Tris(2,2,2-trifluoroethyl) phosphite as an electrolyte additive for high-voltage lithium-ion batteries using lithium-rich layered oxide cathode
Résumé
In this paper, we report positive effect of Tris(2,2,2-trifluoroethyl) phosphite (TTFP) as additive during initial activation and cycling of Li-rich-NMC xLi2 MnO3 -(1 - x)LiMO2 (x >> 1; M = Ni, Co, Mn) cathode in EC/DMC + 1 M LiPF6 electrolyte. Firstly conductivity and viscosity of electrolyte with x wt.% TTFP; 0 wt.% < x < 20 wt.% were studied. From the electrochemical characterization using cyclic voltammetry, galvanostatic charge/discharge and EIS we show that TTFP passives aluminum current collector and the acts as oxygen scavenger during the extended activation plateau up 4.7 V vs. Li+/Li (up to 301 mAh g-1 in charge). The beneficial effect of TTFP improves the long-term cycling stability of the cathode with more than 95% of initial capacity in Gr//Li-Rich -NMC full cell is maintained after 50 cycles at C rate. Finally, XPS analysis of Li-rich -NMC electrodes show presence of TTFP on the surface during cycling and confirm the presence of Mn3+ at the end of discharge. The convergence of all characterizations indicates that TTFP should act as a catalyst to several surface reactions which are beneficial to long cycling cell performances. © 2015 Elsevier B.V. All rights reserved.
Mots clés
Surface reactions
Secondary batteries
Scavenging
Manganese oxide
Manganese
Cathodes
Additives
Chemical activation
Cyclic voltammetry
Electric batteries
Electric discharges
Electrodes
Electrolytes
Lithium alloys
Lithium
Lithium compounds
Cathode activation
Electrolyte additives
Electrochemical characterizations
Li-ion batteries
Lithium-rich layered oxides
Phosphite
Lithium-ion batteries
High voltage
Galvanostatic charge/discharge
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