LiFePO4 Cathode Slurry Composition for Dispersion and Adhesion
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Solution Overview
Problem
Conventional slurry compositions for non-aqueous secondary battery positive electrodes face challenges in dispersibility, adhesiveness, and water shedding ability of the formed positive electrode mixed material layer.
Innovation Solution
A slurry composition containing carbon coating layer-covered olivine-type lithium iron phosphate particles with a specific weak acid group content and a polymer with an acidic group-containing monomer unit in a specific proportion, which enhances dispersibility, adhesiveness, and water shedding ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a water-soluble polymer with high molecular weight is used as a binder, then adhesiveness and flexibility are improved, but dispersibility deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the polymer by specifying it as a water-soluble polymer containing carboxylic acid groups with a specific molecular weight range (100,000 to 500,000). This parameter optimization allows the polymer to maintain both good dispersibility in the slurry and sufficient adhesiveness in the formed electrode, resolving the contradiction between these two properties.
2Reliability
If the positive electrode mixed material layer is dried to remove water, then internal resistance is reduced, but water shedding ability becomes insufficient
Solution Approach 1:
The water-soluble polymer acts as an intermediary substance that facilitates water removal during drying while maintaining electrode integrity. The polymer's hydrophilic nature allows it to interact with water molecules, enabling efficient water shedding from the electrode structure, which in turn reduces internal resistance and improves battery reliability.
3Manufacturing precision
If the slurry composition is optimized for adhesiveness, then close adherence between electrode layer and current collector improves, but dispersibility of the slurry deteriorates
Solution Approach 1:
The patent optimizes the molecular weight parameter of the water-soluble polymer to fall within the range of 100,000 to 500,000. This specific parameter range enables the polymer to provide sufficient adhesion between the positive electrode mixed material layer and current collector while maintaining good dispersibility of the slurry composition during the coating process.
Data Source
AI summary
Provided is a slurry composition for a non-aqueous secondary battery positive electrode that has excellent dispersibility and that can cause a positive electrode mixed material layer to display excellent adhesiveness and water shedding ability. The slurry composition for a non-aqueous secondary battery positive electrode contains carbon coating layer-covered olivine-type lithium iron phosphate particles in which surfaces of olivine-type lithium iron phosphate particles are at least partially covered by a carbon coating layer and a polymer X including an acidic group-containing monomer unit in a proportion of not less than 3 mass% and not more than 40 mass%. Surfaces of the carbon coating layer-covered olivine-type lithium iron phosphate particles have a weak acid group content of not less than 5 µmol/g and not more than 15 µmol/g.