Uniform In Situ Grown ZIF-L Layer for Suppressing Hydrogen Evolution and Homogenizing Zn Deposition in Aqueous Zn-Ion Batteries.

The hydrogen evolution and dendrite of Zn anode are the major troubles hindering the commercialization of aqueous Zn-ion batteries (AZIBs). ZIF-Ls, a typical metal-organic framework (MOF) with a highly ordered structure and abundant functional groups, seem to be the answer for the above bottlenecks. In this paper, a uniform ZIF-L layer was obtained on the Zn surface (Zn@ZIF-L) via an in situ synthesis method to moderate the solvation structure of solid-liquid interface electrolyte reducing the contact between water and Zn, thereby relieving the hydrogen evolution and corrosion. Furthermore, density functional theory (DFT) analysis reveals the binding energy of H (-4.01 eV) and Zn (-0.82 eV) for ZIF-L is superior to that of pure Zn (H (-1.49 eV) and Zn (-0.68 eV)). Due to the multifunctional ZIF-L layer, the Zn@ZIF-L can regulate Zn deposition to overcome the dendrite for obtaining a long-life Zn anode. Consequently, the modified Zn@ZIF-L anode can cycle for 800 h at 0.25 mA cm-2 for 0.25 mAh cm-2, while the bare Zn anode is only maintained for 422 h. Finally, a designed V2O5 grown on carbon cloth (V2O5@CC) was used as the cathode and coupled with the Zn@ZIF-L anode to assemble the full-cell. The Zn@ZIF-L//V2O5@CC full-cell possesses a capacity retention rate of 84.9% after 250 cycles at 0.5 C, prominently higher than Zn//V2O5@CC (40.7%).

Self-Sacrifice Template Construction of Uniform Yolk-Shell ZnS@C for Superior Alkali-Ion Storage.

Secondary batteries have been widespread in the daily life causing an ever-growing demand for long-cycle lifespan and high-energy alkali-ion batteries. As an essential constituent part, electrode materials with superior electrochemical properties play a vital role in the battery systems. Here, an outstanding electrode of yolk-shell ZnS@C nanorods is developed, introducing considerable void space via a self-sacrificial template method. Such carbon encapsulated nanorods moderate integral electronic conductivity, thus ensuring rapid alkali-ions/electrons transporting. Furthermore, the porous structure of these nanorods endows enough void space to mitigate volume stress caused by the insertion/extraction of alkali-ions. Due to the unique structure, these yolk-shell ZnS@C nanorods achieve superior rate performance and cycling performance (740 mAh g-1 at 1.0 A g-1 after 540 cycles) for lithium-ion batteries. As a potassium-ion batteries anode, they achieve an ultra-long lifespan delivering 211.1 mAh g-1 at 1.0 A g-1 after 5700 cycles. The kinetic analysis reveals that these ZnS@C nanorods with considerable pseudocapacitive contribution benefit the fast lithiation/delithiation. Detailed transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses indicate that such yolk-shell ZnS@C anode is a typical reversible conversion reaction mechanism accomplished by alloying processes. This rational design strategy opens a window for the development of superior energy storage materials.

In-Situ Synthesis of Carbon-Encapsulated Atomic Cobalt as Highly Efficient Polysulfide Electrocatalysts for Highly Stable Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have been considered as one of the most promising electrochemical energy storage systems because of their high energy density. However, a series of issues severely limit the practical performances of Li-S batteries such as low conductivity, significant volume change, and shuttle effect. The hollow carbon spheres with huge voids and high electrical conductivity are promising as sulfur hosts. Unfortunately, the nonpolar nature of carbon materials cannot prevent the shuttle effect effectively. In this case, the atomic cobalt is introduced to a nitrogen-doped hollow carbon sphere (ACo@HCS) through polymerization and controlled pyrolysis. The atomic cobalt dopants not only act as active sites to restrict the shuttle effect, but also can promote the kinetics of the sulfur redox reactions. ACo@HCS acting as sulfur host exhibits a high discharge capacity (1003 mAh g-1 ) at a 1.0 C rate after 500 cycles, and the corresponding decay rate is as low as 0.002% per cycle. This exciting work paves a new way to design high-performance Li-S batteries.

Pomegranate-like structured Nb2O5/Carbon@N-doped carbon composites as ultrastable anode for advanced sodium/potassium-ion batteries.

