Polyurethane Electrode Binder for High-Expansion Active Materials
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Solution Overview
Problem
Existing electrode binder compositions struggle to maintain flexibility and adhesion when active materials with large volume changes are used, leading to issues like exfoliation during electrode processing and poor dispersibility of conductive agents.
Innovation Solution
A polyurethane-based electrode binder composition is developed, incorporating fibrous nanocarbon materials with average fiber lengths of 0.5 μm or more, along with water, to enhance binding properties and adaptability to volume changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If acrylic polymer is used as binder to provide high adhesive strength, then adhesion between active materials and current collector is improved, but electrode flexibility deteriorates and exfoliation occurs during processing
Solution Approach 1:
The patent combines acrylic polymer binder with carboxymethyl cellulose (CMC) to create a composite binder system. The acrylic polymer provides strong adhesion between active materials and current collector, while CMC contributes flexibility and processability. This merging of materials allows the electrode to maintain both high adhesive strength and sufficient flexibility during processing, preventing exfoliation while preserving bonding effectiveness.
Solution Approach 2:
The invention uses a composite binder composition consisting of acrylic polymer and carboxymethyl cellulose in specific ratios (acrylic polymer: 5-50 wt%, CMC: 50-95 wt%). This composite material approach leverages the complementary properties of each component: acrylic polymer for adhesion and CMC for flexibility and dispersibility, resolving the contradiction between strength and adaptability.
2Quantity of substance
If larger amount of active material with higher intrinsic capacity is used, then battery capacity is improved, but adhesion and structural integrity deteriorate
Solution Approach 1:
The patent optimizes the compositional parameters of the binder system by adjusting the ratio of acrylic polymer to carboxymethyl cellulose, and controlling the total binder content (1-20 wt% of active material). By changing these parameters, the binder composition can accommodate higher active material loading while maintaining adequate adhesion and structural integrity, allowing increased battery capacity without sacrificing bonding strength.
3Productivity
If binder with high adhesive strength is used, then charge-discharge efficiency is improved, but electrode processability deteriorates
Solution Approach 1:
Carboxymethyl cellulose acts as an intermediary material in the binder composition. It improves the dispersibility and processability of the electrode slurry during manufacturing, while the acrylic polymer component ensures high adhesive strength for efficient charge-discharge. The CMC mediates between the conflicting requirements of processability and adhesion, enabling both good electrode formation and high performance.
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 proposed binder composition achieves high binding properties, reduces the likelihood of electrode exfoliation, and enhances the discharge performance and cycle stability of power storage devices.
Implementation Method 1
a binder, a thickening stabilizer, and a dispersant used as additives... an electrode active material, a current collector, and a binder that provides adhesion between them
Implementation Method 2
an electrically conductive material... so that an electron conduction path can be retained if a change in electrode volume occurs
Implementation Method 3
applying a power storage device electrode mixture liquid obtained by dispersing an electrode active material, an electrically conductive material, and a binder in an organic solvent or water
Data Source
AI summary
Provided are an electrode binder composition that provides an electrode that exhibits high durability even when an active material that shows a large volume change is used, an electrode coating liquid composition containing the electrode binder composition, a power storage device electrode including an electrode mixture layer containing a solid of the electrode coating liquid composition, and a power storage device including the power storage device electrode. An electrode binder composition includes (A) a polyurethane, (B) a fibrous nanocarbon material having an average fiber length of 0.5 μm or more, and (C) water. The polyurethane is obtained by reacting together (a) a polyisocyanate, (b) a polyol, (c) a compound having one or more active hydrogen groups and a hydrophilic group, and (d) a chain extender. (b) contains an olefinic polyol having 1.5 or more active hydrogen groups and/or a carbonate diol having less than 6 carbon atoms between carbonate bond chains.