ABSTRACT
In order to improve the stability of high voltage electrolyte for 5 V-level LiNi0.5Mn1.5O4 cathode material, adiponitrile (ADN) with high oxidation stability was selected as the main solvent, meanwhile, 2% fluoroethylene carbonate (FEC) as the additive with good film forming effect was also used. And then, the effect of 2 mol L-1 LiBF4-GBL/ADN+2% FEC on the electrochemical performance of LiNi0.5Mn1.5O4 was explored at room temperature. The electrolyte system containing FEC can improve the cycle stability of the battery. At 1 C rate, the cycle capacity retention rate can reach 83% after 100 cycles, while the capacity retention rate of the electrolyte system without FEC and the ordinary commercial electrolyte system is only 77 and 68%, respectively. Besides, the rate performance of the battery with the addition of FEC also shows excellent performance, however, this kind of advantage is not obvious under the conditon of large rate. In addition, under the conditon of the synergistic effect between adiponitrile and fluoroethylene carbonate, the high-voltage electrolyte exhibits the good compatibility and lithium reversibility in the full cell with Li4Ti5O12 as the negative electrode.
ABSTRACT
Lithium sulfur batteries (Li-S) have been deemed to be the promising energy-storage systems. Nevertheless, the shuttle effect caused by diffusion of polysulfides limit their application. In this work, the different dimensions of g-C3N4 nanomaterials (2D g-C3N4 nanosheets and 3D g-C3N4 nanomesh) were doped in S electrode. Because of the large specific surface area of 3D g-C3N4 nanomesh and strong chemical adsorption of polysulfides can provide better effect for inhibition of shuttling effect and its proper electron passage make electrochemical kinetics of lithium-sulfur battery enhanced. The discharge specific capacity of the 3D g-C3N4 battery is up to 731 mAh/g and longer cycling performance with 540 mAh/g after 180 cycles. This experiment paves the way forward for the application of g-C3N4 on Li-S batteries.
