Graphite Carbon Composite for Battery Electrodes
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Solution Overview
Problem
Conventional lithium ion secondary battery electrodes, particularly those using graphite, face challenges in achieving high energy density, long cycle characteristics, and large current load capabilities, especially for applications requiring ultralong-term cycle and high power, such as electric vehicles, due to limitations in the internal structure and alignment of graphite particles.
Innovation Solution
A graphite carbon composite material is developed, comprising particles with a specific internal structure characterized by a ratio of optical anisotropic, optical isotropic, and void areas, and a carbon material on the way to graphitization, which is mixed to enhance discharge capacity without compromising large current-input/output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If natural graphite is formed into a paste together with a binder and applied to a collector, then the electrode can be manufactured, but natural graphite aligns in one direction causing the electrode to expand only in one direction which degrades electrode performance
Solution Approach 1:
The patent applies spheroidality by granulating natural graphite into spherical particles. This spherical shape prevents directional alignment during electrode manufacturing, allowing uniform expansion in all directions during charging, thereby resolving the contradiction between ease of manufacture and electrode performance
Solution Approach 2:
The patent creates a composite material by coating artificial carbon on the surface of spherical natural graphite particles. This composite structure combines the advantages of natural graphite (low cost, high capacity) with artificial graphite (spherical shape, uniform expansion), solving both the manufacturing ease and performance reliability issues
2Reliability
If natural graphite is granulated and formed into a spherical shape, then alignment during electrode production is reduced, but the surface of natural graphite is active generating a large amount of gas during initial charging which decreases initial efficiency and degrades cycle characteristic
Solution Approach 1:
The patent introduces artificial carbon as an intermediary coating layer on the surface of natural graphite particles. This coating layer acts as a mediator that reduces the surface activity of natural graphite, suppressing gas generation during initial charging while maintaining the spherical shape and cycle characteristics
Solution Approach 2:
The composite structure of artificial carbon coating on natural graphite core creates a material that combines the low surface activity of artificial graphite with the high capacity and spherical morphology of natural graphite, simultaneously improving initial efficiency and cycle characteristic
3Power
If artificial graphite materials are used to achieve high capacity and large current characteristics, then mobile application requirements are met, but the cycle characteristic for ultralong-term periods required for large batteries cannot be achieved
Solution Approach 1:
The patent creates a composite material combining natural graphite and artificial carbon that synergistically delivers both large current characteristics and ultralong-term cycle stability, achieving performance suitable for large battery applications
Solution Approach 2:
The patent applies local quality by creating a core-shell structure where the natural graphite core provides high capacity and the artificial carbon shell provides structural stability and surface protection, with each layer optimized for its specific function to achieve both power and duration requirements
4Quantity of substance
If graphite particles are coated with artificial carbon to address high-capacity and low-current characteristics, then mobile application requirements are satisfied, but large current and ultralong-term cycle characteristics of large batteries cannot be satisfied
Solution Approach 1:
The patent optimizes the coating thickness and composition parameters of artificial carbon on natural graphite particles to achieve a balance between capacity retention and large current characteristics, while the spherical morphology parameters are controlled to ensure ultralong-term cycle stability
Data Source
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AI summary
The present invention provides a carbon material comprising a graphite material having diversity in the sizes of optical anisotropic structure and optical isotropic structure, the ratio thereof, and crystal direction, and a carbon material on the way to a graphitized structure of easily-graphitizable carbon. Use of the carbon material in the electrodes for the secondary battery can make the secondary battery be excellent in charge-discharge cycle characteristics and the large current load characteristics.