Electrode Mixture Paste Gelation Prevention
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Solution Overview
Problem
The electrode mixture paste used in sodium secondary batteries with PVdF as a binder often experiences gelation, leading to difficulties in coating and weak adhesive forces between the current collector and electrode mixture, resulting in shedding and increased internal resistance, which deteriorates charge and discharge cycle characteristics and shortens battery life.
Innovation Solution
An electrode mixture paste comprising a sodium-containing transition metal compound, a conductive material, and a polymer binder soluble in an organic solvent without a structural unit derived from vinylidene halide, with specific structural units and sodium-containing transition metal oxides, is applied to a current collector to form a non-aqueous electrolyte secondary battery electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PVdF is used as a binder in the electrode mixture paste, then the paste can be prepared with conventional materials, but gelation occurs making coating difficult and adhesive force becomes weak
Solution Approach 1:
The patent changes the chemical structure parameter of the binder by specifying a polymer without vinylidene halide structural units (such as PVdF) that causes gelation. The invention uses alternative polymers with different chemical composition that are soluble in NMP and do not exhibit gelation behavior, thereby maintaining ease of manufacture while eliminating coating difficulties.
Solution Approach 2:
The patent replaces the problematic PVdF binder with alternative polymer materials that are equally effective but do not suffer from gelation issues. This substitution uses different chemical compounds (such as polyacrylic acid or carboxymethyl cellulose) that achieve the same binding function without the harmful gelation side effect.
2Strength
If PVdF is used as a binder, then the electrode mixture can be formed, but adhesive force between current collector and electrode mixture becomes weak causing shedding
Solution Approach 1:
The patent changes the chemical and physical parameters of the binder material. Instead of using PVdF with its specific fluorocarbon structure that causes weak adhesion and gelation, the invention employs polymers with different chemical groups (carboxylic acid, hydroxyl, or amine groups) that provide superior adhesive properties to the current collector while preventing gelation.
3Ease of manufacture
If PVdF-based electrode mixture paste is used, then conventional electrode preparation is possible, but internal resistance increases and cycle characteristics deteriorate
Solution Approach 1:
The patent changes the chemical composition parameter of the binder from PVdF to alternative polymers that are soluble in NMP and lack vinylidene halide units. This chemical parameter change eliminates the gelation phenomenon, maintains good adhesion, and ensures stable electrochemical performance over repeated charge and discharge cycles, thereby improving reliability while keeping the preparation process conventional.
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 solution prevents gelation, enhances adhesive forces, stabilizes the electrode mixture, and improves the charge and discharge capacity of the battery, reducing internal resistance and extending its cycle life.
Implementation Method 1
the binder comprises a polymer soluble in the organic solvent
Implementation Method 2
the obtained electrode has weak adhesive force between the current collector and the electrode mixture
Data Source
AI summary
The present invention provides an electrode mixture paste containing an electrode active material, a conductive material, a binder, and an organic solvent. The electrode active material has a sodium-containing transition metal compound, the binder has a polymer soluble to the organic solvent, and the polymer does not have a structural unit derived from vinylidene halide.