The distinctive pomegranate-like Nb2O5/Carbon@N-doped carbon (Nb2O5/C@NC) composites are fabricated using hydrothermal method integrated with nitrogen doped carbon coating procedure. For the SIBs anode, the Nb2O5/C@NC composites present superior rate character and sustainable capacity (117 mAh g-1 upon 1000 cycles at 5 A g-1). The in-situ X-ray diffraction (XRD) is utilized to research its sodium storage mechanism. Furthermore, for PIBs, the Nb2O5/C@NC composites present sustainable capacity (81 mAh g-1 upon 1000 cycles at 1 A g-1). The outstanding performance of Nb2O5/C@NC composites is ascribed to its unique architecture, in which Nb2O5 nanocrystals embedded in porous carbon can restrain agglomeration of Nb2O5 nanocrystals, enhance electron/ion diffusion kinetics, and ensure electrolyte accessibility, and moreover, NC shell layer can provide effective active sites and further increase ions/electrons transfer.

Direct Detection and Visualization of the H+ Reaction Process in a VO2 Cathode for Aqueous Zinc-Ion Batteries.

Because they are safer and less costly than state-of-the-art Li-ion batteries, aqueous zinc-ion batteries (AZIBs) have been attracting more attention in stationary energy storage and industrial energy storage. However, the electrochemical reaction of H+ in all of the cathode materials of AZIBs has been puzzling until now. Herein, highly oriented VO2 monocrystals grown on a Ti current collector (VO2-Ti) were rationally designed as the research model, and such a well-aligned VO2 cathode also displayed excellent zinc-ion storage capability (e.g., a reversible capacity of 148.4 mAh/g at a current density of 2 A/g). To visualize the H+ reaction process, we used time-of-flight secondary-ion mass spectrometry. With the benefit of such a binder-free and conductor-free electrode design, a clear and intuitive reaction of H+ in a VO2 cathode is obtained, which is quite significant for unraveling the accurate reaction mechanism of VO2 in AZIBs.

Ultrafine ZnS Nanoparticles in the Nitrogen-Doped Carbon Matrix for Long-Life and High-Stable Potassium-Ion Batteries.

Potassium-ion batteries (KIBs) have attracted researchers' widespread attention because of the luxuriant reserves of potassium salts and their low cost. Nevertheless, the absence of suitable electrode materials with a stable electrochemical property is a crucial issue, which seriously hampers the practical applications of KIBs. Herein, a scalable anode material consisting of ultrafine ZnS nanoparticles encapsulated in three-dimensional (3D) carbon nanosheets is explored for KIBs. This hierarchical anode is obtained via a simple and universal sol-gel method combined with a typical solid-phase sulfidation route. The special structure of this anode facilitates good contact with electrolytes and has enough voids to buffer the large volumetric stress changing during K+ insertion/extraction. Thus, the 3D ZnS@C electrode exhibitsour stable cycling performance (230 mAh g-1 over 2300 cycles at 1.0 A g-1) and superior rate capability. The kinetic analysis indicates that a ZnS@C anode with considerable pesoudecapactive contribution benefits a fast potassium/depotassium process. Detailed ex-situ and in-situ measurements reveal that this ZnS@C anode combines reversible conversion and alloying-type reactions. This rationally designed ZnS@C material is highly applicable for KIBs, and the current route opens an avenue for the development of highly stable K+ storage materials.

Freestanding Sodium Vanadate/Carbon Nanotube Composite Cathodes with Excellent Structural Stability and High Rate Capability for Sodium-Ion Batteries.

Sodium vanadate NaV6O15 (NVO) is one of the most promising cathode materials for sodium-ion batteries because of its low cost and high theoretical capacity. Nevertheless, NVO suffers from fast capacity fading and poor rate capability. Herein, a novel free-standing NVO/multiwalled carbon nanotube (MWCNT) composite film cathode was synthesized and designed by a simple hydrothermal method followed by a dispersion technique with high safety and low cost. The kinetics analysis based on cyclic voltammetry measurements reveals that the intimate integration of the MWCNT 3D porous conductive network with the 3D pillaring tunnel structure of NVO nanorods enhances the Na+ intercalation pseudocapacitive behavior, thus leading to exceptional rate capability and long lifespan. Furthermore, the NVO/MWCNT composite exhibits excellent structural stability during the charge/discharge process. With these benefits, the composite delivers a high discharge capacity of 217.2 mA h g-1 at 0.1 A g-1 in a potential region of 1.5-4.0 V. It demonstrates a superior rate capability of 123.7 mA h g-1 at 10 A g-1. More encouragingly, it displays long lifespan; impressively, 96% of the initial capacity is retained at 5 A g-1 for over 500 cycles. Our work presents a promising strategy for developing electrode materials with a high rate capability and a long cycle life.

