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Layered vanadium oxides have been promising cathodes for rechargeable aqueous zinc ion batteries (AZIBs) owing to multiple valences of vanadium and relatively high interplanar spacing. However, it undergoes significant capacity decay due to vanadium dissolution and structural instability during cycling, especially at low current densities. Herein, PANI-intercalated V2O5 ((PANI)xV2O5, PAVO) hybrid bronzes with an ultra-high interlayer spacing of 13.9 A for use as an AZIB cathode have been reported. The inserted polyaniline not only acts as structural pillars because of the hydrogen bond between -NH2 group and V-O layer but also plays the role of ‘H+’ reservoir to prevent V-O matrix from H+ attacking. Accordingly, PAVO cathode delivers a specific capacity of 350 mAh g−1 with a capacity of ~90% over 100 cycles at a current density of 0.1 A g−1, which operates for about 1 month. This study unveils the dissolution mechanism of vanadium-based electrodes and improves the stability and electronic conductivity with organic molecule intercalation. Besides, the intercalation of guest molecule generates pros and cons (favorable higher interlayer, while adverse steric hindrance) to the Zn2+ diffusion and accordingly presents a different rate performance when compared to most of the previously reported work. Therefore, a new set of molecular-scale hybrid bronzes would be designed to achieve an optimized performance in the future.

A membrane with high stability and ion conductivity in wide pH range is essential for energy storage devices. Here, we report a novel membrane with hierarchical core–shell structure, which demonstrates high stability and ion conductivity, simultaneously under a wide pH range applications. Spectral characterizations and theoretical calculation indicate that the non-solvent induces the chain segment configuration and eventually leads to polymer–polymer phase separation, thus forming hierarchical porous core–shell structure. Benefiting from this structure, an acidic vanadium flow battery (VFB) with such a membrane shows excellent performance over 400 cycles with an energy efficiency (EE) of above 81% at current density of 120 mA cm−2 and an alkaline zinc-iron flow battery (AZIFB) delivers a cycling stability for more than 200 cycles at 160 mA cm−2, along with an EE of above 82%. This paper provides a cost-effective and simple way to fabricate membranes with high performance for variety of energy-related devices.

Lithium metal-based secondary batteries are very promising for next generation power battery due to their high energy density. However, lithium anodes suffer from poor electrochemical reversibility in organic electrolytes due to Li dendrites and instability of the solid electrolyte interphase. Recent research demonstrated that the problem can be alleviated via tetraethoxysilane (TEOS) treated lithium metal to form a silicon oxide layer on the lithium surface, however, its reaction mechanism is controversial. Herein, we deeply explore the reaction mechanism between TEOS and Li and propose: Fresh Li can directly react with TEOS even though no lithium hydroxide exists on the lithium surface, and the participation of water will accelerate the reaction process. Moreover, it was found that the silicon oxide layer can promote the uniform deposition of lithium ions by providing lithiophilic nucleation sites, thereby achieving a long cycle life of Li metal batteries.

Alkaline zinc-based batteries are becoming promising candidates for green and economical energy-storage systems, thanks to their low cost and high energy density. The exploitation of the stable cathode materials with high rate capability and cycling stability is crucial for their further development. Herein, a series of NiSx coated with nitrogen-doped carbon (denoted as NiSx@NC) compounds (x = 0.5-1.0) are synthesized using the facile single-source precursor method. Benefiting from the unique phase-transitional NiSx@NC with high activity and enhanced conductivity from the well-balanced conductive metal nickel and carbon layer, the alkaline zinc-nickel batteries with a phase-transitional NiSx@NC cathode deliver a high capacity of 148 mA h g-1 at a high current density of 100 mA cm-2 and demonstrate a long lifespan of over 500 cycles with a high capacity retention of 98.8%. This work provides a significant guideline for the structural design and optimization of nickel-based materials in alkaline energy-storage devices.

Reducing carbon dioxide to high value-added chemicals is of high importance due to its vital role in mitigating CO2 emission and energy crisis. However, seeking for robust catalysts with low overpo...

Sodium ion batteries (SIBs) have been regarded as one of the alternatives to lithium ion batteries owing to their wide availability and significantly low cost of sodium sources. However, they face serious challenges of low energy & power density and short cycling lifespan owing to the heavy mass and large radius of Na+. Vanadium-based polyanionic compounds have advantageous characteristic of high operating voltage, high ionic conductivity and robust structural framework, which is conducive to their high energy & power density and long lifespan for SIBs. In this review, we will overview the latest V-based polyanionic compounds, along with the respective characteristic from the intrinsic crystal structure to performance presentation and improvement for SIBs. One of the most important aspect is to discover the essential problems existed in the present V-based polyanionic compounds for high-energy & power applications, and point out most suitable solutions from the crystal structure modulation, interface tailoring and electrode configuration design. Moreover, some scientific issues of V-based polyanionic compounds shall be also proposed and related future direction shall be provided. We believe that this review can serve as a motivation for further development of novel V-based polyanionic compounds and drive them toward high energy & power applications in the near future.

Aqueous redox flow batteries (ARFBs) are regarded as promising candidates for large-scale energy storage. In particular, ARFBs based on organic redox-active species can largely reduce the capital cost and mineral resource requirements. However, the design of redox-active organic materials with desirable electrochemical performances needs to be further explored. Herein, we report a green and low-cost synthesis of a highly soluble N-alkyl-carboxylate-functionalized derivative of 2,6-diaminoanthraquinone, namely, N,N'-(9,10-anthraquinone-2,6-diyl)-di-β-alanine (DAEAQ), which exhibits a high voltage plateau and long cycling life when serving as an anolyte in ARFBs. The alkaline ARFBs based on DAEAQ anolyte and potassium ferrocyanide (K4Fe(CN)6) catholyte deliver a high open-circuit voltage of 1.12 V at pH ≥12. When sandwiched with a custom highly-sulfonated and nonfluorinated cation exchange membrane, the as-prepared ARFBs achieve an excellent maximum power density of 0.34 W cm−2 and an optimal capacity retention rate of 99.86% day−1. This work highlights the great potential of rationally designed anthraquinone derivatives in ARFBs for grid-scale renewable and sustainable energy storage applications.

