Algae Gum Amps Li-Ion Batteries

Lithium-ion battery technology may get a boost from a gummy substance commonly found in brown algae (Science, DOI: 10.1126/science.1209150). Traditional graphite electrodes in Li-ion batteries suffer from storage capacity problems and short lifetimes. Additionally, graphite electrodes are bound with toxic and environmentally unfriendly polyvinylidene fluoride, which further requires toxic solvents such as N-methyl-2-pyrrolidone. Scientists would like to replace graphite with silicon, which is cheap, plentiful, and has 10 times the theoretical charge capacity of graphite. However, silicon degrades rapidly during operation. Gleb Yushin of Georgia Tech, Igor Luzinov of Clemson University, and their colleagues show that the algal compound, alginate, which is commonly used in dentistry and as a food thickener, greatly stabilizes Si-based electrodes. They combined silicon nanopowder with the nontoxic alginate to create a battery anode that surpasses the reversible capacity of graphite anodes. As the authors note, alginate contains carboxylic acid groups in each of the polymer’s monomeric units. “The higher content of carboxylic groups in the binder should lead to a larger number of possible binder-Si bonds, and thus better Si electrode stability,” they write. They found that the alginate binder also works well with graphite electrodes.