Graphite Composite Material 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 current load and long-term cycle characteristics while maintaining high energy density and discharge capacity, especially for large batteries such as those in electric vehicles.
Innovation Solution
A graphite composite material is developed, comprising particles with a specific internal structure of optical anisotropic and isotropic domains and voids, optimized through a detailed analysis using polarizing microscopy, which balances high energy density, long cycle life, and high current load characteristics. This composite material is mixed with high crystallinity artificial or natural graphite to enhance the battery's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If natural graphite is used as negative electrode material, then cost is reduced, but electrode expansion occurs in one direction during charging which degrades performance
Solution Approach 1:
The patent uses composite materials by combining natural graphite particles with artificial graphite coating layers. The natural graphite core provides cost advantages and high capacity, while the artificial graphite coating prevents harmful alignment and controls expansion behavior, resolving the contradiction between cost and performance reliability
Solution Approach 2:
The patent changes the physical and chemical parameters of the graphite surface through coating treatment. By controlling the coating thickness, composition, and structure, the electrode expansion behavior is modified to prevent one-directional alignment while maintaining the low cost benefit of natural graphite
2Reliability
If natural graphite is granulated into spherical shape, then alignment during electrode production is reduced, but surface activity increases causing large gas generation during initial charging which decreases initial efficiency and degrades cycle characteristic
Solution Approach 1:
The patent introduces an artificial graphite coating as an intermediary layer between the natural graphite core and the electrolyte. This coating layer mediates the surface activity, reducing excessive gas generation during initial charging while maintaining the beneficial spherical shape and cycle characteristics
Solution Approach 2:
The patent applies local quality modification by coating only the surface of natural graphite particles with artificial graphite. This localized treatment addresses the surface activity problem without altering the bulk properties and spherical shape that provide good cycle characteristics
3Quantity of substance
If artificial graphite with high crystallinity is used, then discharge capacity is improved, but large current load characteristics and long-term cycle characteristics are insufficient
Solution Approach 1:
The patent creates a composite structure combining high crystallinity artificial graphite with differently oriented crystalline domains. This composite approach maintains high discharge capacity from the crystalline structure while introducing structural features that improve large current load characteristics and long-term cycle stability
Solution Approach 2:
The patent applies local quality variation within the graphite structure by creating regions with different crystalline orientations and properties. High crystallinity regions provide high discharge capacity, while specific localized structures improve large current load characteristics and cycle life
4Ease of manufacture
If graphite particles are aligned in one direction during electrode formation, then manufacturing process is simplified, but electrode expansion in one direction during charging degrades performance
Solution Approach 1:
The patent uses composite materials where the artificial graphite coating layer has different mechanical and thermal expansion properties than the natural graphite core. This composite structure compensates for the one-directional expansion during charging, maintaining performance reliability while allowing simplified manufacturing processes
Solution Approach 2:
The patent applies the counterweight principle by using the artificial graphite coating layer to counterbalance the harmful one-directional expansion of the natural graphite core during charging. The coating layer's different expansion characteristics compensate for the core's expansion, preventing performance degradation
Data Source
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AI summary
The present invention provides a graphite composite material obtained by mixing graphite material 1 having diversity in the sizes of optical anisotropic structure and optical isotropic structure, the ratio thereof, and crystal direction, and graphite material 2 having a rhombohedron structure, which is different from graphite material 1 and has an average interplanar spacing d002 of plane (002) of 0.3354 nm to 0.3370 nm measured by the powder X-ray diffraction method and Lc of 100 nm or more. Use of the graphite composite 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.