A cobalt-based coordination compound with high capacity as the anode of lithium-ion battery and its stepwise reaction mechanism

Abstract

Metal-coordination compounds are regarded as the most promising electrodes for lithium-ion batteries compared to inorganic anode materials because they are environmentally benign, rich in coordination, abundant in active sites, and low cost. In contrast, their possible molecular structures and reaction mechanisms are still mysteries. Here, using a microwave-assisted solvothermal process, we created the Co-1,3,5-trioxy-2,4,6-Triamino-benzo (Co-TB) coordination compound, which exhibits a flower-like shape of tiny flakes with a typical crystal feature. When applied as the anode of lithium-ion battery (LIB), Co-TB has shown a high reversible capacity of 1092 mAh g−1 at 1 A g−1 after 800 cycles and remarkable rate performances (497 mAh g−1 at 5 A g−1). This is significantly better than pure TB with similar functional groups but without coordination cations. Based on several electrochemical characterization techniques, ex-situ X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and in-situ X-ray diffraction techniques, a possible molecular structure, and stepwise reaction mechanism are postulated. All of them have demonstrated that the stepwise redox reactions between Co-TB and Li relied on these reactions of Li+ ions and Co2+/various multiple organic functional groups in Co-TB, including CO, CN, and CC of benzene rings. The synthesized method and characterization approaches can be extended to study other organic metal-coordination compounds.