Tetrathiafulvalene as a sustainable cathode with high rate and Long Life-span for aqueous Zinc-ion battery at low temperatures

Tetrathiafulvalene (TTF) is introduced as a novel and sustainable cathode material for aqueous zinc ion batteries (AZIBs). Based on an anion insertion/desertion reaction, TTF delivers a capacity of 102 mAh g-1 at 1 A g-1 under-20 degrees C, and obtains a high capacity retention of 96 % after 3500 cycles. Kinetic analysis demonstrates that TTF is more surface-controlled electrochemical process than diffusion-controlled at low temperature. Comprehensive analysis, including ex-situ X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Raman, Electron Spin-Resonance spectroscopy (ESR) characterization combine with density functional theory (DFT) estimation confirm the high reversibility of the transformation from TTF to TTF+ and TTF2+, when further increase the charging cut-off voltage to 1.6 V, TTF2+ is further oxidized to TTF3+. This work not only offers fundamental understanding for reaction mechanism of tetrathiafulvalene and their homologues in battery uses, but also provides a new electrode choice for AZIBs at low temperatures.