Electrochemical in-situ generation of Ni-Mn MOF nanomaterials as anode materials for lithium-ion batteries

Abstract

Due to their low cost and high theoretical lithium storage capacity, binary transition metal materials are very suitable as anode materials for lithium-ion batteries (LIBs). However, the low electrical conductivity and poor cycling stability caused by volume change during the charge-discharge process limit its application as an energy storage material. Herein, in this paper, the preparation of Ni/Mn binary compounds and the in-situ synthesis of metal-organic framework (MOF) nanosheets were realized by the one-step electroconversion method for the first time. In this method, NiMn-MOF nanomaterials were successfully prepared by using the characteristics that the cathode can generate OH- ions and the organic framework (p-phthalic acid, PTA) can be dissolved in alkali solution so that PTA was uniformly coated on the surface of Ni-Mn hydroxide. NiMn-MOF exhibits excellent performance as an anode for Li-ion batteries. Its charge-discharge specific capacity is 1024/1554 mAh·g−1, with a small charge transfer impedance, but it inherits the poor rate performance of transition metals. After 1000 cycles, the coulombic efficiency is 100%. Even after 600 cycles, the charge and discharge capacity rises steadily. MOF-derived porous structures can not only provide conductive pathways and increase the transport of electrons and lithium ions but also alleviate volume expansion. As the first successful in-situ electroconversion of PTA to synthesize NiMn-MOF, this method's low cost and good electrochemical performance provide hope for its large-scale application in Li-ion batteries.