Particulate Polymer Binder for Lithium-Ion Battery Low-Temperature Adhesion
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in improving adhesiveness between electrode members in electrolytic solutions, particularly at low temperatures, with existing binders and adhesive layers increasing internal resistance and not adequately enhancing low temperature output properties.
Innovation Solution
A particulate polymer with specific ion conductivity and tensile strength ranges, incorporating a core-shell structure, (meth)acrylic acid ester and (meth)acrylonitrile monomer units, and aromatic vinyl monomers, is used as a binder to enhance adhesiveness and low temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a binder with good adhesiveness is employed to increase adhesiveness between members in electrolytic solution, then adhesiveness is improved, but low temperature output property is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by incorporating specific monomer units (acrylic acid, methacrylic acid, itaconic acid, or maleic acid) in controlled amounts (1-50 wt%). This compositional parameter change enables the binder to achieve both high adhesiveness and improved low temperature output properties by adjusting the molecular structure and electrochemical characteristics of the binder polymer
Solution Approach 2:
The patent creates a composite binder system by combining multiple monomer units in specific ratios. The binder comprises a polymer formed from (meth)acrylic acid ester monomer units and carboxylic acid-containing monomer units, creating a composite material that synergistically provides both adhesive functionality and low temperature electrochemical performance
2Strength
If an adhesive layer is provided between members to increase adhesiveness, then adhesiveness is improved, but internal resistance increases, resulting in insufficient low temperature output property
Solution Approach 1:
The patent merges the adhesive function and the electrochemically active function into a single component. The binder itself serves as both the adhesive agent holding electrode particles together and as an electrochemically active material that facilitates ion transport. This eliminates the need for separate adhesive layers that would increase internal resistance
Solution Approach 2:
The binder polymer performs multiple functions simultaneously: it provides mechanical adhesion between electrode members, maintains structural integrity in electrolytic solution, and enables efficient ion transport at low temperatures. This multi-functionality is achieved through the specific copolymer structure containing both adhesive functional groups and ion-conductive carboxylic acid groups
Data Source
AI summary
A particulate polymer for a binder of a lithium ion secondary battery, wherein ion conductivity of a film formed by the particulate polymer after being immersed in an electrolytic solution at 60° C. for 72 hours is 1×10−5 S/cm to 1×103 S/cm, and tensile strength of the film is 500 N/cm2 to 4000 N/cm2.