Organic Li4C8H2O6 nanosheets for lithium-ion batteries.

Organic tetralithium salts of 2,5-dihydroxyterephthalic acid (Li4C8H2O6) with the morphologies of bulk, nanoparticles, and nanosheets have been investigated as the active materials of either positive or negative electrode of rechargeable lithium-ion batteries. It is demonstrated that, in the electrolyte of LiPF6 dissolved in ethylene carbonate (EC) and dimethyl carbonate (DMC), reversible two-Li-ion electrochemical reactions are taking place with redox Li4C8H2O6/Li2C8H2O6 at ~2.6 V for a positive electrode and Li4C8H2O6/Li6C8H2O6 at ~0.8 V for a negative electrode, respectively. In the observed system, the electrochemical performance of high to low order is nanosheets > nanoparticles > bulk. Remarkably, Li4C8H2O6 nanosheets show the discharge capacities of 223 and 145 mAh g(-1) at 0.1 and 5 C rates, respectively. A capacity retention of 95% is sustained after 50 cycles at 0.1 C rate charge/discharge and room temperature. Moreover, charging the symmetrical cells with Li4C8H2O6 nanosheets as the initial active materials of both positive and negative electrodes produces all-organic LIBs with an average operation voltage of 1.8 V and an energy density of about 130 Wh kg(-1), enlightening the design and application of organic Li-reservoir compounds with nanostructures for all organic LIBs.