Rechargeable aqueous zinc-ion batteries are highly desirable for grid-scale applications due to their low cost and high safety; however, the poor cycling stability hinders their widespread application. Herein, a highly durable zinc-ion battery system with a NaVO·1.63HO nanowire cathode and an aqueous Zn(CFSO) electrolyte has been developed. The NaVO·1.63HO nanowires deliver a high specific capacity of 352 mAh g at 50 mA g and exhibit a capacity retention of 90% over 6000 cycles at 5000 mA g, which represents the best cycling performance compared with all previous reports. In contrast, the NaVO nanowires maintain only 17% of the initial capacity after 4000 cycles at 5000 mA g. A single-nanowire-based zinc-ion battery is assembled, which reveals the intrinsic Zn storage mechanism at nanoscale. The remarkable electrochemical performance especially the long-term cycling stability makes NaVO·1.63HO a promising cathode for a low-cost and safe aqueous zinc-ion battery.

Aqueous zinc-ion batteries attract increasing attention due to their low cost, high safety, and potential application in stationary energy storage. However, the simultaneous realization of high cycling stability and high energy density remains a major challenge. To tackle the above-mentioned challenge, we develop a novel Zn/VO rechargeable aqueous hybrid-ion battery system by using porous VO as the cathode and metallic zinc as the anode. The VO cathode delivers a high discharge capacity of 238 mAh g at 50 mA g. 80% of the initial discharge capacity can be retained after 2000 cycles at a high current density of 2000 mA g. Meanwhile, the application of a "water-in-salt" electrolyte results in the increase of discharge platform from 0.6 to 1.0 V. This work provides an effective strategy to simultaneously enhance the energy density and cycling stability of aqueous zinc ion-based batteries.

demonstrated to be effective in enhancing the capacitance of carbon-based materials. For example, N, [4,6] O [7,8] and S [9,10] are the most well studied dopants for carbon-based materials. The functions of these dopants depend on their chemical environments in the carbon host structure and they can improve the capacitive performance of carbon-based materials in different manners. It has been reported that the negatively charged pyridinic N and pyrrolic N can serve as faradaic reaction sites and contribute pseudocapacitance, whereas the positively charged quaternary N can facilitate electron transport in carbon lattice. [7,11] The introduction of O and S doping can increase pseudocapacitance and improve the electrode surface wettability. [12,13] Recently, dual and multi ple heteroatom doping carbon materials have been developed and achieved excellent capacitive performance. [14][15][16] Pore engineering is another effective approach to enhance the capacitive performance of carbonbased materials. [17] First, the introduction of pores, especially micropores, can significantly increase the surface area of carbon materials. Second, the pores function as electrolyte reservoirs that can shorten ion diffusion length. Third, the rational construction of an interconnected network consisting of multiple scale pores can facilitate mass transport of ions. The combination of large surface area and efficient ion diffusion will increase the effective ion accessible surface area and therefore, the specific capacitance. This is particular important for ultrafast supercapacitors electrodes that aim to be operated at high charging/discharging rates. Despite that the pore engineering and elemental doping have been demonstrated separately on different carbon materials, the combination of these approaches has rarely been reported. Herein, we demonstrate a new porous carbon electrode with high level of structural complexity for ultrafast supercapacitors through the integration of tri-doping and pore engineering method in preparation of carbon-based electrodes. Results and DiscussionThe preparation of the N,O,S tri-doped hierarchical porous carbon foam is illustrated in Scheme 1. The precursors including graphene oxide (GO) nanosheets, Poloxamer 407 Carbonaceous materials are attractive supercapacitor electrode materials due to their high electronic conductivity, large specific surface area, and low cost. Here, a unique hierarchical porous N,O,S-enriched carbon foam (KNOSC) with high level of structural complexity for supercapacitors is reported. It is fabricated via a combination of a soft-template method, freeze-drying, and chemical etching. The carbon foam is a macroporous structure containing a network of mesoporous channels filled with micropores. It has an extremely large specific surface area of 2685 m 2 g −1 . The pore engineered carbon structure is also uniformly doped with N, O, and S. The KNOSC electrode achieves an outstanding capacitance of 402.5 F g −1 at 1 A g −1 and superior rate capability of 308.5 F g −1 at 100 A g −1...

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The high theoretical capacity and natural abundance of SiO 2 make it a promising high-capacity anode material for lithium-ion batteries. However, its widespread application is significantly hampered by the intrinsic poor electronic conductivity and drastic volume variation. Herein, a unique hollow structured Ni/SiO 2 nanocomposite constructed by ultrafine Ni nanoparticle (≈3 nm) functionalized SiO 2 nanosheets is designed. The Ni nanoparticles boost not only the electronic conductivity but also the electrochemical activity of SiO 2 effectively. Meanwhile, the hollow cavity provides sufficient free space to accommodate the volume change of SiO 2 during repeated lithiation/ delithiation; the nanosheet building blocks reduce the diffusion lengths of lithium ions. Due to the synergistic effect between Ni and SiO 2 , the Ni/SiO 2 composite delivers a high reversible capacity of 676 mA h g −1 at 0.1 A g −1 . At a high current density of 10 A g −1 , a capacity of 337 mA h g −1 can be retained after 1000 cycles.

