One-step solvothermal synthesis of high-capacity Fe3O4/reduced graphene oxide composite for use in Li-ion capacitor

To obtain high-performance lithium-ion capacitors (LICs), superior Fe3O4/reduced graphene oxide (rGO) composite has been synthesized by a facile one-step solvothermal method. The morphologies and structures of materials were characterized by powder X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and N-2 adsorptionedesorption isotherm. Electrochemical performances of materials were evaluated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy in half cell. Compared with the agglomerated pure Fe3O4, the high-crystallinity Fe3O4 particles uniformly distributes onto the rGO sheets and the Fe3O4 particles possess smaller size of 150-250 nm in Fe3O4/rGO composite. Therefore, the introduction of rGO can not only increase the specific surface area but also enhance the electrical conductivity of electrode material, leading to the improvement of electrochemical performances. The Fe3O4/rGO composite can reach high specific capacity of 1065 mAh g(-1) at 0.1 A g(-1), and exhibits good rate capability and cyclic stability. Using the as-prepared Fe3O4/rGO composite as negative electrode and activated carbon (AC) as positive electrode, a Fe3O4/rGO//AC LIC was fabricated. The assembled Fe3O4/rGO//AC LIC presents outstanding energy density of 98.8Wh kg(-1) and power density of 3.4 kW kg(-1). Moreover, 78.9% of capacity can be retained after 1000 charge/discharge cycles. (c) 2019 Elsevier B.V. All rights reserved.