Spherical Li-rich Li 1.2 Mn 0.56 Ni 0.16 Co 0.08 O 2 compound is rapidly synthesized through a facile microwave hydrothermal method followed by a high-temperature solidstate 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.

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Commercial polyolefin separators often cause explosions and thermal runaways in lithium-ion batteries due to their poor thermal stability. Therefore, various polymer separators with high thermal stability have attracted the attention of researchers. In this paper, a kind of special nano-TiO2/Polyimide (TiO2@PI) composite separator was prepared by adding nano-TiO2 particles with certain content to the PAA solution before electrospinning. It is found that the added TiO2 ceramic particles greatly improve the flame retardant performance of the separator, and at the same time, they inhibit lithium dendrites and prevent the internal short circuit of the battery. As a result, the TiO2@PI nanofiber separator (5.0-TiO2@PI) prepared by a spinning solution with a TiO2 concentration of 5.0 wt % is formed by connecting spherical beads with a diameter of about 500 nm, which greatly inhibits lithium dendrites. It has better properties, such as electrolyte uptake (721%) and ionic conductivity (2.52 mS cm–1). The LiCoO2/Li battery based on 5.0-TiO2@PI nanofiber separator has a higher discharge capacity even at a current density of 4 C, which is better than that of PE separator. The use of this 5.0-TiO2@PI nanofiber separator has enlightening significance for the safety of high energy density batteries.

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Traditional polyolefin separators cannot guarantee safety for lithium-ion batteries at high temperature due to their low melting point, especially for high power discharge. Therefore, it is imperative to develop separators with excellent thermal stability. In this paper, we have prepared TiO 2 modified PVDF composite separators by electrospinning. When compared with commercial PE separators, this kind of composite separators show superior thermal stability at 160 C. In addition, it is found that the 0.5-TiO 2 @PVDF separator exhibits excellent flame retardant and optimal tension strength. Meanwhile, the 0.5-TiO 2 @PVDF separator exhibits ideal liquid electrolyte storage capacity, which improves the ionic conductivity (0.68 mS cm À1 ). As a result, the LiCoO 2 jjLi cells with 0.5-TiO 2 @PVDF separator have high discharge capacity retention rate at a current density of 1 C (300 cycles) and excellent rate performance (1.75 mAh at 5 C). In short, nano-TiO 2 modified PVDF separator has a great application prospect in high-performance and high-safety lithium-ion batteries.