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Highlights: Mn-based electrode materials, including oxides, Prussian blue analogues and polyanion compounds, are introduced systematically for aqueous sodium-ion batteries. The composition, crystal structure, morphology and electrochemical performance of Mn-based electrode materials are reviewed. The improvement methods of electrochemical performance, such as electrolyte optimization, element doping or substitution, morphology optimization and carbon modification, are discussed. Aqueous sodium-ion batteries have attracted extensive attention for large-scale energy storage applications, due to abundant sodium resources, low cost, intrinsic safety of aqueous electrolytes and eco-friendliness. The electrochemical performance of aqueous sodium-ion batteries is affected by the properties of electrode materials and electrolytes. Among various electrode materials, Mn-based electrode materials have attracted tremendous attention because of the abundance of Mn, low cost, nontoxicity, eco-friendliness and interesting electrochemical performance. Aqueous electrolytes having narrow electrochemical window also affect the electrochemical performance of Mn-based electrode materials. In this review, we introduce systematically Mn-based electrode materials for aqueous sodium-ion batteries from cathode and anode materials and offer a comprehensive overview about their recent development. These Mn-based materials include oxides, Prussian blue analogues and polyanion compounds. We summarize and discuss the composition, crystal structure, morphology and electrochemical properties of Mn-based electrode materials. The improvement methods based on electrolyte optimization, element doping or substitution, optimization of morphology and carbon modification are highlighted. The perspectives of Mn-based electrode materials for future studies are also provided. We believe this review is important and helpful to explore and apply Mn-based electrode materials in aqueous sodium-ion batteries. [ABSTRACT FROM AUTHOR]

The development of electrode materials which improve both the energy density and cycle life is one of the most challenging issues facing the practical application of sodium-ion batteries today. In this work, FeTiO 3 /C nanoparticles are synthesized as negative electrode materials for sodium-ion batteries. The electrochemical performance and charge-discharge mechanism of the FeTiO 3 /C negative electrode are investigated in an ionic liquid electrolyte at 90 °C. The FeTiO 3 /C negative electrode delivers a high reversible capacity of 403 mAh g −1 at a current rate of 10 mA g −1 , and exhibits high rate capability and excellent cycling stability for up to 2000 cycles. The results indicate that FeTiO 3 /C is a promising negative electrode material for sodium-ion batteries. [ABSTRACT FROM AUTHOR]

In this study, carbon-coated Na 2 Ti 3 O 7 (Na 2 Ti 3 O 7 /C) is synthesized by a solid-state reaction method, and its charge-discharge characteristics as a negative electrode material in an ionic liquid electrolyte, Na[FSA]-[C 3 C 1 pyrr][FSA] (FSA = bis(fluorosulfonyl)amide; C 3 C 1 pyrr = N - methyl - N - propylpyrrolidinium), are investigated at 363 K. The Na 2 Ti 3 O 7 /C negative electrode shows an initial discharge capacity of 215 mAh (g-Na 2 Ti 3 O 7 /C) −1 at a current rate of 20 mA (g-Na 2 Ti 3 O 7 /C) −1 in the voltage range 0.01–2.5 V. The high discharge capacity of the Na 2 Ti 3 O 7 /C negative electrode is attributed to the high operation temperature in the Na[FSA]-[C 3 C 1 pyrr][FSA] ionic liquid electrolyte. Although high discharge capacity is achieved, the Na 2 Ti 3 O 7 /C negative electrode shows relatively poor cycle performance because of the irreversible insertion of some Na ions and the formation of cracks. [ABSTRACT FROM AUTHOR]

