Secondary Battery Binder Composition for Low-Contamination Electrodes
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Solution Overview
Problem
Existing binders for secondary batteries face challenges such as increased ohmic resistance due to particle contact resistance, volume expansion leading to material separation, and contamination during the pressing process, which affect electrode productivity and battery lifetime.
Innovation Solution
A binder composition comprising core-shell-structured emulsion polymer particles and non-core-shell-structured emulsion polymer particles, with a specific ratio and particle size distribution, is used to enhance adhesive strength, reduce contamination, and improve mechanical stability of secondary battery electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional binders are used for secondary battery electrodes, then adhesive strength is provided, but contamination occurs during the pressing process reducing productivity
Solution Approach 1:
The patent changes the physical and chemical parameters of the binder by using emulsion polymer particles with specific glass transition temperatures (Tg ≤ 0°C for core-shell particles, Tg ≤ -10°C for non-core-shell particles) and specific particle size distributions (D50: 50-200 nm for core-shell, D50: 200-500 nm for non-core-shell). These parameter changes reduce contamination during pressing while maintaining adhesive strength, thereby improving electrode productivity.
Solution Approach 2:
The patent employs a composite binder system consisting of two types of emulsion polymer particles with different structures and properties: core-shell structured particles providing adhesive strength and non-core-shell structured particles reducing contamination. This composite approach allows the binder to simultaneously achieve high adhesive strength and low contamination, resolving the contradiction between productivity and harmful factors.
2Quantity of substance
If high discharge capacity materials like silicon and tin are used to increase battery capacity, then discharge capacity is improved, but volume expansion causes separation of anode materials
Solution Approach 1:
The patent changes the binder's glass transition temperature parameter to Tg ≤ 0°C (preferably -20°C to 0°C) for core-shell particles and Tg ≤ -10°C (preferably -40°C to -10°C) for non-core-shell particles. This ensures the binder remains elastic at operating temperatures, accommodating volume expansion of high-capacity materials like silicon and tin while maintaining structural stability and preventing material separation.
Solution Approach 2:
The patent uses emulsion polymer particles that form a flexible binder matrix around electrode active materials. The flexible nature of this matrix, determined by the low glass transition temperature of the polymer, allows it to expand and contract with the electrode materials during charge-discharge cycles, preventing separation and maintaining structural integrity.
3Strength
If binders with high adhesive strength are used to prevent material separation, then structural stability is improved, but resistance and ion conductivity are significantly affected
Solution Approach 1:
The patent optimizes the particle size distribution parameter of the emulsion polymer particles, with core-shell particles having D50 of 50-200 nm and non-core-shell particles having D50 of 200-500 nm. This fine particle size distribution allows the binder to provide adequate adhesive strength while maintaining sufficient porosity and ion conductivity, preventing the trade-off between strength and reliability.
Solution Approach 2:
The patent creates local quality differences between core and shell portions of the emulsion polymer particles. The core provides structural integrity and adhesive strength, while the shell portion allows for ion transport and maintains porosity. This local differentiation enables the binder to simultaneously achieve high adhesive strength and good ion conductivity.
Data Source
AI summary
A secondary battery binder composition includes: emulsion polymer particles A having a core-shell structure, which includes a core part and a shell part occupying a part or all of the surface of the core part; and emulsion polymer particles B having no core-shell structure. The binder composition satisfies 50<N(A)/N(B)<400, wherein N(A) is the number of emulsion polymer particles A having a core-shell structure, and N(B) is the number of emulsion polymer particles B having no core-shell structure.