Nonaqueous Battery Electrode Slurry for Low-Crack Current Collector Bonding
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Solution Overview
Problem
Existing nonaqueous secondary battery electrodes face issues with low bonding properties between active materials and the current collector, leading to peeling and reduced capacity, and existing binders either require complex preparation processes or result in electrode cracking.
Innovation Solution
A nonaqueous secondary battery electrode comprising a current collector with an electrode active material layer containing a copolymer derived from (meth)acrylic acid salt, a nonionic surfactant, and a cellulose derivative, which improves bonding and reduces cracking, while maintaining high cycle capacity retention and low internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF binder containing NMP is used, then the electrode can be formed, but the bonding properties between active materials and current collector are low, requiring large amount of binder which reduces battery capacity
Solution Approach 1:
The invention changes the chemical composition parameters of the binder from conventional PVDF/NMP to a water-based copolymer system containing carboxymethyl cellulose and sodium acrylate-N-vinylacetamide copolymer. This parameter change enables strong bonding properties while using minimal binder amount (1-10 parts by mass relative to 100 parts active material), thereby resolving the contradiction between bonding strength and binder quantity.
2Ease of manufacture
If water-dispersible binder with carboxymethyl cellulose is used, then the binder is easier to prepare, but the bonding properties are insufficient and active material peeling occurs during cutting
Solution Approach 1:
The invention creates a composite binder system combining carboxymethyl cellulose (providing water dispersibility and ease of manufacture) with sodium acrylate-N-vinylacetamide copolymer (providing strong bonding properties). The synergistic combination of these two materials resolves the contradiction by achieving both easy preparation and strong bonding, preventing active material peeling during electrode cutting.
3Quantity of substance
If electrode film thickness is increased to achieve higher capacity, then the battery capacity increases, but cracks are generated frequently in the electrode
Solution Approach 1:
The invention changes the binder composition parameters to include sodium acrylate-N-vinylacetamide copolymer with specific molecular weight (1,000,000-5,000,000) and composition ratio (sodium acrylate 10-90 mass%, N-vinylacetamide 10-90 mass%). This parameter optimization provides excellent film-forming properties and flexibility, enabling the electrode to maintain high capacity with thick active material layers while preventing crack formation during bending and cycling.
Data Source
AI summary
The invention is related to a nonaqueous secondary battery electrode having an electrode active material layer with little crack and high peel strength to a current collector, and can reduce the internal resistance of the battery; and an electrode slurry therefor, and a nonaqueous secondary battery. The electrode active material layer of the nonaqueous secondary battery contains an electrode active material (A), a copolymer (P), a nonionic surfactant (B), and a cellulose derivative (C). A content of the nonionic surfactant (B) to 100 parts by mass of the copolymer (P) is 5.0 to 350 parts by mass, and a content of the cellulose derivative (C) is 10 to 350 parts by mass. The copolymer (P) contains a structural unit (p1) derived from a (meth)acrylic acid salt of 50 to 99% by mass and a structural unit (p2) derived from a compound represented by general formula (1) of 0.50 to 30% by mass.