Mechanically Robust Tapioca Starch Composite Binder with Improved Ionic Conductivity for Sustainable Lithium-Ion Batteries

Binders have an important function in the performance of Li-ion batteries even though they are only used in small quantities. In addition to poor adhesion properties, the traditional polyvinylidene difluoride binder raises many environmental and health concerns because of their processing that involves hazardous organic solvents. In this study, we introduced a water-soluble, environmentally friendly tapioca starch binder modified with polyethylene glycol (PEG) groups as a novel binder for Si anode electrodes in Li-ion batteries. The experiments and density functional theory simulations indicate that abundant hydroxyl groups in the starch improve the binding strength with Si nanoparticles, and the integrated PEG groups facilitate Li-ion transfer in the Si electrode. The mechanical behavior of the electrode is significantly improved, as confirmed by nanoindentation and scratch tests. Excellent electrochemical performance is observed, with an initial lithiation capacity of 3486 mA h g(-1) and a noteworthy second cycle capacity retention of 98%, demonstrating its potential as a cheap and sustainable binder for Li-ion batteries.