Polyalkyleneglycol Binder for Lithium-Ion Battery Adhesion
Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving excellent adhesion and ion permeability due to issues with the binder composition, particularly with polyalkyleneglycol groups causing hydrophilicity and interfering with emulsion polymerization, and the separator's thermal contraction hindering heat drying during electrode active material layer formation.
Innovation Solution
A binder composition with a copolymer containing an ethylenic unsaturated monomer having a polyalkyleneglycol group with an average number of repeating units of 3 or greater, along with other monomers like cycloalkyl acrylate and (meth)acrylic acid esters, is used to form a filler porous layer, enhancing adhesion and ion permeability while minimizing ion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyalkyleneglycol groups are incorporated into an aqueous copolymer to increase solid electrolyte ion permeability, then ion permeability is improved, but the copolymer formation becomes difficult and water removal is interfered with due to hydrophilicity
Solution Approach 1:
The patent changes the parameter of polyalkyleneglycol group length (n≥3) to achieve a balance between ion permeability and manufacturability. By specifying a minimum chain length, the patent optimizes the hydrophilicity to provide sufficient ion transport while reducing excessive water affinity that would interfere with polymerization and drying processes.
Solution Approach 2:
The patent creates a composite binder system combining polyalkyleneglycol-containing copolymer with other polymers (such as polyvinylidene fluoride, carboxymethyl cellulose, and styrene-butadiene rubber) to achieve both high ion permeability and good processability. The composite structure allows each component to contribute its strengths while compensating for individual weaknesses.
2Loss of substance
If the separator base material is heated for drying during electrode active material layer formation, then water removal is achieved, but the separator contracts due to thermal properties
Solution Approach 1:
The patent applies a binder composition containing the optimized copolymer to the separator surface before the drying step. This preliminary coating acts as a protective layer that allows subsequent low-temperature drying to proceed without causing significant separator contraction, as the binder system is designed to remove water effectively at lower temperatures.
Solution Approach 2:
The patent changes the drying temperature parameter from conventional high temperatures to low temperatures (below the separator's contraction point) by using a binder system that enables effective water removal at these reduced temperatures, thereby preventing thermal contraction of the separator.
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 significantly improves the adhesion and ion permeability of the battery, reducing shedding and cracking of the active material layer, and enhances long-term battery characteristics and safety by maintaining ion permeability and flexibility.
Implementation Method 1
because polyalkyleneglycol groups are hydrophilic
Implementation Method 2
the separator base material, which is typically a polyolefin microporous film, has the property of contracting when heated
Data Source
AI summary
A binder for an electricity storage device comprising a copolymer having an ethylenic unsaturated monomer having a polyalkyleneglycol group (P) as a monomer unit, wherein the average number of repeating units (n) of polyalkyleneglycol groups of the ethylenic unsaturated monomer having a polyalkyleneglycol group (P) is 3 or greater.