Metallic Na (K) are considered a promising anode materials for Na‐metal and K‐metal batteries because of their high theoretical capacity, low electrode potential, and abundant resources. However, the uncontrolled growth of Na (K) dendrites severely damages the stability of the electrode/electrolyte interface, resulting in battery failure. Herein, a heterogeneous interface layer consisting of metal vanadium nanoparticles and sodium sulfide (potassium sulfide) is introduced on the surface of a Na (K) foil (i.e., Na2S/V/Na or K2S/V/K). Experimental studies and theoretical calculations indicate that a heterogeneous Na2S/V (K2S/V) protective layer can effectively improve Na (K)‐ion adsorption and diffusion kinetics, inhibiting the growth of Na (K) dendrites during Na (K) plating/stripping. Based on the novel design of the heterogeneous layer, the symmetric Na2S/V/Na cell displays a long lifespan of over 1000 h in a carbonate‐based electrolyte, and the K2S/V/K electrode can operate for over 1300 h at 0.5 mA cm–2 with a capacity of 0.5 mAh cm–2. Moreover, the Na full cell (Na3V2(PO4)3||Na2S/V/Na) exhibits a high energy density of 375 Wh kg–1 and a high power density of 23.5 kW kg–1. The achievements support the development of heterogeneous protective layers for other high‐energy‐density metal batteries.

Sulfides are perceived as promising anode materials for potassium‐ion batteries (PIBs) due to their high theoretical specific capacity and structural diversity. Nonetheless, the poor structural stability and sluggish kinetics of sulfides lead to unsatisfactory electrochemical performance. Herein, Ni3S2–Co9S8 heterostructures with an open‐ended nanocage structure wrapped by reduced graphene oxide (Ni‐Co‐S@rGO cages) are well designed as the anode for PIBs via a selective etching and one‐step sulfuration approach. The hollow Ni‐Co‐S@rGO nanocages, with large surface area, abundant heterointerfaces, and unique open‐ended nanocage structure, can reduce the K+ diffusion length and promote reaction kinetics. When used as the anode for PIBs, the Ni‐Co‐S@rGO exhibits high reversible capacity and low capacity degradation (0.0089% per cycle over 2000 cycles at 10 A g–1). A potassium‐ion full battery with a Ni‐Co‐S@rGO anode and Prussian blue cathode can display a superior reversible capacity of 400 mAh g–1 after 300 cycles at 2 A g–1. The unique structural advantages and electrochemical reaction mechanisms of the Ni‐Co‐S@rGO are revealed by finite‐element‐simulation in situ characterizations. The universal synthesis technology of bimetallic sulfide anodes for advanced PIBs may provide vital guidance to design high‐performance energy‐storage materials.

Intricate hollow carbon structures possess vital function for anchoring polysulfides and enhancing the utilization of sulfur in room-temperature sodium–sulfur batteries. However, their synthesis is extremely challenging due to the complex structure. Here, a facile and efficient strategy is developed for the controllable synthesis of N/O-doped multichambered carbon nanoboxes (MCCBs) by selective etching and stepwise carbonization of ZIF-8 nanocubes. The MCCBs consist of porous carbon shells on the outside and connected carbon grids with a hollow structure on the inside, bringing about a MCCBs structure. As a sulfur host, the multichambered structure has better spatial encapsulation and integrated conductivity via the inner interconnected carbon grids, which combines the characteristics of short charge transfer path and superb physicochemical adsorption along with mechanical strength. As expected, the S@MCCBs cathode realizes decent cycle stability (0.045% capacity decay per cycle over 800 cycles at 5 A g–1) and enhanced rate performance (328 mA h g–1 at 10 A g–1). Furthermore, in situ transmission electron microscopy (TEM) observation confirms the good structural stability of the S@MCCBs during the (de)­sodiation process. Our work demonstrates an effective strategy for the rational design and accurate construction of intricate hollow materials for high-performance energy storage systems.