Fig.1 (a) Schematic illustration of the construction of a Li-S battery cell; (b) General potential profile of a Li-S battery[12]

Fig.2 (a) Schematic illustration of the procedure for fabricating S-PGC-CFF cathode and the microstructures of each component[46]; (b) Schematic of the CCG substrate preparation and its corresponding configurations[48]

Fig.3 (a) Schematic synthesis process of 3DG@NPC and 3DG@NPC/S[55]; (b) Schematic fabrication process of Ni@N-CNSs films[56]

Fig.4 (a) Schematic illustration of the interactions between polysulfides and hydroxyl groups[57]; (b) Preparation procedure of Co-NC@TpBD-Me2 cathode and its working mechanism as sulfur cathode[58]

Fig.5 (a) Chemical structure of MP and PP-C-St-MP diaphragm for reversible clinching effect[62]; (b) Schematic diagram of PDPP modified separator and its effect in Li-S battery[63]; (c) Schematic diagram of TA-Co separator in Li-S battery[64]; (d) Schematic illustration of the Li-S battery with EVA microspheres-coated separators[65]

Fig.6 (a) Chemical reactivity of different metal oxides with LiPSs as a function of redox potential versus Li/Li+, superimposed with a typical Li-S cyclic voltammetry curve (shown in red)[69]; (b) Schematic of the fabrication processes of VO2@rGO/S product[70]; (c) Catalytic conversion mechanism of ultrathin δ-MnO2 nanosheets in the core-shell structure[72]; (d) Schematic of the synthesis steps for the S/CC@NiCo2O4 composite, the NiCo2O4 nanofiber arrays can effectively adsorb and catalyze the conversion reaction of LiPSs[73]

Fig.7 (a) Schematic illustration of the synthesis process of S/CoS2-NC composites[74]; (b) Schematic illustration of the preparation of PCN-SnS2 composites[75]; (c) Schematic illustration of the synthetic processes of NiCo2S4/S composite[76]; (d) Preparation of MoS2@CNF and S@MoS2@CNF composite[77]

Fig.8 (a)—(c) SEM images of WN, VN and Mo2N[78]; (d), (e) SEM image and TEM image of TiN hollow nanospheres[79]

Fig.9 (a) Schematic illustration of Ti3C2@CF preparation and as a multifunctional cathode material to ameliorate the performance of Li-S batteries[80]; (b) Schematic diagram of the effect of S@ZnSe/NHC cathode on Li-S batteries[81]

Fig.10 (a)—(c) The role of perovskite promoter on LiPSs suppression and Li2S regulation in a working Li-S battery and the crystal structure of Ba0.5Sr0.5Co0.8Fe0.2O3-δ PrNP[82]; (d) Schematic illustration of the Li2S nucleation and growth on routine conductive surface (left) and on conductive and catalytic nanotriple-phase interface with uniformly distributed nucleation sites (right)[83]; (e) Schematic illustration of polysulfide redox reaction and Li2S nucleation[83]

Fig.11 Li2S6 polysulfide adsorption test: (a) Optical photos of candidate materials; (b) UV-Vis data of varying concentrations of Li2S6 in DOL/DME solution without candidate materials; (c), (d) UV-Vis data of candidate materials added in 3.0 mmol·L-1 Li2S6[84]

Fig.12 GITT results for Li-S battery at 0.2 C on 2nd cycle

Fig.13 Dimensionless transient profiles of MoO2 (a), α-MoC (b) and MoO2/α-MoC (c) at 2.09 V; SEM images of MoO2, α-MoC and, MoO2/α-MoC electrodes after discharged to maximum current [(d)—(f)] and after Li2S deposition [(g)—(i)][89]

Fig.14 (a) Liquid-phase LiPSs are strongly adsorbed by Co9S8 and therefore cannot be transferred to MoS2 to accomplish fast conversion; (b) Sulfur vacancies can harmonize the chemisorption of components to uniformly adsorb LiPSs; (c)—(e) CV curves within the voltage range of 1.6—2.8 V at different sweep rates of CMG-L, CMG-M and CMG-H; (f) The NTR values of CMG-L, CMG-M and CMG-H at different sweep rates; (g) Long cycle performances of CMG-L, CMG-M and CMG-H at 0.5 C[91]