Sticky Polymers Aid Silicon Anodes

Taking a cue from mussels’ sticky grip, researchers have developed a new adhesive material by decorating polymer backbones with catechol groups. Natural adhesives like those produced by mussels remain sticky when wet because of the binding ability of the catechol’s diol motif. A team led by Jang Wook Choi, Jung-Ki Park, and Haeshin Lee of the Korea Advanced Institute of Science & Technology designed the new adhesive binders to improve the performance of battery anodes made with silicon nanoparticles (Adv. Mater., DOI: 10.1002/adma.201203981). Silicon is considered the next-generation anode material in lithium-ion batteries because it can carry 10 times as much capacity as graphite, which is typically used in the anodes. However, silicon anodes undergo significantly more expansion and contraction than graphite as lithium ions migrate in and out during charge-discharge cycles, causing them to weaken. Battery electrodes contain polymeric binders to hold them together and maintain electrical contacts, but current binders aren’t effective for silicon anodes. The new binders are based on catechol-substituted alginate and other polymers. Because they use adhesion and hydrogen bonding, the binders keep the anodes stable several times longer than is possible with traditional binders, which work by hydrogen bonding or other weak interactions alone.