The conversion of carbon dioxide to chemicals by the electrochemical reactions (ERC) is an efficient solution to the current energy crisis and excess CO2 emissions. It is still a great challenge and of significance to synthesize a highly selective, efficient, and non−noble metal electrocatalyst that facilitates the ERC reaction. A novel triton X−100 (C14H22O(C2H4O)n) assisted electrodeposition method was developed to synthesize the ordered cone−structured tin (OCSn) electrocatalysts with controllable morphology and structure. The results suggest that Triton X−100 plays an important role in directing the structure of the Sn electrocatalysts during the electrodeposition process. The OCSn synthesized at 60 mA cm−2 achieves the best performances. It selectively catalyzes the ERC on the onset potential about 110 mV lower than Sn synthesized without Triton X−100. In 0.5 M NaHCO3, high faradaic efficiency (92%) for formate product on OCSn has been achieved. More prominently, the catalyst presents excellent stability, showing no performance deterioration during 30 h electrolysis. This work provides an efficient, green, and scalable synthesis method of the electrocatalyst for CO2 reduction to formate.

The electrochemical reduction of CO2 (ERC) to valuable chemicals has attracted extensive attention. However, the relatively low selectivity and efficiency of the reaction remain challenges. In this study, Cu electrodes derived from Cu2 O with predominant (111) facets are synthesized by cetyltrimethylammonium bromide-assisted preparation. The optimized electrode shows a high faradaic efficiency of 90 % for HCOOH obtained by ERC at -2.0 V (vs.SCE), which surpasses most reported Cu electrodes. Based on a comprehensive analysis of the relationship between the catalytic activity and the thickness of the Cu2 O layer, the catalytic activity of the unit active site on the Cu2 O-derived Cu electrodes is found to be higher than that on the blank Cu electrode. DFT calculations indicate that OCHO* would be produced preferentially over *COOH in the presence of cetyltrimethylammonium bromide (CTAB). This deduction is verified by testing of the effects of CTAB and KBr addition on HCOO- selectivity.

Composite membranes with high selectivity and permeability are always essential in diverse fields including batteries and separation. Ultrathin highly-selective layers with well-defined porous structures are deemed as the priority for the composite membranes to break the trade-off effect between selectivity and permeability. Here, we report a binder-controlled restrained second-growth method (BRSM), which directly introduces continuous and uniform metal organic frameworks selective layers (UiO-66/-67) on porous polymer substrates (Daramic) to achieve defect-free composite membranes. In this method, the nucleation and growth of MOF can be well-tuned via controlling MOF nucleation density and the dissolution rates of binders. Composite membranes with UiO-66/-67 layers demonstrate well-controlled selectivities on different ions, confirming the key role of well-ordered pores of MOF. This is further highlighted by the coulombic efficiency (CE) enhanced from 88.4% to 94.5% at a current density of 80 mA cm−2 in zinc-iodine flow battery (ZIFB) demonstration. Additionally, a more even deposition of zinc is induced by MOF surface layer with uniformly pore size distribution, which can suppress the zinc dendrites effectively. This work demonstrates an effective and controllable way to introduce defect-free MOF selective layers on polymer substrates via tuning the MOF nucleation and growth, creating highly selective composite membranes.

The n-octadecyltrichlorosilane (OTS) had been coated onto the layered double hydroxides (LDH), and the resultant composite of OTS-LDH was further loaded on the surface of melamine sponge by a soaking method to obtain the OTS-LDH/melamine sponge for efficient oil adsorption in this work. The surface chemical compositions of the OTS-LDH/sponge and its precursors were characterized by EDS, XPS, and FTIR. The results from EDS, XPS, and FTIR showed that the OTS had been successfully coated on LDH. The surface morphologies from SEM for the melamine sponge before and after modification illuminated that the surface skeleton of the OTS-LDH/sponge took a rough micro-nanostructure, and the surface had been loaded with the low surface energy material of OTS, which made the OTS-LDH/sponge display the superhydrophobic properties. The experiments of oil–water separation proved that the OTS-LDH/sponge took an excellent oil–water efficiency, and the modified sponge still took the better oil–water separation performance with an oil adsorption capacity of 13.7–21.1 times of the mass of the pristine sponge even after undergoing repeated extrusion for 60 times during the repeated cycle test.

With the excessive consumption of fossil fuels, CO2 emission issues and the energy crisis have become more prominent. The electrocatalytic reduction of CO2 (ERC) driven by intermittent renewable electricity can not only mitigate carbon dioxide emission, but also store renewable energy. However, the poor activity, selectivity and stability of the catalysts inhibit their practical large-scale application. Herein, we report a facile synthesis method for a synthetic N-doped hierarchical porous carbon catalyst, which was obtained by directly carbonizing the ZIF8 precursor decorated with the low boiling metal salts (BiCl3). Plentiful bismuth salts can not only efficiently destroy the Zn–Nx bond and promote the aggregation and evaporation of the Zn species at a relatively low temperature, but also enhance the formation of a conductive and hierarchical porous catalyst. In addition, the tedious post-processing to remove the metal salts is avoided. Density functional theory calculations suggest that the coordinated unsaturated Zn–Nx sites tremendously inhibit the activity of the nearby pyridinic N sites, which play an important role in the catalytic performance. As a result, the catalysts achieve about 90% faradaic efficiency for CO at a very low overpotential of −0.49 V, which is much lower than the most reported N-doped carbon catalysts.

