Crosslinked Polymer Binder for Lithium-Ion Battery Electrodes
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Solution Overview
Problem
Conventional aqueous binders for lithium-ion secondary batteries lack sufficient flex resistance and dispersion stability, particularly for high-rate and cycle characteristics required in vehicle-mounted applications, and existing solutions do not adequately address the detachment and exfoliation issues of electrode mixture layers during manufacturing processes.
Innovation Solution
A binder comprising a crosslinked polymer with ethylenically unsaturated carboxylic acid monomers and trimethylolpropane diallyl ether or trimethylolpropane triallyl ether, which provides enhanced binding ability and flexibility, improving the durability and uniformity of the electrode mixture layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional aqueous binders (SBR, CMC) are used for negative electrodes, then cost and environmental protection are improved, but binding ability and flex resistance are insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by introducing a crosslinked polymer with specific functional groups (carboxyl, hydroxyl, amine) and controlled crosslinking degree (0.1-10%). This parameter optimization enables the binder to maintain both environmental friendliness (aqueous-based) and superior mechanical properties (binding ability and flex resistance) required for high-rate battery applications
Solution Approach 2:
The patent creates a composite binder system combining crosslinked polymer chains with multiple functional groups that work synergistically. The crosslinked structure provides mechanical strength and flex resistance, while the functional groups enhance binding ability to active materials. This composite approach at the molecular level resolves the contradiction between environmental protection and performance
2Strength
If solvent-based binders (PVDF with NMP) are used for positive electrodes, then binding ability is improved, but environmental protection and cost are worsened
Solution Approach 1:
The patent substitutes the organic solvent NMP with water as the dispersion medium, replacing a harmful chemical system with an environmentally benign alternative. The crosslinked polymer binder maintains its binding ability in aqueous environment through its functional groups, effectively substituting the mechanism used by solvent-based binders while eliminating the environmental and cost disadvantages
3Reliability
If carbon-based active materials are used, then conductivity is improved, but wettability by aqueous media is poor, reducing dispersion stability
Solution Approach 1:
The crosslinked polymer binder acts as an intermediary substance between the hydrophobic carbon-based active materials and the hydrophilic aqueous medium. The polymer's amphiphilic character and functional groups enable it to adsorb onto carbon surfaces while maintaining compatibility with water, thereby mediating the interaction and achieving both good conductivity and dispersion stability
4Quantity of substance
If silicon-based active materials are used to increase capacity, then battery capacity is improved, but volume changes cause detachment and exfoliation, worsening cycle characteristics
Solution Approach 1:
The crosslinked polymer binder provides beforehand cushioning by creating a flexible, adherent matrix that accommodates the volume changes of silicon-based active materials during charging and discharging. The crosslinked structure's elasticity and strong binding ability prevent detachment and exfoliation before they can occur, cushioning the mechanical stress and maintaining electrode integrity throughout cycling
Solution Approach 2:
The patent optimizes the crosslinking degree parameter (0.1-10%) to achieve the right balance between rigidity and flexibility. This parameter control allows the binder to provide sufficient mechanical support while accommodating volume changes, resolving the contradiction between capacity and cycle characteristics
5Quantity of substance
If high capacity or high voltage active materials are used, then energy density is improved, but cycle characteristics deteriorate
Solution Approach 1:
The patent uses parameter changes in the binder composition (crosslinking degree, functional group content, molecular weight) to create a binder system that can handle the extreme conditions imposed by high capacity and high voltage active materials. The optimized parameters provide enhanced stability and adhesion that prevent degradation even under high stress conditions
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 achieves superior binding ability and flex resistance, resulting in electrodes with improved high-rate characteristics and durability, reducing detachment and exfoliation during charging and discharging, and enhancing manufacturing productivity.
Implementation Method 1
a binder having high binding ability and flex resistance
Implementation Method 2
a binder having high binding ability and flex resistance, and with which mixture layer failures do not occur
Data Source
AI summary
A binder for a nonaqueous electrolyte secondary battery electrode and use thereof are described. The binder contains a crosslinked polymer or salt thereof, the crosslinked polymer having an ethylenically unsaturated carboxylic acid and a crosslinkable monomer in constituent monomers thereof, or salt thereof, wherein the crosslinked polymer includes the ethylenically unsaturated carboxylic acid in an amount of 20 to 99.95 mass % of the total constituent monomers, and the crosslinked polymer includes at least one compound selected from the group made of trimethylolpropane diallyl ether and trimethylolpropane triallyl ether as the crosslinkable monomer.