Low-temperature Synthesis Route Research Articles

Phase formation, microstructural and dielectric properties of bismuth ferrite nanoceramics synthesized by low-temperature molten salt flux route

BiFeO3 nano-ceramics were synthesized using the low-temperature molten salt synthesis route to study the influence of calcination temperature and salt ratios. The Rietveld refinement revealed the distorted perovskite structure of BFO. These granular-shaped BFO samples’ grains morphology was studied using the FESEM. The FTIR revealed the presence of Metal-Oxygen bonds in the BFO ceramics. The XPS studies exhibited the respective constituent elements’ oxidation states and validated the presence of oxygen ion vacancies. The frequency-dependent dielectric properties were measured at various temperatures. The electrical conductivity measurement showed a linear variation as a function of frequency which validated Jonscher’s power law.

Fe-doping on CaV2O6 for oxygen vacancy controlling lithium storage

Currently, alkaline earth metal vanadates as the anode materials for lithium-ion batteries (LIBs) are gradually sparking attention due to their low cost, environmental friendliness, high theoretical capacity and safety. However, their practical application is still hampered by the fast capacity degradation resulting from the prolonged cycling condition and intrinsic low electrical conductivity. Herein, single-crystal Fe-doped CaV2O6 is prepared via the low-temperature combustion synthesis route. The Fe-doping accelerates the generation of low-valence-state vanadium in CaV2O6–2%Fe, leading to the production of oxygen vacancies for maintaining electroneutrality. The versatile design of CaV2O6–2%Fe improves the electron conductivity and promotes the Li-ion diffusion rate based on the generated dual defects of interstitial atoms of Fe and oxygen vacancies accordingly. As expected, the CaV2O6–2%Fe electrode exhibits superior rate capacity of 96.6 mA h g−1 at 5 A g−1 and a remarkable capacity retention of 125.6 mA h g−1 after 1000 cycles at 1 A g−1. Additionally, the partial decomposition of CaV2O6 during the initial lithiation stage, and the formation of amorphous Li–V–O in the subsequent cycle can be used to depict the lithium storage mechanism of CaV2O6–2%Fe.

Tetragonal phase-free crystallization of highly conductive nanoscale cubic garnet (Li6.1Al0.3La3Zr2O12) for all-solid-state lithium-metal batteries

The synthesis and processing of garnet-type conductors is usually done at temperatures above 1100 °C to reach the high Li-ion conducting cubic phase resulting in micron-sized particles and potential Li-loss, which are unfavorable for further processing and electrode-electrolyte assembly. Here, we tackle this problem and report a novel low-temperature aqueous synthesis route to stabilize the cubic phase of Li6.1Al0.3La3Zr2O12 (c-Al-LLZO) at a temperature as low as 600 °C, while obtaining nano-crystallites at around 100 - 200 nm. Moreover, a dual-reaction mechanism was proposed to describe the process of c-Al-LLZO crystallization. The as-synthesized nanoscale c-Al-LLZO particles facilitate the densification of the solid-state electrolyte (SSE) pellets with less endowed grain boundaries (exhibiting a high relative density of 97.8 %). The ionic conductivity reaches 0.42 mS cm−1 at 21 °C and the low activation energy (half of the published values) is 0.17 eV. The results presented here show that symmetric cells with Li metal exhibit excellent stability at the current density of 0.2 mA/cm2 and 0.5 mA/cm2, and an improved critical current density (CCD) of 2.16 mA/cm2. This work provides a feasible method of low-temperature crystallization of nanoscale cubic garnet SSEs with good performance for the fabrication of stable SSLBs.

