Vinyl ethylene sulfite (VES) is studied as a new additive in propylene carbonate (PC)-based electrolyte for lithium ion batteries. The electrochemical results show that the artificial graphite material exhibits excellent electrochemical performance in a PC-based electrolyte with the addition of the proper amount of VES. According to our spectroscopic results, VES is reduced to ROSO2Li (R=C4H6), Li2SO3 and butadiene (C4H6) through an electrochemical process which precedes the decomposition of PC. Furthermore, some of the Li2SO3 could be further reduced to Li2S and Li2O. All of these products are proven to be components of the solid electrolyte interface (SEI ) layer.National Natural Science Foundation of China (NNSFC) [29925310, 20433060, 20473068]; Ministry of Science and Technology, China [2007CB209702

The addition of 2% vinyl ethylene carbonate (VEC) into LiPF 6 /EC + DMC electrolyte can significantly improve the cyclic performance of a LiNi 0.8 Co 0.2 O 2 /Li cell at elevated temperatures such as 50 °C. In situ electrochemical mass spectrometry (EMS) was used to investigate the gas evolution spectroscopy in the cell during a charge/discharge process with and without VEC additive. Fourier transform infrared (FTIR), ultraviolet-visible (UV-vis), and liquid nuclear magnetic resonance (NMR) spectroscopies were also carried out to investigate the reactions between various electrolyte components and VEC without the electrochemical reaction. We propose the possible polymerized products based on the spectroscopy and the acting mechanism of the VEC additives.

Fluoroethylene carbonate (FEC) was used as a kind of film-forming electrolyte additive for lithium-ion battery. The cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) were used to study the influence of FEC additive on the electrochemical properties of mesocarbon microbead (MCMB)/Li cell. The results show that a thin, low-resistive and uniform SEI film was formed on the surface of MCMB electrode, which cause the excellent cyclability of the electrode.

LiPF 6 inethylenecarbonate(EC),dimethylcarbonate(DMC),andmethylethylcarbonate(EMC)(1颐1颐1byvolume). TheeffectsofFEConlithiumionbatteryperformanceandonthemesocarbonmicrobead(MCMB)electrode/electrolyte interphasewerestudiedbycyclicvoltammetry(CV),scanningelectronmicroscopy(SEM),energydispersivespectroscopy (EDS)andelectrochemicalimpedancespectroscopy(EIS).Theresultsindicatedthattheapplicationofa2%(volume ratio)ofFECsuppressedelectrolytedecompositionandcausedtheformationofanexcellentsolidelectrolyteinterphase (SEI)filmontheMCMBelectrode.Thebatteryresistancedecreasedwhilethespecificcapacityandcyclicstabilityof thebatteryincreased.