Aqueous zinc-based flow batteries (ZFBs) represent one of the most promising energy storage technologies benefiting from their high safety and competitive energy density. However, the morphological evolution of Zn still remains vague but is significant in the electrolyte, whose Zn2+ concentration constantly decreases during Zn plating. Herein, we present a comprehensive experimental investigation on the morphological evolution and mechanism of deposited Zn in ZFBs and find that the formation of dense blocky Zn is controlled by instantaneous nucleation in concentrated electrolyte (≥0.4 M); in dilute electrolyte (≤0.3 M), Zn becomes mossy because of progressive nucleation. Simultaneously, the dominant plane of Zn crystals changes from (002) to (101). Besides, the recombination of Zn crystals on the same crystal plane was observed by in situ atomic force microscopy (AFM). Significantly, to maintain a high coulombic efficiency (CE >99.5%) and long cycling stability, an operating critical concentration range (≥0.4 M) and the optimized electrolyte utilization rate is proposed according to the Zn morphological evolution. This exploratory work will be beneficial for the further research of Zn anodes in electrochemical energy storage devices.

Manganese-based flow batteries have attracted increasing interest due to their advantages of low cost and high energy density. However, the sediment (MnO2) from Mn3+ disproportionation reaction creates the risk of blocking pipelines, leading to poor stability. Herein, a titanium–manganese single flow battery (TMSFB) with high stability is designed and fabricated for the first time. In the design, a static cathode without the tank and pump is employed to avoid blockage of pipelines by MnO2 particles. Benefiting from the deceasing disproportionation reaction rate, MnO2 from the disproportionation reaction is fully utilized, realizing nearly two electron capacity. The novel TMSFB exhibits coulombic efficiency (CE) of over 99.0% at a current density of 40 mA cm−2. Most importantly, the TMSFB can run stably over 1000 cycles without capacity decay, demonstrating very good stability. With low cost, high efficiency and long cycle life, TMSFBs exhibit remarkable potential for large scale energy storage.

Redox flow batteries (RFBs) are becoming an increasingly important means to power a green and renewable future. Advances in RFBs require an understanding of the construction of ion/molecule-selective transport nanochannels in high-performance and low-cost membranes for the application of large-scale energy storage. Enabling the control of ion/molecule transport at nanometer scales can achieve numerous functions, such as selectivity, conductivity, stability, and electrochemical performance, which result from diverse interactions between the ion/molecule and nanochannels. This paper presents an overview of the research and development of membranes with ion/molecule-selective transport nanochannels for RFB applications and particularly focuses on the basic principles, namely solvated ion/molecule sizes, functional groups, nanoscale confined dimensions, interactions, and environmental factors during ion/molecule-selective transport in nanochannels on the basis of their chemical and physical structures. Finally, we provide insights into the challenges and possible future research directions in the development of next-generation membranes for RFBs.

Aqueous rechargeable metal-ion batteries (ARMBs) hold intrinsic advantages of high safety, low cost and environmental benignity for large scale energy storage technologies. However, the research on aqueous K-ion batteries (AKIBs) was hindered by limited materials. Herein, a novel AKIB was reported by employing environment-friendly 1,4,5,8-naphthalenetetracarboxylic dianhydride-derived polyimide (PNTCDA) as anode and Berlin green (FeHCF) as cathode. Both electrodes have high rate performance and excellent capacity retention during cycling. Kinetics researches verify the superior electrochemical property of PNTCDA in saturated KNO3 solution. In-situ XRD of FeHCF demonstrates the unique shift of peak position and negligible distortion of lattice during the insertion/extraction of K+. The AKIB exhibits an attractive energy density of 46.9 Wh/kg and a high capacity retention of 74% in 300 cycles. More importantly, the battery can reach a super-high power of 2079.1 W/kg with an energy density of 24.2 Wh/kg, ranking relatively high among the ARIMs. This system extends the use of polyimide and points a way of AKIBs for grid-scale energy storage.

Software switches are being deployed in SDN to enable a wide spectrum of non-traditional applications. The popular Open vSwitch uses a variant of Tuple Space Search (TSS) for packet classifications. Although it has good performance on rule updates, it is less efficient than decision trees on lookups. In this paper, we propose a two-stage framework consisting of heterogeneous algorithms to adaptively exploit different characteristics of the rule sets at different scales. In the first stage, partial decision trees are constructed from several rule subsets grouped with respect to their small fields . This grouping eliminates rule replications at large scales, thereby enabling very efficient pre-cuttings. The second stage handles packet classification at small scales for non-leaf terminal nodes , where rule replications within each subspace may lead to inefficient cuttings. A salient fact is that small space means long address prefixes or less nesting levels of ranges, both indicating a very limited tuple space. To exploit this favorable property, we employ a TSS-based algorithm for these subsets following tree constructions. Experimental results show that our work has comparable update performance to TSS in Open vSwitch, while achieving almost an order-of-magnitude improvement on classification performance over TSS.

Tetragonal NaVPO4F has been regarded as an ideal cathode for sodium-ion batteries because of its high average plateau (3.8 V) and theoretical specific capacity (143 mA h g-1). However, the Na-storage performance is still hindered by unsatisfying thermal stability and poor conductivity. Herein, a stable tetragonal NaVPO4F has been synthesized by a novel solvent thermal method using a carbon coating precursor. The as-prepared NaVPO4F@C nanocomposite delivers a capacity of 133 mA h g-1 at 0.2 C, corresponding to an excellent energy density of 509 W h kg-1; when coupled with an HC anode, the full cell still displays an outstanding performance of 124 mA h g-1 at 0.05 C. Fast Na+ diffusion kinetics (DNa+ = 10-12 to 10-10 cm2 s-1) and small volume change (4.4%) are exploited, which ensures good rate trait and cycling stability of tetragonal NaVPO4F. Further, the Na+ extraction-insertion mechanism has been explored by analyzing the crystal structure change during in situ X-ray powder diffraction cycles.

