Li-Ion Battery Binder Copolymer Reducing Internal Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional binder compositions for lithium ion secondary batteries fail to adequately inhibit reduction in life characteristics and internal resistance, leading to suboptimal performance in terms of cycle characteristics and rate capabilities.
Innovation Solution
A binder composition comprising a copolymer with specific percentage contents of ethylenically unsaturated carboxylic acid and a copolymerizable compound, having a degree of swelling in electrolyte solution of less than 120 mass%, is used, along with additional polymers to enhance adherence and conductivity, thereby reducing internal resistance and improving life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binder compositions are used, then electrode structure is maintained, but internal resistance is not sufficiently reduced and life characteristics deteriorate
Solution Approach 1:
The patent uses a composite binder system comprising polyacrylic acid and polyvinylidene fluoride in specific proportions (0.1-5 mass% and 95-99.9 mass% respectively). This composite material combines the high resistance to expansion/contraction of polyacrylic acid with the excellent electrical conductivity and structural stability of polyvinylidene fluoride, thereby simultaneously improving life characteristics and reducing internal resistance
Solution Approach 2:
The patent optimizes the composition parameters of the binder system, specifically controlling the content of polyacrylic acid at 0.1-5 mass% and polyvinylidene fluoride at 95-99.9 mass%. This parameter optimization ensures sufficient adhesion and expansion resistance while maintaining low internal resistance and high ionic conductivity
2Strength
If binder compositions with high swelling rate are used, then close adherence is improved, but electrode structure stability deteriorates
Solution Approach 1:
The patent applies different functional materials in specific locations and proportions within the binder system. Polyacrylic acid (0.1-5 mass%) provides localized adhesion and expansion resistance at the electrode active material interface, while polyvinylidene fluoride (95-99.9 mass%) provides overall structural stability and conductivity throughout the binder matrix
Solution Approach 2:
The patent uses polyvinylidene fluoride as an intermediary material that mediates between the adhesive requirements and structural stability requirements. It provides sufficient close adherence through its binding properties while simultaneously maintaining electrode structure stability through its dimensional stability and low swelling characteristics
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 reduces internal resistance and enhances the life characteristics of lithium ion secondary batteries by maintaining electrode structure integrity and improving lithium ion conductivity.
Implementation Method 1
a degree of swelling in electrolyte solution of less than 120 mass%
Implementation Method 2
improving lithium ion conductivity
Data Source
AI summary
Provided is a binder composition for lithium ion secondary battery electrode-use that reduces internal resistance of a lithium ion secondary battery while also providing the lithium ion secondary battery with excellent life characteristics. The binder composition contains a copolymer X and a solvent. The copolymer X is obtained from a monomer composition X that contains at least 20.0 mass % and no greater than 75.0 mass % of an ethylenically unsaturated carboxylic acid compound (A) composed of either or both of an ethylenically unsaturated carboxylic acid and an ethylenically unsaturated carboxylic acid salt, and at least 20.0 mass % and no greater than 75.0 mass % of a copolymerizable compound (B) that has an ethylenically unsaturated bond and a solubility of at least 7 g in 100 g of water at 20° C. The copolymer X has a degree of swelling in electrolysis solution of less than 120 mass %.