Artificial Graphite Crystallite Control for Li-Ion Battery Energy Density
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Solution Overview
Problem
The high crystallinity of graphite materials used in lithium ion secondary batteries hinders efficient diffusion of solvated lithium ions, limiting charge-discharge rates, which is a barrier for applications in hybrid vehicles and other high-demand devices.
Innovation Solution
The development of artificial graphite with specific structural characteristics, including crystallite sizes and interlayer distances, achieved through a production method involving coking, calcining, and heat treatment of stock oil compositions, enhances both energy density and charge-discharge rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If graphite carbon materials with high crystallinity are used as negative electrode materials, then energy density per unit volume is improved, but charge-discharge rate deteriorates
Solution Approach 1:
The invention changes the structural parameters of graphite by controlling crystallite size (La and Lc dimensions) and interlayer distance (d002) through specific heat treatment processes. By adjusting these parameters - particularly maintaining La within 100-250 nm and Lc within 50-150 nm ranges - the material achieves optimal balance between energy density and ion diffusion rate
Solution Approach 2:
The invention creates local structural variations within the graphite material by controlling the distribution and size of crystallites. The specific crystallite dimensions create localized regions that facilitate lithium ion diffusion while maintaining overall high crystallinity for energy density
2Quantity of substance
If high crystallinity graphite structure is used, then energy density is improved, but lithium ion diffusion efficiency deteriorates
Solution Approach 1:
The invention optimizes the crystallite structural parameters La and Lc through controlled heat treatment. By maintaining specific size ranges (La: 100-250 nm, Lc: 50-150 nm), the material achieves sufficient crystallinity for high energy density while creating adequate diffusion pathways for lithium ions
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 artificial graphite exhibits superior charge-discharge rates and energy density per unit volume, making it suitable for applications in hybrid vehicles, plug-in hybrid vehicles, electric vehicles, and other devices requiring rapid charging, while maintaining high energy storage capacity.
Implementation Method 1
a first step of coking treatment of a stock oil composition obtained by combining two or more different stock oils selected from among vacuum residue oil, FCC heavy oil and desulfurized heavy oil produced in the petroleum refining process
Implementation Method 2
a second step of calcining the treated product obtained from the first step at a temperature of 1200-1500°C
Implementation Method 3
a third step of heat treating the treated product obtained from the second step at a temperature of 2300-2600°C
Data Source
AI summary
The artificial graphite for the negative electrode of a lithium ion secondary battery according to the invention has a crystallite size Lc of 60-120 nm in the c-axial direction according to X-ray diffraction, and a crystallite size Lc of 150 nm or greater when subjected to graphitizing at a temperature of 3000°C in an inert gas atmosphere.