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We present a coral-like FeP composite with FeP nanoparticles anchored and dispersed on a nitrogen-doped 3D carbon framework (FeP@NC). Due to the highly continuous N-doped carbon framework and a spring-buffering graphitized carbon layer around the FeP nanoparticle, a sodium-ion battery with the FeP@NC composite exhibits an ultra-stable cycling performance at 10 A g-1 with a capacity retention of 82.0 % in 10 000 cycles. Also, particle refinement leads to a capacity increase during cycling. The FeP nanoparticles go through a refining-recombination process during the first cycle and present a global refining trend after dozens of cycles, which results in a gradually increase in graphitization degree and interface magnetization, and further provides more active sites for Na+ storage and contributes to a rising capacity with cycling. The capacity ascending phenomenon can also extend to lithium-ion batteries.

Perspective Rechargeable aqueous zinc-ion batteries (AZIBs) have gained increasing attention owing to their low cost and high safety. Although hydrated vanadium oxides exhibit rich redox chemistry and open layer architecture, the insertion of multivalent Zn2+ during cycling inevitably leads to host collapse and severe vanadium dissolution. Accordingly, various ions and conducting polymers have been introduced into the interlayer to produce vanadium bronzes with a robust crystal structure. However, these pre-intercalated vanadium bronzes demonstrate limited improvement and still face the challenge of metal ion displacement and confusing reaction mechanisms. Herein, we report a novel molecular bronze with intercalated 3-phenylpropylamine for use as an AZIB cathode, which produces an ultrahigh interlayer of 18.0 A. The cathode delivered an improved capacity of 420 mAh g−1 at 0.1 A g−1, an impressive rate capability of 158 mAh g−1 at 35 A g−1, and an outstanding lifespan with a capacity retention of 94% over 1200 cycles at 2A g−1. Furthermore, the reaction mechanism of H+/Zn2+ co-insertion was investigated in detail. This work proves that this strategy is universal for vanadium oxide bronzes and opens a new avenue for the fabrication of novel molecular bronzes as advanced AZIB cathodes.

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.

Nitrocellulose (NC) is proposed to stabilize the electrolytes for Li metal batteries. The nitro group of NC preferentially reacts with Li metal, and along with the cellulose skeleton is tightly wrapped on the surface, so that the polymer-inorganic double layer is formed on the Li surface. XPS profile analysis and corroborative cryo-environmental TEM reveal that the flexible outer layer of the bilayer is a C-O organic layer, while the dense inner layer is mainly composed of crystalline lithium oxide, lithium oxynitride, and lithium nitride. The Li deposition process was observed via in situ optical microscopy, which indicated that the NC-derived bilayer facilitates the uniform deposition of Li ions and inhibits the growth of dendrites. After the introduction of NC into the electrolyte, the cycle life of the Li battery is twice than that of the Li battery without NC at 1.0 and 3.0 mA cm-2 .

A high power density vanadium flow battery (VFB) is essential for reducing the cost of a VFB system. The power density of a VFB is currently limited by the negative half-cell since the negative V2+...

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...

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.

Manganese oxides have been widely studied as anode materials for lithium-ion batteries because they have many advantages such as high theoretical capacity, abundant resources, low price and low environmental tox-icity. In this paper, various manganese oxide materials, i.e., MnO2, Mn3O4, MnO, (FeO)0.331(MnO)0.669 were prepared by facile methods. The above compounds were then characterized through X-ray diffraction spec-troscopy (XRD). The oxidation states of Mn in these compounds were found to be: +4, +3/+2, +2 and +2 each of them corresponding to a different crystal system, respectively: hexagonal, tetragonal cubic, cubic. The electrochemical properties of these four different manganese oxides, used as anode materials, were investigated to find the possible relationship between their valence states, crystal systems and their electrochemical properties. The results show that their electrochemical properties are influenced by their crystal system and cell parameters, while incorporating FeO into MnO has an activation effect on the reversible lithium ion in the batteries.

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.

Aqueous organic flow batteries have attracted dramatic attention for stationary energy storage due to their resource sustainability and low cost. However, the current reported systems can normally be operated stably under a nitrogen or argon atmosphere due to their poor stability. Herein a stable air-insensitive biphenol derivative cathode, 3,3′,5,5′-tetramethylaminemethylene-4,4′-biphenol (TABP), with high solubility (>1.5 mol L−1) and redox potential (0.91 V vs. SHE) is designed and synthesized by a scalable one-step method. Paring with silicotungstic acid (SWO), an SWO/TABP flow battery shows a stable performance of zero capacity decay over 900 cycles under the air atmosphere. Further, an SWO/TABP flow battery manifests a high rate performance with an energy efficiency of 85% at a current density of 60 mA cm−2 and a very high volumetric capacity of more than 47 Ah L−1. This work provides a new and practical option for next-generation practical large-scale energy storage.

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.