Cathodes for Aqueous Zn-Ion Batteries: Materials, Mechanisms, and Kinetics.

As concerns about the safety of lithium-ions batteries (LIBs) increases, aqueous zinc-ion batteries (ZIBs) with a lower cost, higher safety, and higher co-efficiency have attracted more and more interest. However, finding suitable cathode materials is still an urgent problem in ZIBs. In recent years, a lot of significant works have been reported, including manganese-based cathodes, vanadium-based cathodes, Prussian blue analog-based materials, and sustainable quinone cathodes. In this review, some typical cathode materials are introduced. The detailed storage mechanisms and methods for improving the reaction kinetics of the zinc ions are summarized. Finally, the issues, challenges, and the research directions are provided.

Ni-Rich Layered Oxide with Preferred Orientation (110) Plane as a Stable Cathode Material for High-Energy Lithium-Ion Batteries.

The cathode, a crucial constituent part of Li-ion batteries, determines the output voltage and integral energy density of batteries to a great extent. Among them, Ni-rich LiNixCoyMnzO2 (x + y + z = 1, x ≥ 0.6) layered transition metal oxides possess a higher capacity and lower cost as compared to LiCoO2, which have stimulated widespread interests. However, the wide application of Ni-rich cathodes is seriously hampered by their poor diffusion dynamics and severe voltage drops. To moderate these problems, a nanobrick Ni-rich layered LiNi0.6Co0.2Mn0.2O2 cathode with a preferred orientation (110) facet was designed and successfully synthesized via a modified co-precipitation route. The galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) analysis of LiNi0.6Co0.2Mn0.2O2 reveal its superior kinetic performance endowing outstanding rate performance and long-term cycle stability, especially the voltage drop being as small as 67.7 mV at a current density of 0.5 C for 200 cycles. Due to its unique architecture, dramatically shortened ion/electron diffusion distance, and more unimpeded Li-ion transmission pathways, the current nanostructured LiNi0.6Co0.2Mn0.2O2 cathode enhances the Li-ion diffusion dynamics and suppresses the voltage drop, thus resulting in superior electrochemical performance.

Scalable One-Pot Synthesis of Hierarchical Bi@C Bulk with Superior Lithium-Ion Storage Performances.

Lithium-ion batteries (LIBs), the most successful commercial energy storage devices, are now widespread in our daily life. However, the lack of appropriate electrode materials with long lifespan and superior rate capability is the urgent bottleneck for the development of high-performance LIBs. Herein, a hierarchical Bi@C bulk is developed via a scalable pyrolysis method. Due to the ultrafine size of Bi nanoparticles and in situ generated porous carbon framework, this Bi@C anode evidently facilitates the diffusion of Li+/electron, availably inhibits the agglomeration of active nano-Bi, and effectively mitigates the volume fluctuation. This hierarchical Bi@C bulk exhibits stable cycling performance for both LIBs (256 mAh g-1 at 1.0 A g-1 over 1400 cycles) and potassium-ion batteries (271 mAh g-1 at 0.1 A g-1 for 200 cycles). More importantly, when coupled with a commercial LiCoO2 cathode, the assembled LiCoO2//Bi@C cells provide an output voltage of 2.9 V and retain a capacity of 202 mAh g-1 at 0.15 A g-1. Moreover, kinetic analysis and in situ X-ray diffraction characterization reveal that the Bi@C anode displays a dominated pseudocapacitance behavior and a typical alloying storage mechanism during the cycling process.

Fe3 O4 @C Nanotubes Grown on Carbon Fabric as a Free-Standing Anode for High-Performance Li-Ion Batteries.

