Raw Coke Composition for Li-Ion Battery Negative Electrode
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Solution Overview
Problem
The high crystallinity of graphite carbon materials used in lithium ion secondary batteries limits the diffusion of solvated lithium ions, resulting in inadequate high-speed charge-discharge characteristics, particularly for applications in hybrid vehicles.
Innovation Solution
A method for producing a raw coke composition as a negative electrode material, involving a stock oil composition with specific heavy oils undergoing hydrodesulfurization and fluidized catalytic cracking, followed by coking treatment to achieve a carbon material with optimized crystallite size and lattice constants, graphitized at 2800°C to enhance lithium ion diffusion channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphite carbon material with high crystallinity is used as negative electrode material, then energy density per unit volume is improved, but high-speed charge-discharge characteristics deteriorate due to limited lithium ion diffusion
Solution Approach 1:
The invention creates local quality differences within the graphite crystal structure by controlling the orientation and arrangement of crystallites. By adjusting the stacking direction and creating specific crystallographic orientations during the coking process, the patent enables preferential lithium ion diffusion pathways while maintaining overall high crystallinity. This local structural optimization allows simultaneous achievement of high energy density and fast charge-discharge performance.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the coking temperature (400-600°C), pressure (300-800 kPa), and stock oil composition to achieve the desired crystallite size and lattice constant ratios. By optimizing these parameters, the invention produces graphite with specific crystal structure characteristics (La(110)/ao(110) ≤ 1500 and Lc(002)/co(002) ≤ 180) that enable both high energy density and fast lithium ion diffusion.
2Quantity of substance
If graphite structure with regular hexagonal mesh is used, then energy density is improved, but lithium ion diffusion channels are limited
Solution Approach 1:
The invention introduces dimensional diversity by creating multi-oriented crystallite arrangements rather than uniform single-direction stacking. By controlling the formation of crystallites with different orientation directions during coking, the patent generates three-dimensional diffusion pathways for lithium ions while maintaining the hexagonal mesh structure. This dimensional approach enables lithium ions to access multiple intercalation sites simultaneously, enhancing diffusion capacity without compromising energy density.
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
This approach stabilizes the production of a carbon material with improved high-speed charge-discharge characteristics, achieving higher charge capacity and faster charging capabilities for lithium ion secondary batteries.
Implementation Method 1
needle coke is produced by a process in which heavy oil is subjected to high-temperature treatment to cause thermal decomposition and polycondensation reaction
Implementation Method 2
thermal decomposition and polycondensation reaction, producing liquid crystal spheres referred to as the 'mesophase'
Implementation Method 3
when graphitizing is carried out at a temperature of 2800°C
Implementation Method 4
graphitizing in an inert gas atmosphere at a temperature of 2800°C
Implementation Method 5
when the bulk mesophase undergoes polycondensation to carbonization and solidification
Implementation Method 6
polycondensation to carbonization and solidification
Data Source
AI summary
In the raw coke composition of the invention, as the starting material for a negative electrode material of a lithium ion secondary battery, the ratio of the crystallite size Lc(002) and lattice constant co(002) (Lc(002)/co(002)) on the 002 face is no greater than 180, and the ratio of the crystallite size La(110) and the lattice constant ao(110) (La(110)/ao(110)) on the 110 face is no greater than 1500, as determined by X-ray diffraction upon graphitizing in an inert gas atmosphere at a temperature of 2800°C.