MnO₂ nanosheets@carbon nanotube-in-nanotube is rationally constructed through carbonization of tannic acid-treated zeolitic imidazolate framework-8 string of carbon nanotubes and subsequent chemical reaction of KMnO₄ and carbon. The ultrathin MnO₂ nanosheets are intimately coupled on the surface of carbon nanotube-in-nanotube. The composite shows large specific surface area (126.6 m² g⁻¹) and pore volume (0.4 cm³ g⁻¹). Comparative studies of cyclic voltammetry curves and galvanostatic charge-discharge profiles indicate that for MnO₂ nanosheets@carbon nanotube-in-nanotube, electrochemical activities and charge-discharge capabilities of MnO₂ and carbon are both significantly improved. The cycling measurements reveal that the composite shows much higher reversible capacity and cycling stability than pure MnO₂, carbon nanotubes, carbon nanotube-in-nanotube and MnO₂ nanosheets@carbon nanotubes. The superior Li storage performance is attributed to synergistic effect of MnO₂ nanosheets and carbon nanotube-in-nanotube. The ultrathin nanosheet structure of MnO₂ and the unique nanotube-in-nanotube structure of carbon remarkably shorten diffusion paths of Li ions, facilitate transport of electrolyte ions, promote contact between electrode material/electrolyte, improve structural stability of the composite, increase electronic conductivity of MnO₂, enhance reaction kinetics.

MnO ₂纳米片@碳纳米管纳米管是通过单宁酸处理的沸石咪唑酯骨架-8 碳纳米管串的碳化和随后的KMnO ₄与碳的化学反应合理构建的。超薄的 MnO ₂纳米片紧密耦合在纳米管中的碳纳米管表面。该复合材料显示出大的比表面积（126.6 m ² g ^-1）和孔体积（0.4 cm ³ g ^-1）。循环伏安曲线和恒电流充放电曲线的比较研究表明，对于 MnO ₂nanosheets@carbon nanotube-in-nanotube，MnO ₂和碳的电化学活性和充放电能力均得到显着提高。循环测量表明，复合材料显示出比纯 MnO ₂、碳纳米管、纳米管中的碳纳米管和 MnO ₂纳米片@碳纳米管更高的可逆容量和循环稳定性。优异的锂存储性能归因于MnO ₂纳米片和纳米管中碳纳米管的协同效应。MnO ₂的超薄纳米片结构独特的碳纳米管纳米管结构显着缩短锂离子的扩散路径，促进电解质离子的传输，促进电极材料/电解质之间的接触，提高复合材料的结构稳定性，增加MnO _{2 的}电子电导率，增强反应动力学.