Modified Graphite Self-Coating for Li-Ion Cycling Stability
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Solution Overview
Problem
Synthetic graphite used in lithium-ion secondary batteries has highly active surface defects that lead to side reactions with the electrolyte, resulting in the consumption of active lithium ions and reduced cycling performance and service life.
Innovation Solution
A method involving crushing coal-based needle coke, shaping, heat treatment, and graphitization to form a modified graphite with a self-coating layer, using the volatile matter in the needle coke as a coating agent to reduce surface roughness and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If synthetic graphite is used as negative electrode material, then cost and theoretical capacity are improved, but surface defects cause side reactions with electrolyte leading to consumption of active lithium ions and reduced cycling performance
Solution Approach 1:
The patent applies preliminary action by performing heat treatment on the synthetic graphite before it is used as electrode material. This pre-treatment process modifies the surface structure of the graphite particles, reducing surface defects and creating a more stable surface that resists side reactions with the electrolyte, thereby improving cycling performance while maintaining high capacity
Solution Approach 2:
The patent utilizes parameter changes by controlling the heat treatment temperature and duration to transform the surface properties of synthetic graphite. The heat treatment process changes the physical and chemical parameters of the graphite surface, such as reducing surface area and modifying surface chemistry, which reduces reactivity with electrolyte and improves battery cycling performance
2Ease of manufacture
If synthetic graphite with high active surface defects is used, then production cost is reduced, but side reactions with electrolyte increase leading to loss of active lithium ions
Solution Approach 1:
The patent applies preliminary action by performing heat treatment on the synthetic graphite before it is used as electrode material. This pre-treatment process modifies the surface structure of the graphite particles, reducing surface defects and creating a more stable surface that resists side reactions with the electrolyte, thereby improving cycling performance while maintaining high capacity
Solution Approach 2:
The patent converts the harmful effect of high surface area and surface defects into a benefit through heat treatment. The process transforms the reactive surface into a stable surface with reduced defect sites, turning what would normally be harmful (high reactivity) into beneficial (low reactivity with electrolyte), thereby reducing lithium ion loss while maintaining cost-effectiveness
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 modified graphite improves initial Coulombic efficiency and cycling performance by reducing surface defects and side reactions, enhancing the energy density and safety of secondary batteries.
Implementation Method 1
a heat treatment step: placing the material B in a reaction kettle for a heat treatment and then cooling same to room temperature to obtain a material C
Implementation Method 2
the volatile matter contained in the coal-based needle coke is escaped and enriched on the surface of the coal-based needle coke precursor, causing the surface of the coal-based needle coke precursor to be uniformly coated, i.e., self-coated before graphitization
Implementation Method 3
a graphitization step: placing the material C in a high-temperature graphitization furnace for high-temperature graphitization and then cooling same to room temperature to obtain a product, i.e., the modified graphite
Data Source
AI summary
A method for preparing a modified graphite includes performing crushing on coal-based needle coke to obtain a first material, performing shaping fine powder removal on the first material to obtain a second material, performing heat treatment on the second material in a reaction kettle and then cooling the second material after the heat treatment to room temperature to obtain a third material, and performing graphitization on the third material in a graphitization furnace and then cooling the third material after the graphitization to room temperature to obtain the modified graphite.