Water-based binder for silicon anodes containing a Lambda Carrageenan-based polymer, a silicon anode comprising the same, and a lithium secondary battery comprising the same

Water-based silicon anode binder with enhanced adhesion and ionic conductivity via dual-action hydroxyl and sulfonate groups

This technology introduces Lambda Carrageenan, which contains hydroxyl (-OH) and sulfonate (-SO3-) groups, as a water-based binder to improve the structural stability and adhesion of silicon anodes. The hydroxyl groups form hydrogen bonds with silicon to strengthen adhesion, while the sulfonate groups enhance lithium-ion conductivity.

Silicon anodes undergo volume expansion of up to 400% during charge and discharge cycles, leading to particle pulverization, electrical isolation, side reactions with electrolytes, electrode structural degradation, and reduced initial efficiency and capacity. Furthermore, conventional synthetic polymer binders require organic solvents, imposing environmental and process constraints.

This technology adopts Lambda Carrageenan, a natural polysaccharide polymer, as a water-based binder to eliminate the need for organic solvents during electrode manufacturing. The hydroxyl and sulfonate groups form strong hydrogen bonds and an ion-conductive network with silicon particles. This suppresses structural deformation caused by volume expansion and increases adhesion to the current collector. It can be applied to eco-friendly anode production processes that aim to reduce the use of organic solvents like NMP and to high-capacity cells based on silicon nanoparticles, reducing the burden of solvent recovery equipment while securing cost competitiveness through low-cost, seaweed-derived materials.

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Key Features:

• A water-based binder for silicon anodes composed of Lambda Carrageenan containing both sulfonate (SO3-) and hydroxyl (-OH) groups
• Lambda Carrageenan polymer included at a content of 10 wt% to 30 wt% relative to 100 wt% of the binder
• Hydroxyl (-OH) functional groups contained in Lambda Carrageenan that form hydrogen bonds with the silicon anode
• A step of preparing a slurry by mixing the Lambda Carrageenan polymer binder, silicon nanoparticles, and a conductive agent in a mass ratio of 2:6:2

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