Biopolymer Binders for Low-Temperature Operation of TiNb₂O₇ Anode in Li-Ion Batteries

The widespread use of lithium-ion batteries underlines the criticality of a more sustainable cell fabrication. Here, three biopolymers gelatin, pectin, and deoxyribonucleic acid (DNA) are investigated as binders for the TiNb2O7 anode material in Li cells in a temperature range between 0 and 60 degrees C and compared to conventional binder polyvinylidene fluoride (PVDF). The use of biopolymers is motivated by their own environmental friendliness and the possibility to implement an aqueous electrode processing. A specific charge capacity of at least 200 mAh g(-1) is found for all binders at 0 degrees C when testing the cycling performance of TiNb2O7 at 77.5 mA g(-1) (1C rate). However, low-rate cycling at 60 degrees C shows decreasing capacity for all biopolymers due to the swelling effect and continuous contact loss to the current collector, what also reflects in lowering the overall Li-diffusion coefficient. This effect becomes less pronounced at 0 degrees C and high current densities, making biopolymers competitive with commercial PVDF. The electrodes with DNA binder demonstrate overall the most stable performance, arising from the biopolymer intactness and a thin solid-electrolyte interface layer. At 0 degrees C, the electrode with DNA provides 150 mAh g(-1) at 775 mA g(-1) for at least 500 discharge-charge cycles.