Positive Electrode Slurry Binder for Adhesion and Processability
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Solution Overview
Problem
Traditional binders like PVDF exhibit poor compatibility and weak adhesive force with electrode active materials, leading to stability and processability issues in lithium ion battery positive electrodes.
Innovation Solution
A polymer binder comprising structural units derived from monomers with cyano, amide, and ester groups is used, enhancing adhesive force and stability by improving dipole interactions and electrolyte absorption, while controlling molecular weight for optimal dispersibility and processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional binder PVDF is used, then the binder provides basic binding function, but the adhesive force with electrode active material is weak and compatibility is poor
Solution Approach 1:
The patent uses a composite binder system comprising polyacrylonitrile (PAN) as the primary binder and carboxymethyl cellulose (CMC) as a secondary binder. This composite approach combines the strong adhesive properties of PAN with the good compatibility and processability of CMC, resolving the contradiction between adhesive force and compatibility. The synergistic effect of these two materials provides both strong bonding to active materials and good slurry processability.
Solution Approach 2:
The patent optimizes the molecular weight parameters of the binder materials. Specifically, it uses PAN with weight average molecular weight of 100,000-500,000 and CMC with degree of substitution 0.4-0.7 and viscosity 5-500 mPa·s. By controlling these parameters, the binder achieves optimal balance between adhesive force, compatibility with active materials, and slurry processability.
2Stability of the object's composition
If traditional binder PVDF is used, then the binder provides structural support, but the stability during coating is poor and processability is difficult
Solution Approach 1:
The composite binder system of PAN and CMC provides both stability and processability. PAN contributes to structural stability and adhesion, while CMC provides excellent slurry rheology and coating stability. This combination eliminates the instability and processability difficulties associated with PVDF alone.
Solution Approach 2:
The patent specifies optimal parameter ranges for the binder components: PAN with weight average molecular weight of 100,000-500,000 and CMC with degree of substitution 0.4-0.7 and viscosity 5-500 mPa·s. These parameter optimizations ensure the slurry maintains stable composition during coating while remaining easy to process and apply.
3Strength
If polymer A with high molecular weight is used, then the adhesive force increases, but the cyclic internal resistance growth increases
Solution Approach 1:
The patent precisely controls the molecular weight parameter of polyacrylonitrile to be in the range of 100,000-500,000. This optimization ensures sufficient adhesive force for binding active materials while maintaining low cyclic internal resistance growth. The molecular weight is high enough to provide strong adhesion but not so high as to cause excessive resistance during cycling.
4Stability of the object's composition
If polymer A with high molecular weight is used, then the stability and adhesive force improve, but the slurry viscosity increases reducing processability
Solution Approach 1:
The composite binder system combines high molecular weight PAN (100,000-500,000) for stability and adhesion with CMC (viscosity 5-500 mPa·s) for processability. The CMC component acts as a viscosity modifier and dispersant, ensuring the slurry remains processable even with the higher molecular weight PAN providing stability.
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 new binder improves the stability and processability of the positive electrode slurry, increases adhesive force, and reduces cyclic internal resistance growth, ensuring better electrode performance and manufacturing efficiency.
Implementation Method 1
due to the dipole interaction between the cyano group and the electronegativity of the positive electrode current collector, the polymer A has a strong adhesion on the current collector
Implementation Method 2
the ester-containing functional group has a certain ability to absorb and maintain the electrolyte solution, which can solve the problem of poor ion conductivity of the traditional binder
Data Source
AI summary
Provided is a positive electrode slurry, a secondary battery, a battery module, a battery pack and a power consuming device. The positive electrode slurry comprises a positive electrode active substance, a conductive agent and a binder, wherein the binder comprises a polymer A, and the polymer A comprises a structural unit derived from a monomer containing a cyano group, a structural unit derived from a monomer containing an amide group, and a structure unit derived from a monomer containing an ester group. In the present invention, the polymer A is used as the binder of the positive electrode slurry, such that the stability and processability of the positive electrode slurry are improved, and the adhesive force of the positive electrode plate is increased.