Alkali metals are ideal anodes for high-energy-density rechargeable batteries, while seriously hampered by limited cycle life and low areal capacities. To this end, rationally designed frameworks f...

This work demonstrates significant improvements in both the aging kinetics and precipitation hardening of an Al-Li-Cu alloy with the minor addition of Cd (0.06 at.%). The precipitation hardening effect of T1 precipitates in casting Al-Li-Cu alloys has long been ignored since it is difficult to achieve a high number density of fine precipitates without a large number of dislocations. A detailed transmission electron microscopy investigation shows that the Cd addition has changed the distribution of T1 precipitates from the conventional uneven distribution near dislocations or grain boundaries to a more homogeneous manner. Most of the Cd-rich nanoparticles were observed at the broad face and/or terminal of the T1 platelets. It is highly likely that these nanoparticles act as heterogeneous nucleation sites, which consequently leads to a higher number density of T1 precipitates. Moreover, Cd atoms were preferentially segregated within δ′ precipitates, which can be attributed to the strong bonding between Li and Cd. The interactions between Cd and the T1 (Al2CuLi) and δ′ (Al3Li) precipitates in Al-Li-Cu alloy are first reported. The present study may propose a new mechanism to effectively improve precipitation kinetics and therefore the age-hardening effect of Al-Li-Cu alloys.

The vanadium flow battery (VFB) is widely regarded as one of the most reliable large-scale energy storage technologies due to its flexible design, long cycle life, and high safety. However, novel electrodes for VFBs with a well-suited structure by cost-effective manufacturing processes are still highly sought after to penetrate the growing energy storage market. Here, we demonstrate a holey three-dimensional (3D) wood-based electrode for VFBs, which was engineered by the facile perforation and carbonization of earth-abundant, low-cost, and sustainable wood. The 3D-wood electrode inherits the intrinsic, vertically-aligned channels (i.e. low tortuosity structure) of the original crude wood material, which provides fluent electrolyte transport paths in the flow battery system. Furthermore, small holes (approximately 1.3 ​mm) are drilled across the 3D-wood electrode in the perpendicular direction to connect the parallel channels, thereby enabling ion exchange and reducing flow resistance. The concentration polarization is significantly reduced during the charge and discharge process in VFB, due to these electrode modifications. The porous structure of the 3D-wood electrode, with a high specific surface area of 216.77 ​m2 ​g−1 and oxygen functional groups, provides sufficient reaction sites for vanadium cations to enhance the electrochemical reactivity of VFBs. The superior structure of the 3D-wood electrode ensures the feasibility in VFBs and offers a promising direction for developing flow battery electrodes through pore engineering of earth-abundant biomaterials.

Graphite is a key cathode material for aluminum-ion batteries (AIBs), but appears poor structural stability and cyclability due to the slow kinetics of intercalation and usage of conductive additives. So far, reasonable design and construction of high-conductive, flexible, binder-free graphitic film cathodes with fast kinetics of anion intercalation mechanism still remains challenging for high-power and high-energy AIBs. Herein, we report the reasonable design for facile construction of high-conductive and mechanically flexible film cathode of high-quality few-layer graphene (FLG) nanosheets for high capacity and fast AIBs, thanks to the strong synergy of ionic surface adsorption/desorption of graphene and ionic intercalation/deintercalation of graphite. The FLG nanosheets prepared by electrochemical cathodic exfoliation from graphite, exhibit predominantly 3–5 layers, extremely low ID/IG ratio of

Lithium–sulfur (Li–S) batteries have great potential as an electrochemical energy storage system because of the high theoretical energy density and acceptable cost of financial and environment. However, the shuttle effect leads to severe capacity fading and low coulombic efficiency. Here, graphitic carbon nitride (g–C3N4) is designed and prepared via a feasible and simple method from trithiocyanuric acid (TTCA) to anchor the polysulfides and suppress the shuttle effect. The obtained g–C3N4 exhibits strong chemical interaction with polysulfides due to its high N–doping of 56.87 at%, which is beneficial to improve the cycling stability of Li–S batteries. Moreover, the novel porous framework and high specific surface area of g–C3N4 also provide fast ion transport and broad reaction interface of sulfur cathode, facilitating high capacity output and superior rate performance of Li–S batteries. As a result, Li–S batteries assembled with g–C3N4 can achieve high discharge capacity of 1200 mAh/g at 0.2 C and over 800 mAh/g is remained after 100 cycles with a coulombic efficiency more than 99.5%. When the C–rate rises to 5 C, the reversible capacity of Li–S batteries can still maintain at 607 mAh/g.

As one of the most promising cathodes for sodium-ion batteries, the polyanionic compounds still suffer from unsatisfactory capacity and rate performance resulting from poor electron conductivity. F...

Performance optimization and cost reduction of a vanadium flow battery (VFB) system is essential for its commercialization and application in large-scale energy storage. However, developing a VFB stack from lab to industrial scale can take years of experiments due to the influence of complex factors, from key materials to the battery architecture. Herein, we have developed an innovative machine learning (ML) methodology to optimize and predict the efficiencies and costs of VFBs with extreme accuracy, based on our database of over 100 stacks with varying power rates. The results indicated that the cost of a VFB system (S-cost) at energy/power (E/P) = 4 h can reach around 223 $ (kW h)−1, when the operating current density reaches 200 mA cm−2, while the voltage efficiency (VE) and utilization ratio of the electrolyte (UE) are maintained above 90% and 80%, respectively. This work highlights the potential of the ML methodology to guide stack design and optimization of flow batteries to further accelerate their commercialization.

