Biocarbon-directed vertical δ-MnO2 nanoflakes for boosting lithium-ion diffusion kinetics

Manganese dioxide (MnO2) with high theoretical capacity (1230 mAh/g) and low cost is considered as a promising anode material for next generation high energy density lithium-ion (Li+) batteries. However, the intrinsic low electric conductivity and volume change during cycling process limit its applications. In this work, a unique delta-MnO2/C composite has been synthesized through the directed growth of 2D delta- MnO2 nanosheets on the cabbage-leaf-derived biocarbon. The biocarbon acts as both structure buffer to accommodate the volume expansion and conductive agent to promote electron and ion transport. Moreover, oriented delta-MnO2 nanosheets are beneficial for increasing contact area between electrode and electrolyte, thus providing more active sites and shortening the Li+ transmission routes. Electrochemical performances show that delta-MnO2/C displays large reversible capacity (754 mAh/g after 250 cycles at current density of 0.1 A/g), excellent rate capability as well as low charge transfer resistance (17.3 U), and high Li+ diffusion rate (D-Li(+) = 2.91 x 10(-14) cm(2)/s) during the cycles. Furthermore, the density functional theory calculations reveal the lower Li+ migration barrier energies and improved Li+ diffusion kinetics in delta-MnO2/C hetero-layer. This study provides a novel strategy to design advanced nanocomposites, using natural plant-leaf derivatives as structure-directing agents, for the next generation energy storage and conversion systems. (C) 2022 Elsevier Ltd. All rights reserved.

Automated summary

A novel composite of manganese dioxide and biocarbon has been synthesized, which exhibits excellent electrochemical performance with high capacity, good rate capability, low charge transfer resistance, and high Li+ diffusion rate.