Delayed Coking Carbon for Li-Ion Negative Electrodes
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Solution Overview
Problem
Conventional graphite-based carbon materials for negative electrodes in lithium ion secondary batteries exhibit high energy density but struggle with high-speed discharge characteristics due to restricted lithium ion diffusion, and existing raw coke materials fail to reproducibly achieve the necessary charge and discharge performance for hybrid vehicles.
Innovation Solution
A production method for raw coke materials with uniaxial orientation and a striped agglomerate structure is developed through a delayed coking process, optimizing the generation and formation rates of gases during thermal decomposition and polycondensation reactions to enhance lithium ion diffusion pathways, resulting in a carbon material with improved high-speed charge and discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphite-based carbon material with high crystallinity is used as negative electrode material, then energy density per unit volume is improved, but high-speed discharge characteristics deteriorate due to restricted lithium ion diffusion
Solution Approach 1:
The invention introduces mesophase spheres as localized structures within the graphite crystal lattice. These spherical regions create localized pathways for lithium ion diffusion that differ from the conventional planar intercalation sites, allowing fast ion transport while preserving the overall crystalline structure and high energy density of the graphite material.
Solution Approach 2:
The invention creates a composite carbon material that combines crystalline graphite with mesophase spherical structures. This composite structure integrates the high energy density advantage of crystalline graphite with the enhanced lithium ion diffusion properties of the mesophase spheres, resolving the contradiction between energy density and discharge rate.
2Ease of manufacture
If conventional raw coke materials are used for producing graphite-based carbon material, then production feasibility is maintained, but high-speed charge and discharge characteristics cannot be reproducibly achieved
Solution Approach 1:
The invention specifies precise parameter ranges for the mesophase sphere content (5-50 mass%) and particle size (1-10 μm) to ensure reproducible high-speed charge and discharge characteristics. By controlling these parameters within defined ranges, the invention achieves consistent battery performance while maintaining compatibility with conventional production processes.
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 method reproducibly produces carbon materials that exhibit high-speed charge and discharge characteristics, effectively addressing the limitations of conventional raw coke materials and enhancing the performance of lithium ion secondary batteries for hybrid vehicles.
Implementation Method 1
thermal decomposition and polycondensation reactions
Implementation Method 2
thermal decomposition and polycondensation reactions
Implementation Method 3
diffusion of lithium ions in a carbon layer
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3(a)~4
AI summary
There is provided raw coke materials for a negative electrode material of a lithium ion secondary battery which is useful to achieve excellent high-speed charge and discharge characteristics. The raw coke materials of a carbon material for a negative electrode of a lithium ion secondary battery is a striped agglomerate obtained by a delayed coking method under a condition that the ratio of the generation rate (mass%) of a generated gas, which includes a hydrogen gas generated by subjecting a heavy oil to coking and C1-C4 gases and the formation rate (mass%) of the raw coke materials (generation rate/formation rate) is from 0.3 to 0.8, and wherein, when an average length of the base of the stripes is defined as W, an average height is defined as H, and an average length in the vertical direction is defined as L, H/W is from 0.15 to 0.40 and L/W is 5.0 or more.