Ionic liquid is a promising electrolyte for sodium secondary batteries because of its negligible volatility, low flammability, and high thermal and electrochemical stabilities. In this study, Na 2/3 Fe 1/3 Mn 2/3 O 2 as a positive electrode material was synthesized by a solid-state reaction, and its charge-discharge performance was investigated at 90 °C in the ionic liquid electrolyte Na[FSA]-[C 3 C 1 pyrr][FSA] (FSA = bis(fluorosulfonyl)amide; C 3 C 1 pyrr = N - methyl - N - propylpyrrolidinium). The Na 2/3 Fe 1/3 Mn 2/3 O 2 positive electrode delivered an initial discharge capacity of 227 mAh g −1 at a current rate of 20 mA g −1 in the voltage range of 2.0–4.3 V. This study is the first where the Na 2/3 Fe 1/3 Mn 2/3 O 2 positive electrode demonstrated a high reversible discharge capacity, larger than 220 mAh g −1 , due to the high operation temperature in the ionic liquid electrolyte. [ABSTRACT FROM AUTHOR]

Sodium ion batteries (SIBs) have been attracting much attention as promising next-generation energy storage devices for large-scale applications. The major safety issue with SIBs, which arises from the flammability and volatility of conventional organic solvent-based electrolytes, is resolved by adopting an ionic liquid (IL) electrolyte. However, there are only a few reports on the study of negative electrodes in ILs. Here, we report the electrochemical performance of a hard carbon (HC) negative electrode in Na[FSA]-[C 3 C 1 pyrr][FSA] (FSA = bis(fluorosulfonyl)amide, C 3 C 1 pyrr = N -methyl- N -propylpyrrolidinium) IL over a wide temperature range of −10 °C to 90 °C. High-temperature operation, which is realized for the first time by using an IL, can take full advantage of the high capacity of HC even at a very high discharge rate of 1000 mA (g-HC) −1 : the discharge capacity is 230 mAh (g-HC) −1 at 90 °C and 25 mAh (g-HC) −1 at 25 °C. Moreover, surprisingly stable cycleability is observed for the HC electrode at 90 °C, i.e. a capacity retention ratio of 84% after 500 cycles. Finally, a high full-cell voltage of 2.8 V and stable full-cell operation with Coulombic efficiency higher than 99% are achieved for the first time when using NaCrO 2 as the positive electrode at 90 °C. [ABSTRACT FROM AUTHOR]

Abstract: The physicochemical properties of NaFSA–C1C3pyrFSA ionic liquids were investigated to explore their potential as new electrolytes for sodium secondary batteries operating over a wide temperature range. The viscosity and ionic conductivity of NaFSA–C1C3pyrFSA with a molar ratio of 2:8 were 16.7 cP and 15.6 mS cm−1, respectively, at 353 K. The electrochemical window of this ionic liquid was 5.2 V at 353 K with sodium metal deposition determining the cathode limit. A Na/NaFSA–C1C3pyrFSA/NaCrO2 cell exhibited stable charge–discharge behaviour at 298 and 353 K. The discharge capacities of 92 and 106 mAh (g-NaCrO2)−1 were observed at 298 and 353 K, respectively, at 20 mA g−1. The Coulombic efficiency was higher than 99% during the charge–discharge tests except for the initial few cycles. The cell also showed high discharge rates, reaching 500 mA g−1 at 353 K. [Copyright &y& Elsevier]

Abstract: In this study, NiO–Ce0.9Gd0.1O1.95 (NiO–GDC) nanocomposite powders, which were applied as anode materials of low temperature solid oxide fuel cells (SOFCs), were synthesized by hydroxide and oxalate reverse co-precipitation methods, respectively. The crystal phases, crystallite size, particle size, particle size distribution, and sintering characteristics of the synthesized NiO–GDC nanocomposite powders were investigated and compared. Results showed that the different co-precipitation methods affected strongly the synthesis and characteristics of the NiO–GDC nanocomposite powders. The NiO–GDC nanocomposite powders could be synthesized at lower temperature by the hydroxide reverse co-precipitation method, and the synthesized NiO–GDC nanocomposite powders had better sinterability. The NiO–GDC nanocomposite powders synthesized by the oxalate reverse co-precipitation method had smaller particle size and uniform particle size distribution and, however, were easy to result in crack formation in the sintered disks. [Copyright &y& Elsevier]