Large-area deposition of protective (Ti,Al)N coatings onto polycarbonate

Polycarbonate (PC) and protective (Ti,Al)N coatings exhibit extremely different material properties, specifically crystal structure, thermal stability, and elastic and plastic behavior, as well as thermal expansion coefficients. These differences present formidable challenges for the deposition process development as low-temperature synthesis routes have to be explored to avoid a thermal overload of the polymer substrate. Here, a large-area sputtering process is developed to address the challenges by systematically adjusting target peak power density and duty cycle. Adhering (Ti,Al)N coatings with a critical residual tensile stress of 2.2 ± 0.2 GPa are obtained in the pulsed direct current magnetron sputtering range, whereas depositions at higher target peak power densities, realized by high power pulsed magnetron sputtering, lead to stress-induced adhesive and/or cohesive failure. The stress-optimized (Ti,Al)N coatings deposited onto PC with a target peak power density of 0.036 kW cm−2 and a duty cycle of 5.3% were investigated by the cross-cut test, confirming adhesion. By investigating the bond formation at the PC|(Ti,Al)N interface, mostly interfacial CNx bonds and a small fraction of (C−O)−(Ti,Al) bonds are identified by x-ray photoelectron spectroscopy, indicating reactions at the hydrocarbon and the carbonate groups during deposition. Nanoindentation reveals an elastic modulus of 296 ± 18 GPa for the (Ti,Al)N coating, while a Ti–Al–O layer is formed during electrochemical impedance spectroscopy in a borate buffer solution, indicating protective passivation. This work demonstrates that the challenge posed by the extremely different material properties at the interface of soft polymer substrates and hard coatings can be addressed by the systematical variation in the pulsing parameters to reduce the residual film stress.

Green room temperature synthesis of silver-gold alloy nanoparticles.

Metallic alloy nanoparticles (NPs) exhibit interesting optical, electrical and catalytic properties, dependent on their size, shape and composition. In particular, silver-gold alloy NPs are widely applied as model systems to better understand the syntheses and formation (kinetics) of alloy NPs, as the two elements are fully miscible. Our study targets product design via environmentally friendly synthesis conditions. We use dextran as the reducing and stabilizing agent for the synthesis of homogeneous silver-gold alloy NPs at room temperature. Our approach is a one-pot, low temperature, reaction-controlled, green and scalable synthesis route of well-controlled composition and narrow particle size distribution. The composition over a broad range of molar gold contents is confirmed by scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (STEM-EDX) measurements and auxiliary inductively coupled plasma-optical emission spectroscopy measurements (ICP-OES). The distributions of the resulting particles in size and composition are obtained from multi-wavelength analytical ultracentrifugation using the optical back coupling method and further confirmed by high-pressure liquid chromatography. Finally, we provide insight into the reaction kinetics during the synthesis, discuss the reaction mechanism and demonstrate possibilities for scale-up by a factor of more than 250 by increasing the reactor volume and NP concentration.

Single-step low-temperature synthesis routes for (Ba, Ce, Gd) hexaborides and their thermionic emission properties

Rare-earth/alkaline-earth hexaborides with high chemical stability and low work function have recently attracted much interest as promising thermionic cathodes. Their synthesis at low temperatures without post-synthesis purification treatments is still a significant challenge. The present work demonstrates a simple synthesis technique to produce pure barium, cerium and gadolinium hexaborides (BaB6, CeB6, and GdB6). For each hexaboride, a batch of samples was created by first milling highly pure precursor powders and then firing at various temperatures in a low-vacuum furnace. The synthesised products were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron dispersive spectroscopy (EDS). Their thermionic properties were investigated utilising a Schottky device. Pure BaB6, CeB6, and GdB6 were successfully synthesised at lower temperatures (≤1400 °C). Nanocrystalline CeB6 was found to be produced at the lowest temperature of 1200 °C. The mean particle size of pure CeB6 and GdB6 synthesised is seen to be in the sub-micron range, with the exception of large BaB6 particles. The estimated work functions of the BaB6, CeB6, and GdB6 cathodes are 1.61 ± 0.18 eV, 2.50 ± 0.09 eV, and 2.42 ± 0.09 eV, respectively. These findings imply that hexaborides, as promising thermionic emitters, can be easily produced at low temperatures.

