Binder Composition for Secondary Battery Adhesion and Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face issues with electrode peeling and increased resistance due to insufficient adhesion between active materials and the current collector, leading to deteriorated electrochemical performance and shortened cycle lifespan.
Innovation Solution
A binder composition for secondary batteries incorporating a copolymer with an alkali metal ion, which enhances adhesion and reduces electrical resistance, comprising a combination of conjugated diene-based and acryl-based copolymers with specific particle sizes and weight ratios to maintain stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an excess amount of binder is used to enhance adhesion between current collector and active material, then adhesion is improved, but capacity and conductivity of electrode are reduced
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by incorporating specific functional groups (carboxyl, hydroxyl, amine) and controlling the molecular weight distribution. This allows achieving high adhesion with reduced binder quantity by enhancing the binding efficiency per unit mass through functional group interactions with active material surfaces.
Solution Approach 2:
The binder is formulated as a composite system combining multiple polymer components with complementary properties. This composite structure provides both strong adhesion through functional groups and maintains conductivity through conductive filler incorporation, eliminating the need for excessive binder quantity.
2Strength
If an excess amount of binder is used to enhance adhesion between current collector and active material, then adhesion is improved, but conductivity of electrode is reduced
Solution Approach 1:
The binder composition is designed with local quality differentiation: functional groups are concentrated at the binder-active material interface to maximize adhesion, while conductive fillers are distributed throughout the binder matrix to maintain bulk conductivity. This spatial differentiation allows low binder quantity to suffice for both adhesion and conductivity functions.
Solution Approach 2:
Conductive fillers act as intermediary components that bridge the electrical connection between active material particles. This intermediary conductive network compensates for the reduced binder quantity, maintaining electrode conductivity while allowing the binder to focus primarily on adhesion functions with minimal quantity required.
3Quantity of substance
If insufficient adhesion is present, then binder quantity is reduced, but electrode peeling occurs during drying and pressing processes
Solution Approach 1:
The invention changes the adhesive parameters of the binder by incorporating high-density functional groups (carboxyl, hydroxyl, amine) that form strong chemical interactions with active material surfaces. This enhanced binding efficiency per unit mass provides sufficient adhesion strength to prevent electrode peeling during processing with reduced binder quantity.
4Quantity of substance
If insufficient adhesion is present, then binder quantity is reduced, but contact resistance between electrode material and current collector increases
Solution Approach 1:
The binder's chemical composition parameters are optimized with high concentrations of functional groups that form strong interfacial bonds with both current collector and active material. This enhanced interfacial adhesion ensures low contact resistance is maintained even with reduced binder quantity by maximizing the effectiveness of each binder molecule at the contact interface.
5Quantity of substance
If negative active material undergoes volumetric change during charging and discharging, then discharge capacity is improved, but separation from current collector occurs and cycle lifespan is shortened
Solution Approach 1:
The binder forms a flexible binding matrix that can accommodate the volumetric expansion and contraction of negative active material during charging and discharging cycles. This flexible binding structure maintains continuous contact between active material and current collector despite volume changes, preventing separation and maintaining cycle lifespan while preserving high discharge capacity.
Solution Approach 2:
The binder's mechanical properties are optimized through molecular weight control and functional group selection to provide both flexibility for volume accommodation and sufficient adhesion strength. This parameter optimization allows the binder to dynamically adapt to volume changes without losing adhesion, preventing separation during cycling while maintaining capacity.
6Quantity of substance
If silicon or tin is used to increase discharge capacity, then discharge capacity is improved, but volumetric change is greatly increased causing separation and resistance increase
Solution Approach 1:
The binder forms a flexible binding network that accommodates the large volumetric changes of silicon or tin during lithium insertion/extraction. This flexible structure maintains continuous mechanical contact despite significant volume expansion and contraction, preventing separation and maintaining adhesion strength even with high-capacity materials that undergo extreme volume changes.
Solution Approach 2:
The binder's mechanical and chemical parameters are optimized to provide enhanced flexibility and adhesion strength simultaneously. This allows the binder to withstand the large volumetric stresses of silicon or tin while maintaining strong bonding, preventing separation and resistance increase even with these high-capacity but high-volume-change materials.
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 significantly improves adhesion and electrochemical performance, reducing electrode defects and maintaining stable battery performance over cycles, while optimizing particle size and composition to prevent swelling and resistance issues.
Implementation Method 1
a binder including a copolymer which comprises a certain amount of an alkali metal ion
Implementation Method 2
exhibits low resistance, and thus may enhance battery electrochemical performance
Data Source
AI summary
The present invention relates to a binder composition for a secondary battery, including: a copolymer having a functional group; and an alkali metal ion bound to the functional group of the copolymer or with which a constituent element of the functional group is substituted. The binder composition exhibits enhanced adhesive strength and also exhibits low resistance due to the alkali metal ion included in the copolymer, and thus may exhibit more stable electrochemical performance.