Abstract: In this study, NiO–Ce0.8Sm0.2O1.9 (SDC) nanocomposite powders with NiO content of 40–60 mass% were successfully synthesized by hydroxide co-precipitation method. The effect of NiO content on crystal phase, crystallite size, average particle size and particle size distribution of the NiO–SDC nanocomposite powders was investigated. The average particle size of the NiO–SDC nanocomposite powders increased and the particle size distribution became wider with an increase in the NiO content. Anode-supported solid oxide fuel cells (SOFCs) were fabricated from the NiO–SDC nanocomposite powders with different NiO content and electrochemical performance was tested at 500–650 °C using humidified hydrogen as fuel. Results showed that the NiO–SDC nanocomposite powders were suitable to be applied as anode materials for low-temperature SOFCs. The anode-supported SOFC fabricated from the NiO–SDC nanocomposite powders with 50 mass% NiO demonstrated the highest electrical performance among the anode-supported SOFCs fabricated from the NiO–SDC nanocomposite powders with the NiO content of 40–60 mass%. [Copyright &y& Elsevier]

Abstract: Anode-supported solid oxide fuel cells (SOFCs) have attracted much attention in recent years because of their lower operating temperature. For the preparation of anode-supported SOFCs, one of the key steps is the production of dense electrolyte films on the porous anode substrate. In this study, Ce0.9Gd0.1O1.95 (GDC) electrolyte films with the thickness range of 1–75μm are successfully prepared on porous NiO-GDC substrates by simple, rapid and cost-effective methods: dry co-pressing method and spray dry co-pressing method. The open porosity of the NiO-GDC substrates is approximately 23%, and the porosity including closed pores of the GDC electrolyte films is less than 2.6%. The prepared GDC electrolyte films are homogenous, dense and well adhered to the porous NiO-GDC substrates, without cracks and connecting pores observed. The results of helium gas permeability tests show that the prepared GDC electrolyte films are gas-tight. Therefore, it is expected that the developed method for thin electrolyte films provides a simple and useful technique for producing electrolytes for anode-supported SOFCs. [Copyright &y& Elsevier]

Abstract: In the present paper, we investigated the electrical performance of anode-supported solid oxide fuel cells (SOFCs) composed of Gd0.1Ce0.9O1.95 (GDC) electrolyte films of 1–75μm in thickness prepared by simple and cost-effective methods (dry co-pressing process and spray dry co-pressing process), and discussed the effect of thickness of the GDC electrolyte films on the electrical performance of the anode-supported SOFCs. It was shown that reducing the thickness of the GDC electrolyte films could increase the maximum power densities of the anode-supported SOFCs. The increase of the maximum power densities was attributed to the decrease of the electrolyte resistance with reducing the electrolyte thickness. However, when the thickness of the GDC electrolyte films was less than a certain value (approximately 5μm in this study), the maximum power densities decreased with the decrease in the thickness of the GDC electrolyte films. The calculated electron fluxes through the GDC electrolyte films increased obviously with reducing the thickness of the GDC electrolyte films, which was the reason why the maximum power densities decreased. Therefore, for anode-supported SOFCs based on electrolytes with mixed electronic–ionic conductivity, there was an optimum electrolyte thickness for obtaining higher electrical performance. [Copyright &y& Elsevier]

Abstract: In this study, NiO–Ce0.9Gd0.1O1.95 (NiO–GDC) nanocomposite powders were synthesized by hydroxide co-precipitation method, and applied to improve the microstructure of solid oxide fuel cell (SOFC) anodes. The NiO–GDC anodes prepared from the NiO–GDC nanocomposite powders showed uniform microstructure with uniform distribution of NiO and GDC phases. Due to the uniform phase distribution, the Ni–GDC anodes prepared from the NiO–GDC nanocomposite powders had longer triple phase boundary (TPB), which resulted in enhanced electrochemical reactions. The anode-supported SOFC fabricated from the co-precipitated NiO–GDC nanocomposite powders exhibited higher electrochemical performance than the anode-supported SOFC fabricated from the mechanically mixed NiO–GDC nanopowders. The experimental results show that the use of the Ni–GDC anodes with uniform microstructure can effectively improve the electrochemical performance of anode-supported SOFC. [ABSTRACT FROM AUTHOR]

