Fig. 2: Advanced materials design, reaction mechanisms, and electrochemical performance in Al–S battery systems.

a Schematic representation of the fabrication process for binder-free S@Ti₃C₂Tx film, pure Ti₃C₂T_x film, and traditional sulfur–Ti₃C₂T_x composite cathodes. b Gibbs free energy profiles for the transformation of S₈ and Al₂S_x intermediates on monolayer graphene (blue) and Ti₃C₂O₂ (red), highlighting catalytic activity and stability differences. c Schematic illustration of the distinct electrochemical reaction pathways in working Al–S cells for both S@Ti₃C₂T_x and conventional S + Ti₃C₂T_x cathodes¹³. d Adsorption energy (E__b) values of S₈ and various Al₂S_n species (n = 3, 6, 12, 18) on SA@Ti₃C₂O₂ nanosheets, visualized as colored lines (short red: S₈*, orange: Al₂S₁₈*, green: Al₂S₁₂*, blue: Al₂S₆*, purple: Al₂S₃*), with corresponding solid lines denoting their binding energies to Ti₃C₂O₂¹⁴. e Strategy for membrane modification via in situ polymerization incorporating AlCl₃/AcA electrolyte, enhancing ion transport and suppressing polysulfide crossover. f Theoretical voltage profiles of different sulfur species referenced against the Al³⁺/Al redox couple, shedding light on redox behavior during cycling¹⁶. g Voltage-capacity profiles of BN/S/C composite cathode at various charge/discharge stages¹⁷. h Optical image of a fully assembled Al//[EMIM]Cl–AlCl₃//BN/S/C pouch cell with an open-circuit voltage of 1.2 V vs. AlCl₄⁻/Al; inset shows the cell structure¹⁸. i Galvanostatic charge–discharge curves of GCNT/S composite at different current densities, with accompanying rate capability and long-term cycling stability (600 cycles at 100 mA g⁻¹. j Gibbs free energy diagram of the discharge process on β-germanene, revealing its thermodynamic feasibility as a sulfur host¹⁹. k Ab initio molecular dynamics (AIMD) simulations at 400 K showing stable adsorption of Al₂S₆ species on β-germanene; optimized structures from top and side views show multilayer Al₂S₃ clustering. l Schematic of the synthesis process of Se_2.9S_5.1@MCNF (metal–carbon nanofiber host) and subsequent energy barrier analysis for Al atom diffusion across SeS₂, SeS, Se_2.9S_5.1, and Se_2.9S_5.1@MCNF surfaces²⁰. m Synthetic scheme for ZIF-8@ZIF-67 precursor and conversion to Co–NCNHP nanocomposites via thermal treatment²¹. n Schematic depiction of the formation pathways of NMC–Al₂O₃ and dual-modified NMC–Al₂O₃–S cathode materials for improved cycling and interface compatibility in Al–S systems²².