Nonaqueous Battery Electrode Slurry for Crack-Resistant Adhesion
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Solution Overview
Problem
Existing nonaqueous secondary battery electrodes face issues with cracking and low peel strength to current collectors, leading to reduced capacity and increased internal resistance, particularly due to insufficient bonding properties of existing binders.
Innovation Solution
A nonaqueous secondary battery electrode comprising a current collector with an electrode active material layer formed using a copolymer, nonionic surfactant, and cellulose derivative, where the copolymer includes specific structural units and the nonionic surfactant has a particular HLB value, enhancing bonding and dispersibility to achieve high peel strength and reduced cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF binder containing NMP is used, then bonding properties are improved, but manufacturing cost increases and capacity is reduced due to large binder amount required
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by using a copolymer consisting of acrylic acid and N-vinyl-2-pyrrolidone in specific ratios (acrylic acid: 5-50 mol%, N-vinyl-2-pyrrolidone: 50-95 mol%). This parameter optimization provides sufficient bonding properties while reducing the total binder amount required compared to conventional PVDF binders
Solution Approach 2:
The invention creates a composite binder system by combining acrylic acid units and N-vinyl-2-pyrrolidone units in a copolymer structure. This composite material approach leverages the complementary properties of both monomers: acrylic acid provides carboxyl groups for strong bonding, while N-vinyl-2-pyrrolidone provides polarity and solubility, achieving high bonding efficiency with reduced binder quantity
2Ease of manufacture
If water-dispersible binder is used, then manufacturing cost is reduced, but bonding properties become insufficient and active material peeling occurs
Solution Approach 1:
The invention optimizes the molecular structure parameters of water-dispersible binders by incorporating N-vinyl-2-pyrrolidone units (50-95 mol%) which provide strong polarity and water solubility, while maintaining acrylic acid units (5-50 mol%) for bonding. This parameter balance enables both water dispersibility and sufficient bonding strength, preventing active material peeling during cutting processes
Solution Approach 2:
The invention creates a composite polymer structure combining hydrophilic N-vinyl-2-pyrrolidone units with carboxyl-containing acrylic acid units. This composite structure provides both water dispersibility (from N-vinyl-2-pyrrolidone) and bonding capability (from acrylic acid carboxyl groups), resolving the contradiction between ease of manufacture and bonding strength
3Quantity of substance
If electrode film thickness is increased, then capacity is improved, but cracks are generated frequently in the electrode
Solution Approach 1:
The invention changes the binder composition parameters to include N-vinyl-2-pyrrolidone units (50-95 mol%) which provide enhanced polarity and flexibility. This parameter adjustment improves the binder's ability to accommodate volume changes and stress distribution in thick electrodes, preventing crack formation while maintaining high capacity
Solution Approach 2:
The composite copolymer structure combines the bonding capability of acrylic acid with the flexibility and polarity of N-vinyl-2-pyrrolidone. This composite material provides both strong adhesion and mechanical flexibility, enabling thick electrode films to maintain integrity without cracking while achieving high capacity
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 results in a battery with improved cycle capacity retention, reduced internal resistance, and enhanced bonding between active materials and the current collector, addressing the limitations of existing binders by minimizing cracks and increasing peel strength.
Implementation Method 1
the binder serves to bond the active materials to each other and to bond the active material to the current collector
Implementation Method 2
a nonionic surfactant (B), wherein a content of the nonionic surfactant (B) with respect to 100 parts by mass of the copolymer (P) is 5.0 parts by mass or more and 350 parts by mass or less
Implementation Method 3
a cellulose derivative (C); wherein a content of the cellulose derivative (C) with respect to 100 parts by mass of the copolymer (P) is 10 parts by mass or more and 350 parts by mass or less
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.