Fig 1

(a) Chemical structures and HOMO energy level diagrams of salts, solvents, and additive. (b) LSV profiles of Li||Al cells with ED and PFB electrolytes at a constant scan rate of 0.1 mV·s−1. (c) CV curves for Li||LCO half cells with ED and PFB electrolytes (3.0–4.6 V, 0.1 mV·s−1)."

Fig 2

Electrochemical performances of Li||LCO half cells using different electrolytes. (a) The rate performance of LCO cathode with ED, PF, and PFB electrolytes. (b) Charge and discharge curves of the GITT measurements conducted after first cycle, and the corresponding Li+ diffusion coefficient (DLi+) during (c) charging and (d) discharging in different electrolytes. (e) Cycling performance of Li||LCO half cells at 0.5C in the voltage range of 3.0–4.6 V. (f–h) The charge and discharge curves of the 1st cycle and the 50th cycle and voltage decay comparison of Li||LCO half cells at 0.5C under cut-off voltage of 4.6 V in (f) ED, (g) PF, and (h) PFB electrolytes."

Fig 3

Chemical composition of CEIs on LCO surface cycled in different electrolytes. The typical XPS (a) C 1s, (b) O 1s, (c) F 1s, and (d) B 1s spectra of CEIs derived from ED, PF, and PFB electrolytes. (e) The intensity of CEIs chemical components and (f) the element weight ratio obtained from XPS measurement of CEIs formed in different electrolytes."

Fig 4

(a–c) TEM images of LCO cathodes cycled in (a) ED, (b) PF, and (c) PFB electrolytes at 4.6 V. (d–f) Variation of CEI component ratio with etching time in (d) ED, (e) PF, and (f) PFB electrolytes. (g–i) Contour plots of the (g) O 1s, (h) F 1s, (i) B 1s spectra for the CEI derived from PFB electrolyte."

Fig 5

Structural characterizations of the cycled LCO cathodes in different electrolytes at 4.6 V. (a–c) In situ XRD characterization for LCO cathodes cycled in different electrolytes. The voltage profile and corresponding contour plot of the (003) peaks evolution in (a) ED, (b) PF, and (c) PFB electrolytes during the first charge-discharge process (the amplitudes of the peak shifts are marked by the arrows and the O3 to H1-3 phase transition is highlighted in the white rectangle). (d–g) Top view and (h–k) cross-section view SEM images of (d, h) pristine LCO cathode and LCO cathodes cycled in (e, i) ED, (f, j) PF, and (g, k) PFB electrolytes for 100 cycles in the voltage range of 3.0–4.6 V, the cracks are highlighted in the yellow rectangles."

Fig 6

Electrochemical performance of Graphite||LCO full cells. (a) Galvanostatic charge-discharge profiles for the 1st cycle and 50th cycle and (b) cycling performance of graphite anode with PFB electrolyte at 0.3C. (c) Electrode potential and cell voltage of Graphite||LCO full cells with PFB electrolyte during charge and discharge process at 0.1C within the voltage range of 3–4.5 V. (d) The galvanostatic charge-discharge curves for the 1st cycle and the 50th cycle and (e) cycling performance of Graphite||LCO full cells in PFB electrolyte at 0.5C within the voltage range of 3.0–4.5 V. (f) Capacity retention of Graphite||LCO full cells at varied temperatures compared to room temperature (25 ℃) (the insert is corresponding to the charge and discharge curves at the corresponding temperature)."