Alginate Binder Improves the Battery

Published:2011/9/12 22:40:00 Author:Li xiao na From:SeekIC

Alginate binders，which is able to improve lithium ion anodes, is found by US researchers. Binders are used to suspend the graphite, or more recently silicon, particles that interact with the electrolyte to hold charge.

The inspiration for alternative binders was found from the sea. The researchers always looked at materials that had evolved in natural systems, such as aquatic plants which grow in water with a high concentration of ions. Because the electrodes in batteries are immersed in a liquid electrolyte, they felt that the plants which grow in an aggressive environment as salt water can be suitable to be natural binders. Compared with carbon anodes, silicon-based anodes offer more capacity, providing provision can be made for the swelling and contraction that silicon undergoes as ions are transferred.

On the surface of anodes, an interface is needed. It is required to be stable, porous to lithium ions, and impervious to fresh electrolyte. The graphite particle whose volume does not change makes the interface keep stable. However, because the volume of silicon nanoparticles changes during operation of the battery, cracks forms and allows additional electrolyte decomposition until the pores that allow ion flow become clogged, causing battery failure. Moreover, alginate not only binds silicon particles to each other and to the metal foil of the anode, but they also coat the silicon particles themselves and offer a strong support for the interface, preventing degradation.

The argument for retro-fitting alginates into carbon anode production is different, and to do with toxicity. The alginates in question are natural polysaccharides with uniformly distributed carboxylic groups, and are extracted from brown seaweed through a simple soda (Na2CO3) process. Anodes that are compatible with existing battery production techniques can be made with from a water-based slurry of alginate and suspended silicon or graphite particles, said Georgia Tech.

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