Sodium‐ion batteries are considered as a promising technology for large‐scale energy storage applications, owing to their low cost. However, there are many challenges for developing sodium‐ion batteries with high capacity, long cycle life, and high‐rate capability. Herein, the development of high‐performance sodium‐ion batteries using ZnS nanospheres as anode material and an ether‐based electrolyte, which exhibit improved electrochemical performance over the pure alkyl carbonate electrolytes, is reported. ZnS nanospheres deliver a high specific capacity of 1000 mA h g−1 and high initial Columbic efficiency of 90%. Electrochemical testing and first‐principle calculations demonstrate that the ether‐based solvent can facilitate charge transport, reduce the energy barrier for sodium‐ion diffusion, and thus enhance electrochemical performances. Ex situ measurements (X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) mapping) reveal that ZnS nanospheres maintain structural integrity during the charge and discharge processes over 100 cycles. As anode material for sodium‐ion batteries, ZnS nanospheres deliver high reversible sodium storage capacity, high Coulombic efficiencies, and extended cycle life.

The development of anode materials remains a challenge to satisfy the requirements of sodium-ion storage for large-scale energy-storage applications, which is ascribed to the low kinetics of ionic/electron transfer of electrode materials. Here we show that the controlled anisotropic assembly of highly conductive Ti 3 C 2 T x MXene nanosheets to form a porous structure can enhance the sodium-ion storage kinetics. At high current densities of 1 and 10 A g −1 , the porous Ti 3 C 2 T x electrode delivered capacities of 166 and 124 mA h g −1 , respectively. Even at an extremely high current density of 100 A g −1 , a capacity of 24 mA h g −1 could be achieved. The porous Ti 3 C 2 T x electrode also exhibited a long cycle life that can be extended to 1000 cycles with no capacity decay at a current density of 1 A g −1 . This work demonstrates successful control of the Ti 3 C 2 T x architecture to push electrochemical sodium-ion storage closer to large-scale applications and is expected to shed light on the rational utilization of the outstanding properties of MXenes by controlling their microscopic assembly.

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As a new family member of room-temperature aprotic metal-O batteries, Na-O batteries, are attracting growing attention because of their relatively high theoretical specific energy and particularly their uncompromised round-trip efficiency. Here, a hierarchical porous carbon sphere (PCS) electrode that has outstanding properties to realize Na-O batteries with excellent electrochemical performances is reported. The controlled porosity of the PCS electrode, with macropores formed between PCSs and nanopores inside each PCS, enables effective formation/decomposition of NaO by facilitating the electrolyte impregnation and oxygen diffusion to the inner part of the oxygen electrode. In addition, the discharge product of NaO is deposited on the surface of individual PCSs with an unusual conformal film-like morphology, which can be more easily decomposed than the commonly observed microsized NaO cubes in Na-O batteries. A combination of coulometry, X-ray diffraction, and in situ differential electrochemical mass spectrometry provides compelling evidence that the operation of the PCS-based Na-O battery is underpinned by the formation and decomposition of NaO . This work demonstrates that employing nanostructured carbon materials to control the porosity, pore-size distribution of the oxygen electrodes, and the morphology of the discharged NaO is a promising strategy to develop high-performance Na-O batteries.

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