| Abstract |
Effects of electrolyte additives for high-voltage lithium-ion batteries on electrochemical performance are studies. High voltage batteries, Li|1.0 M LiPF6-EC/DEC (= 1/1, v/v)|LiNi0.5Mn1.5O4, contain phosphorous additives, such as tris(1,1,1,3,3,3-hexafluoropropan-2-yl) phosphate, tris(2,2,2-trifluoro ethyl) phosphite, tris(4-fluorophenyl)phosphine, (perfluorophenyl)diphenylphosphine, (difluoromethyl)(diphenyl)phosphine oxide, tris(pentafluorophenyl)phosphine, tris(3,5-bis(trifluoromethyl)phenyl)phosphine, triphenylphosphine oxide, and trio-tolylphosphine. The electrochemical properties of the batteries were investigated by cyclic voltammetry, charge-discharge measurements, and cycle-life tests. The cycle-life result shows that the battery with 2 wt.% of tris(4-fluorophenyl)phosphine has improved cyclabilty. The observation of scanning electron microscopy indicates that the additive can suppress the formation of solid electrolyte interphase (SEI) film on the LiNi0.5Mn1.5O4 cathode electrode. Furthermore, the X-ray photoelectron spectroscopy (XPS) results show that the additive indeed inhibits the formation of LiF growing thick SEI. Therefore, the Li|1.0 M LiPF6-EC/DEC (= 1/1, v/v)|LiNi0.5Mn1.5O4 with 2 wt.% of tris(4-fluorophenyl)phosphine has enhanced cycle-life performance. |
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