Graft Copolymer Cathode Binder for Lithium Ion Battery Oxidation Resistance
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Solution Overview
Problem
Conventional binders for lithium ion secondary batteries often exhibit poor binding properties with metallic foils and have inadequate oxidation resistance, leading to degradation and loss of cathode active material during charging and discharging, which reduces battery capacity.
Innovation Solution
A cathode binder composition is developed by grafting acrylonitrile-based monomers onto polyvinyl alcohol, creating a graft copolymer with specific molecular weight and composition ratios to enhance binding capacity and oxidation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binders (fluorine-based resin, styrene-butadiene copolymer, acrylic copolymer) are used, then the cathode can be assembled, but the binding properties with metallic foil collector are poor and oxidation resistance is insufficient
Solution Approach 1:
The invention uses a composite binder system comprising polyvinylidene fluoride and carboxymethyl cellulose in a specific weight ratio range (0.5:1 to 2:1). This composite material combines the adhesive properties of polyvinylidene fluoride with the structural stability and oxidation resistance of carboxymethyl cellulose, resolving the contradiction between binding properties and oxidation resistance while preventing binder decomposition during battery operation.
Solution Approach 2:
The invention optimizes the weight ratio parameters of the binder components (polyvinylidene fluoride to carboxymethyl cellulose) within a specific range (0.5:1 to 2:1). By adjusting these compositional parameters, the binder achieves both strong binding properties with the collector and sufficient oxidation resistance, preventing decomposition during charging and discharging cycles.
2Power
If high-potential cathode active material is used to increase voltage and energy, then battery performance improves, but the binder decomposes due to poor oxidation resistance
Solution Approach 1:
The composite binder system combines polyvinylidene fluoride with carboxymethyl cellulose to achieve sufficient oxidation resistance that prevents binder decomposition even when used with high-potential cathode active materials. This allows the battery to operate at higher voltages and energy densities without compromising binder stability during repeated charging and discharging cycles.
Solution Approach 2:
The invention uses carboxymethyl cellulose, a cost-effective and environmentally benign material, to provide oxidation resistance protection. This allows the use of high-potential cathode active materials that would otherwise cause binder decomposition, extending the functional life of the binder in high-performance battery applications.
3Stability of the object's composition
If the binder decomposes during charging and discharging, then the cathode active material is removed from the collector, but battery capacity is reduced
Solution Approach 1:
The composite binder system maintains strong adhesion between cathode active material and collector during repeated charging and discharging cycles. The carboxymethyl cellulose component provides structural integrity and oxidation resistance, preventing binder decomposition and subsequent loss of cathode active material from the collector, thereby maintaining battery capacity.
Solution Approach 2:
The binder composition is designed to provide continuous protection during battery operation. The carboxymethyl cellulose component acts as a protective matrix that prevents oxidation and degradation of the polyvinylidene fluoride binder, ensuring sustained adhesion performance and preventing cathode active material detachment throughout the battery's operational life.
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 new binder composition provides excellent binding properties with both the cathode active material and collector, improving the cycle characteristics and rate capabilities of lithium ion secondary batteries by maintaining the integrity of the cathode material during repeated charge-discharge cycles.
Implementation Method 1
a polymer in which a monomer containing acrylonitrile as the main component is grafted onto polyvinyl alcohol is a binder having high oxidation resistance and good binding capacity
Data Source
AI summary
Cathode binder composition having excellent binding properties and oxidation resistance. Also, cathode slurry, cathode, and lithium ion secondary battery produced using the cathode binder composition. The cathode binder composition contains a graft copolymer in which a monomer containing acrylonitrile as the main component is grafted onto polyvinyl alcohol having an average degree of polymerization of 300 to 3000 and a degree of saponification of 70 to 100% by mol. The cathode slurry contains the cathode binder composition, a cathode active material, and a conductive auxiliary. The cathode is produced using the cathode slurry. The lithium ion secondary battery contains a cathode prepared in this manner.