High Energy Organic Cathode for Sodium Rechargeable Batteries

Organic electrodes have attracted significant attention as alternatives to conventional inorganic electrodes in terms of sustainability and universal availability in natural systems. However, low working voltages and low energy densities are inherent limitations in cathode applications. Here, we propose a high-energy organic cathode using a quinone-derivative, C6Cl4O2, for use in sodium-ion batteries, which boasts one of the highest average voltages among organic electrodes in sodium batteries (similar to 2.72 V vs Na/Na+). It also utilizes a two-electron transfer to provide an energy of 580 Wh kg(-1). Density functional theory (DFT) calculations reveal that the introduction of electronegative elements into the quinone structure significantly increased the sodium storage potential and thus enhanced the energy density of the electrode, the latter being substantially higher than previously known quinone-derived cathodes. The cycle stability of C6Cl4O2 was enhanced by incorporating the C6Cl4O2 into a nanocomposite with a porous carbon template. This prevented the dissolution of active molecules into the surrounding electrolyte.