is located below lithium in the periodic table and shares similar physical/chemical properties with lithium in many aspects. Thus, sodium is a promising candidate for replacing lithium in energy storage systems. [ 11 ] Recently, sodium ion batteries have been widely reconsidered for largescale applications. Undoubtedly, the exploration and development of sodium-ion batteries is a new and important direction in the fi eld of energy storage.Recently, potassium containing compounds have been investigated in sodiumion batteries. Liu et al. found that the potassium ion intercalated manganese oxide (K 0.27 MnO 2 ) with large ion diffusion channels shows superior cycling stability and rate capability for sodium storage. [ 12 ] This inspiring work indicates that the potassium-containing compounds have great potentials in energy storage. On the other hand, phosphates have been widely studied because of their high redox potential, good safety, and low cost. Compared with metal oxides, phosphates possess higher electrochemical voltage and thus higher energy density due to the inductive effect of PO 4 3− . [ 4,5 ] In addition, the phosphates also provide higher thermal stability for elevated temperature operation. However, the phosphates face the defects of regular impure phase and poor electronic conductivity. [ 4,5 ] The formation of impurity phases can be suppressed by thoroughly mixing the reactants before sintering, and the conductivity can be improved by compositing with carbon. [13][14][15][16][17][18][19] Among the phosphate compounds, Li 3 V 2 (PO 4 ) 3 [ 20,21 ] and Na 3 V 2 (PO 4 ) 3 [22][23][24][25] have been widely studied as lithium or sodium-ion battery cathodes. For example, Jian et al. reported the synthesis of Na 3 V 2 (PO 4 ) 3 /C composite by a one-step solid state reaction; when used as the cathod for sodium-ion battery, it delivers an initial discharge capacity of 93 mAh g −1 .[ 23 ] Saravanan et al. reported the preparation of porous Na 3 V 2 (PO 4 ) 3 /C with excellent cycling stability and superior rate capability in sodium-ion battery. [ 25 ] Despite the numerous reports on Li 3 V 2 (PO 4 ) 3 and Na 3 V 2 (PO 4 ) 3 , the crystal structure and electrochemical performance of K 3 V 2 (PO 4 ) 3 has never been reported. Herein, a novel potassium containing phosphate material, K 3 V 2 (PO 4 ) 3 , is designed and explored in energy storage. The K 3 V 2 (PO 4 ) 3 /C bundled nanowires were synthesized by a facile organic acid-assisted method. With a highly stable framework for sodium storage, porous nanostructure for fast Sodium-ion battery has captured much attention due to the abundant sodium resources and potentially low cost. However, it suffers from poor cycling stability and low diffusion coeffi cient, which seriously limit its widespread application. Here, K 3 V 2 (PO 4 ) 3 /C bundled nanowires are fabricated usinga facile organic acid-assisted method. With a highly stable framework, nanoporous structure, and conductive carbon coating, the K 3 V 2 (PO 4 ) 3 /C bundled nanowires manifest excellent e...

A unique hollow Li3VO4/CNT composite is synthesized via a facile method as an anode material in lithium batteries. Our work opens up the way for a promising material with high rate capability and good cycling stability due to its efficient Li(+) diffusion and relatively high structure stability.

Emerging sodium-ion batteries (SIBs) have attracted a great attention as promising energy storage devices because of their low cost and resource abundance. Nevertheless, it is still a major challenge to develop anode materials with outstanding rate capability and excellent cycling performance. Compared to intercalation-type anode materials, conversion-type anode materials are very potential due to their high specific capacity and low cost. A new insight and summary on the recent research advances on nanostructured conversion-type anode materials for SIBs is provided herein. The corresponding synthesis methods, sodium storage properties, electrochemical mechanisms, advanced techniques on studying the crystal structures, and optimization strategies for high-performance batteries are presented. Finally, the remaining challenges and perspectives for the future development of conversion-type anode materials in the energy storage fields are proposed. Figure 17. a) Time-lapse images showing the evolution of morphology of a CuO NW at an applied voltage of −3 V during the first sodiation process. b,c) In situ TEM images showing the 1st sodiation and the 1st desodiation of the single SnO 2 nanowire, respectively. d) Time-resolved TEM images from video frames show morphology and structure evolution as a function of sodiation time and its electron diffraction (ED) patterns. Schematic and structural evolution of e,f) the V 2 O 3 ⊂C-NTs and g,h) V 2 O 3 ⊂C-NTs⊂rGO electrodes observed by in situ TEM experiments, respectively, during constant potential discharge at 5 V. i,k) The morphology evolution of two α-MoO 3 nanobelts during the first sodiation process in a low magnification, in which the red arrows denote the reaction front. j) The measured relationship between the sodiation front position and the sodiation time for above two α-MoO 3 nanobelts. l) Time-resolved TEM images from video frames show the sodiation process of an individual Co 9 S 8 -filled CNT with an open end. All scale bars are 200 nm. m) Time-resolved TEM images from video frames reveal the appearance of fractures during the electrochemical sodiation process of an individual Co 9 S 8 -filled CNT with closed ends. All scale bars are 100 nm. n) Schematic showing the setup of the in situ experiment. HAADF-STEM images showing o) pristine and p) sodiated FeF 2 NPs and q) cropped time-lapse frames throughout the sodiation process. a) Reproduced with permission. [131]