Conductive Coating for Battery Current Collector Adhesion
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Solution Overview
Problem
Conventional batteries and electrical double layer capacitors face issues with high internal resistance, poor adhesion between the current collector and active material layer, leading to unsatisfactory high-rate charge/discharge cycle characteristics and deterioration under long-term cycling and high-temperature conditions.
Innovation Solution
A conductive composition comprising a vinylsilane copolymer, polycarboxylic acid, and a conductive auxiliary is used to coat the current collector, forming a stable bonding with the active material layer, reducing internal resistance and enhancing adhesion, thereby improving cycle life and float life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional conductive coating layer is applied to the current collector, then the resistance at the interface between the metal current collector and the active material layer is reduced, but the adhesion force between the metal current collector and the active material layer remains unsatisfactory
Solution Approach 1:
The patent applies a composite coating layer comprising multiple components: polyvinylidene fluoride (PVdF) as binder, acetylene black as conductive auxiliary, and polyvinyl alcohol modified with silane coupling agent as adhesion promoter. This composite structure simultaneously provides electrical conductivity, mechanical adhesion, and chemical bonding capabilities, resolving the contradiction between reducing interface resistance and improving adhesion force.
Solution Approach 2:
The patent uses polyvinyl alcohol modified with silane coupling agent as an intermediary substance that chemically bonds to both the metal current collector surface (via silanol groups reacting with metal hydroxyl groups) and the PVdF binder matrix. This intermediary layer acts as a bridge that transfers and enhances adhesion forces while maintaining electrical conductivity through the conductive auxiliary network.
2Productivity
If the battery is subjected to long-term charge/discharge cycle test or high-temperature shelf test, then the initial performance is achieved, but the deterioration of battery characteristics cannot be satisfactorily prevented
Solution Approach 1:
The patent modifies the chemical and physical parameters of the coating layer by incorporating crosslinkable functional groups in the polyvinyl alcohol modified with silane coupling agent. Upon curing treatment, these groups form crosslinked networks that enhance the thermal and mechanical stability of the coating, preventing deterioration during long-term cycling and high-temperature storage while maintaining the electrical conductivity parameters necessary for high charge/discharge rates.
Solution Approach 2:
The patent applies a conductive coating layer with specifically designed composition and structure before the battery undergoes long-term cycling or high-temperature storage. The coating layer serves as a protective cushion that prevents direct contact and potential damage between the active material and current collector, while the crosslinked network structure provides beforehand resistance against thermal degradation and mechanical stress, cushioning against deterioration during extended operation.
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 conductive composition significantly enhances the adhesion properties between the current collector and active material layer, resulting in improved charge/discharge cycle characteristics, reduced internal resistance, and increased durability under long-term and high-temperature conditions.
Implementation Method 1
a silane coupling agent, which is capable of being chemically bonded to a hydroxyl group on the surface of a metal current collector
Implementation Method 2
the resistance between the metal current collector and the active material layer is so high
Data Source
Figure 1~2
Figure 3
AI summary
Provided are a conductive composition for coating a current collector of, e.g., a battery, which is advantageous in that the adhesion properties between, e.g., a battery current collector and an active material layer are increased to improve the battery characteristics, and, e.g., a battery using a battery current collector using the composition. A conductive composition for coating a current collector of, e.g., a battery, the composition comprising a vinylsilane copolymer, a polycarboxylic acid, and a conductive auxiliary, wherein the vinylsilane copolymer is represented by the following formula (1): wherein U represents a unit represented by the following formula (2): wherein X represents a single bond or a bonding chain excluding oxygen, each of R2 to R4 independently represents a group selected from the group consisting of -OR5 (wherein R5 represents a group selected from the group consisting of H, a C1-C6 alkyl group, and a group derived from a cation capable of constituting an electrolyte for, e.g., a. battery), a C1-C6 alkyl group, and a halogen group, and each of R21 to R23 independently represents H or a C1-C6 alkyl group, V represents a unit derived from a vinyl monomer having an active hydrogen group, m represents a number of from 1 to 10,000, and n represents a number of from 20 to 100,000, wherein the ratio of m to n (m/n) is 0.0001 to 1.