Na-alginate as a binder in an aqueous solvent has been applied in the preparation of sulfur cathodes for lithium-sulfur batteries.Their electrochemical performances have been investigated by a charge-discharge cycle test and electrochemical impedance spectroscopy (EIS).The EIS tests indicated that the alginate sulfur cathode had lower resistance and better kinetic characteristics than those of the poly (vinylidene fluoride) (PVDF) sulfur cathode using PVDF as a binder in a N-methy-2-pyrrolidone (NMP) solvent.The charge-discharge tests showed that the discharge capacity and the capacity retention rate of Na-alginate sulfur cathode were 508 mAh·g-1and 65.4% at the 50th cycle with a current density of 335 mA·g-1.Compared with PVDF sulfur cathode,the alginate sulfur cathode showed a remarkably better cycle performance.These results show that the alginate binder has promising potential for lithium-sulfur battery applications.
Weizhai BaoZhian ZhangYongqing GanXiwen WangJie Lia
Lithium difluoro(axalato)borate (LiODFB) was synthesized in dimethyl carbonate (DMC) solvent and purified by the method of solventing-out crystallization. The structure characterization of the purified LiODFB was performed by Fourier transform infrared (FTIR) spectrometry and nuclear magnetic resonance (NMR) spectrometry. The electrochemical properties of the cells using 1 mol/L LiPF6 and 1 mol/L LiODFB in ethylene carbonate (EC)/DMC were investigated, respectively. The results indicate that LiODFB can be reduced at about 1.5 V and form a robust protective solid electrolyte interface (SEI) film on the graphite surface in the first cycle. The graphite/LiNi1/3Mn1/3Co1/3O2 cells with LiODFB-based electrolyte have very good capacity retention at 55 ℃, and show very good rate capability at 0.5C and 1C charge/discharge rate. Therefore, as a new salt, LiODFB is a most promising alternative lithium salt to replace LiPF6 for lithium ion battery electrolytes in the future.
The activated carbon wound supercapacitors with TEABF4/propylene carbonate(PC)and TEABF4/acetonitrile(AN) electrolytes were prepared.The effects of the electrolyte and temperature on the capacitance behavior were investigated by cyclic voltammetry(CV)and constant current charge-discharge.Compared with the PC-based supercapacitor,the AN-based supercapacitor has higher capacitance and lower equivalent serial resistance(RES)at discharge currents ranging from 5 to 1 000 mA and 25℃. Moreover,temperature effects are more prominent for PC-based supercapacitor than for AN-based supercapacitor.When the measurement temperature ranges from 60℃to-40℃the capacitance changes from 5.1 to 2.5 F and RES changes from 135 to 876 mΩfor the PC-based supercapacior,while the AN-based supercapacitor shows less change in capacitance and RES.Thus AN-based supercapacitor exhibits excellent power characteristics and temperature property.