Abstract: A simple, rapid and cost-effective technique, spray dry co-pressing process, was developed to prepare dense electrolyte thin films on porous anode substrates. Gadolinium doped ceria (GDC) electrolyte thin film with the thickness of 4μm was prepared successfully on porous NiO–GDC anode substrate by the spray dry co-pressing process. The GDC electrolyte thin film was dense and uniform, and was well bonded to the porous NiO–GDC anode substrate. An anode-supported solid oxide fuel cell (SOFC) with 4μm GDC electrolyte thin film was fabricated and its performance was evaluated at 400–600°C with humidified hydrogen (3 vol.% H2O) as the fuel. The single cell showed an open circuit voltage (OCV) of 0.91V and maximum power density of 771mWcm−2 at 600°C. The results demonstrate that the dense GDC thin films prepared by the spray dry co-pressing process are suitable for low-temperature anode-supported SOFC applications. [Copyright &y& Elsevier]

Spray coating method is a cost-effective technique suitable for the preparation of uniform and large-area thin films. This article presents findings on the preparation of dense electrolyte thin films by spray coating method. Dense, crack-free Gd-doped CeO2 (GDC) thin films with a thickness of approximately 2 µm were successfully prepared on porous NiO-GDC substrates. The influence of the dispersion of GDC nanopowders in susupension on the microstructure of the thin films was investigated. Results show that agglomeration of GDC nanopowders in suspension resulted in a porous microstructure and a densely packed microstructure was obtained for the film prepared from a well-dispersed suspension. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline fluorite type samarium doped ceria (SDC) electrolyte thin film for intermediate temperature-solid oxide fuel cells (IT-SOFCs) application were prepared on the dense and porous substrates at low temperatures of 573–1373K using a novel citrate sol–gel route combined with a sol suspension spray coating technique. Thermogravimetric analysis showed that the decomposition of the citrate gel film and the initial crystallization of the SDC occurred at a low temperature of about 590K. XRD examination revealed that the annealing of the green film at temperatures of 573–1373K provided cubic nanocrystalline SDC phase. The crystallite sizes were in the range of 9–19nm. Microscopic observations indicated that the derived film was homogeneous, dense and crack-free without pinholes. The desired thickness for preparation of thin electrolyte films from hundreds of nm to several μm should be controllable and feasible by repeating the simple and inexpensive citrate sol–gel spray coating process. [Copyright &y& Elsevier]

Antimony doped tin dioxide nanometer powders have been prepared by the hydrothermal method using SbCl3 as the source of antimony. The doped powders are examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The crystal phase composition, particle size, crystal appearance characteristics and dispersity of the doped powders are investigated. The results show that doped powders are well crystallized and dispersed. The crystal phase composition of doped powders is SnO2 of tetragonal structure. The particle size of doped powders is ∼3–12 nm. The crystal appearance characteristics of doped powders are mainly round. Antimony enters crystal lattice of tin dioxide via Sb3+. The doping effect of antimony is very good. [Copyright &y& Elsevier]

