deposition (physical)

Data Source

PatentUS20260038830A1Manufacturing method of anode active material and secondary battery comprising the same

Publication Date: 2026.02.05 FIC ADVANCED MATERIALS INC

AI summary

Provided is a method for preparing an anode active material and a secondary battery including the anode active material. The anode active material may be prepared by a method including the steps of: obtaining byproduct particles that have not been spheroidized in a step of pulverizing and spheroidizing flaky graphite particles; preparing coated particles by mixing the graphite byproduct particles with composite particles and performing a mechanochemical reaction thereon to coat the surface of the graphite byproduct particles with the composite particles; and spheroidizing the coated particles and coating the surface thereof with amorphous carbon to prepare spherical graphite.