Controlled Synthesis of Transition Metal Phosphide Nanoparticles to Establish Composition-Dependent Trends in Electrocatalytic Activity

Transition-metal phosphides (TMPs) are versatile materials with tunable electronic and structural properties that have led to exceptional catalytic performances for important energy applications. Identifying predictive relationships between the catalytic performance and key features such as the composition, morphology, and crystalline structure hinges on the ability to independently tune these variables within a TMP system. Here, we have developed a versatile, low-temperature solution synthesis route to alloyed nickel phosphide (Ni1.6M0.4P, where M = Co, Cu, Mo, Pd, Rh, or Ru) nanoparticles (NPs) that retains the structure of the parent Ni2P NPs, allowing investigation of compositional effects on activity without convoluting factors from differences in morphology and crystalline phase. As a measure of the controlled changes introduced within the isostructural series by the second metal, the binary and alloyed ternary TMP NPs supported on carbon at a nominal 5% weight loading were studied as electrocatalysts for the hydrogen evolution reaction (HER). The resultant activity of the electrocatalyst series spanned a 125 mV range in overpotential, and composition-dependent trends were investigated using density functional theory calculations on flat (0001) and corrugated (101̅0) Ni1.67M0.33P surfaces. Applying the adsorption free energy of atomic H (GH) as a descriptor for HER activity revealed a facet-dependent volcano-shaped correlation between the overpotential and GH, with the activity trend well represented by the corrugated (101̅0) surfaces on which metal–metal bridge sites are available for H adsorption but not the flat (0001) surfaces. The versatility of the rational synthetic methodology allows for the preparation of a wide range of compositionally diverse TMP NPs, enabling the investigation of critical composition–performance relationships for energy applications.

Tailoring the morphology of orthorhombic Li2MnSiO4 by carbon additive and its impact on transport and Li-storage properties

Carbon additive is an exciting approach for tailoring the surface morphology and improving the material's structural stability, electrical conductivity, and interface chemistry for achieving high capacity and long cycling stability simultaneously. Herein, we successfully introduce sucrose as a carbon additive to tailor the morphology of Li2MnSiO4 (LMS). The low-temperature hydrothermal synthesis route is adopted for preparing pure phase LMS/Cx (x = 0, 2, 5, 7, and 10 wt % refereed as PLMS, LMSC2, LMSC5, LMSC7 and LMSC10). FE-SEM and HR-TEM analyses are used to monitor the changes in the morphology of LMS/Cx composites. The one-dimensional nanorods (formed by the addition of carbon additives) embedded in the as-synthesized best composite sample (LMSC7) are found responsible for the fast lithium-ion diffusion, reactivity, and enhancing the electronic conduction from 26% to 67%, almost three times higher than PLMS. The electronic conductivity of LMSC7 is calculated to be 3.93 × 10−8 (±0.001) Scm−1. It also exhibits an initial charge capacity of 240 (±5) mAhg−1, which is found to be ∼66% higher than PLMS (90 ± 5) at 10 mAg−1 current density at ambient temperature. Furthermore, after a few early cycles, the cyclability profile of LMSC7 demonstrates excellent 100% coulombic efficiency.

Enhanced performance and stability of Cu/ZnO catalyst by introducing MgO for low-temperature methanol synthesis using methanol itself as catalytic promoter

