Oxygen-rich vacancies in micro-caged NiMn2O4 derived from metal-organic frameworks enabling high-performance lithium-ion batteries

Transition metal oxides (TMOs) are increasingly attracting the interest of researchers with advantages of high theoretical capacity, abundant reserves, and ease of preparation. However, low coulombic efficiency, severe volume expansion, and poor electronic conductivity severely limit their application. The introduction of oxygen vacancies as well as morphology modulation is currently an effective solution to the above problems. Herein, we have synthesized a series of different MOF-derived NiMn2O4 (NMO) anodes for lithium-ion battery via the proposed hydrothermal synthesis method. Through the rational introduction of oxygen vacancies, all the synthesized 1,4-dicarboxybenzene-NiMn2O4 (BDC-NMO), 1,3,5-Benzenetricarboxylic acid-NiMn2O4 (BTC-NMO) and 1,2,4,5-Benzenetetracarboxylic acid-NiMn2O4 (PMA-NMO) electrodes achieved excellent cycle stability performance and rate performance. Meanwhile, BTC-NMO achieves superior cycling performance of 940 mAh g−1 after 250 cycles at 0.1 A g−1 compared to BDC-NMO and PMA-NMO electrodes, which was attributed to its hollow micro-cage structure, which could effectively shorten the Li+ diffusion path, alleviate volume expansion during the cycling and provide more Li+ reaction active sites. Theoretical calculations and experimental studies indicated that oxygen vacancies could enhance electronic conductivity, improve Li+ diffusion kinetics and promote the contribution of pseudo-capacitance. This strategy of regulating the electronic structure and reaction kinetics through oxygen vacancies and the hollow micro-cage structure design provides ideas for the commercialization path of TMOs as anodes for Li-ion battery.