A High-Performance Solid-State Secondary Battery Using a Triple-Phase-Interface Anode Displaying Excellent Capacity...

Solid-state sodium-ion batteries (SSSIBs) combining with good safety and appropriate cost are considered as a promising emerging energy-storage system. However, poor electrochemical reversibility and sluggish kinetics of anodes remain critical bottlenecks. Here, we develop a CoS/Co₉S₈/SnS composite coated with nitrogen-doped carbon (named as CoS/Co₉S₈/SnS@NC), where a triple-phase-interface heterostructure is constructed among CoS, Co₉S₈ and SnS, which enables synergistically amplifying of electric field network and thus improving electron/ion transport kinetics. The CoS/Co₉S₈/SnS@NC as SSSIB anode exhibits excellent compatibility with conventional Na₃PS₄ solid-electrolyte, and delivers a large capacity of 441 mAh g^{- 1} after 120 cycles at 0.5 A g^{- 1}, and superior rate-performance of 348.7 mAh g^{- 1} at 5.0 A g^{- 1}. Stable high-temperature tolerance (capacity keeps 502 mAh g^{- 1} after 50 cycles), and solid-state full-cells paring with Na₃V₂(PO₄)₃ cathode, are also achievable. Synergistic enhancement effect of the heterostructure is demonstrated via ex situ characterizations and in situ electrochemical impedance spectroscopy, which verifies that the triple-phase-interface efficiently reduces the charge transfer resistance and promotes ion diffusion. These findings provide a general strategy for engineering triple-phase-interface heterostructures for energy-storage with optimal interfaces, and sheds light on the fundamental understanding of interface-enhanced solid-state batteries.