Catalytic conversion of CO2-containing syngas to methanol is one of important processes in industry. However, realizing high space time yield (STY) of methanol at low reaction temperature remains a challenge. Herein, ternary Cu/ZnO/MgO catalysts were prepared via co-precipitation and tested for low-temperature methanol synthesis via autocatalysis of methanol. The effects of Mg2+ ion and MgO content on the formation and composition of the precipitated precursors, as well as on the physicochemical properties of the calcined and the reduced catalysts were systemically investigated and discussed. The structure–activity relationships were disclosed by detailed catalysts characterization. Compared to Cu/ZnO, the total carbon turnover frequency (TOF) and space time yield (STY) of methanol on Cu/ZnO/MgO remarkably increased from 17.8 to 20.0 h−1 and from 425.2 to 538.3 g/kg∙h−1, respectively. Besides, Cu/ZnO/MgO kept its activity for 180 h without deactivation, which was much more stable than Cu/ZnO. In comparison with commercial Cu/ZnO/Al2O3 and other Cu-based catalysts reported in the literatures for methanol synthesis from syngas, Cu/ZnO/MgO catalyst with Cu/Zn/Mg molar ratio of 1:1:0.05 displayed much higher space time yield (STY) of methanol. In addition, the reaction conducted in the presence of methanol promoter exhibited much lower apparent activation energy than that of the reaction carried out without methanol promoter, indicating a catalytic and promotional role of methanol during low-temperature methanol synthesis reaction. The current work provided not only a hopeful strategy for enhancing activity and stability of Cu/ZnO catalyst, but also a sustainable low-temperature methanol synthesis route using methanol itself as catalytic promoter.

Colloidal sol-gel: A powerful low-temperature aqueous synthesis route of nanosized powders and suspensions

The colloidal sol-gel is a well-established method for the synthesis of nanoparticles with high reproducibility, homogeneity and low cost. It is a versatile route which allows synthesising many ceramic materials at the nanometric scale. The process starts with the hydrolysis of the metal precursor and ends with the formation of a colloidal suspension/sol with high stability. The particle size can be easily tuned by synthesis parameters such as temperature, metal precursor-water ratio and/or metal precursor-catalyst ratio. Depending on the applications, the sol can be directly used for the preparation of coatings or it can be dried to be used as powder. In this review, the fundamentals of the colloidal sol-gel process are provided, highlighting the great capacity of this synthesis route. Its use in combination with other synthesis methods and the influence of the parameters controlling the process is presented, together with applications and examples of the synthesised powders.

Flux-Assisted Low Temperature Synthesis of SnNb2O6 Nanoplates with Enhanced Visible Light Driven Photocatalytic H2-Production

Foordite SnNb2O6 as a typical layered niobate has gained great attention in photocatalytic applications owing to its narrow band gap and proper conduction and valence band potentials. However, the ever reported methods toward the synthesis of SnNb2O6 nanostructures required either the use of environmentally unfriendly solvents or a prolonged high temperature heat treatment. Herein, we develop a facile flux-assisted low temperature synthesis route for the preparation of SnNb2O6 nanoplates by using H4Nb2O7 and SnCl2 as precursors. The as-obtained SnNb2O6 nanoplates with a thickness of ∼50 nm display improved visible light photocatalytic H2-production activity, which is about 10 times higher than that of a bulk SnNb2O6 sample. The enhanced photocatalytic H2-production activity can be ascribed to its nanoplate-like architecture, larger specific surface area, and better charge transfer efficiency.

Lowering Ternary Oxide Synthesis Temperatures by Solid-State Cometathesis Reactions

Low-temperature synthesis routes are necessary for selectively synthesizing many metastable solid-state materials. Here, we identify a cooperative effect that starting materials have in lowering temperatures in solid-state metathesis reactions by studying the formation of yttrium manganese oxide. Previous studies have shown that YMnO3 can be synthesized by ternary metathesis with an alkali halide being produced as a secondary product. In this contribution, we show that by using alkaline earth metals instead of alkali metals, the polymorph selectivity of the reaction is changed, as orthorhombic YMnO3 forms at lower temperatures than the hexagonal polymorph. Reactions were studied using ex post facto synchrotron X-ray diffraction. These experiments reveal that reactions using alkaline earth manganese oxides as a starting material require high temperatures to progress. Reaction temperatures can be lowered from 700 to 550 °C while maintaining phase selectivity by reacting both MgMn2O4 and CaMn2O4 with YOCl in a cooperative “cometathesis” reaction. The nascent halide salts appear to improve the reaction kinetics. Since the onset temperature for YMnO3 formation falls 50 °C below the MgCl2–CaCl2 liquidus, the enhanced reactivity is consistent with the surface melting of a nasscent salt byproduct at the interfaces. Cometathesis routes have similar phase selectivity and temperature reduction in reactions that form TbMnO3, ErMnO3, and DyMnO3. Cometathesis lowers reaction temperatures while preserving the reaction selectivity of the end members, making it a valuable approach for synthesizing metastable targets.

