Experimental and Theoretical Studies of Trisodium-1,3,5-Benzene Tricarboxylate as a Low-Voltage Anode Material for Sodium-Ion Batteries

A tricarboxylate-based organic compound for Na storage at low voltage, trisodium-1,3,5-benzene tricarboxylate (Na3BTC) is reported. The effect of increasing the number of carboxyl redox active groups on the aromatic system versus previously reported dicarboxylate-based Na electrodes is explored. Sodiation and desodiation of this material occur at average voltages of 0.4 and 0.5V, respectively, suitable for anode application. The galvanostatic profile of desodiation consists of two plateaus at 0.5 and 0.2V. The material delivers a capacity of 250mAhg(-1) at a C/5 rate, with a retention of 80% after 100 cycles. It also has an excellent rate capability, delivering 100mAhg(-1) with a 75% retention after 1500 cycles at a 10C rate. Ex situ attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), ex situ H-1 NMR studies, and first principles calculations are performed to understand the sodium storage mechanism. The mechanism is found to be different from those previously observed in lithium dicarboxylates and sodium dicarboxylates in that there is apparently almost no charge donation from the inserted Na to the organic moiety.