Development in the ionic liquid based electrolytes for lithium-ion batteries

Lithium-ion batteries nowadays are widely used as the power source for many consumer electronics including cell phones and portable computers. Electricity storage required strict safety protocols starting with the electrolyte choice, where organic carbonate electrolytes, under abuse conditions can lead to crack, ignition, or explosion of the cell. The new approach evolved based on ionic liquids (IL) due to their thermal and electrochemical stability, non-flammability and negligible vapor pressure. The new electrolyte based on imidazolium cation (C
₁
C
₆
Im
⁺
) with bis(fluorosulfonyl) imide anion, (FSI
^-
), was mixed with lithium bis(trifluoromethane-sulfonyl)imide, (LiNTf
₂
) salt and tested in full system configuration graphite (Cgr) and LiFePO
₄
(LFP). The capacity at C/20 rate for the first 10 cycles was 120 mAh.g
^-1
, afterwards, the capacity fades to 110 mAh.g
^-1
and remain stable for next 20 cycles. The XPS studies performed on the neat and cycled electrode (after first and tenth cycle) showed presence of LiF, Li
₃
N, poly-oxysulfurs and Li
₂
S. The film created on graphite surface during the first cycle was stable, also after 10 cycles. The results proved that ionic liquid based electrolytes with FSI anion is suitable for graphite electrodes and shows excellent capacities.