Silicon Electrode Binder Using Blended Polyacrylate Molecular Weights
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional lithium-ion battery electrodes, particularly those using silicon as the active material, face degradation due to volume expansion during lithiation, leading to integrity issues, reduced capacitance, and stress on the battery components, which existing polymer binders fail to adequately address in terms of mechanical stability and electrochemical performance.
Innovation Solution
A lithium-ion battery electrode incorporating a binder formed from a blend of two polymers, where the first polyacrylate or its derivative has a molecular weight between 150,000 and 400,000 g/mol, and the second polyacrylate or carboxymethyl cellulose derivative has a molecular weight between 650,000 and 1,500,000 g/mol, along with a conductive agent and silicon as the active material, to enhance mechanical stability and electrochemical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single polymer binder is used, then the electrode achieves basic cohesion, but the mechanical stability and electrochemical performance are insufficient under silicon volume expansion
Solution Approach 1:
The patent applies composite materials by combining two different polymer binders (first polyacrylate with molecular weight 150,000-400,000 g/mol and second polyacrylate or CMC with molecular weight 650,000-1,500,000 g/mol) to create a blended binder system. This composite binder provides both mechanical stability to accommodate silicon expansion and adequate electrochemical performance, resolving the contradiction between reliability and complexity.
2Strength
If high molecular weight polymer is used, then the electrode cohesion is improved, but the ink viscosity increases making coating difficult
Solution Approach 1:
The patent segments the binder function into two polymer components with different molecular weights. The first polyacrylate (lower molecular weight: 150,000-400,000 g/mol) provides adequate cohesion while maintaining lower viscosity for easy coating, and the second polyacrylate or CMC (higher molecular weight: 650,000-1,500,000 g/mol) enhances electrode strength and stability. This segmentation resolves the contradiction between strength and ease of manufacture.
Solution Approach 2:
The patent changes the molecular weight parameter of the polymer binders to optimize both cohesion and processability. By selecting specific molecular weight ranges (150,000-400,000 g/mol for first polyacrylate and 650,000-1,500,000 g/mol for second polyacrylate/CMC), the ink achieves appropriate viscosity for coating while the resulting electrode maintains strong cohesion and mechanical stability.
3Ease of operation
If polymer binder with high elasticity is used, then the electrode flexibility is improved, but the structural integrity during coiling deteriorates
Solution Approach 1:
The blended polymer binder system acts as a composite material where the first polyacrylate provides elasticity and flexibility for easy electrode handling and coiling, while the second polyacrylate or CMC contributes to structural integrity and mechanical strength. This composite approach resolves the contradiction between ease of operation and stability of composition.
Data Source
AI summary
Electrode for a lithium storage battery, or a lithium battery, including: an active electrode material, made from silicon, a conductive agent, a binder comprising a mixture of two polymers: the first polymer having a first molecular weight, the first polymer being a first polyacrylate or one of its derivatives, the second polymer having a second molecular weight, the second polymer being a second polyacrylate or a carboxymethyl cellulose, or one of their respective derivatives. The first molecular weight is less than or equal to 400,000 g/mol and greater than or equal to 150,000 g/mol. The second molecular weight is greater than or equal to 650,000 g/mol and less than or equal to 4,000,000 g/mol.