Composite Binder for Negative Electrode Slurry
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Solution Overview
Problem
Secondary batteries face issues with insufficient dispersion of electrode active material and inadequate adhesion of the electrode active material layer to the collector, leading to poor high-temperature storage and low-temperature output properties.
Innovation Solution
A slurry for a negative electrode containing a combination of an electrode active material, a water-insoluble polymer with aliphatic conjugated diene and ethylenically unsaturated carboxylic acid monomer units, and a water-soluble polymer with ethylenically unsaturated carboxylic acid and sulfonic acid monomer units, applied at specific ratios to enhance dispersion stability and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binder compositions are used to produce electrodes, then the electrode can be manufactured with basic binding function, but the dispersion stability of electrode active material is insufficient and adhesion property with collector is inadequate
Solution Approach 1:
The invention uses a composite binder system combining water-insoluble polymer (A) and water-soluble polymer (B) in specific ratios. The water-insoluble polymer (A) containing aliphatic conjugated diene monomer units provides strong adhesion to the collector, while the water-soluble polymer (B) containing sulfonic acid group-containing monomer units improves dispersion stability of the electrode active material. This composite material approach resolves the contradiction by integrating two polymers with complementary functions.
Solution Approach 2:
The invention optimizes the molecular weight parameters of the polymers (water-insoluble polymer (A) with weight average molecular weight of 10,000 to 1,000,000 and water-soluble polymer (B) with weight average molecular weight of 1,000 to 100,000) and their composition ratios (0.1 to 10 parts by weight of polymer (A) and 0.01 to 5 parts by weight of polymer (B) relative to 100 parts by weight of electrode active material). These parameter changes enable simultaneous achievement of good adhesion and dispersion stability.
2Reliability
If conventional binder compositions are used, then manufacturing process can be simplified, but high-temperature storage property and low-temperature output property of secondary battery are poor
Solution Approach 1:
The composite binder system of water-insoluble polymer (A) and water-soluble polymer (B) with specific molecular weight ranges and composition ratios improves the thermal stability and electrochemical performance of the electrode. The water-insoluble polymer provides thermal stability for high-temperature storage, while the water-soluble polymer with sulfonic acid groups enhances low-temperature output properties by improving ion conductivity and electrolyte wetting.
Solution Approach 2:
By controlling the molecular weights and composition ratios of the two polymers, the invention optimizes the binder's performance across different temperature conditions without requiring complex multi-component systems. The specific parameter ranges enable the binder to maintain effectiveness from low-temperature discharge to high-temperature storage conditions.
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 solution results in improved adhesion of the electrode active material layer, enhancing the high-temperature storage and low-temperature output properties of secondary batteries.
Implementation Method 1
a water-soluble polymer (B), and wherein: the water-soluble polymer (B) contains 20 wt % to 60 wt % of an ethylenically unsaturated carboxylic acid monomer unit (b1)... a ratio (A)/(B) in parts by weight of the water-insoluble polymer (A) relative to the water-soluble polymer (B) is 80/20 to 95/5
Implementation Method 2
dispersion stability of the slurry for a negative electrode of a secondary battery
Implementation Method 3
the water-insoluble polymer (A) contains 20 wt % to 60 wt % of an aliphatic conjugated diene monomer unit (a1), 0.5 wt % to 10 wt % of an ethylenically unsaturated carboxylic acid monomer unit (a2)... adhesion property of an electrode active material layer with a collector
Data Source
AI summary
A composition containing an electrode active material, a water-insoluble polymer (A), and a water-soluble polymer (B), wherein: the water-insoluble polymer (A) contains 20 wt % to 60 wt % of an aliphatic conjugated diene monomer unit (a1), 0.5 wt % to 10 wt % of an ethylenically unsaturated carboxylic acid monomer unit (a2), and 30 wt % to 79.5 wt % of a unit (a3) of a monomer that is copolymerizable therewith; the water-soluble polymer (B) contains 20 wt % to 60 wt % of an ethylenically unsaturated carboxylic acid monomer unit (b1), 25 wt % to 78 wt % of a (meth)acrylic acid ester monomer unit (b2), and 2 wt % to 15 wt % of a unit (b3) of a sulfonic acid group-containing monomer that is copolymerizable therewith; and a ratio (A)/(B) of the water-insoluble polymer (A) relative to the water-soluble polymer (B) is 80/20 to 95/5.