A redox-active metal-organic compound for lithium/sodium-based dual-ion batteries

Currently, there is considerable interest in developing new electrode materials to construct the new-generation dual-ion batteries (DIBs) with the potential advantages of higher working voltage, good safety, low cost, and environmental friendliness. Herein, a well-known charge-transfer metal-organic compound, copper-tetracyanoquinodimethane (CuTCNQ), is synthesized and then used as an anode material, which can reversibly store Li⁺/Na⁺ ions under the lower working voltage. Consequently, the lithium/sodium-based DIBs (LDIBs/SDIBs) are constructed by coupling CuTCNQ anode with graphite cathode and their working mechanisms are also understood in detail. As expected, LDIBs exhibit a high average potential of 4.26 V, a high initial discharge capacity of 195.4 mAh g^-1 at 0.1 A g^-1, long cycling performance after 200 cycles with good capacity retention and excellent rate capability of 106.2 mAh g^-1 at 5 A g^-1. Especially, high average potential of 4.23 V and good rate capability of 34.5 mAh g^-1 at 5 A g^-1 could be maintained in SDIBs. These results may open a new avenue for using metal-organic compound in the field of high-performance energy-storage devices.