Step 1: The diffusion process of Na+ in the bulk phase of the composites. Step 2: Charge transfer reaction process. Step 3: The transport process of Na+ through SEI layer. The accuracy of kinetic interpretation is significantly improved by combining ex-situ TEM with distribution of relaxation times (DRT) to analyses electrochemical processes. [Display omitted] • A template method is employed to construct Sb/Sb 2 O 3 embedded N-doped porous carbon. • The accuracy of kinetic analysis is improved by combining ex-situ TEM with DRT. • N-doping creates more Na+ storage sites to improve the capacity. • The Sb/Sb 2 O 3 @NPC anode exhibits excellent cycle performance. Sb-based materials are considered as promising anode materials for sodium-ion batteries (SIBs) due to their excellent sodium storage capacities and suitable potentials. However, the Sb-based anodes usually suffer from intense volume expansion and severe pulverization during the alloying-dealloying process, resulting in poor cycling performance. Herein, a composite anode with Sb/Sb 2 O 3 nanoparticles embedded in N-doped porous carbon is prepared by the gas–solid dual template method. The volume change of the anode material is mitigated by the carbon layer enwrapping and the confinement of the porous structure. Nitrogen doping provides abundant sodium storage sites, thus enhancing the storage capacity of sodium ion. Furthermore, to gain the accurate kinetic interpretation of the electrochemical process, an ex-situ transmission electron microscope (TEM) characterization combined with distribution of relaxation times (DRT) is conducted. The Sb/Sb 2 O 3 @NPC-1.0 demonstrates excellent electrochemical performance, achieving 340.3 mAh g−1 at 1A g−1, and maintains a capacity of 86.7 % after 1000 cycles. This work paves the way for the practical application of SIBs with high-performance and long-life Sb-based anodes. [ABSTRACT FROM AUTHOR]

Homogenous NiO–Ce0.9Gd0.1O1.95 (GDC) nanocomposite powders were successfully synthesized by a hydroxide co-precipitation method. The synthesized powders consist of NiO and GDC double phases, and the average particle size is in the range of 10–40nm. A solid oxide fuel cell (SOFC) with anode prepared from the synthesized NiO–GDC nanocomposite powders shows high electrical performance at low operating temperatures. Results indicate that the synthesized NiO–GDC nanocomposite powders are suitable anode materials for low-temperature SOFCs. [Copyright &y& Elsevier]

Highlights: Optimization strategies for high-performance Na3V2(PO4)3 (NVP) cathode material are well summarized and discussed, including carbon coating or modification, foreign-ion doping or substitution and nanostructure and morphology design. The foreign-ion doping or substitution is highlighted, involving the Na, V, and PO43− sites, which include single-site doping, multiple-site doping, single-ion doping and multiple-ion doping. Challenges and future perspectives for high-performance NVP cathode material are presented. Na3V2(PO4)3 (NVP) has garnered great attentions as a prospective cathode material for sodium-ion batteries (SIBs) by virtue of its decent theoretical capacity, superior ion conductivity and high structural stability. However, the inherently poor electronic conductivity and sluggish sodium-ion diffusion kinetics of NVP material give rise to inferior rate performance and unsatisfactory energy density, which strictly confine its further application in SIBs. Thus, it is of significance to boost the sodium storage performance of NVP cathode material. Up to now, many methods have been developed to optimize the electrochemical performance of NVP cathode material. In this review, the latest advances in optimization strategies for improving the electrochemical performance of NVP cathode material are well summarized and discussed, including carbon coating or modification, foreign-ion doping or substitution and nanostructure and morphology design. The foreign-ion doping or substitution is highlighted, involving Na, V, and PO43− sites, which include single-site doping, multiple-site doping, single-ion doping, multiple-ion doping and so on. Furthermore, the challenges and prospects of high-performance NVP cathode material are also put forward. It is believed that this review can provide a useful reference for designing and developing high-performance NVP cathode material toward the large-scale application in SIBs. [ABSTRACT FROM AUTHOR]