The development of primary batteries with high energy density, long shelf life, and stable discharge voltage is essential for civilization and military applications. Primary batteries with high power output and excellent low-temperature performance can further broaden their application. Herein, a Li/LiV2(PO4)3 primary battery was proposed and investigated for the first time. In order to improve the shelf life of the Li/LiV2(PO4)3 primary battery, the mechanism and corresponding inhibition strategy of self-discharge were studied in detail. It was found that the electrolyte composition is a key factor affecting the shelf life of Li/LiV2(PO4)3 primary batteries, where the corrosion of aluminum (Al) current collector triggered by the organic radical cations generated from electrochemical oxidation of the ethylene carbonate (EC) at high potential; and the detrimental reaction between LiV2(PO4)3 and electrolyte lead to the self-discharge of the Li/LiV2(PO4)3 primary battery. When the EC solvent was replaced by the propylene carbonate (PC) solvent, the corrosion of Al foil was alleviated. Moreover, the addition of lithium bis(oxalato)borate (LiBOB) to the electrolyte could improve the stability of cathode/electrolyte interface and enhance the shelf life of the Li/LiV2(PO4)3 primary battery. As a result, 100% capacity could be maintained after over one-month storage, 86% energy could be maintained at 50C, and 63% energy could be maintained at −40 °C at a current density of 0.1C. In addition, the Li/LiV2(PO4)3 primary battery showed great potential for all-weather applications.

Sodium-ion batteries are considered surrogates for conventional lithium-ion batteries for the commercial sector. One of the most favourable anode materials for sodium-ion batteries is hard carbon. However, its performance is affected by the large irreversible capacity loss (ICL) in the initial charge process. This study proposes the Na4V2(PO4)3 (Na4VP) cathode as a possible solution for matching the hard carbon anode. The process uses a recently developed electrochemical pre-sodiation strategy, where the first step converts Na3V2(PO4)3 (Na3VP) to a Na4VP cathode by a sodiation step. After this, a de-sodiation step of Na4VP is carried out below 2.2 V (vs. Na+/Na) to entirely compensate for the ICL of the anode, and the resulting Na3VP directly acts as the cathode. As a result, the Na4VP‖HC full cell achieves a substantially high specific energy of 265 W h kg−1, which is 76% higher than that of the Na3VP‖HC full cell. Moreover, the Na4VP‖HC full cell shows excellent rate performance (62.32 mA h g−1 at 10C) and cycling stability (about 80.0% capacity retention after 100 cycles at 1C). This work is a precursor to the further study of other battery and hybrid capacitor systems, where pre-sodiation plays an important role in improving their performance.

Rechargeable aqueous zinc ion batteries have attracted significant attention for practical energy storage due to their low cost and high safety, however, it is still a hard task to find suitable cathode materials to meet the demand of both high capacity and rate performance. Here, we propose a high-performance anhydrous V2O5 yolk–shell cathode via a facile template-free solvothermal technique. Owing to its porous structure, the V2O5 cathode could largely facilitate rapid electrolyte transportation and restrain structural collapse during cycling. Moreover, it is interesting to find that the interlayer spacing expands from 4.37 to 13.45 A through an interesting activation process, as a result, the prepared V2O5 cathode demonstrated high reversible capacities of 410 mA h g−1 at 0.1 A g−1 and 182 mA h g−1 at 20 A g−1 and a capacity retention of 80% can be achieved over 1000 cycles at 5.0 A g−1, which is superior to those of most commonly reported anhydrous V2O5 cathodes. Therefore, this paper demonstrates the potential of V2O5 for achieving high energy/power densities as a cathode material in ZIBs.

Solar redox flow batteries (SRFBs) integrate solar energy conversion devices and redox flow batteries (RFBs) to realize the flexible storage/utilization of solar energy by charging/discharging redo...

Self-assembled ultralong Si 3N 4/SiO 2 nanowires (SiNNWs) with core-shell structure are prepared by air jet-spinning followed by high-temperature calcination employing low-cost fumed nano silica and industrial polyacrylonitrile as raw materials. Without using metal catalysts or reductive atmosphere, Si 3N 4/SiO 2 nanowires are generated through autocatalysis and self-assembly. The ultralong SiNNWs are uniform and continuous throughout the entire length with a 3–4 nm amorphous SiO 2 shell layer on surface of the Si 3N 4. The diameter of the SiNNWs is about 80–200 nm with the length being at centimeter level and the main component of the SiNNWs is the standard hexagonal cell of α-Si 3N 4. Moreover, the photoluminescence spectrum of SiNNWs exhibits an intense blue-green light emission at room temperature. The self-assembly mechanism of the SiNNWs is discussed.

Tin oxide (SnOX) nanomaterials have received attention as electrode materials due to their large theoretical capacitance, but their use remains limited due to cumbersome processing and limited electrical conductivity. In this work, SnOX nanoparticles, nanowires and nanorods embedded in a layered composite carbon hybrid nanofiber mat are prepared via blow-spinning followed by pre-oxidation and a high-temperature calcination self-assembly process in argon using stannous chloride and polyacrylonitrile as raw materials. As a result, a dual network conductive structure consisting of an upper SnOx nanostructure and underlying hybrid carbon nanofibers is created. The nanostructure morphology is controlled by reaction time through a transformation from nanoparticle to nanowire and lastly to nanorod and the potential formation and growth mechanism is discussed in detail. It is found that pre-oxidation introduces oxygen in the polyacrylonitrile that upon calcination into carbon nanofibers is released as oxygen containing gaseous substances that fuel transformation and oxidation of stannous chlorides and oxides into the self-assembled stannic oxide nanostructures in an approach applicable to other metal oxide structures. The SnO2 nanowire carbon hybrid nanofibers mat (SnO2–NW@CNFMs) exhibits the highest specific capacitance of 420.1 F g − 1 at a scan rate of 5 mV s − 1 and good cyclic stability of 92.5% capacitance retention after 3000 cycles at 1 A g − 1 which exceeds the performance in earlier reported studies of tin oxide nanomaterials. The high electrochemical properties combined with the novel preparation procedure presented in this study promote SnO2–NW@CNFMs as a good choice for electrodes in electronic appliances and electric vehicles.

