With high theoretical specific capacity, high density, and low discharge-charge potential, MnO has attracted tremendous interest as a promising anode material for next-generation Li ion batteries. However, its cycling performance and rate capacity are still far from satisfactory due to the drastic volume change and the inferior electrical conductivity. Herein, we report the high-yield and cost-low preparation of MnO embedded carbon nanosheets (MnO/C nanosheets) by hydrolysis of metal coordination polymers in Ar gas. Through this simple synthetic method, MnO nanoparticles are homogeneously embedded in mesoporous N-doped carbon nanosheets, which not only could optimize the charge transfer between each embedded MnO nanoparticles, but also help to accommodate the volume expansion of the MnO nanoparticles. Most importantly, when evaluated as anode materials, MnO/C nanosheets exhibit a high reversible capacity of 701 mAh g-1 after 500 cycles at 1 A g-1 (with capacity retention of 109%). The outstanding cycling performance of MnO/C nanosheets is systematically investigated, and is found to be enabled by a self-compensated mechanism, which is strongly associated with the ever-increasing amount of Mn3+/4+ in MnO/C nanosheets. During the long-term cycling process, the capacity loss related to Mn2+ is compensated by Mn ions in higher state, which could offer extra reversible capacity through a high-valence redox reaction. The novel synthesis developed in this work provides a new way to construct novel metal oxide/carbon framework composites, and the self-compensated mechanism proposed here may help to explain the cycling stabilities of other conversion-type anode material.

Self-compensated reversible capacity in MnO-embedded carbon nanosheets for Li-ion battery anode with long cycle life

2019 Spring National Meeting

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