Synchronously Consolidating Li, Se, S, and C for Robust Li-SeS Batteries.

S-redox involving solvated polysulfides is accompanied by volumetric change and structural decay of the S-based cathodes. Here, we propose a synchronous construction strategy for consolidating Li, Se, S, and C elements within a composite cathode via a paradigm reaction of 8Li+2Se+CS 2 = 2Li 4 SeS+C. The obtained composite features crystalline Li 4 SeS encapsulated in a carbon nanocage (Li 4 SeS@C), exhibiting ultrahigh electrical conductivity, ultralow activation barrier, and excellent structural integrity, accordingly enabling large specific capacity (615 mAh g -1 ) and high capacity retention (87.3% after 350 cycles) at 10 A g -1 . TOF-SIMS demonstrates its superior volumetric efficiency to a similar derivative SeS@C (2Se+CS 2 = 2SeS+C), and DFT reveals its lower activation barrier than Li 2 S@C and Li 2 Se@C. This consolidation design significantly improves the electrochemical performance of S-based cathodes, and the paradigm reaction guarantees structural diversity and flexibility. Moreover, employing a synchronous construction mechanism to maximize the synergistic effect between element consolidation and carbon encapsulation opens up a new approach for developing robust S or chalcogenide cathodes.