Aqueous Extrusion of LiFePO4 Cathodes for High Active Material Loading
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Solution Overview
Problem
Current methods for preparing positive electrodes for lithium batteries, particularly those based on iron phosphate (LiFePO4), face challenges in achieving high active material content, minimizing porosity, and obtaining thin, homogeneous films without complexing steps, while incorporating lithium salts and maintaining electrochemical quality.
Innovation Solution
A process involving extrusion with a twin-screw extruder using an aqueous solvent mixture, which reduces viscosity and allows direct rolling or calendering on a current collector, enabling high active material content (>60%) and thin films (<65 μm) with low porosity, and allows lithium salt incorporation before assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If organic solvents are used to decrease viscosity and allow paste application, then the electrode can be manufactured, but the solvents must be eliminated by evaporation requiring special installations and energy consumption
Solution Approach 1:
The invention changes the solvent parameter from organic to aqueous, fundamentally altering the evaporation characteristics. Water-based solvents eliminate the need for special solvent recovery installations and reduce energy consumption compared to organic solvent evaporation, while still allowing paste application and subsequent drying
2Object-affected harmful factors
If aqueous solution is used to avoid pollution, then environmental impact is reduced, but lithium salts cannot be incorporated due to hygroscopic properties retaining water
Solution Approach 1:
The invention performs preliminary action by incorporating lithium salts into the aqueous paste formulation before electrode manufacturing. The controlled water content and rapid processing allow lithium salts to be integrated without excessive water retention, enabling both environmental benefits and functional requirements to be met
Solution Approach 2:
The invention changes the water content parameter to an optimized level that prevents excessive hygroscopic retention. By controlling the aqueous phase quantity and processing conditions, the patent enables lithium salt incorporation while maintaining the environmental advantages of water-based formulations
3Quantity of substance
If high active material content is achieved, then electrode performance is improved, but porosity increases making electrolyte incorporation difficult
Solution Approach 1:
The invention changes the porosity parameter through optimized paste formulation and processing conditions. By adjusting water content, polymer binder ratio, and extrusion parameters, the patent achieves high active material content while maintaining controlled porosity that allows subsequent electrolyte saturation without requiring complexing steps
4Length of stationary object
If thin films are produced, then battery assembly is simplified, but mechanical stresses during manufacturing increase
Solution Approach 1:
The invention changes the mechanical strength parameter through optimized polymer binder content and crosslinking. The enhanced matrix strength allows production of thin films while minimizing mechanical stresses and preventing current collector breakage during rolling or calendering operations
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 process achieves high active material content, low porosity, and improved electrochemical performance by minimizing mechanical and thermal stresses, reducing energy consumption, and maintaining polymer integrity, enabling wide film production without width alterations.
Implementation Method 1
the aqueous solvent being used to reduce the viscosity of the mixture used to manufacture the cathode
Implementation Method 2
the organic solvent is evaporated by heating
Data Source
Figure 1~2
AI summary
The present invention relates to a method for preparing a positive electrode that is made up of a composite material containing at least one active positive electrode material made of iron and phosphate and at least one water-soluble polymer having ionic conduction properties in the presence of a lithium salt, said method comprising at least one step for mixing ingredients of the composite material through extrusion so as to obtain an extruded composite material and wherein said extrusion step is carried out by means of a co-kneader or extruder in the presence of an aqueous solvent and at a temperature from 20° to 95° C. The invention also relates to the positive electrode obtained according to said method, to the use of said electrode for manufacturing a lithium battery, and to the lithium battery having such electrode built therein. The electrode is particularly characterized in that it contains a level of active material greater than 60 wt %.