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Wang et al. Energy Mater 2023;3:300040 https://dx.doi.org/10.20517/energymater.2023.28 Page 3 of 14

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high-voltage full-cell cycling, was used as a control electrolyte . The results show that the fluorinated ether
electrolyte system behaves better stabilities than the carbonate electrolyte system against both high-voltage
layered oxides cathodes and graphite anodes. The NCM811||graphite cells with the fluorinated ether
electrolyte exhibit stable cycling at a cut-off voltage of 4.4 V, maintaining capacity retention greater than
90% after 200 cycles at 0.33 C. When the fluorinated ether electrolyte is applied to the LCO||graphite cells
with a cut-off voltage of 4.5 V, the cells deliver capacity retention of 97% after 100 cycles at 0.33 C.
Moreover, the large-capacity NCM811||graphite pouch cells (1,780 mAh) using the fluorinated ether
electrolyte perform better cycling performance than the carbonate electrolyte at both room temperature and
elevated temperature.

EXPERIMENTAL DETAILS
Electrolytes and cells preparation, density functional theory (DFT) calculation
All the reagents, including lithium salts and solvents with a purity of above 99.9%, were provided by
Capchem Technology Co., Ltd. (Shenzhen, China). The fluorinated ether electrolyte was formed by
dissolving 374 mg LiFSI in 1 mL mixed solvent with TTME and DME at a volume ratio of 4:1. The final
concentration of lithium salt was 1.4 mol/L. A conventional ether electrolyte containing DME with
1.4 mol/L LiFSI and a commercial carbonate electrolyte containing 1 mol/L LiPF in a mixture of EC/DEC
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(30:70, wt./wt.) with 1 wt.% VC and 1 wt.% PS were used as the two control electrolytes. All molecules were
drawn and calculated with the Gaussian software. The density functional theory (DFT) calculation was
carried out in Opt+Freq job type, a Ground State method with default Spin was set, and a 6-31 G basis set
was used.

Electrochemical measurements
Electrochemical measurements were carried out using 2032-type coin cells or pouch cells. Dry NCM811||
artificial graphite (AG) pouch cells (with 1,780 mAh capacity) were provided by Capchem Technology Co.
Ltd. For coin cells, all the electrode plates, except lithium metal, were obtained from pouch cell disassembly.
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The active material loading of NCM811 was 3.13 mAh/cm , and the loading of LCO was 2.96 mAh/cm . All
coin cells were fabricated in an argon (Ar)-filled glovebox, with 50 μL electrolyte and one layer of Celgard
2400 separator used in each cell. For pouch cells, the dry pouch cells were cut and then dried at 85 °C under
vacuum for 24 h. The pouch cells were then injected with 5.8 g of the fluorinated ether electrolyte (or
control electrolytes) and were then sealed in an Ar-filled glove box. The commercial-standard formation
and aging processes were applied to the assembled pouch cells before further electrochemical
measurements .
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Cyclic voltammetry (CV) was performed over a voltage range from an open circuit voltage to 0.01 V and
then to 2.0 V. Electrochemical impedance spectrometry (EIS) was conducted in the frequency range of
0.01 Hz to 106 Hz at an amplitude voltage of 10 mV. The CV and EIS measurements were carried out using
a Solartron electrochemical workstation (1470E, UK), in which the EIS measurements were investigated at
50% state of charge (SOC). NCM811 coin cells were cycled between 2.8 V and 4.4 V (1 C = 200 mA/g), and
LCO coin cells were cycled between 3.0 V and 4.5 V (1 C = 180 mA/g). After the first two activation cycles
at 0.1 C charge/discharge, the cells were cycled at a rate of 0.33 C. For pouch-cell measurements, the voltage
range was set as 3.0-4.25 V. Discharge direct current internal resistance (DCIR) was measured at 50% SOC
during each cycle of pouch cells.

In situ gas analysis
Differential electrochemical mass spectrometry (DEMS) experiments were carried out with a Hiden
Analytical mass spectrometer system (HPR20, UK). Filtered high-purity Ar gas was used as the carrier gas.
The electrodes were prepared by mixing active materials (graphite or NCM811), super P, and