Battery Functional Layer Binder for Low-Temperature Charge Acceptance
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Solution Overview
Problem
Secondary batteries face challenges in maintaining performance at low temperatures and preventing post-cycling swelling, which affects charge carrier acceptance and battery stability.
Innovation Solution
A binder composition for non-aqueous secondary battery functional layers comprising a block copolymer with aromatic vinyl and aliphatic conjugated diene units, and a random copolymer with 1,3-pentadiene units, which forms a functional layer that inhibits swelling and enhances charge carrier acceptance at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binder compositions are used, then manufacturing simplicity is maintained, but post-cycling swelling occurs and charge carrier acceptance at low temperatures is poor
Solution Approach 1:
The patent uses a composite binder system comprising a first polymer (styrene-butadiene block copolymer with Tg of -50°C to -100°C) and a second polymer (polymer with Tg of -100°C to -150°C) in specific proportions (first polymer: 30-90 mass%, second polymer: 10-70 mass%). This composite approach combines the advantages of both polymers to simultaneously achieve swelling inhibition and low-temperature charge carrier acceptance without excessive complexity
Solution Approach 2:
The patent optimizes specific parameters including the glass transition temperature (Tg) ranges of the polymers, the proportion of each polymer in the binder composition, and the volume-average particle diameter (0.6-2.5 μm for first polymer, 0.01-0.5 μm for second polymer). These parameter optimizations enable the binder to maintain structural integrity (inhibit swelling) while providing good charge carrier acceptance at low temperatures
2Reliability
If binder composition is optimized for low temperature performance, then charge carrier acceptance improves, but post-cycling swelling inhibition may be compromised
Solution Approach 1:
The patent employs a composite binder system where the first polymer (styrene-butadiene block copolymer) provides structural stability to inhibit swelling, while the second polymer (with very low Tg of -100°C to -150°C) provides low-temperature flexibility for charge carrier acceptance. The synergistic combination in specific proportions (first polymer: 30-90 mass%, second polymer: 10-70 mass%) resolves the contradiction between stability and low-temperature performance
Solution Approach 2:
The patent creates different functional zones within the binder composition: the first polymer with higher Tg (-50°C to -100°C) provides structural framework for swelling inhibition, while the second polymer with very low Tg (-100°C to -150°C) creates flexible regions for low-temperature ion transport. This local differentiation of polymer properties enables simultaneous achievement of both objectives
3Reliability
If particle size of binder is reduced, then charge carrier acceptance at low temperatures improves, but mechanical strength and swelling inhibition may be affected
Solution Approach 1:
The patent divides the binder system into two polymer components with different particle size specifications: first polymer particles (0.6-2.5 μm) provide mechanical strength and structural integrity, while second polymer particles (0.01-0.5 μm) fill the interstices and provide low-temperature flexibility. This segmentation of particle sizes enables the functional layer to maintain strength while achieving good charge carrier acceptance at low temperatures
Solution Approach 2:
The patent creates a hierarchical particle size distribution where larger first polymer particles (0.6-2.5 μm) form the structural framework providing mechanical strength, while smaller second polymer particles (0.01-0.5 μm) fill the gaps and provide low-temperature charge carrier pathways. This local differentiation of particle sizes resolves the contradiction between strength and low-temperature performance
Data Source
AI summary
Provided is a binder composition capable of forming a functional layer that can both inhibit post-cycling swelling of a secondary battery and increase charge carrier acceptance of the secondary battery at low temperatures. The binder composition contains a first polymer, a second polymer, and a solvent. The first polymer is a block copolymer including a block region formed of an aromatic vinyl monomer unit and a block region formed of an aliphatic conjugated diene monomer unit and/or a hydrogenated aliphatic conjugated diene monomer unit. The second polymer is a random copolymer including a 1,3-pentadiene unit and/or a hydrogenated 1,3-pentadiene unit.