Manganese Oxide/carbon Nanofiber Composite Membrane As Anode For Lithium Ion Batteries

In order to meet the growing performance requirements for the next generation lithium ion batteries (LIBs), it is imminent to find an anode material with high capacity and long cycle-life. MnO has great potential for the advantages of high specific capacity (756 mA h g-1), low working voltage (1.032 V vs Li/Li+), rich national resources and envirmental-friendly. However, the low conductivity (10-8?10-6 S cm-1)and intense volume expansion severely limit the applicaton of MnO in practice. Nanosized MnO can not noly increase the specific area and active site which is good for enlarging the contact area with the electrolyte, but also shorten the diffusion length for electrons and Li+, as a result improving the electrochemical performance. Coating MnO with carbon materials provides an advanced avenue for enhancing the conductivity and buffer the structural expansion caused by Li+insertion/extraction to ensure the integrity of the electrode materials.Electrostatic spinning technology is a commonly used method for preparing fiber membrane. The process is simple and the controllability is high. In this paper, MnO/CNFs composite membrane with different morphologies was prepared by electrospinning, and the effect of the content of active substances on the electrochemical performance was investigated.MnO nanoparticles/CNFs composite membrane was prepard by Mn(CH3COO) 2·4H2O, KMnO4 and PAN as raw materials. MnO2 nanoparticles were achieved by solid-state reaction at low temperature.The content of active materials in the composite was increased to 62.51 wt%. The electrochemical performance of electrode was not as good as expected due to searious aggregation of nanoparticles. The maximus specific capacity was only 300 mA h g-1 after 100 cycles at a current density of 200 mA g-1.Ultra-fine MnO/CNFs composite membrane was prepared derived from Mn (CH3COO) 2·4H2O and PAN after high temperature heat treatment. SEM and TEM images showed that the diameter of the fiber changed with different content of active material. The composite membrane was assembled into a half-cell as a freestanding anode and tested for electrochemical performance. Rate capability was significantly improved, indicating that the carbon layer was coated to improve the electrical conductivity. However, due to the low content of active materials in the systerm, the specific capacity of the electrode is low.In order to solve the problem of agglomeration of nanoparticles,MnO2 nanorods were prepared by hydrothermal method. Hollow MnO nanoprods/CNFs composite membrane was prepared with high flexibility.SEM and TEM images show that there is no agglomeration within the fibers, and a lot of channels and pores are produced, which shorten the transmission distance of Li+ and buffer the volume expansion of Li+during insertion/extraction. The content of MnO in the composite is up to 65.97 wt%. The memebrane electrode exhibits high reversible capacity,excellent rate capability and long cycle life. The membrane electrode shows remarkble value of 773 mA h g-1 after 100 cycles at a current density of 200 mA g-1 between 0 and 3 V when the content of hollow Mn02 nanorods was 30 wt%.