PVDF Binder Composition for High-Nickel Cathode Gelation Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing binders for lithium-ion secondary battery positive electrodes, such as vinylidene fluoride polymers, suffer from insufficient adhesiveness and promote gelation when mixed with positive electrode active materials, particularly those with high nickel ratios, which hinders the development of high-capacity batteries.
Innovation Solution
A vinylidene fluoride polymer containing structural units derived from vinylidene fluoride and two or more kinds of structural units represented by General Formula (1) is used, which suppresses gelation and enhances adhesiveness by incorporating carboxy groups that bond to the active material and current collector, even in small amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a known vinylidene fluoride polymer is used as a binder, then the battery capacity can be increased by reducing binder amount, but the adhesiveness becomes insufficient
Solution Approach 1:
The patent modifies the chemical structure parameters of the vinylidene fluoride polymer by introducing carboxy groups through copolymerization with acrylic acid or methacrylic acid. This changes the functional groups present in the binder, enabling chemical bonding with the active material surface and current collector, thereby maintaining high adhesiveness even at reduced binder concentrations (5-20 mass%).
Solution Approach 2:
The patent creates a composite binder system by copolymerizing vinylidene fluoride with small amounts of acrylic acid or methacrylic acid (1-20 mol%). This composite polymer structure combines the electrochemical stability and binding capability of vinylidene fluoride with the adhesion-promoting carboxy groups from the acid monomers, achieving both reduced binder amount and sufficient adhesiveness.
2Quantity of substance
If a known vinylidene fluoride polymer is used as a binder, then the battery capacity can be increased by reducing binder amount, but the electrode mixture becomes easily gelled
Solution Approach 1:
The patent changes the molecular structure parameters by controlling the copolymer composition and introducing carboxy groups, which modify the interaction between binder molecules and active material. This structural modification prevents excessive adhesion that would cause gelation, while still providing sufficient binding at reduced concentrations (5-20 mass%).
Solution Approach 2:
The patent applies local quality modification by introducing carboxy groups at specific locations within the polymer chain through controlled copolymerization. These localized functional groups provide necessary adhesion and gelation control without requiring high overall binder concentration, enabling use of only 5-20 mass% binder while preventing gelation.
3Quantity of substance
If a ternary compound with high nickel ratio is used as positive electrode active material, then the battery capacity is increased, but the gelation progress is further promoted
Solution Approach 1:
The carboxy groups in the modified vinylidene fluoride polymer act as intermediaries that form chemical bonds with the high-nickel active material surface. This intermediary bonding mechanism provides stable adhesion and controls gelation tendency, enabling the use of high-capacity ternary compounds with high nickel ratios without suffering from gelation problems.
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 provides stable electrode mixtures with high adhesiveness and prevents gelation, enabling the production of lithium-ion secondary batteries with high capacity and long-term stability.
Implementation Method 1
incorporating carboxy groups that bond to the active material and current collector
Implementation Method 2
the binder hardly causes gelation of an electrode mixture even when mixed with a positive electrode active material
Data Source
AI summary
An object is to provide a binder that hardly causes gelation even when mixed with a positive electrode active material containing nickel, and has sufficient adhesiveness in a small amount. The binder that solves the issue described above contains a vinylidene fluoride polymer, and the vinylidene fluoride polymer includes a structural unit derived from vinylidene fluoride and two or more kinds of structural units represented by a specific structural formula.