Three dimensional hierarchically porous crystalline MnO₂ structure design for a high rate performance lithium-ion battery anode

A reasonably designed anode of hierarchically porous crystalline manganese dioxide on nickel foam has been successfully synthesized by facile anodic electrochemical deposition in combination with heat treatment. The three dimensional structure avoids the application of binder and conductive additives. The Ni foam provides a highly electronically conductive network in conjunction with a large surface area to support well contacted MnO₂ nanoparticles and effectively increases the mechanical strength of the MnO₂ anode as well as suppresses the aggregation of MnO₂ nanoparticles during discharge/charge processes. The hierarchical pores composed of a large amount of macropores and mesopores can not only accommodate the volume change of MnO₂ nanoparticles during Li ion insertion/extraction, but also accelerate the penetration of electrolyte and promise fast transport and intercalation kinetics of Li ions. The crystalline MnO₂ anode exhibits a higher electrochemical performance than the amorphous one. As a result, the hierarchically porous crystalline MnO₂ anode shows a long cycling life of 778.0 mA h g^-1 after 200 cycles at a current density of 0.4 A g^-1 and high-rate capability of up to 82% capacity retention even after the current density increases 20 times from 0.1 to 2.0 A g^-1.