Design and Synthesis of Heterometallic Ni–Co Organic Frameworks as Anode Materials for High-Performance Lithium Storage

Abstract

Reasonable design of high-rate, long-life anode materials is the key to manufacturing advanced lithium-ion batteries. Herein, we synthesized the heterometallic (Ni, Co) 4,4′-biphenyldicarboxylic metal organic framework (NiCo-MOF-1) and heterometallic (Ni, Co) 2,2′-bipyridine-5,5′-dicarboxylic metal organic framework (NiCo-MOF-2) by solvothermal method, and explored the applications as anode materials for lithium-ion batteries in depth. It was demonstrated that the initial discharge/charge specific capacities of NiCo-MOF-1 and NiCo-MOF-2 reached 2.04/1.12 and 1.99/1.11 mAh cm −2 at a current density of 0.1 mA cm −2 and the voltage window of 0.01 ∼ 3.0 V, respectively. Similarly, NiCo-MOF-2 could maintain a specific discharge/charge capacity of 0.65/0.64 mAh cm −2 after 150 cycles, which was higher than that of NiCo-MOF-1 (0.45/0.43 mAh cm −2 ). In addition, NiCo-MOF-2 delivers outstanding rate performance (0.29/0.29 mAh cm −2 at 1.0 mA cm −2 ), which came down to the strong conjugated carboxylate π – π interaction and the synergistic effect of nickel and cobalt bimetals. Through the kinetic analysis, the pseudocapacitance contribution was as high as 61.7% at 0.5 mV s −1 . Ex-situ XPS verified the coordination mechanism of Li + and COO − rings with benzene ring in NiCo-MOF-2 thus achieving high lithium storage capacity.