Spherical Graphite Electrode Pore Structure
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Solution Overview
Problem
Current graphite materials for lithium ion secondary batteries face challenges in achieving high energy density, ultra-long cycle characteristics, and large current load capabilities, especially for large batteries, while maintaining economic efficiency and safety.
Innovation Solution
A graphite material with specific pore structures, including diameters of 15 nm to 200 nm, circularity degrees of 0.75 to 1.0, and major axis/minor axis ratios of 1.0 to 1.5, along with optimized total and accumulated pore volumes, specific surface areas, and interplanar spacing, is developed to enhance lithium ion diffusion and electrode performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If natural graphite is used as electrode material, then cost is reduced, but alignment occurs in one direction causing electrode expansion only in that direction which degrades performance
Solution Approach 1:
The patent applies spheroidality by granulating natural graphite into spherical shapes. This spherical morphology prevents directional alignment during electrode formation, allowing uniform expansion in all directions during charging, thereby resolving the contradiction between cost-effectiveness and performance reliability.
2Reliability
If natural graphite is granulated into spherical shape, then alignment problem is reduced, but surface activity increases causing large gas generation during initial charging which decreases initial efficiency
Solution Approach 1:
The patent introduces porous artificial graphite materials with controlled pore structures (孔径15nm至200nm) to coat or combine with spherical natural graphite. The porous structure provides缓冲 space for volume changes during lithium insertion/extraction, reducing surface activity and gas generation while maintaining good cycle characteristics.
3Reliability
If artificial graphite is used, then cost is relatively low, but crystalline needle-shaped coke aligns in scale shape causing similar performance issues
Solution Approach 1:
The patent transforms needle-shaped artificial graphite into spherical particles through granulation and spheroidization processes. This shape transformation prevents scale-like alignment during electrode formation, ensuring uniform electrochemical performance while maintaining the cost advantages of artificial graphite.
Solution Approach 2:
The patent introduces controlled porous structures into artificial graphite materials, creating interconnected pore networks that prevent dense scale formation and improve electrolyte penetration, thereby enhancing electrochemical performance while maintaining spherical morphology.
4Speed
If graphite material with high porosity is used, then rapid charge and discharge is achieved, but structural stability may be compromised
Solution Approach 1:
The patent creates composite structures combining spherical natural graphite cores with porous artificial graphite shells, or integrates porous structures within a graphitic matrix. This composite approach provides rapid lithium ion transport pathways through pores while the graphitic structure maintains structural stability during cycling.
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 material improves lithium ion diffusion, maintaining high capacity, coulomb efficiency, and cycle characteristics, enabling fast charge and discharge while ensuring economic efficiency and mass productivity with improved safety.
Implementation Method 1
improves lithium ion diffusion
Data Source
AI summary
A graphite material having pores which, when 200 rectangular regions of 6 μm×8 μm are randomly selected in a surface image of the graphite material observed by a scanning electron microscope, in the surface of the graphite material appearing in the regions, a pore appearing on the surface and having an aperture in a shape having a diameter of 15 nm to 200 nm, a circularity degree of 0.75 to 1.0 and a major axis/minor axis ratio of 1.0 to 1.5 is visible in two regions or more. Also disclosed is a carbon material for battery electrodes, a paste for electrodes, an electrode and a lithium ion secondary battery including the graphite material.