On-site hydrogen generation from ammonia decomposition is a promising technology to address the challenges of direct transportation and storage of hydrogen. The main problems with the existing support materials for ammonia decomposition catalysts are their high cost and time-consuming preparation process. In this work, ammonia decomposition catalysts consisting of in situ-formed nano-Ru particles supported on a naturally abundant mineral fiber, attapulgite (ATP), were proposed and studied. Also, 1 wt.% Ru was uniformly dispersed and anchored onto the surface of ATP fibers via the chemical method. We found that the calcination temperatures of the ATP support before the deposition of Ru resulted in little difference in catalytic performance, while the calcination temperatures of the 1Ru/ATP precursor were found to significantly influence the catalytic performance. The prepared 1 wt.% Ru/ATP catalyst (1Ru/ATP) without calcination achieved an ammonia conversion efficiency of 51% at 500 °C and nearly 100% at 600 °C, with the flow rate of NH3 being 10 sccm (standard cubic centimeter per minute). A 150 h continuous test at 600 °C showed that the 1Ru/ATP catalyst exhibited good stability with a degradation rate of about 0.01% h−1. The 1Ru/ATP catalyst was integrated with proton ceramic fuel cells (PCFCs). We reported that PCFCs at 650 °C offered 433 mW cm−2 under H2 fuel and 398 mW cm−2 under cracked NH3 fuel. The overall results suggest low-level Ru-loaded ATP could be an attractive, low-cost, and efficient ammonia decomposition catalyst for hydrogen production. [ABSTRACT FROM AUTHOR]

Multidimensional porous carbon nanosheet frameworks decorated with CoSe 2 nanoparticles (CoSe 2 -CNF) was produced by a metal salt-assisted polymer-blowing method. Unique structure endows CoSe 2 -CNF with exceptional battery capacity and fast-charging capability as anode for sodium-ion batteries in various electrolyte systems. In situ techniques and DFT calculations further investigate the sodium storage mechanism and excellent electrochemical properties. [Display omitted] • A metal salt-assisted polymer-blowing method is proposed to construct CoSe 2 -CNF. • Unique nanoarchitecture offers more active sites for Na+ storage and transmission. • The CoSe 2 -CNF as anode exhibits exceptional battery capacity and fast-charging capability in diverse electrolyte systems. • Sodium storage mechanism and fast electrochemical kinetics are investigated. Transition metal selenides (TMSs) possess relatively high theoretical capacity and unique structures emerge as promising anode materials for sodium-ion batteries (SIBs). However, TMSs anode materials suffer from challenges such as substantial volume expansion, undesired side reactions, and poor active reaction dynamics. Herein, we propose a novel synthesis method that integrates metal salt-assisted polymer-blowing technique with in situ selenization strategy to fabricate multidimensional porous 3D carbon nanosheet frameworks modified by cobalt diselenide nanoparticles (CoSe 2 -CNF). Such unique architecture bestows intimate structural interconnectivity with high mechanical strength and abundant ion diffusion channels on CoSe 2 -CNF, exhibiting remarkable reversible capacity and fast-charging capability within diverse electrolyte systems. For instance, the CoSe 2 -CNF anode in ether electrolyte exhibits prominent rate performance of 349 mAh/g at 15 A/g. Sodium storage mechanism and fast electrochemical kinetics in the discharge/charge processes are investigated by in situ XRD and in situ EIS techniques. Additionally, DFT calculations are utilized to analyze the electrochemical differences observed in various electrolyte systems. When coupled with Na 3 V 2 (PO 4) (NVP) cathodes, the full batteries also afford enhanced reversible capacity of 105 mAh/g over 100 cycles. The proposed structural engineering for CoSe 2 -CNF is beneficial for designing fast-charging energy storage devices. [ABSTRACT FROM AUTHOR]

