Graphite Negative Electrode Composite Coating for Battery Cycle Stability
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Solution Overview
Problem
Lithium ion battery graphite negative electrode materials face issues with poor compatibility with electrolytes, material swelling, and poor adhesion during lithium deintercalation, leading to low cycle stability and high internal resistance, especially at high and low temperatures.
Innovation Solution
A composite material comprising graphite substrates with a surface-coating layer of amorphous carbon and carbon nanotubes or nanofibers grown in situ, formed through a combination of solid-phase and gas-phase processes, enhancing compatibility and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface-coating technology is used to construct core-shell structure, then electrochemical properties are improved, but contact between electrode material particles and current collector deteriorates
Solution Approach 1:
The invention uses a composite coating structure combining amorphous carbon and crystalline graphite carbon. The amorphous carbon layer provides good electrochemical performance and compatibility with electrolyte, while the crystalline graphite carbon layer provides mechanical strength and good contact with current collector. This composite material approach resolves the contradiction between electrochemical properties and contact strength.
2Reliability
If vapor deposition method is used to form surface-coating layer, then electrochemical properties are improved, but surface resistance increases
Solution Approach 1:
The dual-layer carbon coating structure combines amorphous carbon with good electrochemical activity and crystalline graphite carbon with high conductivity. The crystalline graphite carbon layer specifically addresses the high surface resistance issue by providing a conductive network, while maintaining the electrochemical benefits of the amorphous carbon layer.
3Productivity
If specific surface area is increased, then discharge capacity is improved, but SEI membrane stability deteriorates
Solution Approach 1:
The invention applies different carbon phases to different functional requirements: amorphous carbon provides high surface area for lithium ion insertion and high discharge capacity, while the crystalline graphite carbon layer provides structural stability and stable SEI membrane formation. This local differentiation of material properties resolves the contradiction between capacity and stability.
4Productivity
If cycle swelling occurs during charge-discharge process, then electrochemical activity is improved, but adhesion to current collector deteriorates
Solution Approach 1:
The composite carbon coating structure allows the amorphous carbon layer to provide electrochemical activity and lithium ion insertion sites, while the crystalline graphite carbon layer provides mechanical stability and strong adhesion to the current collector. The combination prevents cycle swelling while maintaining high electrochemical activity.
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 improves the rate performance and cycle stability of lithium ion batteries, achieving high first charge-discharge efficiency and capacity retention, with the composite material demonstrating excellent performance at both high and low temperatures.
Implementation Method 1
The surface-coating layer is amorphous carbon formed by carbonization of a carbon material precursor
Implementation Method 2
The carbon nanotubes and/or carbon nanofibers are conductive carbon nanotubes and/or carbon nanofibers formed on the surface of the surface-coating layers by vapor deposition method
Data Source
AI summary
A lithium ion battery graphite negative electrode material and preparation method thereof. The lithium ion battery graphite negative electrode material is a composite material including graphite substrates, surface coating layers coated on the graphite substrates and carbon nanotubes and/or carbon nanofibers grown in situ on the surface of the surface coating layers. The preparation method thereof includes, in solid phase or liquid phase circumstance, the coated carbon material precursor forms the surface coating layer of amorphous carbon by carbonization, and then carbon nanotubes and/or carbon nanofibers having high conductive performance are formed on the surface of the surface coating layers by vapor deposition. This coating mode of the combination of solid phase with gas phase or of liquid phase and gas phase makes the amorphous carbon formed on the surface of the graphite substrates more uniform and dense. The lithium ion battery graphite negative electrode material has properties of high charging-discharging efficiency at first time and excellent cycle stability at either high or low temperatures. The charging-discharging efficiency at first time is up to more than 95%, and the capacity retention after 528 cycles is more than 92%.