Graphite Composite Anode Material for Lithium-Ion Battery
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Solution Overview
Problem
Conventional anode materials for lithium-ion secondary batteries face issues such as high production costs, complex manufacturing processes, and reduced cycle life due to dendritic crystal formation, surface modifications, and large specific surface areas leading to poor charge/discharge performance and capacity retention.
Innovation Solution
A method involving mixing natural and artificial graphite with high hard carbon content resins, followed by mist spray drying and carbonization heat treatment, and subsequent coating with a special resin to create a graphite composite with reduced specific surface area and improved charge/discharge performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pitch is coated onto the surface of graphite, then the specific surface area is reduced and first irreversibility is reduced, but the capacity is reduced with the number of times of charges and discharges
Solution Approach 1:
The patent uses a composite coating material consisting of polyacrylonitrile resin and carboxymethyl cellulose sodium salt in a specific weight ratio (1:0.05 to 1:0.5). This composite material combines the benefits of reduced first irreversibility from the polyacrylonitrile resin with the protective and capacity-retaining properties of carboxymethyl cellulose sodium salt, thereby improving cycle life while maintaining low first irreversibility.
Solution Approach 2:
The patent optimizes the weight ratio of polyacrylonitrile resin to carboxymethyl cellulose sodium salt, as well as the coating amount and drying conditions, to achieve the best balance between first irreversibility and cycle life. By adjusting these parameters, the coating provides both low first charge/discharge loss and excellent capacity retention over multiple cycles.
2Reliability
If ethanol or equivalent solvent is used for dissolving resin of high hard carbon content to coat graphite, then the first irreversibility is reduced, but the specific surface area becomes too large causing graphite particles to stick together
Solution Approach 1:
The patent uses water as an intermediary solvent instead of ethanol or other organic solvents. The carboxymethyl cellulose sodium salt acts as a dispersing agent that prevents graphite particles from sticking together while allowing the polyacrylonitrile resin to form a uniform coating. This approach maintains low first irreversibility without increasing specific surface area or causing particle aggregation.
Solution Approach 2:
The patent changes the solvent system from organic solvents to an aqueous system with carboxymethyl cellulose sodium salt. This parameter change fundamentally alters the coating process to prevent particle aggregation while maintaining effective coating formation, thereby reducing first irreversibility without increasing specific surface area.
3Ease of manufacture
If natural graphite is used as anode material, then the production cost is reduced, but a greater irreversible capacity occurs at the first cycle
Solution Approach 1:
The patent applies a preliminary coating treatment to natural graphite particles before battery assembly. The coating of polyacrylonitrile resin and carboxymethyl cellulose sodium salt is applied in advance to the natural graphite surface, which prevents direct exposure of the graphite to the electrolyte and reduces first-cycle irreversible capacity. This allows the use of cost-effective natural graphite while achieving acceptable first irreversibility.
Solution Approach 2:
The patent creates a composite structure where natural graphite particles are coated with a composite material of polyacrylonitrile resin and carboxymethyl cellulose sodium salt. This composite coating provides both cost-effectiveness (by using natural graphite) and performance improvement (by reducing first irreversibility through the optimized coating formulation).
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 results in a stable anode material with enhanced charge/discharge performance, reduced irreversible capacity, and improved cycle life, addressing the limitations of existing carbon-based anode materials.
Implementation Method 1
processing the mixture by a mist spray drying process
Implementation Method 2
carbonization heat treatment
Data Source
AI summary
In an anode material of a lithium-ion secondary battery and its preparation method, a natural graphite, an artificial graphite or both are mixed to form a graphite powder, and the graphite powder is mixed with a resin of a high hard carbon content and processed by a mist spray drying process, and finally added or coated with a special resin material after a carburizing heat treatment takes place to prepare a graphite composite of the anode material of the lithium-ion secondary battery and achieve a smaller surface area of an anode graphite composite of the battery and extended cycle life and capacity.