Shaojun Shi

Rapid Self-Assembly Spherical Li1.2Mn0.56Ni0.16Co0.08O2 with Improved Performances by Microwave Hydrothermal Method as Cathode for Lithium-Ion Batteries

Spherical Li-rich Li1.2Mn0.56Ni0.16Co0.08O2 compound is rapidly synthesized through a facile microwave hydrothermal method followed by a high-temperature solid-state reaction. Homogenous spherical precursor can be precipitated through the microwave hydrothermal (MH) method within 30 min without rigorous coprecipitation condition. The as-prepared Li-rich compound exhibits a hierarchical structure composed of spherical secondary particles (2-3 μm) and small primary particles (150-250 nm) with pores. X-ray diffractometry (XRD) and Brunauer-Emmett-Teller (BET) tests prove that a well-formed layered structure and a large specific surface area containing pores are obtained through the MH method. Such structure is a benefit for the thorough contact between active materials and electrolyte to increase the reactive points. Thus, the as-prepared Li-rich compound exhibits perfect electrochemical performances with a high discharge capacity of 235.6 mAh g(-1) at a current density of 200 mA g(-1). Even at higher current densities of 1000 and 2000 mA g(-1), discharge capacities of 168.6 and 131.2 mAh g(-1) are still maintained, respectively. Furthermore, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic intermittent titration technique (GITT) are carried out to study the material prepared by microwave hydrothermal method. It is considered as an efficient way to synthesize Li-rich compound as cathode material for applications.

2D film of carbon nanofibers elastically astricted MnO microparticles: A flexible binder-free anode for highly reversible lithium ion storage

MnO as anode materials has received particular interest owing to its high specific capacity, abundant resources, and low cost. However, serious problems related to the large volume change (>170%) during the lithiation/delithiation processes still results in poor rate capability and fast capacity decay. With homogenous crystals of MnO grown in the network of carbon nanofibers (CNF), binding effect of CNF can effectively weaken the volume change of MnO during cycles. In this work, a CNF/MnO flexible electrode for lithium-ion batteries is designed and synthesized. The CNF play the roles of conductive channel and elastically astricting MnO particles during lithiation/delithiation. CNF/MnO as binder-free anode delivers specific capacity of 983.8 mAh g-1 after 100th cycle at a current density of 0.2 A g-1 , and 600 mAh g-1 at 1 A g-1 which are much better than those of pure MnO and pure CNF. The ex-situ morphologies clearly show the relative volume change of MnO/CNF as anode under various discharging and charging times. CNF can elastically buffer the volume change of MnO during charging/discharging cycles. A facile and scalable approach for synthesizing a novel flexible binder-free anode of CNF/MnO for potential application in highly reversible lithium storage devices is presented.