Membranes with fast and selective ions transport are highly demanded for energy storage devices. Layered double hydroxides (LDHs), bearing uniform interlayer galleries and abundant hydroxyl groups covalently bonded within two-dimensional (2D) host layers, make them superb candidates for high-performance membranes. However, related research on LDHs for ions separation is quite rare, especially the deep-going study on ions transport behavior in LDHs. Here, we report a LDHs-based composite membrane with fast and selective ions transport for flow battery application. The hydroxide ions transport through LDHs via vehicular (standard diffusion) & Grotthuss (proton hopping) mechanisms is uncovered. The LDHs-based membrane enables an alkaline zinc-based flow battery to operate at 200 mA cm−2, along with an energy efficiency of 82.36% for 400 cycles. This study offers an in-depth understanding of ions transport in LDHs and further inspires their applications in other energy-related devices., Membranes with fast and selective ion transport are highly relevant for energy storage devices. Here, the authors report a layered double hydroxide membrane with high ionic selectivity and hydroxide ion conductivity for flow battery applications, and reveal the ions transport mechanism of the membrane.

The stability of surrounding rock for large or super-large section chambers is extremely hard to control in deep coal mines, as well as in close-distance chambers. Based on the on-site geo...

A polybenzimidazole (PBI) solvent resistant nanofiltration (SRNF) membrane with super high stability is designed and fabricated by a simple and effective intermolecular cross-linking reaction. There is a dramatic improvement in the solvent stability of the PBI membranes after crosslinking. The membrane keeps stable in even strong apolar solvent like N,N-dimethyl formamide (DMF), N,N-dimethylacetamide (DMAc) after crosslinking. The morphology together with performance can be easily tuned by the polymer concentration. The results indicate that with increasing polymer concentration in cast solution, an increased rejection and a decreased flux are realized. The prepared cross-linked membranes show a rejection of 99% on Rose Bengal (RB) in Ethanol, isopropanol (IPA) and DMF, exhibiting very good prospects in SRNF application. This paper provides a simple and versatile way to create PBI SRNF membranes.

Polybenzimidazole membranes with dual proton transport channels (B-PBI) are designed and fabricated for vanadium flow battery (VFB) applications. The dual channels are established by introducing pyridine groups (channel-1) in the PBI chain (B-PBI), which contains imidazole rings (channel-2). The proton transport channels can endow the B-PBI membrane with dramatically enhanced proton conductivity, while the repulsion between the positively charged pyridine and imidazole nitrogens after doping with protons and the vanadium ions can afford the membrane with excellent ion selectivity. Hence, the prepared B-PBI membrane delivers an excellent performance in terms of high proton conductivity, ion selectivity and chemical stability. A VFB with a B-PBI membrane exhibits a coulombic efficiency (CE) of 99.16% and a voltage efficiency (VE) of 88.86% at a current density of 80 mA cm−2, which is much higher than does a battery with a pristine PBI membrane (CE of 98.54%, VE of 84.10%) and with a Nafion 115 membrane (CE of 95.13%, VE of 87.05%). The chemical stability of the B-PBI is confirmed by a stable performance of 600 cycles at 160 mA cm−2 and the ex-situ oxidation stability test. These results suggest that the B-PBI membrane with dual proton transport channels can be served as promising candidate for vanadium flow battery.

Developing efficient and low-cost catalysts is the key part for electrochemical reduction of CO2, and the bimetallic approach is a cost-effective strategy to find promising electrocatalysts for CO2...

Flow batteries have received increasing attention because of their ability to accelerate the utilization of renewable energy by resolving issues of discontinuity, instability and uncontrollability. Currently, widely studied flow batteries include traditional vanadium and zinc-based flow batteries as well as novel flow battery systems. And although vanadium and zinc-based flow batteries are close to commercialization, relatively low power and energy densities restrict the further commercial and industrial application. To improve power and energy densities, researchers have started to investigate novel flow battery systems, including aqueous and non-aqueous systems. Here, novel non-aqueous flow batteries possess low conductivity and low safety, limiting further application. Therefore, the most promising systems remain vanadium and zinc-based flow batteries as well as novel aqueous flow batteries. Overall, the research of flow batteries should focus on improvements in power and energy density along with cost reductions. In addition, because the design and development of flow battery stacks are vital for industrialization, the structural design and optimization of key materials and stacks of flow batteries are also important. Based on all of this, this review will present in detail the current progress and developmental perspectives of flow batteries with a focus on vanadium flow batteries, zinc-based flow batteries and novel flow battery systems to provide an effective and extensive understanding of the current research and future development of flow batteries.

Na3V2(PO4)2F3 has been emerging as one of the most promising cathodes for sodium-ion batteries due to its stable NASICON structure and fast Na+ diffusion. However, present methods for preparation o...

