Aqueous Cathode Slurry Binder Composition for Cycling Stability
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Solution Overview
Problem
Current methods for producing cathode slurries for lithium-ion batteries face challenges with binder materials, such as polyvinylidene fluoride (PVDF) requiring hazardous solvents and alternative binders like carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) offering poor adhesion and cycling stability, especially in high-voltage environments.
Innovation Solution
A method involving the use of a two-step process to create a cathode slurry by dispersing a binder composition A and cathode active material in an aqueous solvent, followed by adding a second binder composition B, utilizing copolymers with specific structural units to enhance dispersion and adhesion, thereby improving battery cycling stability and electrochemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVDF is used as binder material, then battery cycling stability is improved, but hazardous organic solvents are required
Solution Approach 1:
The invention changes the solvent parameter from organic (NMP) to aqueous, eliminating hazardous solvent requirements while maintaining binder performance through copolymer design with specific functional groups that enable water solubility and effective binding
Solution Approach 2:
The invention uses a composite binder system comprising copolymer P1 and copolymer P2 with specific functional units that combine the benefits of water solubility, adhesion, and cycling stability, replacing the single-component PVDF system
2Object-affected harmful factors
If water is used as solvent, then safety and environmental issues are improved, but adhesion capability and cycling stability deteriorate
Solution Approach 1:
The invention modifies the binder material parameters by designing copolymers with specific functional units (amide, hydroxyl, carboxyl, nitrile, ether, epoxy) that enable effective adhesion and cycling stability in aqueous environments, transforming water from a problematic solvent into a safe and effective medium
Solution Approach 2:
The copolymer structure acts as an intermediary that bridges the incompatibility between water and effective binding, using hydrophilic functional groups to ensure water solubility while maintaining adhesion capability through specific functional unit interactions with active material particles
3Stability of the object's composition
If SBR or CMC is used as binder, then water dispersibility is improved, but adhesion capability and cycling stability worsen
Solution Approach 1:
The invention creates a composite binder system with copolymer P1 and copolymer P2 that combines water dispersibility with enhanced adhesion and cycling stability, overcoming the limitations of single-component systems like SBR or CMC
Solution Approach 2:
The copolymer structure incorporates different functional units at specific positions to provide localized functions: water solubility through hydrophilic groups, adhesion through functional unit interactions, and cycling stability through structural design, with each unit contributing to specific performance aspects
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 ensures well-dispersed binder materials, reducing cathode defects and enhancing battery cycling stability, leading to improved electrochemical performance and safety in the manufacturing process.
Implementation Method 1
dispersing a binder composition A and a cathode active material in an aqueous solvent to form a first mixture
Implementation Method 2
wherein each of the structural unit (a1) and the structural unit (a2) is independently derived from a monomer containing an acid group; wherein each of the structural unit (b1) and the structural unit (b2) is independently derived from a monomer selected from the group consisting of an amide group-containing monomer, a hydroxyl group-containing monomer
Data Source
AI summary
The invention provides a method of preparing a cathode slurry for a secondary battery, comprising a binder material, comprising a copolymer P1 and a copolymer P2. Both copolymers each independently comprise a structural unit derived from a monomer containing an acid group; a structural unit derived from a monomer selected from the group consisting of an amide group-containing monomer, a hydroxyl group-containing monomer, and combinations thereof; and a structural unit derived from a monomer selected from the group consisting of a nitrile group-containing monomer, an ether group-containing monomer, an epoxy group-containing monomer, and combinations thereof. As a result of the chemical compositions of the respective copolymers and the method itself, the cathode slurry is well dispersed, and batteries made therefrom have good cycling stability.