at an average storage voltage of 3.2 V with long cycle life. When coupled with hard carbon anode, a prototype rechargeable sodium-ion battery offers an energy density of 210 Wh kg −1 , a round-trip energy effi ciency of 90%, high rate capability, and excellent cycling stability. These desired performances make this system to be closer to the level of practical applications. The Na 0.9 [Cu 0.22 Fe 0.30 Mn 0.48 ]O 2 (Na 0.9 [Cu II 0.22 Fe III 0.30 Mn III 0.16 Mn IV 0.32 ]O 2 ) material was synthesized by a simple solid-state reaction at 850 °C in air atmosphere using precursors of Na 2 CO 3 , CuO, Fe 2 O 3 , and Mn 2 O 3 . The crystal structure of the as-synthesized material was determined by X-ray diffraction (XRD) as shown in Figure 1 a together with its refi nement results by the Rietveld method (see Table S1, Supporting Information). It can be seen that all the Bragg diffraction peaks are in excellent agreement with the JC DS No. 01-0821495 (O3-type α-NaFeO 2 ) and can be indexed to a hexagonal layered structure with a space group of 3 R m − , indicative of a typical O3-type layered structure (note that the letter “O” refers to the Na coordination environment of octahedral site whereas the number “3” refers to the number of MO 2 slab according to Delmas’ notation. [ 13 ] A schematic illustration of the O3-type structure is also shown in Figure 1 b. The structure refi nement gives the lattice parameters a = 2.9587(7) A, c = 16.3742(6) A. The lattice parameter of c -axis is slightly larger than that of other O3-type materials [ 5f–h , 6b , 8a ] because the Na content is less than 1. The inductively coupled plasma (ICP) result confi rms the composition of Na 0.89 [Cu 0.22 Fe 0.30 Mn 0.48 ]O 2 (see Table S2, Supporting Information). The morphology of the resulting sample is shown in Figure 1 c. The distribution of the particle size is in the range of 10–30 μm with about 3 μm sized primary particle agglomerations together (Figure 1 d). Most importantly, unlike other O3-type materials, [ 4–9,12 ] this material is very stable against water. In order to confi rm this, we intentionally design an accelerated aging experiment as described in the Experimental Section which was verifi ed by LiMO 2 as shown in Figure S1 (Supporting Information). We placed the as-synthesized material in deionized water for 3 d and then dried the material at 100 °C for overnight. The obtained material was checked by XRD again. It can be seen that the XRD pattern is nearly identical to that of the as-synthesized material, which is very different from other O3-type materials as shown in Figure S2 (Supporting Information). These results suggest that the O3-Na 0.9 [Cu 0.22 Fe 0.30 Mn 0.48 ]O 2 is very stable against water. Furthermore, after the material was stored in air for one month Large-scale electrical energy storage systems are one of the core technologies in renewable energies and smart grid, among which sodium-ion batteries show great promise due to the abundant sodium resources. Layered metal oxides (of general formula: A x MO 2 , where A = Li, Na; M = Co, Ni, Mn, Cr, Fe, etc.) with alternating alkali metal layer and transition metal layer have long been of particular interest since the early 1980s as an important class of cathode materials for rechargeable batteries due to their easy synthesis and high energy density. [ 1 ] One of the most successful examples is LiCoO 2 , [ 1a ] which is commonly used as a cathode in lithium-ion batteries with the highest volumetric energy density for portable electronic devices. Its metal substituted materials (LiCo 1− x − y − z Ni x Mn y Al z O 2 ) are being used in power batteries for electric vehicles. In the case of sodiumion batteries operated at room temperature which are proposed for large-scale electrical energy storage owing to the naturally abundant sodium resources in recent years. [ 2,3 ] Na x CoO 2 that can electrochemically and reversibly intercalate Na is the fi rst example, [ 1b ] then a large number of layered metal oxides have been extensively exploited. [ 4–12 ] However, the practical applications have been hindered by two major challenges. First, unlike LiMO 2 , almost all the Na x MO 2 are not stable against moisture (either they can be oxidized by water or water/carbon dioxide molecules can be intercalated into alkali metal layer). [ 4–9,11,12 ]