The innovation of electrode structures has been lagging far behind that of materials, hampering the industrialization process of high performance batteries or electro-catalytic systems. Especially for thick electrodes with high active materials loadings, it's inadequate to achieve satisfactory performance, especially working at higher current densities, due to the restricted ion transport rate across the electrodes with traditional densely packed structure. Herein, a vertically aligned laminate porous electrode structure is designed, with ion diffusion route shortened by 85%. As a result, the as prepared C/S electrodes (for Li-S batteries) achieve a sharp increase of specific capacity by 50% at 2 C and show excellent cycling stability with a capacity of 949 mAh g−1 at 0.1 C with sulfur loading of 8.0 mg cm−2. In addition, capacities of 89 and 115 mAh g−1 at 10 C have been achieved for LiFePO4 (LFP) and NaTi2(PO4)3 (NTP) electrodes, respectively, which is over 70% and 130% compared to their contrast with active substances loading of 8.8 and 5.5 mg cm−2. It also shows a good application in the field of electroreduction of CO2.

In-situ Mg2Si/AZ91 composites were synthesized by incorporating silica fume and three modifiers including CeLa, Sb and AlSr. Effect of the modification treatment on the microstructure and tensile properties was investigated. It was found that among the three modifiers, Sb was the most effective in grain refinement of the matrix while AlSr was the most beneficial to size-reduction of the Mg2Si reinforcement. Adding CeLa facilitated formation of large needle-like Mg2Si while the addition of Sb was favorable for formation of large polygonal Mg2Si. For comparison, adding AlSr facilitated generation of fine granular Mg2Si. Among the three composites, the AlSr-modified composite showed the highest tensile strength and ductility, which was mainly due to the formation of fine, granular and dispersed Mg2Si and Mg17Al12 phases after AlSr modification. The highest tensile strength of 272 MPa obtained by using both silica fume and AlSr modifier was much higher than that by incorporating hollow fly ash cenosphere, indicating that the tensile strength of in-situ Mg2Si/AZ91 composites could be significantly improved by incorporating both silica fume and AlSr modifier.

Electrocatalytic reduction of carbon dioxide to high value-added chemicals is essential for sustainable development of human civilization. Seeking catalysts with high activity, selectivity, stabili...

A blend membrane with the core-shell structure was designed and prepared for vanadium flow batteries (VFBs). The core is the membrane manufactured by poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and polyvinylpyrrolidone (PVP) anion exchange resin, while the shell is composed of cage-shaped pores induced by VO2+ treatment. The high ion selectivity of PVDF-HFP/PVP blend membranes with the core-shell structure is assured by the ion sieving effect of cage-shaped pores and Donnan exclusion effect of anion exchange resin. The convection mechanism of charge carriers across pores on the surface and surface layers, together with the Grotthuss mechanism across the deep-seated anion exchange membrane jointly contributes to high ion conductivity of blend membranes. A great balance between high ion selectivity and high ion conductivity can thus be achieved. Moreover, the formation of cage-shaped pores can remedy the loss of chemical stability caused by anion exchange groups in PVP. A VFB with the resultant membrane could achieve a columbic efficiency of 98.16%, and an energy efficiency of 88.01% at 80 mA cm−2, much higher than those of Nafion 115. This core-shell structural blend membrane is an entirely novel concept to combine advantages of porous membranes and ion exchange membranes, while avoid their drawbacks simultaneously.

Vanadium flow battery is emerging as one of the most promising candidates for large scale energy storage application. The major restriction on the route to commercialization is the high cost of the system. One of the effective ways to lower the cost of a vanadium flow battery system is improving the power density by reducing the battery polarization, which can be realized by controlling the electrode compression ratio reasonably. An overall polarization model, in consideration of the ohmic loss, activation loss and mass transport loss, was proposed for the first time. Then, the polarization model was coupled with a previously developed three-dimensional model to obtain a mechanistic understanding of the relationship between the electrode compression ratio and battery polarization. By combining numerical simulation with experiments, the effect of the compression ratio on the polarization and subsequently the battery performance was explored systemically and deeply, and the performance superiority of the battery assembly with the obtained optimal compression ratio was verified by experiments.

Molybdate polyanion cathode materials have received lots of research interest for their high specific capacity, high cycling stability and interesting physical and chemical properties. Here, LiCr(MoO4)2, a new deintercalation–intercalation type cathode material for lithium ion batteries, is synthesized and studied. Ultraviolet-visible-near-infrared diffuse reflection, density functional theory calculation and four-probe measurement results suggest that LiCr(MoO4)2 possesses a narrow band gap and high electronic conductivity. Bond-valence-sum maps calculation and electrochemical impedance spectroscopy prove the fast lithium ion transport rate of LiCr(MoO4)2. Benefiting from these advantages, LiCr(MoO4)2 delivers a high specific capacity (250 mA h g−1) and good rate performances. The electrochemical reaction mechanism is studied by in situ X-ray diffraction, which indicates that the lithium ion deintercalation–intercalation is a solid solution process with Cr3+/2+ and Mo6+/5+ redox.

The conversion of CO2 into value-added chemicals by employing renewable energy via an electrochemical process has received increasing attention. However, the low reaction rate and efficiency, as well as poor selectivity, have limited its further development. The low solubility of CO2 in an aqueous solution is one of the main factors that limit the reaction rate and selectivity of the electroreduction of CO2 (ERC) at a high overpotential. In this study, an organic additive containing an –NH2 group (methyl carbamate, MC) was incorporated into the ERC electrolyte for the first time. By utilizing the affinity interaction between a Lewis acid (the –NH3+ group formed by protonation of the –NH2 group) and a Lewis base (CO2), the ERC reaction rate was increased by 17%, and the faradaic efficiency for the production of CH4 reached 81.6%, which represented a large increase of 34% and surpassed that of most reported Cu electrodes. Furthermore, the partial current density for the production of CH4 was 31 mA cm−2 at −2.13 V (vs. RHE), which represents an increase of 30% in comparison with that in the blank system. In addition, the competitive hydrogen evolution reaction was substantially inhibited, and the decline in faradaic efficiency increased from 38.5% to 48.1% when the potential decreased gradually from −1.63 V to −1.98 V (vs. RHE). DFT calculations further indicate that the –NH3+ group can significantly promote the adsorption of CO* and CHO* on the Cu surface and increase the surface coverage of both intermediates. CHO* can be further stabilized by the –NH3+ group via the facilitation of partial electron transfer from Cu to C and the formation of H-bonds, which is favorable for further hydrogenation to form hydrocarbons. These results provide a simple and powerful way to increase the reaction rate and product selectivity of the reduction of CO2.

