Application of a nonflammable electrolyte containing Pp13TFSI ionic liquid for lithium-ion batteries using the high capacity cathode material Li[Li0.2Mn0.54Ni0.13Co0.13]O2

Abstract

A mixture of an organic carbonate solvent and a nonflammable ionic liquid (IL) has been investigated as a new electrolyte to improve the performance of lithium-ion batteries and their safety at high voltage. In this work, we have studied the thermal stability and electrochemical properties of N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (Pp13TFSI)-containing electrolyte and applied it in a lithium-ion battery using the high capacity cathode material Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂. The thermogravimetric analysis and flammability tests indicated that the electrolyte exhibited non-flammablility when the Pp13TFSI content was 40–100 vol%. Using this nonflammable Pp13TFSI-based electrolyte, Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ showed a high discharge capacity, low irreversible capacity loss and an enhanced cyclability. The initial discharge capacity of this cathode material reached 246 mAh g⁻¹ in the 40 vol% Pp13TFSI electrolyte at 20 mA g⁻¹. The initial charge/discharge coulombic efficiency increased to 80.2% as the Pp13TFSI content increased. Furthermore, the cell displayed good cyclability. After 60 cycles using 40 vol% Pp13TFSI, the discharge capacity was still above 230 mAh g⁻¹. Therefore, the nonflammable Pp13TFSI-based electrolyte can be used as a safe electrolyte for Li-rich lithium-ion batteries and it has good electrochemical performance.