Fig. 1

Illustration of three-phase interface in a GDE[11].

Fig. 2

Illustration of the anti-permission mechanism of a GDE

Fig. 3

Schematic illustration of the double-chamber electrochemical device for estimating the internal pressure of the catalytic layer.

Fig. 4

Demonstration of the flooding of a GDE in a non-aqueous electrolyte[22]

Fig. 5

Constant-current discharge curves of Li-O2 cells at (A) 1 mA·cm-2; (B) 5 mA·cm-2; (C) diagram of a micro-cavity powder electrode and (D) linear sweep voltammetric curves of oxygen reduction on a Norit-A carbon micro-cavity electrode (cavity diameter: 0.05 mm), scan-rate: 1 mV·s-1[11].

Fig. 6

Schematic illustration of the salt precipitation in the waterproof GDE.

Fig. 7

(A-C) The correlation of discharge time with DFT surface area of different pore sizes; (D) accommodation of Li oxides in the pores of various sizes; (E) the discharge time vs. the average pore size[22].

Fig. 8

(A) Comparison of the discharge curves for the GDE made with pristine and surface modified carbon. The electrodes were discharged at 1 mA·cm-2; (B) typical example of AC impedance for GDEs and the equivalent circuit used for the fitting (inset); (C) comparison of the double-layer capacitance on the GDEs made with pristine and surface modified carbon at various depths of discharge; (D) the surface reaction between the functional groups on the carbon surface and fluoroaliphatic polyoxyethylene[26].

Fig. 9

Pore distribution curves of carbons M-30 (A) and M-20 (B); (C) the comparison of the discharge capacity at various rates for the electrode made by carbons M-30 and M-20[31].

Tab. 1

Surface area in the pores of different sizes

Fig. 10

(A) Transmission line in the pores of a porous electrode; (B) transmission line of a porous electrode without faradic reaction; (C) transmission line of a porous electrode with redox reaction[35].

Fig. 11

(A) Impedance spectrum; (B) Pore-size distribution comparison; (C) The accumulated capacitance and (D) transmission-line equivalent circuit[27].

Fig. 12

The equivalent circuit model used to replace the one shown in Fig. 10C. Rs is the Ohmic resistance; Rct, the Faradaic resistance; CPE, the constant phase element.

Fig. 13

Equivalent circuit and fitting results[40].

Fig. 14

The comparison of the impedance spectrum and DRT. (A) and (A′): baseline (BL) electrolyte at room temperature (RT); (B) and (B′): improved electrolyte at room temperature; (C) and (C′): BL electrolyte at -20 oC; (D) and (D′): improved electrolyte at -20 oC[40].