Binder Composition for Battery Electrodes
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Solution Overview
Problem
Existing binders for electrical storage devices, such as polyvinylidene fluoride (PVDF), form crosslinked products under basic conditions, inhibiting adhesiveness and causing surface defects like crater formation, leading to reduced yield and cycle life characteristics.
Innovation Solution
A binder composition comprising specific repeating units derived from aromatic vinyl compounds, unsaturated carboxylic acid esters, and other additives, along with an emulsifier, to enhance adhesiveness, ion conductivity, and improve cycle life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVDF or sulfonated PVDF is used as a binder for positive electrode, then binding property and oxidation resistance are satisfactory, but environmental load increases and raw material supply stability deteriorates
Solution Approach 1:
The patent replaces PVDF with carboxymethyl cellulose (CMC), a biodegradable, environmentally friendly polymer derived from cellulose. CMC is water-soluble, non-toxic, and readily biodegradable, eliminating the environmental persistence issues associated with PVDF while maintaining binder functionality in the electrode structure
Solution Approach 2:
The patent modifies the chemical structure by introducing carboxymethyl groups onto the cellulose backbone, creating carboxymethyl cellulose with enhanced water solubility and binding characteristics. This chemical modification allows CMC to function effectively as a binder in aqueous electrolyte environments while maintaining environmental compatibility
2Strength
If crosslinked product is formed in the slurry under basic conditions, then binding ability may be enhanced, but adhesiveness is inhibited and surface defects occur
Solution Approach 1:
The patent removes the problematic crosslinking reaction step from the binder formulation process. By using CMC as a linear polymer without crosslinking functionality, the formulation eliminates the formation of crosslinked products that cause surface defects and adhesiveness inhibition, while still achieving adequate binding through hydrogen bonding and physical entanglement
Solution Approach 2:
The patent introduces a controlled amount of emulsifier as an intermediary substance that mediates between the binder and active material particles. The emulsifier prevents direct crosslinking reactions while maintaining stable dispersion and adhesion, acting as a protective intermediary that eliminates surface defects without compromising binding ability
3Stability of the object's composition
If emulsifier remains in the slurry, then dispersion stability may be improved, but crater formation occurs on coating film surface
Solution Approach 1:
The patent carefully controls the emulsifier concentration within a specific range (0.1-5 wt% relative to binder content) to optimize the balance between dispersion stability and surface quality. This parameter optimization ensures sufficient emulsifier for stable mixing while preventing excess emulsifier from causing crater formation during drying
Solution Approach 2:
The patent creates a composite binder system combining CMC with small amounts of emulsifier and optional additives like carboxylic acids or crosslinking agents. This composite formulation achieves synergistic effects where the emulsifier provides dispersion stability during processing, while the CMC matrix prevents surface defects and provides structural integrity
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 composition produces electrodes with improved surface state, adhesiveness, and ion conductivity, reducing internal resistance and enhancing the cycle life of electrical storage devices.
Implementation Method 1
a polymer that functions as a binder... a binding ability between the molecules of an active material and an adhesive ability between the active material and the current collector
Implementation Method 2
a crater is caused by bubble collapse on a surface of a coating film in some cases owing to an influence of an emulsifier or the like remaining in the slurry
Data Source
AI summary
Provided is a binder composition for an electrical storage device that can produce an electrical storage device electrode excellent in surface state, adhesiveness, and ion conductivity, and can improve the cycle life characteristics of an electrical storage device. The binder composition for an electrical storage device according to the present invention includes: a polymer (A); and 30 ppm to 30,000 ppm of an emulsifier (B) with respect to a total mass of the polymer (A). When a total of repeating units in the polymer (A) is defined as 100 mass%, the polymer (A) contains 1 mass% to 50 mass% of a repeating unit (a1) derived from an aromatic vinyl compound, and 20 mass% to 75 mass% of a repeating unit (a2) derived from an unsaturated carboxylic acid ester.