Enhancement of Operating Voltage and Temperature Range by Adding Lithium bis(fluorosulfonyl)imide as Electrolyte Additive

Abstract

Electrolytes consisting of carbonate solvents and LiPF 6 readily decompose at high operating voltages, causing poor battery performances. In order to meet the needs of high voltage and high specific energy cells, electrolytes with improved electrochemical stabilities are urgently required. Here, we have introduced the lithium bis(fluorosulfonyl)imide (LiFSI) as an electrolyte additive to accomplish this goal. Through the research in this paper, it is found that the electrolyte system with LiFSI can form more stable and uniform solid electrolyte interphase (SEI) film during the cycle, which can be used to suppress the decomposition of carbonate-based electrolytes. Subsequently, this finding is supported by the density functional calculations and the structural analysis. Li-Ni 0.5 Co 0.2 Mn 0.3 O 2 /graphite full cells with different amounts of LiFSI additive are fabricated to demonstrate the improvement of electrochemical performance. Working at 4.4 V and 1 C, the capacity retention rate of cells with 5 wt.% LiFSI is significantly enhanced compared with non-LiFSI (52.4 % for none and 85.0 % for 5 wt. % loading at room temperature after 120 cycles; 47.5 % for none and 80.0 % for 5 wt. % loading at 45°C after 100 cycles).

Unveiling the Mystery of Lithium Bis(fluorosulfonyl)imide as a Single Salt in Low-to-Moderate Concentration Electrolytes of Lithium Metal and Lithium-Ion Batteries

“…Research also showed that different sources of LiFSI do not lead to visible differences in the cycling performance of Li/LiFePO 4 cells. 10 Owing to the concern with Al corrosion, LiFSI is at present mainly employed as an additive [11][12][13] or a co-salt [14][15][16][17] to improve the performances of Li and Li-ion batteries. In efforts to use LiFSI as a single electrolyte solute in the Li metal and Li-ion batteries, several strategies have shown success in suppressing Al corrosion, for example, high concentration electrolytes (HCEs), [18][19][20][21][22][23] fluorinated solvents 24,25 and particularly using fluorinated co-solvents to form localized high concentration electrolytes (LHCEs), [26][27][28] and ionic liquids (ILs).…”

A functional electrolyte containing propyl 4-methylbenzene sulfonate (PMBS) additive to improve the cycling performance of the LiNi0.8Co0.1Mn0.1O2/graphite full cell under the low temperature of −10 °C

“…In the C 1s and O 1s spectra, the C–O (286.6 eV in C 1s and 533.2 eV in O 1s) and C–C (284.8 eV) bonds correspond to the CMC and graphite active materials in the graphite anode, while the Li 2 CO 3 (289.9 eV) peak and CO (288.6 eV in C 1s and 531.7 eV in O 1s) correspond to the decomposition products of the electrolyte. 48–50 The intensity of the C–C peak on the surface of the anode without additives is significantly lower than that of the anode with PMBS, and the intensity of the C–O peak is also reduced, indicating that a thicker SEI film was formed on the surface of the graphite anode with blank electrolyte. 36 Compared with the anode with PMBS, the intensity of the Li 2 CO 3 signal peak on the anode surface with blank electrolyte is higher than the corresponding intensity with PMBS.…”

“…In the S 2p spectrum, the characteristic peaks at 168.7 eV and 164.2 eV (corresponding to ROSO 2 Li and C-S bond, respectively) were detected on the surface of the cathode with PMBS, which suggests that PMBS participated in the construction of the CEI lm. 29,[45][46][47] The XPS test results of the cycled graphite anode are shown in [48][49][50] The intensity of the C-C peak on the surface of the anode without additives is signicantly lower than that of the anode with PMBS, and the intensity of the C-O peak is also reduced, indicating that a thicker SEI lm was formed on the surface of the graphite anode with blank electrolyte. 36 Compared with the anode with PMBS, the intensity of the Li 2 CO 3 signal peak on the anode surface with blank electrolyte is higher than the corresponding intensity with PMBS.…”

Enhancing the polymer electrolyte–Li metal interface on high-voltage solid-state batteries with Li-based additives inspired by the surface chemistry of Li7La3Zr2O12

“…This compound passivates and protects the surface of the cathode and anode from further electrolyte decomposition, and promotes Li-ion transport. 15,48,[53][54][55][56] Due to the unexpected augmented presence of LiF in the inner part of the SEI layer with the LiOH containing electrolyte, ssNMR measurements of both SPEs have been performed prior to applying any current or voltage.…”