A superoleophilic polyurethane sponge had been constructed by means of an immersion method in an ethanol solution of n-octadecyltrichlorosilane. SEM, FTIR, TGA, and XPS unanimously confirmed that PODS had been successfully coated onto the skeleton of polyurethane sponge. The PODS-modified sponge displayed both excellent hydrophobicity with high water contact angle of 152° and good oil affinity. The PODS-modified sponge took the high adsorptive capabilities for the silicone oil, toluene, and peanut oil with 62.1, 73.7, and 98.2 g · g–1 after 50 cycles of extrusion-release, respectively. The superoleophilic sponge in this work exhibited promising opportunities on the oil/water separation and the oil spill remediation.

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.

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.

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...

The capability to maintain a constant system temperature is vital in nature, since it endows the system with enhanced lifetime. This trait also works for zinc-based batteries, because their cycle-life is limited by notorious zinc dendrite/accumulation, which are highly affected by the inhomogeneous distribution of temperature on electrode and relatively low mechanical strength of membrane. Herein, boron nitride nanosheets (BNNSs) with high mechanical strength serving as heat-porter are introduced onto a porous substrate to enable uniform deposition of zinc and further a zinc-based flow battery with long-cycle life. The results indicate that BNNSs can effectively adjust the deposited zinc from needle-like to French fries-like morphology, thus affording the battery with a stable performance for nearly 500 cycles at 80 mA cm-2 . Most importantly, an energy efficiency of above 80 % can be obtained even at 200 mA cm-2 , which is by far the highest value ever reported among zinc-based flow batteries.

Li3N is an excellent zero-residue positive electrode pre-lithiation additive to offset the initial lithium loss in lithium-ion capacitors. However, Li3N has an intrinsic problem of poor compatibility with commonly used aprotic polar solvents in electrode manufacture procedure due to its high reactivity with commonly used solvents like N-methy-2-pyrrolidone (NMP) and etc. It is the Valley of Death between research and large-scale commercialization of Li-ion capacitors using Li3N as prelithiation agent. In this work, Li3N containing electrode is prepared by a commercially adoptable route for the first time, using N,N-dimethylformamide (DMF) to homogenate the electrode slurry. The DMF molecular stabilizing mechanism is confirmed via experiment analysis and DFT simulation, indicating that the dehydrogenation energy for DMF is obviously larger than other commonly used solvents such as NMP and etc. The soft package lithium-ion capacitors (LIC250) with only 12 wt% Li3N addition in AC positive electrode exhibits excellent rate capability, cyclic stability and ultrahigh specific energy. Its specific energy is 2.3 times higher than the Li3N-free devices, with energy retention as high as 90% after 10,000 cycles.

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.

Manganese (Mn) based batteries have attracted remarkable attention due to their attractive features of low cost, earth abundance and environmental friendliness. However, the poor stability of the positive electrode due to the phase transformation and structural collapse issues has hindered their validity for rechargeable batteries. Here we presented a highly reversible and stable two electron transfer solid–liquid reaction based on MnO2 and soluble Mn(CH3COO)2(Mn(Ac)2) under neutral medium. Benefiting from the coordination effect of Ac−, the Mn2+ can directly deposit on the electrode in the form of MnO2, which is completely different from other manganese salts (MnSO4 or MnCl2). Compared with the common intercalation mechanism cathode, the dissolution/deposition reaction completely avoided the structure collapse issue, which results in a dramatic improvement in stability. Furthermore, in contrast to the redox pair of Mn3+/Mn2+, the intrinsic problems caused by the disproportionation of Mn3+ can be totally avoided. The proof of concept can be confirmed by a neutral Zn–Mn flow battery with an optimized electrolyte. The MnO2 could be perfectly deposited on the graphite fiber with an areal capacity of 20 mA h cm−2, which is the highest value ever reported. Unlike the alkaline electrolytes, a neutral flow system can effectively avoid the zinc dendrite issues. As a result, a Zn–Mn flow battery demonstrated a CE of 99% and an EE of 78% at 40 mA cm−2 with more than 400 cycles. Combined with excellent electrochemical reversibility, low cost and two-electron transfer properties, the Zn–Mn battery can be a very promising candidate for large scale energy storage.

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.

Aqueous zinc-based energy storage (ZES) devices are promising candidates for portable and grid-scale applications owing to their intrinsically high safety, low cost, and high theoretical energy density. However, the conventional aqueous electrolytes are not capable of working at low temperature. Here we report a frigostable, cost-effective, safe and eco-friendly hybrid electrolyte with high zinc-ion conductivity (6.9 mS cm−1 at −40 °C), and high reversibility of Zn plating/stripping, which consists of water, ethylene glycol (EG) and zinc sulfate salt (ZnSO4). Experiments together with theoretical calculations demonstrated that the unique solvation interaction of Zn2+ with EG can effectively enhance the hydrogen bonding between EG and H2O and weaken the solvation interaction of Zn2+ with H2O, thus providing the hybrid electrolyte with a lower freezing point and reversible Zn/Zn2+ chemistry. As a proof-of-concept, both Zn-ion hybrid supercapacitors (ZHSCs) and Zn-ion batteries (ZIBs) with the hybrid electrolytes delivered high energy densities (36 W h kg−1 for the ZHSC and 121 W h kg−1 for the ZIB), high power densities (3.1 kW kg−1 for the ZHSC and 1.7 kW kg−1 for the ZIB) and long-cycle life (5500 cycles over 110 days for the ZHSC and 250 cycles for the ZIB) at −20 °C. This work provides a new option for low-temperature energy storage devices.

