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.