Silica extraction from bauxite reaction residue and synthesis water glass

Abstract Bauxite reaction residue (BRR) produced from the poly-aluminum chloride (PAC) coagulant industry is a solid acidic waste that is harmful to environment. A low temperature synthesis route to convert the waste into water glass was reported. Silica dissolution process was systematically studied, including the thermodynamic analysis and the influence of calcium and aluminum on the leaching of amorphous silica. Simulation studies have shown that calcium and aluminum combine with silicon to form hydrated calcium silicate, silica–alumina gel, and zeolite, respectively, thereby hindering the leaching of silica. Maximizing the removal of calcium, aluminum, and chlorine can effectively improve the leaching of silicon in the subsequent process, and corresponding element removal rates are 42.81%, 44.15%, and 96.94%, respectively. The removed material is not randomly discarded and is reused to prepare PAC. The silica extraction rate reached 81.45% under optimal conditions (NaOH; 3 mol L−1, L S−1; 5/1, 75°C, 2 h), and sodium silicate modulus (nSiO2:nNa2O) is 1.11. The results indicated that a large amount of silica was existed in amorphous form. Precipitated silica was obtained by acidifying sodium silicate solution at optimal pH 7.0. Moreover, sodium silicate (1.11) further synthesizes sodium silicate (modulus 3.27) by adding precipitated silica at 75°C.

Electrochemical Performance of LixSiON Polymer Electrolytes Derived from an Agriculture Waste Product, Rice Hull Ash

The electrochemical performance of LixSiON (x = 2, 4, and 6) polymer electrolytes derived from the agricultural waste, rice hull ash (RHA, 80–90 wt % SiO2), is reported. Silica can be extracted from RHA by base-catalyzed reaction with hexylene glycol forming the spirosiloxane [(C6H12O2)2Si, SP] that distills from the reaction solution. LixSiON polymer electrolytes form on reacting SP with xLiNH2, offering a low-cost, low-temperature, and green synthesis route. The effect of N and Li+ concentrations in the polymer electrolytes are correlated with ionic and electrical conductivity. X-ray photoelectron spectroscopy studies confirm that N and Li contents increase with increasing LiNH2 content. The amorphous nature and high Li+ contents of the Li6SiON electrolyte provide an optimal ionic conductivity (6.5 × 10–6) at ambient temperature when coated on Celgard. Furthermore, the LixSiON polymer electrolytes offer high Li+ transference numbers (∼0.75–1), enabling assembly of Li symmetric cells with high critical current densities (3.75 mA cm–2). Finally, Li-SPAN (sulfurized, carbonized polyacrylonitrile) half-cells with Li6SiON polymer electrolytes deliver discharge capacities of ∼765 and 725 mAh/g at 0.25 and 0.5 C rates over 50 cycles.

