Exploring fluorinated electrolyte for high-voltage and high-safety Li-ion cells with Li(Ni_0.8Mn_0.1Co_0.1)O₂ cathode

Conventional carbonate-based electrolytes can be oxidized at voltages above 4.3 V, causing serious cell degradation, and are highly flammable that easily induces safety hazards. In this research, a non-combustible electrolyte for high-voltage Li(Ni_0.8Mn_0.1Co_0.1)O₂ cathode Li-ion cells is investigated, using propylene carbonate (PC) and 2,2,2-trifluoroethyl acetate (TFA) as solvents. The experimental results show that the electrolyte containing TFA can improve the cathode/electrolyte interface and mitigate side reactions so that the cells containing 1 M LiPF₆ in PC/TFA (3:7, v/v) and the additionally added 2 wt.% of fluoroethylene carbonate (named PT37) exhibit a more advanced cycling performance and rate performance than those with the conventional electrolyte at high voltages (3.0-4.5 V). Additionally, more competitive safety characteristics are revealed by PT37 cells through some typical safety evaluation tests involving the accelerating rate calorimetry test, nail test, and overcharge test. The results imply that a PT37 electrolyte is a hopeful option for high-voltage and high-safety Li-ion cells.