Graft Copolymer Binder for Lithium Battery Separator Adhesion
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Solution Overview
Problem
Lithium batteries face challenges with adhesion issues due to the use of polyvinylidene fluoride-based polymers, which provide insufficient binding when used in small amounts and do not form durable coating layers against electrolyte impregnation and lithium ion migration, and existing binders fail to simultaneously adhere well to both porous substrates and inorganic oxide particles.
Innovation Solution
A binder composition incorporating a graft copolymer with a polyvinylidene fluoride-based backbone partially substituted with chlorine, bromine, or iodine, and a pendant chain with a hydrophilic repeating unit, which is applied between the porous substrate and inorganic oxide particles, enhancing adhesion through both hydrophilic and hydrophobic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If small amount of binder is used, then productivity is improved, but adhesion strength and durability deteriorate
Solution Approach 1:
The chemical composition parameters of the binder are optimized to achieve maximum adhesion efficiency. By incorporating specific functional groups (hydroxyl, carboxyl) in optimized ratios and molecular weight ranges, the binder achieves superior adhesion strength at lower concentrations, improving productivity without sacrificing durability.
Solution Approach 2:
The binder molecules are designed with multiple adhesive functional groups that create multiple bonding points per molecule, effectively amplifying the binding capability per unit mass. This molecular-level design allows small amounts of binder to achieve large total adhesion strength through cumulative bonding effects.
2Reliability
If coating layer is formed to prevent lithium ion migration, then reliability is improved, but adhesion durability against electrolyte impregnation deteriorates
Solution Approach 1:
The coating layer is designed with spatially differentiated properties: the binder composition is optimized to provide strong adhesion to the porous substrate while simultaneously providing lithium ion barrier functionality. Functional groups are positioned to create specific interaction zones that maintain adhesion durability even when exposed to electrolyte impregnation, while preventing lithium ion migration through the coating layer.
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 binder composition improves the adhesion between the porous substrate and inorganic oxide particles, leading to enhanced durability and extended lifetime characteristics of lithium batteries by maintaining binding strength and preventing lithium ion migration.
Implementation Method 1
a binder between the porous substrate and the inorganic oxide or between adjacent particles of the inorganic oxide, the binder including a graft copolymer
Implementation Method 2
the pendant chain including a hydrophilic repeating unit
Data Source
AI summary
A separator for a battery, a battery, and a method of preparing a graft copolymer for a binder, the separator including a porous substrate; a coating layer on at least one surface of the porous substrate, the coating layer including an inorganic oxide; and a binder between the porous substrate and the inorganic oxide or between adjacent particles of the inorganic oxide, the binder including a graft copolymer, wherein the graft copolymer has a backbone of a polyvinylidene fluoride-based polymer or a polyvinylidene fluoride-based copolymer, and a pendant chain grafted to the backbone, the pendant chain including a hydrophilic repeating unit, and fluorine atoms in the backbone of the graft copolymer are partially substituted with at least one of chlorine, bromine, or iodine.