Block Polymer Electrode Binder for High-Solids Slurry Coating
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Solution Overview
Problem
Secondary battery electrodes face challenges with high slurry viscosity at increased solids concentration, which hinders coating properties and binding ability, especially when using silicon-based active materials that undergo volume changes during charge and discharge, leading to peeling and reduced durability.
Innovation Solution
A block polymer binder with specific composition and structure, containing polymer blocks A and B, where block A has a high content of ethylenically unsaturated carboxylic acid monomers and block B has a lower content, is used to reduce slurry viscosity and enhance binding ability, allowing for improved coating and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the solids concentration of the electrode slurry is increased to improve drying efficiency and productivity, then the slurry viscosity increases, making it difficult to ensure good coating properties
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by incorporating specific ratios of carboxyl-containing polymer and polyacrylonitrile, which fundamentally alters the slurry's rheological properties. This allows the slurry to maintain low viscosity even at high solids concentrations (90 wt% or more), thereby improving drying efficiency without sacrificing coating properties
Solution Approach 2:
The patent creates a composite binder system by combining carboxyl-containing polymer and polyacrylonitrile in specific ratios (0.1-10 parts by weight of polyacrylonitrile per 1 part by weight of carboxyl-containing polymer). This composite material approach enables the slurry to achieve both high solids concentration and good coating properties through synergistic interaction between the two polymers
2Reliability
If conventional binders are used with silicon-based active materials, then the electrode mixture layer peels and detaches after repeated use, leading to decreased battery capacity and reduced cycle characteristics
Solution Approach 1:
The patent optimizes the binder composition parameters by using carboxyl-containing polymer in amounts of 0.5-10 parts by weight per 100 parts by weight of silicon-based active material, and polyacrylonitrile in amounts of 0.05-10 parts by weight per 100 parts by weight of silicon-based active material. These parameter changes enhance binding strength while accommodating the volume expansion of silicon during charge-discharge cycles
Solution Approach 2:
The patent uses a binder composition that can accommodate the mechanical stress from silicon volume changes without requiring complex crosslinking agents or expensive modifications. The simple polymer blend provides sufficient binding durability through its inherent flexibility and adhesion properties
Data Source
AI summary
A secondary battery electrode binder exhibits superior binding capacity as compared to conventional binders and makes it possible to reduce slurry viscosity, even when the solid concentration of an electrode slurry is high. A secondary battery electrode binder contains a block polymer having a polymer block (A) and a polymer block (B), wherein: the polymer block (A) includes a structural unit derived from an ethylenically unsaturated carboxylic acid monomer; the content of a structural unit derived from an ethylenically unsaturated carboxylic acid monomer in the polymer block (B) is less than 30 mass % (and is different from that in the polymer block (A)) with respect to all the structural units of the polymer block (B); the ratio of the polymer block (A) in the block polymer is 10-90 mass %; and the block polymer does not contain a structural unit derived from a crosslinkable monomer.