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Prototype Sodium-Ion Batteries Using Air-Stable and Co/Ni-Free O3-Layered Metal Oxide Cathode

The growth in energy devices and the role of supercapacitors are increasingly important in today’s world. Designing an electrode material for supercapacitors using metals that have high performance, superior structure, are eco-friendly, inexpensive and highly abundant is essentially required for commercialization. In this point of view, quaternary chalcogenide Cu2NiSnS4 with fascinating marigold flower like microstructured electrodes are synthesized using different concentrations of citric acid (0, 0.05 M, 0.1 M and 0.2 M) by employing solvothermal method. The electrode materials physicochemical characteristics are deliberated in detail using the basic characterization techniques. The electrochemical studies revealed better electrochemical performances, in particular, Cu2NiSnS4@0.1 M-CA electrode revealed high 1029 F/g specific capacitance at 0.5 A/g current density. Further, it retained 78.65% capacity over 5000 cycles. To prove the practical applicability, a full-cell asymmetric solid-state device is fabricated, and it delivered 41.25 Wh/Kg and 750 Wh/Kg energy and power density at 0.5 A/g. The optimum citric acid added Cu2NiSnS4 electrode is shown to be a promising candidate for supercapacitor applications.

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Marigold flower like structured Cu2NiSnS4 electrode for high energy asymmetric solid state supercapacitors

Nickel chalcogenide (S and Se) based nanostructures intrigued scientists for some time as materials for energy conversion and storage systems. Interest in these materials is due to their good electrochemical stability, eco-friendly nature, and low cost. The present review compiles recent progress in the area of nickel-(S and Se)-based materials by providing a comprehensive summary of their structural and chemical features and performance. Improving properties of the materials, such as electrical conductivity and surface characteristics (surface area and morphology), through strategies like nano-structuring and hybridization, are systematically discussed. The interaction of the materials with electrolytes, other electro-active materials, and inactive components are analyzed to understand their effects on the performance of energy conversion and storage devices. Finally, outstanding challenges and possible solutions are briefly presented with some perspectives toward the future development of these materials for energy-oriented devices with high performance.

Emergence of Ni-Based Chalcogenides (S and Se) for Clean Energy Conversion and Storage

Rapid urbanization and growing population have led to an increase in the consumption of resources, resulting in water pollution and energy shortage, calling for advanced solutions. For that, transition metal chalcogenides have gained interest because of their earth abundance, tunable bandgaps, modifiable elemental composition, catalytic stability, visible light activity and optoelectrical properties. Here, we review the history, basics, preparation, characterization and environmental applications of transition metal chalcogenides. Methods are hot-plate, solvothermal and hydrothermal, one-pot heat-up and electrospinning. Applications include adsorption, photocatalysis, electrocatalysis, dye-sensitized solar cells and antimicrobials. Transition metal chalcogenide are compared with traditional nanomaterials.

Transitional metal chalcogenide nanostructures for remediation and energy: a review

Facile one-step growth of nickel sulfide nano-architecture as binder less electrodes for efficient supercapacitor applications

The global energy crisis and environmental pollution have resulted in an increase in research efforts to develop renewable energy devices including lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), zinc-air batteries (ZABs), supercapacitors (SCs), and so on. Transition metal chalcogenides (TMCs) have been attracting increasing attentions as electrode materials, mainly thanks to the abundant redox sites, unique crystal structures, and rich physiochemical properties. When introducing carbon substrate with high conductivity as support, TMC-based composites exhibited high electrochemical performance. As anode materials for LIBs and SIBs, TMCs based composites demonstrated high lithium/sodium storage, great specific capacity, high rate capability and excellent cyclic stability. For ZABs, TMCs as air-cathode catalysts can catalyze both oxygen reduction and oxygen evolution reactions with high efficiency and excellent durability. When TMCs are employed as electrode materials, high specific capacity, enhanced energy density and outstanding stability can be achieved for SCs. In summary, TMCs have shown great promises for developing renewable energy technologies.

Zhenghua Tang

Papers

Transition metal chalcogenides for energy storage and conversion