Copolymerized PVDF Binder for Low-Viscosity Lithium-Ion Electrodes
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Solution Overview
Problem
Existing PVDF resins used in lithium ion battery binders face issues such as high production costs, high energy requirements for solvent evaporation, poor bonding ability, and mechanical flexibility leading to electrode cracking and instability.
Innovation Solution
A copolymerized PVDF resin is developed by optimizing polymerization formula, temperature, and feeding method, using vinylidene fluoride monomer, comonomer, pH buffer regulator, metallocene synergist, initiator, and dispersant to improve bonding to electrode active material and current collector, reducing rotational viscosity and preparation requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If graft-modified PVDF resins are used to improve bonding performance, then bonding ability is improved, but rotational viscosity of NMP solution increases and preparation requirements become more stringent
Solution Approach 1:
The patent changes the chemical structure parameters of PVDF by introducing comonomers (acrylic acid, methacrylic acid, itaconic acid) to create copolymerized resins with different molecular weights and functional groups. This modifies the bonding mechanism from relying on complex graft modifications to utilizing carboxyl groups and molecular weight optimization, thereby improving bonding ability while simplifying preparation requirements
Solution Approach 2:
The patent creates composite polymer structures by copolymerizing vinylidene fluoride with acrylic acid, methacrylic acid, or itaconic acid. This composite approach integrates the electrochemical stability of PVDF with the bonding capabilities of carboxyl-containing monomers, achieving both improved bonding performance and easier processing without requiring complex graft modification procedures
2Strength
If chemical grafting or radiation grafting is used to improve bonding performance, then bonding ability is improved, but rotational viscosity of NMP solution increases
Solution Approach 1:
The patent optimizes molecular weight parameters (inherent viscosity between 0.55-1.35 dL/g) and introduces carboxyl functional groups through copolymerization, enabling improved bonding without the high rotational viscosity associated with graft-modified resins. The carboxyl groups provide bonding capability while the controlled molecular weight maintains low viscosity
Solution Approach 2:
The patent extracts the essential bonding function from complex graft modification processes by incorporating carboxyl-containing comonomers directly into the polymer chain during copolymerization. This eliminates the need for separate grafting steps and the associated high viscosity problems while retaining the bonding enhancement
3Reliability
If PVDF is used as binder, then electrochemical inertness is achieved, but LiF formation accelerates chemical decomposition
Solution Approach 1:
The patent creates a composite polymer system where PVDF provides electrochemical inertness and stability, while copolymerized comonomers with carboxyl groups (acrylic acid, methacrylic acid, itaconic acid) provide improved bonding and reduced LiF formation. This composite structure mitigates the decomposition issue by distributing stress and reducing direct PVDF-electrolyte contact through enhanced interfacial bonding
4Reliability
If PVDF is used as binder, then electrochemical inertness is achieved, but lack of flexibility causes electrode cracking during cycling
Solution Approach 1:
The patent creates a composite polymer structure where PVDF chains provide electrochemical stability while copolymerized comonomers introduce flexibility and adaptability. The carboxyl groups form flexible bonding interfaces that can accommodate volume changes during lithium ion insertion and extraction, preventing electrode cracking while maintaining electrochemical inertness
Solution Approach 2:
The patent introduces dynamic flexibility to the otherwise rigid PVDF structure through copolymerization with comonomers containing carboxyl groups. These flexible segments allow the binder to dynamically adapt to electrode volume changes during cycling, maintaining integrity and preventing cracks while preserving the electrochemical stability of PVDF
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 copolymerized PVDF resin enhances bonding performance, reduces rotational viscosity, improves mechanical flexibility, and increases capacity retention, peeling strength, and reduces internal resistance in lithium ion batteries.
Implementation Method 1
optimizing polymerization formula, the polymerization method, the polymerization reaction temperature, feeding method and other factors that affect the polymerization reaction
Implementation Method 2
PVDF and NMP form a slurry
Data Source
AI summary
Disclosed are a copolymerized PVDF resin for lithium battery binders and its preparation method. 300 to 600 parts of deionized water, 0.04 to 0.25 part of a pH buffer regulator, 85 to 99.5 parts of a vinylidene fluoride (VDF) monomer, 0.5 to 15 parts of a comonomer, 0.3 to 3 parts of a metallocene synergist, 0.2 to 1.0 part of an initiator, 0.08 to 0.35 part of a dispersant react at 40 to 65° C., 5.5-8.0 Mpa. At the end of the reaction, the unreacted monomers are recovered, and then the operations of washing, filtering, and drying are carried out to obtain the copolymerized PVDF resin. For the copolymerized PVDF resin for lithium battery binders, the binding of PVDF resin to a positive electrode active material and current collector is improved, and the rotational viscosity of the NMP solution and the preparation and dispersion requirements for PVDF resin slurry are reduced.