Yanxia Sun

Investigation of the synergetic effects of LiBF4 and LiODFB as wide-temperature electrolyte salts in lithium-ion batteries

Herein, we present the use of lithium tetrafluoroborate (LiBF4) as an electrolyte salt for wide-temperature electrolytes in lithium-ion batteries. The research focused on the application of blend salts to exhibit their synergistic effect especially in a wide temperature range. In the study, LiCoO2 was employed as the cathode material; LiBF4 and lithium difluoro(oxalate)borate (LiODFB) were added to an electrolyte consisting of ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC). The electrochemical performance of the resulting electrolyte was evaluated through various analytical techniques. Analysis of the electrical conductivity showed the relationship among solution conductivity, the electrolyte composition, and temperature. Cyclic voltammetry (CV), charge-discharge cycling, and AC impedance measurements were used to investigate the capacity and cycling stability of the LiCoO2 cathode in different electrolyte systems and at different temperatures. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were applied to analyze the surface properties of the LiCoO2 cathode after cycling. The results indicated that the addition of a small amount of LiODFB into the LiBF4-based electrolyte system (LiBF4/LiODFB of 8:2) may enhance the electrochemical performance of the LiCoO2 cell over a relatively wide temperature range and improve the cyclability of the LiCoO2 cell at 60xa0°C.

Large-scale synthesis of uniformly dispersed hexagram-like gibbsite by a controlled replacement reaction

A facile, convenient, and mild method has been developed for large-scale synthesis of uniformly dispersed 2D six-pointed star-like gibbsite micro–nano crystals with lateral size around 2.5 μm and thickness around 100 nm, through a replacement reaction between Al powder and water. Investigation of the influence of solvent in a series allows for conclusion that replacing the reactant solvent water with ethylene glycol not only effectively moderates the reaction, but also benefits control of shape, crystal structure, and dispersibility. In contrast, besides decreasing the reaction speed, the same function cannot be attributed to another inorganic solvent candidate absolute ethanol. This conclusion was supported by XRD, FE-SEM, TEM, FT-IR, TGA and PSD measurements. Moreover, the band gap of as-prepared gibbsite powder in EG–H2O mixture is 5.78 eV, which is mainly attributed to its surface low coordinated O2−. Theoretically, scale-up of this simple synthetic procedure for large-scale production of gibbsite powder with high crystallinity and purity should be very easy.