Revealing the effect of cobalt-doping on Ni/Mn-based coordination polymers towards boosted Li-Storage performances

In this work, a nickel-based coordination polymer is synthesized through a facile microwave-assisted solvothermal method. Cobalt ions are further introduced by a cation-exchange process to construct the nickel-cobalt bimetallic coordination structure. This bimetallic coordination polymer (Co–Ni-BTC) exhibits substantially improved cycling performance than the single nickel coordination polymer (Ni-BTC) and previous Ni/Co-based coordination polymers with various organic ligands for lithium ion batteries. A reversible charge capacity of 1051 mAh g−1 is achieved at 100 mA g−1 after 300 cycles for Co–Ni-BTC, which is more than 4 times as large as that for Ni-BTC (258 mAh g−1) after same cycle number. The superior lithium-ion storage performance of the Co–Ni-BTC can be ascribed to its regular and porous structure inherited from the coordinated interaction between nickel/cobalt and 1,3,5-benzenetricarboxylic acid (BTC) and a highly reversible Li-reaction with the coordination polymer. The cobalt-doping is found to activate the electrochemical activity of nickel ions and facilitate the ion/electron diffusion process. The similar beneficial effect of Co-doping can also be applied to the Mn-BTC coordination polymer. These observations may shed lights on the design and development of new coordination polymer electrodes with large reversible capacities.