Multidimensional porous carbon nanosheet frameworks decorated with CoSe 2 nanoparticles (CoSe 2 -CNF) was produced by a metal salt-assisted polymer-blowing method. Unique structure endows CoSe 2 -CNF with exceptional battery capacity and fast-charging capability as anode for sodium-ion batteries in various electrolyte systems. In situ techniques and DFT calculations further investigate the sodium storage mechanism and excellent electrochemical properties. [Display omitted] • A metal salt-assisted polymer-blowing method is proposed to construct CoSe 2 -CNF. • Unique nanoarchitecture offers more active sites for Na+ storage and transmission. • The CoSe 2 -CNF as anode exhibits exceptional battery capacity and fast-charging capability in diverse electrolyte systems. • Sodium storage mechanism and fast electrochemical kinetics are investigated. Transition metal selenides (TMSs) possess relatively high theoretical capacity and unique structures emerge as promising anode materials for sodium-ion batteries (SIBs). However, TMSs anode materials suffer from challenges such as substantial volume expansion, undesired side reactions, and poor active reaction dynamics. Herein, we propose a novel synthesis method that integrates metal salt-assisted polymer-blowing technique with in situ selenization strategy to fabricate multidimensional porous 3D carbon nanosheet frameworks modified by cobalt diselenide nanoparticles (CoSe 2 -CNF). Such unique architecture bestows intimate structural interconnectivity with high mechanical strength and abundant ion diffusion channels on CoSe 2 -CNF, exhibiting remarkable reversible capacity and fast-charging capability within diverse electrolyte systems. For instance, the CoSe 2 -CNF anode in ether electrolyte exhibits prominent rate performance of 349 mAh/g at 15 A/g. Sodium storage mechanism and fast electrochemical kinetics in the discharge/charge processes are investigated by in situ XRD and in situ EIS techniques. Additionally, DFT calculations are utilized to analyze the electrochemical differences observed in various electrolyte systems. When coupled with Na 3 V 2 (PO 4) (NVP) cathodes, the full batteries also afford enhanced reversible capacity of 105 mAh/g over 100 cycles. The proposed structural engineering for CoSe 2 -CNF is beneficial for designing fast-charging energy storage devices. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical properties of a Na2FeP2O7 positive electrode were investigated in the ionic liquid sodium bis(fluorosulfonyl)amide (NaFSA)–N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)amide (C3C1pyrrFSA). A stable charge–discharge behavior was obtained over the temperature range 253–363K. The cell offered nearly a one-electron theoretical capacity of about 90 mAh g−1 at 298–363K. The rate capability showed considerable enhancement with increasing temperature, delivering 50 mAh g−1 at a very high rate of 4000mAg−1 (ca. 41C) at 363K. Furthermore, the Na2FeP2O7 positive electrode demonstrated excellent cyclability, exceeding 300 cycles, in terms of both capacity retention and coulombic efficiency at 298–363K, as only negligible capacity fade (<1%) was observed. This good performance over a wide temperature range will meet the requirements of the versatile applications expected for Na secondary batteries. [Copyright &y& Elsevier]

Microextrusion printing is employed for increasing the interfacial area between the electrode and electrolyte of anode-supported solid oxide fuel cells (SOFCs) to enhance their electrochemical performance. A homogeneous anode paste is prepared as an extrusion material and its rheological properties are measured. Then, the printing resolution (line width of the printed paste) is evaluated by extruding the paste under various printing conditions to determine the appropriate stage speed and flow rate for cell fabrication. A mathematical model is also developed to predict the printing resolution from the printing parameters, and the experimental data of the line width agree well with the predicted values, particularly when the contact angle between the paste and substrate is considered. By varying a paste coverage area, two types of anode-supported SOFCs having different interfacial area enlargement ratios are prepared by extruding the anode paste onto the flat anode substrates. The electrochemical performance of the cell is improved by increasing the interfacial area; the current density at the terminal voltage of 0.7 V at 600 °C is 0.17 A cm−2 in a flat cell, whereas 0.32 A cm−2 in a patterned cell whose enlargement factor is 1.14 compared with that of the flat cell. Image 1 • Microextrusion printing is used to increase the electrode–electrolyte interface. • Mathematical model of the microextrusion printing is developed. • SOFC performance is improved by increasing the interfacial area. • Performance improvement is greatest at a low operating temperature. [ABSTRACT FROM AUTHOR]