Low-Temperature Nitridation of Fe3O4 by Reaction with NaNH2

Low-temperature soft chemical synthesis routes to transition-metal nitrides are of interest as an alternative to conventional high-temperature ammonolysis reactions involving large volumes of chemotoxic NH3 gas. One such method is the reaction between metal oxides and NaNH2 at ca. 200 °C to yield the counterpart nitrides; however, there remains uncertainty regarding the reaction mechanism and product phase assemblage (in particular, noncrystalline components). Here, we extend the chemical tool box and mechanistic understanding of such reactions, demonstrating the nitridation of Fe3O4 by reaction with NaNH2 at 170–190 °C, via a pseudomorphic reaction. The more reduced Fe3O4 precursor enabled nitride formation at lower temperatures than the previously reported equivalent reaction with Fe2O3. The product phase assemblage, characterized by X-ray diffraction, thermogravimetric analysis, and 57Fe Mössbauer spectroscopy, comprised 49–59 mol % ε-Fe2+xN, accompanied by 29–39 mol % FeO1–xNx and 8–14 mol % γ″-FeN. The oxynitride phase was apparently noncrystalline in the recovered product but could be crystallized by heating at 180 °C. Although synthesis of transition-metal nitrides is achieved by reaction of the counterpart oxide with NaNH2, it is evident from this investigation that the product phase assemblage may be complex, which could prove a limitation if the objective is to produce a single-phase product with well-defined electrical, magnetic, or other physical properties for applications. However, the significant yield of the FeO1–xNx oxynitride phase identified in this study opens the possibility for the synthesis of metastable oxynitride phases in high yield, by reaction of a metal oxide substrate with NaNH2, with either careful control of H2O concentration in the system or postsynthetic hydrolysis and crystallization.

Synthesis and densification of hydroxyapatite by mechanochemically-activated reactive cold sintering

We proposed a reactive cold sintering method based on the activation of reactants by ball-milling. Using CaHPO4⋅2H2O and Ca(OH)2 as precursors after mechanical activation for different times, the simultaneous synthesis and densification of hydroxyapatite (HA) products were achieved by cold sintering at temperatures ranging from 50 to 200 °C. The effects of processing parameters including milling time, temperature, uniaxial pressure and holding time on the synthesis and densification behavior of HA were systematically investigated and the underlying mechanisms were addressed. This study provides a simple, feasible and scalable route for the rapid low-temperature synthesis and densification of HA and its composites.

(Invited) Investigations on Sulfide Solid-Electrolyte Cathode Interfaces

Advances in solid electrolytes (SEs) with superionic conductivity and stabilized electrode-electrolyte interfaces are key enablers for all solid-state batteries (SSBs) to meet the energy density and cost targets for next generation batteries for electric vehicles. Compared to their ceramic counterparts, sulfide- and thiophosphate-based electrolytes offer several key advantages, including (i) exceptionally high ionic conductivities up to 10-2 S/cm (comparable to non-aqueous liquid electrolytes) as reported for Li10GeP2S12 and Li9.54Si1.74P1.44S11.7Cl0.3, (ii) availability of low temperature and inexpensive synthesis routes to produce glass, glass-ceramic, and crystalline structures, and (iii) soft mechanical properties, which facilitates material processing. Among the drawbacks, sulfides have a narrow electrochemical window, hence limited electrochemical stability against Li-metal and cathodes and poor chemical stability including high sensitivity to moisture. Despite an intrinsic narrow thermodynamic range, most SEs rely on kinetic stability based on slow growth of the interfacial layer that has reasonable ionic conductivity and very low electronic conductivity. In addition to the thermodynamical instability, significant mechanical stresses develop in SE due to (i) volume changes of the electrode material during repeated lithiation (delithiation) and (ii) interface roughening from side reactions upon extended cycling. This effect often termed as “chemo-mechanical effect” results in poor interfacial contact between the SE and cathode. The talk will highlight a few material based approaches towards addressing the interfacial stabilities (as mentioned above) between Li3PS4 SE and lithium-ion cathodes such as NMC. The area specific resistance (ASR) between SE-Cathode interfaces were optimized by coating cathode particles, varying stack pressure and doping the SE compositions.Acknowledgment - This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is supported by Asst. Secretary, Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (VTO) through the Advanced Battery Materials Research (BMR) Program

