Manganese silicate hollow spheres enclosed in reduced graphene oxide as anode for lithium-ion batteries

摘要

Herein is presented a new composite material consisting of nanostructured Mn silicate hollow spheres enclosed in a matrix of reduced graphene oxide (rGO), synthesized via a facile and low-cost hydrothermal method. The hollow structure provides free space to accommodate the volume expansion occurring upon lithiation, while the rGO facilitates the electron transport, thus enhancing the lithiation kinetics. Remarkably, the composite provides a continuously increasing reversible capacity up to ca. 1300 mAh g(-1) after 350 cycles. This increase in capacity is ascribed in part to the steadily rising fraction of Mn2+/Mn3+ being oxidized to Mn4+ as well as the reversible formation of the solid electrolyte interphase. The particle morphology, in fact, remains unaltered, as evidenced by ex situ scanning electron microscopy - even after 350 cycles. Additionally, the implementation of manganese as transition metal for the reversible conversion reaction appears advantageous with regard to the overall electrochemical performance and the relatively lower lithiation potential. (C) 2017 Elsevier Ltd. All rights reserved.