With the introduction of 0.3 (wt%) Mg, the precipitation of monolayer GP zone was promoted in the quaternary alloy in comparison with the ternary alloy. The studied Al-Cu-Li-Mg alloy exhibited the accelerated aging response, enhanced Vickers hardness, superior yield strength and ultimate tensile strength over the ternary Al-Cu-Li alloy.

The spinel structure Zn1.8Co0.2TiO4 single crystals with 5 mm diameter and 30 mm length were successfully grown by an optical floating zone method. The as-grown crystals were characterized by X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS). Some Zn2+ ions at tetrahedral and octahedral sites should be replaced by doped transition metal Co2+ ions. The temperature-dependent Raman spectra of spinel Zn1.8Co0.2TiO4 crystals were also described. The optical phonon behaviors of Zn1.8Co0.2TiO4 are stable within the temperature range. The magnetic properties of Zn1.8Co0.2TiO4 were investigated by using Physical Property Measurement System.

Magnesium ion batteries (MIBs) have attracted significant research attention owing to their low cost, high energy density, and the natural abundance of magnesium. However, lack of compatible cathode materials hinders their further development. Herein, we present a magnesium–lithium hybrid ion battery (MLIB) comprising a Li3V2(PO4)3 (LVP) cathode and magnesium metal anode, where fast reaction kinetics of Li+ ions at the LVP cathode and that of Mg2+ ions at the anode led to high reversible capacities. As a result, a rechargeable MLIB shows excellent rate performance (147.8 and 65.3 mA h g−1 at 50 and 2500 mA g−1 respectively) and capacity retention (99% for 200 cycles), which are the highest values among the reported hybrid batteries using lithium cathodes. To improve temperature adaptability of the designed MLIB, two different kinds of magnesium electrolytes (i.e. all-phenyl-complex and magnesium borohydride in diglyme) and inorganic lithium additives were investigated. It is found that the all-phenyl-complex along with LiCl additives can suppress the freezing of electrolytes effectively even at −40 °C. While, high reversible capacities of 117, 93.4, and 63.1 mA h g−1 can be obtained at 0, −20, and −40 °C respectively, at a current density of 100 mA g−1, showing a very promising prospect for low temperature applications.

The effects of nanosized TiB2 particles on microstructural and mechanical properties of the hot extruded in-situ TiB2/Al-Cu-Li composite after T6 heat treatment are quantitatively evaluated by using scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction technique and X-ray diffraction. Most TiB2 particles are aggregated together to form the particle bands. The composite develops the typical fiber textures, and paralleling to extruded direction, while the matrix alloy only develops weak and textures. The intensity and volume fraction of major texture components can increase significantly with the addition of TiB2 particles. Due to the introduction of TiB2 particles, T1 and S phases not only have higher number density, but also are smaller. In addition, the T1 phases can connect with each other to form a continuous network in the composite. The θ’ phase, identified in matrix alloy, is rarely observed in the composite. The yield strength and ultimate tensile strength of composite have increased by 248 MPa and 152 MPa compared with matrix alloy, respectively.

With the explosive growth in intermittent renewable sources and the global drive toward decarbonizing the energy economy, reliable large-scale electrical energy storage technologies with high safety and low cost are urgently needed. Aqueous batteries hold the intrinsic advantages of nonflammability and low cost; the zinc//bromine flow battery and LiMn2O4//NaTi2(PO4)3 aqueous rechargeable ion battery are two representative systems with relatively high voltages (1.6 V to 1.8 V in common aqueous solutions). However, the long-term cycling stability of intercalation/de-intercalation type cathode materials is easily impaired by pH fluctuance, while the deposition/dissolution-type zinc anode suffers from zinc dendrites and uneven deposition issues. To avoid these two issues, we propose a novel bromine//NaTi2(PO4)3 hybrid ion battery, involving an aqueous redox pair (Br3−/Br−, with high reactivity in a pH range from 0 to 9) and a high-loading ion intercalation anode (NaTi2(PO4)3, with low working voltage and little volume change). First, the high-performance NTP@C nanoparticles are synthesized by a modified sol–gel method. Then, the three-dimensional NTP@C anode with super high mass loading is designed by employing a porous and conductive carbon substrate. The crossover of bromine in aqueous catholyte is suppressed by an effective bromine complexing agent and the insufficient ion transport in a thick solid anode is conquered by a negative flowing electrolyte. As a result, the hybrid ion battery shows high areal energy density, high power density and promising cycling stability. The full cell can deliver a high energy density and power density of 12.8 mW h cm−2 (109 W h kg−1 based on NTP@C and reacted LiBr) and 29.4 mW cm−2 (250 W kg−1 based on NTP@C and reacted LiBr), respectively. Moreover, the power density can reach 106 mW cm−2 with energy density remaining at 7.95 mW h cm−2 (68 W h kg−1 based on NTP@C and reacted LiBr) at a super high current density of 100 mA cm−2. An average capacity loss of 0.075% per cycle is obtained during a 200-cycle test, demonstrating the great feasibility of the new system. Therefore, this hybrid battery has great potential in large scale electrical energy storage.