Recently, Li-ion batteries (LIBs) have attracted extensive attention owing to their wide applications in portable and flexible electronic devices. Such a huge market for LIBs has caused an ever-increasing demand for excellent mechanical flexibility, outstanding cycling life, and electrodes with superior rate capability. Herein, an anode of self-supported Fe3 O4 @C nanotubes grown on carbon fabric cloth (CFC) is designed rationally and fabricated through an in situ etching and deposition route combined with an annealing process. These carbon-coated nanotube structured Fe3 O4 arrays with large surface area and enough void space can not only moderate the volume variation during repeated Li+ insertion/extraction, but also facilitate Li+ /electrons transportation and electrolyte penetration. This novel structure endows the Fe3 O4 @C nanotube arrays stable cycle performance (a large reversible capacity of 900 mA h g-1 up to 100 cycles at 0.5 A g-1 ) and outstanding rate capability (reversible capacities of 1030, 985, 908, and 755 mA h g-1 at 0.15, 0.3, 0.75, and 1.5 A g-1 , respectively). Fe3 O4 @C nanotube arrays still achieve a capacity of 665 mA h g-1 after 50 cycles at 0.1 A g-1 in Fe3 O4 @C//LiCoO2 full cells.

B,N Codoped Graphitic Nanotubes Loaded with Co Nanoparticles as Superior Sulfur Host for Advanced Li-S Batteries.

Lithium-sulfur batteries (LSBs) are considered as one of the best candidates for novel rechargeable batteries due to their high energy densities and abundant required materials. However, the poor conductivity and large volume expansion of sulfur and the "shuttle effect" of lithium polysulfides (LPSs) have significantly hindered the development and successful commercialization of LSBs. Bean-like B,N codoped carbon nanotubes loaded with Co nanoparticles (Co@BNTs), which can act as advanced sulfur hosts for the novel LSB cathode, are fabricated. Uniform graphitic nanotubes improve the conductivity of the electrode and load more electroactive sulfur and buffer volume expansion during the electrochemical reaction. In addition, loaded Co nanoparticles and codoped B,N sites can significantly suppress the "shuttle effect" of LPSs with strong chemical interaction. It is established that the Co nanoparticles and codoped B,N can provide more active sites to catalyze the redox reaction of sulfur cathode. This stable Co@BNTs-S cathode displays an exceptional electrochemical performance (1160 mA h g-1 after 200 cycles at 0.1 C) and outstanding stable cycle performance (1008 mA h g-1 after 400 cycles at 1.0 C with an extremely low attenuation rate of 0.038% per cycle).

Large-size and high performance visible-light photodetectors based on two-dimensional hybrid materials SnS/RGO.

We report a facile solvothermal method to synthesize two-dimensional hybrid materials consisting of layered SnS nanosheets and reduced graphene oxide (SnS/RGO). Large-size photodetectors with a channel length/width = 2 mm/7 mm are fabricated on Si/SiO2 substrates, showing an excellent photoresponsivity of 0.18 A W-1 under visible-light illumination with a detectivity of 4.18 × 1010 Jones, as well as fast rise and decay times (τ rise = τ decay = 0.4 s). SnS/RGO hybrids are therefore promising candidates for potential applications in optoelectronics and low cost, high performance, and reliable photodetectors.

Preparation of mono-dispersed, high energy release, core/shell structure Al nanopowders and their application in HTPB propellant as combustion enhancers.

Mono-dispersed, spherical and core/shell structure aluminum nanopowders (ANPs) were produced massively by high energy ion beam evaporation (HEIBE). And the number weighted average particle size of the ANPs is 98.9 nm, with an alumina shell (3-5 nm). Benefiting from the passivation treatment, the friction, impact and electrostatic spark sensitivity of the ANPs are almost equivalent to those of aluminum micro powders. The result of TG-DSC indicates the active aluminum content of ANPs is 87.14%, the enthalpy release value is 20.37 kJ/g, the specific heat release S 1/Δm 1* (392-611 °C) which determined the ability of energy release is 19.95 kJ/g. And the value of S 1/Δm 1* is the highest compared with ANPs produced by other physical methods. Besides, the ANPs perfectly compatible with hydroxyl-terminated polybutadiene (HTPB), 3 wt. % of ANPs were used in HTPB propellant replaced micron aluminum powders, and improved the burning rate in the 3-12 MPa pressure range and reduced the pressure exponential by more than 31% in the 3-16 MPa pressure range. The production technology of ANPs with excellent properties will greatly promote the application of ANPs in the field of energetic materials such as propellant, explosive and pyrotechnics.