Multifunctional Polymeric Binder for Silicon Anode in Li-ion Battery

Abstract

Silicon as an anode material in lithium-ion batteries has great potentials due to its high charge capacity. However, the practical application of Si is quite challenging because severe volume change during charging/discharging process results in breaking anode film and fading the reversible charge capacity. Therefore, the efficient polymeric binder to stably accommodate active materials in the anode is highly demanded. We demonstrated the systematic molecular design and synthetic approaches of novel binder is one of the solution which is capable of preserving electrode integrity and maintaining electrical contact during expansion/contraction of silicon anode. We have introduced multifunctional group-containing poly(acrylic acid-co-vinyl alcohol) copolymer binders. Polymeric binders with three different functional groups, namely, carboxylic acid (COOH), carboxylate (COO–), and hydroxyl (OH), in a single polymer backbone have been synthesized and characterized via 1H NMR and FTIR spectroscopies. A systematic study that involved varying the ratio of the functional groups indicated that a material with an acid-to-alcohol molar ratio of 60:40 showed promise as an efficient binder with an initial columbic efficiency of 89%. The strong interaction of the polymer binder with Si nanoparticle from PAA, and high viscosity form PVA could give a synergetic effect on making uniform anode film. Further more, three dimensionally interconnected networks provide sufficient mechanical properties to prevent the destruction of the electrode during numerous cycling.