A three-dimensional core-shell nanostructured composite of polypyrrole wrapped MnO(2)/reduced graphene oxide/carbon nanotube for high performance lithium ion batteries

Abstract

Manganese oxides are promising anode materials for their high-energy density. However, they suffer from poor rate capability and fast capacity fading. Herein, we construct a three-dimensional (3D) core-shell structured polypyrrole (PPy)/MnO₂-reduced graphene oxide (rGO)-carbon nanotubes (CNTs) composite via a facile two-step method. In the structure, the CNTs can facilitate fast electron conduction and keep structural integrity. The flexible and conductive rGO nanosheets work as both a reactive material and a carrier for MnO₂ in-situ growth. The MnO₂ nanosheets well distributed on the rGO/CNTs scaffold favor the energy storage by way of fast Li⁺ insertion and extraction. PPy nanoparticles (∼10nm) well wrapped on the MnO₂ nanosheets not only enable the interfacial stabilization, but also provide a buffer layer to accommodate the volume expansion. As a result, the as-prepared PPy/MnO₂-rGO-CNTs composite exhibits high specific capacity, excellent cycling stability and good rate capability. A reversible specific capacity of 1748.1mAhg^-1 is achieved at the current density of 100mAg^-1 after 200 cycles. Even at a high current density of 1000mAg^-1, the composite still exhibits 941.1mAhg^-1 after 1200 cycles. The design strategy of the composite can be extended to other high-capacity metal oxide material.

Keywords: Carbon nanotubes; Lithium ion batteries; MnO(2); Polypyrrole; Reduced grapheneoxide.