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...

Stimuli-responsive membranes exhibit a flexible adjustment in response to environmental stimuli and have been established many applications. In this paper, dual-stimuli-responsive ultrafiltration m...

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.

Lithium-sulfur (Li-S) batteries have received extensive attention because of their high theoretical energy density and low cost. However, the low sulfur utilization and the shuttle effect of polysulfide cause low initial capacity and serious capacity decay. Herein, fluorinated graphite (FG) is introduced to the cathode to alleviate these issues. The results indicated that the FG could provide additional capacity during the first discharge process and increase the porosity and polarity of the cathode via in situ formation of lithium fluoride (LiF) nanocrystals, which can enhance the infiltration of electrolyte and polysulfide adsorption. As a result, the as-prepared cathode containing FG shows a high initial specific capacity of 1602 mA h g-1 and the reversible specific capacity is 650 mA h g-1 at 0.5C after 300 cycles. Moreover, its specific capacity remains at 860 mA h g-1 at 5C, which is 367% higher than that of the sample without FG. This paper provides a new strategy to improve the energy density and the cycle stability of Li-S batteries.

Zinc-based batteries are promising for use as energy storage devices owing to their low cost and high energy density. However, zinc chemistry commonly encounters serious dendrite issues, especially at high areal capacities and current densities, limiting their application. Herein, we propose a novel membrane featuring ordered undulating stripes called "Turing patterns", which can effectively suppress zinc dendrites and improve ion conductivity. The crests and troughs in the Turing membrane can effectively adjust the Zn(OH)42- distribution and provide more zinc deposition space. The coordinated Cu ions during membrane formation can interact with Zn(OH)42-, further smoothing zinc deposition. Even at a high current density of 80 mA·cm-2, the Turing membrane enables an alkaline zinc-iron flow battery (AZIFB) to work stably with an ultrahigh areal capacity of 160 mA·h·cm-2 for approximately 110 cycles, showing an energy efficiency of 90.10%, which is by far the highest value ever reported among zinc-based batteries with such a high current density. This paper provides valid access to zinc-based batteries with high areal capacities based on membrane design and promotes their advancement.

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.

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.

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.

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.

An ultra-high voltage viologen/Br2 flow battery was designed based on a novel two-electron viologen derivative, a highly-conductive and low-cost porous polyolefin membrane, and an effective complexing agent, making the battery one of the most stable two-electron viologen-based flow batteries with superior energy and power density at the same time.

Self-standing electrodes have attracted great attention due to their promising applications in advanced electronic devices with high-energy demands. Inspired by the 3D framework and well-controlled porous structure of the porous membrane prepared via the phase separation method, for the first time, a binder-free 3D porous self-standing electrode has been designed and fabricated by using a porous polybenzimidazole (PBI) membrane as the template. Various methods were investigated in detail, in which the ethanol phase separation-derived method resulted in a sponge-like cross section and porous structure of both surfaces, leading to the best electrochemical performance. Meanwhile, considering the carbon content, the optimized self-standing Na3V2(PO4)3@C electrode exhibited excellent rate performance (110.4 mA h g−1 at 0.5C and 108.1 mA h g−1 at 40C) and cycling stability (capacity retention of 90.4% after 2000 cycles at 1C). The superior electrochemical performance can be ascribed to the high electron conductivity due to the 3D N-doped cross-linked carbon matrix and the fast Na+ diffusion in the spongy macro-porous structure. The self-standing electrode prepared via this method exhibited high flexibility in the electrode mass loading, pore structures (sponge-like, finger-like, etc.) and electrode shapes (fiber, coil, spiral, letter, etc.). This phase separation-derived method will greatly promote the development and large-scale application of self-standing electrodes.

An advanced porous membrane containing slit-like selective layer on its top surface is designed and prepared for flow battery application. The structure is realized by regulating the parameters during membrane formation process. The porous membrane exhibits a thick skin layer with narrow slits and sponge-like support layer in the cross-section. The thick and comparatively hydrophobic skin layer hinders the passage of vanadium ions. Meanwhile, the slit structure and comparatively hydrophilic support layer facilitates the transport of protons. The resulting poly(ether sulfone) (PES)/sulfonated poly(ether ether ketone) (SPEEK) porous membrane containing slit-like selective layer achieves an excellent balance between ion selectivity and proton conductivity, resulting in a columbic efficiency of 98.5%, a voltage efficiency of 91.7%, and an energy efficiency of 90.4% at 80 mA cm−2, which is much higher than a vanadium flow battery (VFB) with the commercial Nafion 115. Therefore, this paper provides a simple and economical method to develop high-performance, low-cost membranes for VFB applications.