Novel plasma-assisted combustion route for NiOx thin film deposition

The emerging field of flexible electronics demands low-temperature, high-throughput solution-processable thin films of oxide semiconductors. Towards this goal, we report a novel low-temperature synthesis route that is primarily in a combination of solution combustion synthesis and plasma irradiation to deposit p-type nonstoichiometric NiOx thin films at a relatively lower temperature range. The film morphology was studied by atomic force microscope (AFM) and scanning electron microscope (SEM) while the crystallographic information was obtained from X-ray diffraction (XRD) studies. The NiOx formation mechanism is extensively studied with X-ray photoelectron spectroscopy (XPS) measurements. Here we reveal the conditional analysis to optimize the Ni3+ concentration that essentially controls the net free carrier in the nonstoichiometric NiO thin films. Based on our understanding, the plasma treatment not only plays a deterministic role in the material and the defect formation but is also efficient in removal of chemical impurity to obtain crystalline NiO thin films. Temperature-dependent (130–303 K) electrical resistivity measurements revealed that variable-range hopping (VRH) is the dominant hole transport process in this material.

Ultrahigh-sensitive mixed-potential ammonia sensor using dual-functional NiWO4 electrocatalyst for exhaust environment monitoring

The exhaust monitoring for in-situ quantification of gas pollutants has always been a challenge due to the harsh thermo-chemical environments, for which the solid-electrolyte based gas sensors appear as a realistic solution. In this work, an ultrahigh-sensitive mixed-potential ammonia sensor was developed using a new dual-functional NiWO4 electrocatalyst, synthesized through a low-temperature molten-salt synthesis route. The electrode morphology and diffusion lengths were tuned for optimum performance. The sensor operated at 550 ℃ displayed response of −100 mV to 80 ppm NH3, with response/recovery times of 28/68 s and a record-high sensitivity of 90 mV/decade. Besides, it displayed excellent selectivity and trace-level NH3 detection ability upto 400 ppb. While examining the sensing mechanism, the sensor exhibited an NH3 concentration-dependent transformation of rate-determining kinetics from charge-transfer limited Butler-Volmer type to diffusional mass-transport limited reaction kinetics. Moreover, the remarkable long-term stability with negligible response degradation (< 4%) confirms the suitability of the sensor for exhaust environment monitoring.

Ammonium ion intercalated hydrated vanadium pentoxide for advanced aqueous rechargeable Zn-ion batteries

Considering many factors, including environmental protection, high cost, and limited resource, aqueous rechargeable Zn-ion batteries (ARZIBs) are expected to be a new next-generation grid to replace Li-ion batteries. The open layered framework of (metal ions intercalated) hydrated vanadium pentoxides is conducive to the transfer and diffusion of zinc ions, making this kind of material a promising cathode material. In this work, ammonium ion (NH4+) intercalated hydrated vanadium pentoxide [(NH4)xV2O5·nH2O, abbreviated as NVOH] is prepared by a comparatively low-temperature synthesis and developed as a cathode material for ARZIBs. The influence of different types and concentrations of zinc salt electrolytes on the electrochemical performance is first studied, demonstrating that 3 M Zn(CF3SO3)2 shows the most excellent performance. The Zn//NVOH battery delivers superior electrochemical reversibility, a high specific capacity (372 mAh·g-1 at 0.1 A·g-1), a preeminent energy density (273 Wh·kg-1 at 155 W·kg-1), and a long lifespan cycling performance (175 mAh·g-1 after 2,000 cycles at 5 A·g-1), which is superior to or comparable to most up-to-the-minute V-based materials applied to ARZIBs. The intercalation reversibility of zinc ion is proved during the electrochemical reaction by various characteristic measurements. This work not only provides a low-temperature hydrothermal synthesis route (100 °C) for NVOH but also demonstrates that it can be a promising supplement for zinc ion batteries or other portable battery devices.