Lithium-sulfur (Li-S) batteries with high energy density and long cycle life are considered to be one of the most promising next-generation energy-storage systems beyond routine lithium-ion batteries. Various approaches have been proposed to break down technical barriers in Li-S battery systems. The use of nanostructured metal oxides and sulfides for high sulfur utilization and long life span of Li-S batteries is reviewed here. The relationships between the intrinsic properties of metal oxide/sulfide hosts and electrochemical performances of Li-S batteries are discussed. Nanostructured metal oxides/sulfides hosts used in solid sulfur cathodes, separators/interlayers, lithium-metal-anode protection, and lithium polysulfides batteries are discussed respectively. Prospects for the future developments of Li-S batteries with nanostructured metal oxides/sulfides are also discussed.

Sodium-ion batteries are emerging as a highly promising technology for large-scale energy storage applications. However, it remains a significant challenge to develop an anode with superior long-term cycling stability and high-rate capability. Here we demonstrate that the Na þ intercalation pseudocapacitance in TiO 2 /graphene nanocomposites enables high-rate capability and long cycle life in a sodium-ion battery. This hybrid electrode exhibits a specific capacity of above 90 mA h g -1 at 12,000 mA g -1 (B36 C). The capacity is highly reversible for more than 4,000 cycles, the longest demonstrated cyclability to date. First-principle calculations demonstrate that the intimate integration of graphene with TiO 2 reduces the diffusion energy barrier, thus enhancing the Na þ intercalation pseudocapacitive process. The Na-ion intercalation pseudocapacitance enabled by tailor-deigned nanostructures represents a promising strategy for developing electrode materials with high power density and long cycle life.

class of materials show great potential for the insertion/extraction of multivalent ions (Zn 2+ , Mg 2+ , Al 3+ ) owing to the characteristic of large layer spacing and high conductivity. Among all the TMDs, VS 2 is a typical family member of TMDs with hexagonal system, which shows similar crystal structure to that of graphite lamellar with an interlayer spacing of 5.76 Å. [25,30] There is a vanadium layer between two sulfur layers to form a kind of sandwich structure. In VS 2 crystal structure, each V atom is arranged around six S atoms and connected with S atoms with covalent bonds. The interlayer spacing of VS 2 is so large that enables the convenient insertion/extraction of lithium ions (0.69 Å), sodium ions (1.02 Å), zinc ions (0.74 Å) or their solvation sheath in electrolyte. However, to the best of our knowledge, there is no report about VS 2 as the electrode materials for ZIBs.Herein, the VS 2 nanosheets are synthesized via a facile hydrothermal reaction (Supporting Information), which deliver a high capacity of 190.3 mA h g −1 at a current density of 0.05 A g −1 and exhibit long-term cyclic stability as the cathode for ZIBs. The electrochemical reaction mechanism of such VS 2 electrodes is further investigated systematically through a series of measurements including ex situ X-ray diffraction (XRD), ex situ X-ray photoelectron spectroscopy (XPS), in situ Raman, ex situ transmission electron microscopy (TEM). A reversible insertion/extraction process can be observed from all aspects. Both the ex situ TEM and ex situ XRD results demonstrate that the interlayer space of VS 2 can self adapt to the intercalation of Zn 2+ with an expansion along the c-axis (only 1.73%) and a slightly shrink along the a-and b-axes, which plays a key role in the realization of long-life ZIBs. All the above evidences reveal that the VS 2 is a promising cathode material with high capacity and good cyclic stability for ZIBs.The crystal structure of the as-prepared VS 2 is tested by XRD. All characteristic peaks are in accordance with the standard card of VS 2 (JCPDS NO. 01-089-1640) (Figure 1a). The Raman spectrum of the VS 2 in the range of 100-1100 cm −1 is shown in Figure 1b. Six peaks located at 140.4, 192.0, 282.0, 406.6, 687.8, and 993.2 cm −1 are observed, which correspond to the rocking and stretching vibrations of V-S bonds or their combination. [25] The morphology and microstructures of as-prepared VS 2 are investigated by field emission scanning electron microscopy (SEM) and high-resolution TEM (HRTEM). As shown in Figure 1c, The VS 2 flowers are assembled by nanosheets with a diameter of 5-8 µm and a thickness of 50-100 nm. The d-spacing calculated from selected area electron diffraction (SAED) patterns are 2.89 and 1.64 Å (Figure 2f), which match the d-spacing values of (002) and (110) crystal planes of VS 2 , respectively. TEM and corresponding HRTEM images in Figure 2e show VS 2 nanosheets with a d-spacing of ≈5.76 Å,The continuous researches of energy-storage devices have gained considerable attention in our world ...

Hard carbon is one of the most promising anode materials for sodium‐ion batteries, but the low Coulombic efficiency is still a key barrier. In this paper, a series of nanostructured hard carbon materials with controlled architectures is synthesized. Using a combination of in situ X‐ray diffraction mapping, ex situ nuclear magnetic resonance (NMR), electron paramagnetic resonance, electrochemical techniques, and simulations, an “adsorption–intercalation” mechanism is established for Na ion storage. During the initial stages of Na insertion, Na ions adsorb on the defect sites of hard carbon with a wide adsorption energy distribution, producing a sloping voltage profile. In the second stage, Na ions intercalate into graphitic layers with suitable spacing to form NaC x compounds similar to the Li ion intercalation process in graphite, producing a flat low voltage plateau. The cation intercalation with a flat voltage plateau should be enhanced and the sloping region should be avoided. Guided by this knowledge, nonporous hard carbon material has been developed which has achieved high reversible capacity and Coulombic efficiency to fulfill practical application.

The development of manganese dioxide as the cathode for aqueous Zn-ion battery (ZIB) is limited by the rapid capacity fading and material dissolution. Here, a highly reversible aqueous ZIB using graphene scroll-coated α-MnO as the cathode is proposed. The graphene scroll is uniformly coated on the MnO nanowire with an average width of 5 nm, which increases the electrical conductivity of the MnO nanowire and relieves the dissolution of the cathode material during cycling. An energy density of 406.6 Wh kg (382.2 mA h g ) at 0.3 A g can be reached, which is the highest specific energy value among all the cathode materials for aqueous Zn-ion battery so far, and good long-term cycling stability with 94% capacity retention after 3000 cycles at 3 A g are achieved. Meanwhile, a two-step intercalation mechanism that Zn ions first insert into the layers and then the tunnels of MnO framework is proved by in situ X-ray diffraction, galvanostatic intermittent titration technique, and X-ray photoelectron spectroscopy characterizations. The graphene scroll-coated metallic oxide strategy can also bring intensive interests for other energy storage systems.