MnO@CoMn$_{\textbf{2}}$O$_{\textbf{4}}$/N-C纳米线复合材料的制备及其作为锂离子电池阳极材料的电化学性能

过渡金属氧化物作为锂离子电池(lithium-ion batteries, LIBs)阳极材料时具有较高的理论容量, 但因其电导率低, 以及充放电过程中的体积膨胀效应常会导致容量的快速衰减. 碳包覆是提升金属氧化物导电性的有效方法, 二者之间的协同效应也可以有效提升材料的电化学性能. 以MnO$_{2}$纳米线为模板制备出MnO$_{2}$@ZIF-67有机-无机杂化纳米结构, 再通过退火处理合成了氮掺杂碳包覆的MnO@CoMn$_{2}$O$_{4}$纳米线复合材料(MnO@CoMn$_{2}$O$_{4}$@N-C). ZIF-67的有机配体在高温煅烧过程中发生碳化反应, 产生了氮掺杂碳, 提升了导电性. 当作为锂离子电池阳极材料时, MnO@CoMn$_{2}$O$_{4}$/N-C纳米线复合材料在0.1 A/g电流密度下的首次放电比容量为1 594.6 mA$\cdot$h/g, 并且在100次充放电循环后的放电比容量仍保持在 925.8 mA$\cdot$h/g, 在0.5 A/g电流密度下经200次充放电循环后的放电比容量仍维持在837.6 mA$\cdot$h/g, 同时具有优异的倍率循环性能. 这种优异的电化学储能特性主要来源于复合材料的特殊结构, 以及氮掺杂碳的包覆.

Preparation and electrochemical properties as anode materials for lithium-ion batteries of MnO@CoMn$_{\textbf{2}}$O$_{\textbf{4}}$/N-C nanowire composites

Transition metal oxides have a higher theoretical capacity as anode materials for lithium-ion batteries (LIBs). However, they often suffer from poor capacity retention owing to their low electrical conductivity and large volume variations during the charge/discharge process. Carbon coating is an effective way to enhance the electrical conductivity of metal oxides. The synergistic effects of the two components can also effectively improve the electrochemical performance of the material. In this study, MnO$_{2}$@ZIF-67 organic-inorganic hybrid nanostructures were prepared using MnO$_{2}$ nanowires as a template. N-doped carbon-coated MnO@CoMn$_{2}$O$_{4}$ nanowire composites (MnO@CoMn$_{2}$O$_{4}$@N-C) were synthesised by annealing. The organic ligand of ZIF-67 underwent carbonisation during high-temperature calcination to produce N-doped carbon, which improved the electrical conductivity. When MnO@CoMn$_{2}$O$_{4}$/N-C nanowire composites were used as the anode material for LIBs, a discharge capacity of 1 594.6 mA$\cdot$h/g was achieved in the first cycle, with a retention capacity of 925.8 mA$\cdot$h/g even after 100 cycles at current density of 0.1 A/g and a reversible capacity of 837.6 mA$\cdot$h/g at 0.5 A/g. It also had an excellent rate cycling performance. The outstanding electrochemical performance was attributed to the unique structure as well as the coating effect of N-doped carbon.