Synthetic Graphite Anode Material for Low-Temperature Capacity Retention
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Solution Overview
Problem
Lithium ion batteries using graphite as a negative electrode material experience capacity degradation at low temperatures due to lithium metal deposition, which affects their performance in wide temperature ranges, particularly in industrial applications like automobiles and power storage systems.
Innovation Solution
A synthetic graphite material with specific properties, including a crystallite size of 4 to 30 nm, a surface area of 0.22 to 1.70 m2/cm3, oil absorption of 67 to 147 mL/100 g, and a Raman spectrum half width of 19 to 24 cm-1, is developed for use in negative electrodes, along with a production method involving coking treatment, pulverization, and heat treatment of raw material oil compositions containing gas oil and heavy oil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If graphite is used as a negative electrode material in lithium ion batteries, then the batteries can operate in a wide temperature range, but lithium metal deposition occurs at low temperatures (0°C or lower) causing capacity degradation
Solution Approach 1:
The invention changes the physical and chemical parameters of the graphite material, specifically controlling the crystallite size L(002) to be within 1-30 nm and the full width at half maximum (FWHM) of the (002) diffraction peak to be 2.8-4.5°. These parameter changes modify the graphite structure to suppress lithium metal deposition while maintaining wide temperature range operation.
Solution Approach 2:
The invention uses composite material characteristics by combining graphite with specific structural properties (controlled crystallite size and orientation). The synthetic graphite material has a specific composition and structure that integrates the benefits of graphite's wide temperature adaptability with modified properties that prevent lithium deposition at low temperatures.
2Reliability
If the crystallite size L(002) of synthetic graphite is reduced to suppress lithium metal deposition, then low temperature performance improves, but the manufacturing complexity increases
Solution Approach 1:
The invention specifies precise parameter ranges for crystallite size L(002) of 1-30 nm and FWHM of 2.8-4.5° that can be achieved through controlled heat treatment processes. By defining these specific parameter ranges, the invention makes the complex structural modification achievable through standardized industrial heat treatment procedures rather than requiring complex multi-step manufacturing 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 synthetic graphite material effectively suppresses discharge capacity degradation even at low temperatures, ensuring stable performance for lithium ion batteries in industrial applications by preventing lithium metal deposition and maintaining charge and discharge efficiency.
Implementation Method 1
the amount of lithium ions that can move between the positive electrode and the negative electrode decreases
Implementation Method 2
a size L (112) of a crystallite in a c-axis direction as calculated from a (112) diffraction line obtained by an X-ray wide angle diffraction method is in a range of 4 to 30 nm
Implementation Method 3
a step of performing a coking treatment on a raw material oil composition by performing a delayed coking process to generate a coking coal composition
Implementation Method 4
a step of performing a heat treatment on the coking coal powder to obtain graphite powder
Data Source
AI summary
Provided is a synthetic graphite material, in which a size L (112) of a crystallite in a c-axis direction as calculated from a (112) diffraction line obtained by an X-ray wide angle diffraction method is in a range of 4 to 30 nm, a surface area based on a volume as calculated by a laser diffraction type particle size distribution measuring device is in a range of 0.22 to 1.70 m2/cm3, an oil absorption is in a range of 67 to 147 mL/100 g, and a half width ΔvG of a peak present in a wavelength range of 1580 cm−1±100 cm−1 is in a range of 19 to 24 cm−1 in Raman spectrum analysis using argon ion laser light having a wavelength of 514.5 nm.