Guihuang Fang

Enhancing the High-Voltage Cycling Performance of LiNi1/3Co1/3Mn1/3O2/Graphite Batteries Using Alkyl 3,3,3-Trifluoropropanoate as an Electrolyte Additive

The present study demonstrates that the use of alkyl 3,3,3-trifluoropropanoate, including methyl 3,3,3-trifluoropropanoate (TFPM) and ethyl 3,3,3-trifluoropropanoate (TFPE), as new electrolyte additive can dramatically enhance the high-voltage performance of LiNi1/3Co1/3Mn1/3O2/graphite lithium-ion batteries (3.0-4.6 V, vs Li/Li+). The capacity retention was significantly increased from 45.6% to 75.4% after 100 charge-discharge cycles due to the addition of 0.2 wt % TFPM in the electrolyte, and significantly increased from 45.6% to 76.1% after 100 charge-discharge cycles due to the addition of 0.5 wt % TFPE in the electrolyte, verifying their suitability in this application. Electrochemical impedance spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy were employed to study the effect of TFPM and TFPE on cell performance. The data indicates that the improved cycling activity can be ascribed to the participation of TFPM or TFPE in the formation of a thinner cathode/electrolyte interfacial film, thereby enhancing the cell cycling performance owing to a reduced interfacial resistance at high voltage.

(4-Methoxy)-phenoxy pentafluorocyclotriphosphazene as a novel flame retardant and overcharge protection additive for lithium-ion batteries

We evaluate (4-methoxy)-phenoxy pentafluorocyclotriphosphazene (4-MPPFPP) as a novel flame retardant and overcharge protection additive for lithium-ion batteries. The flammability of electrolytes containing 4-MPPFPP was studied by measuring the self-extinguishing time of the electrolytes. We found that 4-MPPFPP suppresses the flammability of the electrolyte. Moreover, 4-MPPFPP can be electrochemically polymerized on the surface of an electrode. This will protect batteries from voltage runaway. The influence of proper 4-MPPFPP addition on the cycling performance and capacity is negligible. The results may be helpful for the further design of advanced lithium ion battery electrolytes. We discuss the effect of the additive on the electrode/electrolyte interface and propose possible reaction paths.