Graphite Powder Coating for Lithium-Ion Battery Electrode Expansion
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in achieving high capacity, long cycle characteristics, and large current load capabilities due to limitations in graphite electrode materials, including natural and artificial graphite, which suffer from low initial charge-discharge efficiency, high electrode expansion, and poor cycle retention.
Innovation Solution
A graphite powder with specific properties, including scale-like particles, a carbon coating layer, and a production method involving graphitization at high temperatures and oxidation treatment, is developed to enhance electrode density, charge-discharge efficiency, and cycle retention, while minimizing electrode expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If natural graphite is used as negative electrode active material, then cost is reduced, but initial charge-discharge efficiency is low and cycle characteristics are poor
Solution Approach 1:
The invention uses a composite structure consisting of natural graphite particles with a carbon coating layer. The natural graphite provides cost advantage and basic electrochemical performance, while the carbon coating layer addresses the issues of low initial charge-discharge efficiency and poor cycle characteristics by providing a stable interface and preventing electrolyte decomposition.
Solution Approach 2:
The carbon coating layer is applied specifically on the surface of natural graphite particles, creating a localized modification. This allows the bulk natural graphite to maintain its cost advantage while the surface layer provides the necessary stability and efficiency improvements for good cycle characteristics.
2Stability of the object's composition
If natural graphite is granulated and formed into spherical shape, then electrode expansion is reduced, but particles align due to crushing and initial charge-discharge efficiency remains low
Solution Approach 1:
The spherical natural graphite particles are combined with a carbon coating layer to form a composite structure. This composite approach maintains the spherical shape benefits (reduced expansion) while adding the carbon layer to improve initial charge-discharge efficiency by providing stable lithium ion insertion/extraction sites.
3Reliability
If artificial graphite is used as negative electrode active material, then cycle characteristics are improved, but discharge capacity is lower
Solution Approach 1:
The invention applies a carbon coating layer with specific properties (amorphous or graphitic structure, controlled thickness) on the surface of natural graphite particles. This localized modification enhances cycle characteristics without significantly reducing discharge capacity, as the coating is optimized to balance stability and capacity retention.
4Quantity of substance
If needle-shaped coke is used for artificial graphite production, then discharge capacity is high, but particles align in scale shape and orientation occurs in electrode
Solution Approach 1:
Instead of using needle-shaped coke that tends to align in scale shape, the invention uses spherical natural graphite particles as the base material. This inverts the approach by starting with particles that naturally resist alignment and then adding a carbon coating layer to achieve the desired performance, thereby avoiding the orientation problem while maintaining high discharge capacity.
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 graphite powder improves the lithium ion battery's capacity, initial charge-discharge efficiency, and cycle retention, achieving high electrode density and rapid charging/discharging capabilities with reduced electrode expansion during charging and discharging.
Implementation Method 1
a production method involving graphitization at high temperatures
Implementation Method 2
oxidation treatment
Data Source
AI summary
A graphite powder, preferably including scale-like particles, which satisfies the following formulae (1) and (2), wherein e(0.5) represents the initial charge-discharge efficiency of a coin cell fabricated from an electrode (work electrode) produced by compressing an electrode material employing graphite powder as an active material under a pressure of 0.5 t/cm2, a lithium metal counter electrode, a separator and an electrolytic solution; and e(3) represents the initial charge-discharge efficiency of a coin cell fabricated from an electrode (work electrode) produced by compressing an electrode material employing graphite powder as an active material under a pressure of 3 t/cm2, a lithium metal counter electrode, a separator and an electrolytic solution:e(3)(%)−e(0.5)(%)≥1, formula (1):e(3)(%)>85. formula (2):Also disclosed is a method of producing the graphite powder; a graphite material for a battery electrode; an electrode for a lithium ion; and a lithium-ion secondary battery.