Negative Electrode Binder Composition for Clean Battery Cutting
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Solution Overview
Problem
Existing non-aqueous electrolyte secondary batteries face issues with negative electrode mixture layer breakage during cutting, leading to internal short circuits and inadequate low-temperature regeneration characteristics, particularly when used in electric vehicles.
Innovation Solution
The battery design incorporates a negative electrode mixture layer with a high tap density negative electrode active material (1.00 g/cm3 to 1.20 g/cm3), CMC content of 0.6% to 0.8% by mass, and SBR content of 0.4% to 0.8% by mass, maintaining a mass ratio of CMC to SBR less than 2 and total content below 1.5% by mass, to enhance flexibility and reduce breakage while improving low-temperature regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the negative electrode mixture layer is made brittle to improve manufacturing precision, then cutting precision is improved, but reliability deteriorates due to mixture breakage and internal short circuits
Solution Approach 1:
The patent changes the physical and chemical parameters of the negative electrode mixture layer by controlling the particle size distribution (D50: 8-13 μm, D90: 15-20 μm), tap density (1.00-1.20 g/cm³), and binder content ratios (CMC: 0.6-0.8%, SBR: 0.4-0.8%, mass ratio < 2). These parameter optimizations enable the mixture layer to achieve both adequate brittleness for clean cutting and sufficient flexibility to prevent breakage during charging/discharging cycles.
2Reliability
If the negative electrode mixture layer is made flexible to improve reliability, then resistance to breakage is improved, but manufacturing precision deteriorates due to mixture layer deformation
Solution Approach 1:
The patent optimizes the binder composition parameters specifically: CMC content at 0.6-0.8% provides structural integrity and cutability, while SBR content at 0.4-0.8% with mass ratio CMC/SBR < 2 provides flexibility and adhesion. This precise parameter control creates a balanced mixture layer that maintains shape during manufacturing yet resists breakage during operation.
Solution Approach 2:
The patent uses a composite binder system combining two different materials (CMC and SBR) with complementary properties. CMC provides rigidity and structural support for manufacturing precision, while SBR provides elasticity and flexibility for reliability. The synergistic combination of these composite materials resolves the contradiction between brittleness and flexibility requirements.
3Ease of manufacture
If conventional binders are used to maintain manufacturing simplicity, then ease of manufacture is preserved, but low-temperature regeneration characteristic deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the binder system by selecting specific ratios of CMC and SBR (mass ratio < 2, total content < 1.5%). This optimized composition improves low-temperature regeneration characteristics by enhancing electrolyte wettability and ion transport at low temperatures, while maintaining compatibility with conventional manufacturing processes and slurry preparation methods.
Data Source
AI summary
This non-aqueous electrolyte secondary battery is provided with: an electrode body that has a positive electrode and a negative electrode; and an outer package in which the electrode body is accommodated. The negative electrode comprises a negative electrode core body and a negative electrode mixture layer formed on the surface of the negative electrode core body. The negative electrode mixture layer comprises: a negative electrode active material that has a tap density of 1.00-1.20 g/cm3; CMC, the content of which accounts for 0.6-0.8 mass % in the negative electrode mixture layer; and SBR, the content of which accounts for 0.4-0.8 mass % in the negative electrode mixture layer. The mass ratio of the content of CMC to the content of SBR in the negative electrode mixture layer is less than 2, and the total content of CMC and SBR in the negative electrode mixture layer is less than 1.5 mass %.