Coal Tar Pitch Coating for Graphite in Water-Based Electrode Production
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Solution Overview
Problem
Current methods for creating coal tar pitch dispersions for Li-ion battery electrodes face challenges in using aromatic organic solvents, which are environmentally unfriendly and require additional steps for solvent recovery, and existing solutions often require surfactants or chemical alteration of the pitch, complicating the process and increasing costs.
Innovation Solution
Aqueous or non-aromatic aliphatic solvents are used to create a coal tar pitch dispersion with specific ratios of coal tar pitch and dispersant, allowing for the coating of graphite particles without the need for aromatic solvents, surfactants, or chemical alteration, facilitating a more environmentally friendly and efficient process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aromatic organic solvents are used to create coal tar pitch dispersion, then the pitch disperses easily and coating process is simplified, but the process becomes environmentally unfriendly and requires additional solvent recovery steps
Solution Approach 1:
The patent changes the fundamental parameter of solvent type from aromatic organic solvent to aqueous solvent. This parameter change transforms the dispersion system from oil-based to water-based, eliminating environmental harm while maintaining dispersion functionality through careful formulation of the aqueous system with appropriate pH and ionic strength control.
Solution Approach 2:
The patent introduces an intermediary agent (dispersant or surfactant) that mediates between the hydrophobic coal tar pitch and the hydrophilic aqueous solvent. This intermediary reduces interfacial tension and enables stable dispersion of pitch particles in water without requiring aromatic solvents, thus resolving the contradiction between ease of manufacture and environmental harm.
2Object-affected harmful factors
If surfactants or chemical alteration are used to enable pitch dispersion in aqueous solvents, then environmental friendliness is improved, but the process complexity and cost increase
Solution Approach 1:
The patent applies self-service by utilizing the natural surface properties of coal tar pitch particles and the inherent dispersing capability of properly formulated aqueous solutions. The system self-organizes into a stable dispersion through controlled aggregation of pitch particles, eliminating the need for additional surfactants or chemical modification steps, thus maintaining environmental friendliness while reducing process complexity.
Solution Approach 2:
The patent changes key parameters of the aqueous solution (pH, ionic strength, temperature) to optimize the natural dispersing behavior of coal tar pitch. By adjusting these parameters, the system achieves stable dispersion without requiring complex surfactant formulations or chemical alteration processes, thereby reducing overall process complexity while maintaining environmental benefits.
3Reliability
If coal tar pitch is coated on graphite particles using traditional methods, then electrode performance is achieved, but battery longevity is reduced due to contamination and degradation
Solution Approach 1:
The patent applies a thin film coating of coal tar pitch on graphite particles that acts as a protective shell. This flexible coating layer prevents direct contact between the electrolyte and graphite surface, blocking contamination and degradation pathways while maintaining the electrical conductivity and electrochemical performance necessary for battery operation, thus extending battery longevity.
Solution Approach 2:
The patent converts the naturally hydrophobic and chemically reactive properties of coal tar pitch, which are typically considered drawbacks, into beneficial protective features. The pitch coating forms a stable, chemically inert barrier that protects graphite from electrolyte degradation and SEI layer formation, transforming potential harm into extended battery life while maintaining performance.
4Productivity
If aromatic solvents are used for pitch dispersion, then coating efficiency is improved, but additional solvent capture and storage steps are required
Solution Approach 1:
The patent uses an intermediary aqueous solvent system that eliminates the need for complex solvent recovery infrastructure. Water-based dispersions can be directly applied and the water evaporates naturally or through simple heating, removing the time-consuming solvent capture and storage steps required for aromatic solvents while maintaining coating efficiency through optimized dispersion 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 coated graphite particles that enhance the longevity and efficiency of Li-ion batteries by forming a protective barrier against contamination and degradation, with improved charge capacity and reduced irreversible capacity loss, while being more environmentally friendly and cost-effective.
Implementation Method 1
A dispersion of coal tar pitch is disclosed, as well as methods of making such dispersion
Implementation Method 2
an amount of dispersant, such as 60% by weight of the composition or less, preferably 15% by weight of the composition or less
Implementation Method 3
Coal tar pitch is highly aromatic in chemical composition so it will not readily react with the electrolyte solution of the battery, and thus can form an effective protective barrier for the graphite from contamination and degradation
Implementation Method 4
The thickness of this layer increases as the battery ages, mostly on the graphite electrode. The SEI will grow even if the battery is not used. Coulombic efficiency, the ratio of the discharge capacity to charge capacity of the battery in the same cycle, in the first charging cycle of Li-ion batteries is less than desired. This is a result of the formation of the SEI layer along with other undesirable byproducts of use which lower the capacity of the battery
Data Source
AI summary
A dispersion, methods of making the same, applications of the dispersion to graphitic material and the resulting coated particles are disclosed. The dispersion includes ≤55% wt. coal tar pitch (softening point 100° C.-195° C.), ≤60% wt. dispersant, and the balance a non-aromatic solvent such as water or alcohol. Pitch particles in the dispersion are preferably <10 μm with a distribution of D50<15 μm. The pitch particles are micronized, such as by dry and/or wet milling with the dispersant and aqueous solvent to achieve the desired pitch particle size and distribution. This aqueous dispersion may be mixed with natural or synthetic graphitic material having a diameter of 5-20 μm in a ratio of 5%-30% pitch to graphite, dried and carbonized to form coated particles having a graphitic core at least partially coated by pitch particles.