Scheme 1. Schematic illustration of the synthesis of Ni/PC and S@Ni/PC composites.

Fig. 1. (a, b) SEM and (c, d) TEM images of PC from corn. (e, f) SEM, (g, i) TEM images of Ni/PC; (h) EDS elemental mapping for Ni, C, and O. (j) HRTEM image of Ni/PC (FFT pattern in the selected area marked by the blue square), (k) inverse FFT crystalline lattice image, (l) lattice spacing profiles along the selected area marked by the pink square.

Fig. 2. (a) XRD patterns of Ni/PC and PC; XPS spectra of S@Ni/PC and S@PC: (b) Ni 2p3/2, (c) C 1s, and (d) S 2p; (e) N2 adsorption-desorption isotherms (inset: pore size distribution curve) of Ni/PC and PC; (f) TG curves of S@Ni/PC and S@PC.

Fig. 3. (a) Initial three cyclic voltammetry (CV) cycles of S@Ni/PC cathode; (b) the second CV cycle curves of the S@Ni/PC and S@PC cathodes; c) typical charge and discharge profiles of the S@Ni/PC cathode at the 1 st, 2nd, 3rd, 50th, 100th, and 150th cycles at 0.2 C; d) cycling performance of the S@Ni/PC and S@PC cathodes at 0.2 C over 150 cycles; (e) rate capability of the S@Ni/PC and S@PC cathodes; (f) Nyquist plots of the S@Ni/PC and S@PC cathodes before cycling at a frequency range from 100 kHz to 0.1 Hz at room temperature (the inset is the best fitting equivalent circuit model); (g) prolonged cycling performance of the S@Ni/PC and S@PC cathodes at 1 C (1 C = 1675 mA g-1); (h) the optical image of a “HEBUT” light-emitting diodes (LEDs) powered by two cells based on S@Ni/PC cathode.

Fig. 4. (a) DFT optimized binding geometries of polysulfide molecules (Li2Sx, x = 2, 4, 6, 8) and S8 on Ni (111) surface. Here, the blue, yellow, and purple spheres represent Ni, S, and Li atoms, respectively. (b) binding energies of various polysulfides anchored on Ni (111) surface obtained from DFT calculations.

Fig. 5. (a) UV-vis spectra and images of LiPSs solutions samples adsorbed by Ni/PC and PC; b) S 2p and c) Ni 2p high-resolution XPS spectra of Li2S6 adsorbed by Ni/PC. (d) multi-cycle voltammograms of the Ni/PC symmetric cell at 6 mV s-1; (e) cyclic voltammograms of symmetric cells for Ni/PC at different scan rates. (f) Electrochemical impedance spectra of symmetric cells with Ni/PC and PC electrodes (the inset is the best fitting equivalent circuit model).

Fig. 6. Potentiostatic discharge curves of (a) Ni/PC and (b) PC cathodes based lithium polysulfide batteries with Li2S8/tetraglyme solution at 2.05 V. The current-axis scale is indicated by a bar in the right part of the Fig. The light color indicates the precipitation of Li2S whereas the dark color represents the reduction of Li2S8/Li2S6. The capacity of Li2S deposition is indicated correspondingly. CV curves of the electrodes at various scan rates and corresponding linear fits of the peak currents of Li-S cells with (c), (d) S@Ni/PC cathode and (e), (f) S@PC cathode.