Water-Based Lithium Electrode Drying Process
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Solution Overview
Problem
Current methods for producing lithium-based electrochemical cell electrodes face challenges in being cost-effective and environmentally friendly, particularly in handling organic solvents and incorporating lithium salts, which are hygroscopic and difficult to dry, leading to residual water issues affecting cell capacity and cycling performance.
Innovation Solution
A process involving a water-based solution with a polyether polymer or copolymer, lithium salt, and electrochemically active material, using a water/organic solvent ratio of up to 50% organic solvent by volume, followed by drying under controlled temperature and nitrogen sweep to achieve an electrode thin sheet with less than 1000ppm residual water and low porosity, incorporating the electrolyte within the electrode matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If organic solvents are used to dissolve electrode materials and binders for coating, then the electrode mixture can be spread into thin layers with good flowability, but large quantities of solvent must be evaporated and recovered, increasing process complexity and environmental burden
Solution Approach 1:
The patent changes the fundamental parameter of solvent type from organic to aqueous. The electrode slurry uses water as the primary solvent instead of organic solvents, eliminating the need for complex organic solvent recovery systems while maintaining proper slurry flowability and coating characteristics through aqueous-based formulation
Solution Approach 2:
The patent employs a disposable aqueous slurry formulation that can be directly coated and dried without requiring expensive solvent recovery infrastructure. The water-based slurry is designed to be applied and then evaporated, with the water simply evaporating into the environment rather than requiring capture and recovery equipment
2Quantity of substance
If lithium salt is incorporated into the electrode mixture, then the electrolyte is already present in the electrode, but the hygroscopic nature of lithium salt makes it very difficult to dry the electrode after spreading, requiring extensive drying time
Solution Approach 1:
The patent employs an inert or controlled atmosphere during the drying process to prevent atmospheric moisture from being absorbed by the hygroscopic lithium salt. By conducting drying in a controlled environment with reduced humidity, the lithium salt does not absorb additional moisture from the air, significantly reducing the drying time required while still achieving the necessary water content reduction
Solution Approach 2:
The patent performs preliminary actions to minimize drying time by optimizing the slurry formulation and drying conditions before the actual drying process begins. This includes pre-heating the drying chamber, optimizing the slurry composition to facilitate faster water evaporation, and preparing the drying environment to prevent moisture reabsorption, thereby reducing the overall extensive drying time required
3Object-affected harmful factors
If water is used as solvent for electrode mixture, then the drying process becomes difficult due to hygroscopic lithium salt, but organic solvents require environmental protection installations
Solution Approach 1:
The patent uses an inert or controlled low-humidity atmosphere during the drying process to prevent the hygroscopic lithium salt from absorbing atmospheric moisture. This allows the use of water as a benign, environmentally friendly solvent while still achieving effective drying by preventing moisture reabsorption during the drying phase
Solution Approach 2:
The patent changes the drying environment parameters by controlling atmospheric humidity and temperature to create conditions favorable for water evaporation while preventing moisture absorption by the lithium salt. This enables the use of water as solvent without the environmental issues of organic solvents and without the excessive drying times that would otherwise be required
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
This method enables the production of a solid, flexible electrode with reduced porosity and minimal residual water, ensuring effective ionic transport and improved electrochemical cell performance while minimizing environmental impact by utilizing water as a solvent and incorporating the electrolyte within the electrode structure.
Implementation Method 1
a polyether polymer or copolymer soluble in water, at least one lithium salt
Implementation Method 2
drying the electrode thin film to obtain an electrode thin sheet having less than 1000ppm of residual water
Data Source
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AI summary
A process for making an electrode sheet for lithium electrochemical cells is disclosed. The process comprises the steps of : a) admixing a polyether polymer or copolymer soluble in water, at least one lithium salt, at least one electrochemically active material and water to form a water-based solution/suspension containing by weight at least 20% active electrode material, at least 5 % of a polyether polymer or copolymer, and at least 1.5 % lithium salt; b) coating the water-based solution/suspension in the form of an electrode thin film onto an electrode support; and, c) drying the electrode thin film to obtain an electrode thin sheet having less than 1000ppm of residual water. The electrode thin sheet thereby formed has less than 10% porosity after drying. The drying step is preferably carried out through a dryer/oven tunnel having incremental drying zones.