Halogenated Carboxylates as Organic Anodes for Stable and Sustainable Sodium-Ion Batteries.

Organic materials are competitive as anodes for Na-ion batteries (NIBs) due to the low cost, abundance, environmental benignity, and high sustainability. Herein, we synthesized three halogenated carboxylate-based organic anode materials to exploit the impact of halogen atoms (F, Cl, and Br) on the electrochemical performance of carboxylate anodes in NIBs. The fluorinated carboxylate anode, disodium 2, 5-difluoroterephthalate (DFTP-Na), outperforms the other carboxylate anodes with H, Cl, and Br, in terms of high specific capacity (212 mA h g), long cycle life (300 cycles), and high rate capability (up to 5 A g). As evidenced by the experimental and computational results, the two F atoms in DFTP reduce the solubility, enhance the cyclic stability, and interact with Na during the redox reaction, resulting in a high-capacity and stable organic anode material in NIBs. Therefore, this work proves that fluorinating carboxylate compounds is an effective approach to developing high-performance organic anodes for stable and sustainable NIBs.