1. Schematic diagram of (a) lithium-sulfur battery configuration and (b) corresponding charge-discharge process^[7]

2. (a) Structural models of different borophenes and their corresponding charge density distributions, (b) adsorption energies of polysulfides on different borophenes^[25]

3. (a) Scheme of B-doped carbon backbone, (b) S2p XPS spectra of sulfur composites based on different element-doped porous carbon; and (c) scheme of charge-discharge process of NBCGN/S composite, (d) cycling at 0.2C and (e) rate performances of sulfur electrodes based on different element-doped curved graphene nanoribbons^[44]

4. Conductivity comparison with several categories of metal compounds^{[48,49,50,51,52,53,54,55,56]}

5. (a) Li₂S₄ adsorption configurations on Co₂B and Co₂B@MXene surfaces, (b) scheme of the electron redistribution at the interfaces between Co₂B and MXene, (c) cycling performances of cells based on Co₂B@MXene and other separators, (d) long-term cycling performance of the Co₂B@MXene cell^[63]; (e) schematic illustration of surface-chemical entrapment of polysulfides on TiB₂, (f) adsorption configurations and (g) energies of sulfur species on (001) and (111) surfaces of TiB₂, (h) high-loading performance and (i) long-term cycling of TiB₂-based sulfur electrode^[63,65]

6. (a) TEM image and schematic atomic structure of v-BN^[78]; (b) Scheme of g-C₃N₄/BN/graphene composite ion-sieve and (c) the corresponding Li-S cell cycling performance^[80]; (d) Schematic and optical image of BN/Celgard/carbon trilayer separator, and (e) the corresponding cell cycling performance^[83]; (f) Scheme and (g) SEM image of B₄C@CNF and the model of B₄C nanowire, (h) Li₂S₄ adsorption energies on different facets of B₄C^[87]