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Lead-free ferroelectric ceramics have aroused widespread concerns, due to their properties of rapid charge/discharge and electric-induced strain without harming the environment. However, compared with thin-film capacitors, ceramics have a larger energy loss. In addition, the large time lag between electric field and strain also reduces its accuracy as an actuator. Therefore, the relaxor ternary solid solution (BaTiO 3 –Bi 0.48 Na 0.48 La 0.03 TiO 3 –NaNbO 3) was constructed in this work, aiming to obtain large energy storage efficiency and low time delay. The strategy and optimization aim to improve the relaxation degree and reduce the maximum permittivity temperature to room temperature, building a special crossover region where high and low dynamic polar nano regions co-existence. Thus a recoverable energy density of 1.24 J/cm3 under a low electric field (135 kV/cm) and a high energy storage efficiency (96%) are obtained and low hysteresis electrostriction with a large electrostriction coefficient (Q 33 = 0.0367 m4/C2) is also achieved in this system. This work suggests that this system can be considered promising materials as high-efficiency capacitors and high-precision actuators. It also attracts interest in the basic research on the dynamic changes of polar nano regions. [ABSTRACT FROM AUTHOR]

Dielectric capacitors are widely used in pulse devices because of their fast charge/discharge speed. However, the low energy storage density limits their application. In this work, (1 − x)(Bi0.5Na0.5)0.94Ba0.06Ti0.99(Y0.5Nb0.5)0.01O3-xKNbO3 (BNBTYN-100xKN) lead-free relaxor ferroelectric ceramics were fabricated via a solid-state sintering technique. K+ and Nb5+ were completely diffused into the BNBTYN lattice and formed solid solutions. The incorporation of KNbO3 reduced the symmetry of BNBTYN-100xKN ceramics and destroyed the long-range ordered ferroelectric domains, leading to thinning of hysteresis loops. The relaxor degree increased with the KN content, resulting in the improvement of efficiency. Therefore, using BNBTYN-5KN ceramics an energy storage density of 1.246 J cm−3 and an efficiency of 78.7% at 104 kV cm−1 were obtained. In addition, the BNBTYN-5KN ceramics exhibited this energy storage density with outstanding temperature stability (in the range of 20–120 °C) and excellent fatigue resistance. These results reveal that BNBTYN-5KN ceramics is a promising material for energy storage. [ABSTRACT FROM AUTHOR]

Highlights: The formation mechanism of solid electrolyte interface (SEI) is analyzed based on charge distributions at the electrode/electrolyte interface and molecular orbital theory. The factors affecting the formation of SEI are generalized from four aspects: Zn anode, electrolyte, current density and temperature. The design strategies for SEI layer are proposed from regulating temperature, electric and magnetic fields. Due to its high theoretical capacity (820 mAh g−1), low standard electrode potential (− 0.76 V vs. SHE), excellent stability in aqueous solutions, low cost, environmental friendliness and intrinsically high safety, zinc (Zn)-based batteries have attracted much attention in developing new energy storage devices. In Zn battery system, the battery performance is significantly affected by the solid electrolyte interface (SEI), which is controlled by electrode and electrolyte, and attracts dendrite growth, electrochemical stability window range, metallic Zn anode corrosion and passivation, and electrolyte mutations. Therefore, the design of SEI is decisive for the overall performance of Zn battery systems. This paper summarizes the formation mechanism, the types and characteristics, and the characterization techniques associated with SEI. Meanwhile, we analyze the influence of SEI on battery performance, and put forward the design strategies of SEI. Finally, the future research of SEI in Zn battery system is prospected to seize the nature of SEI, improve the battery performance and promote the large-scale application. [ABSTRACT FROM AUTHOR]

Lead-free relaxor ferroelectric ceramics are attracting attention due to their fast charge/discharge and environmentally friendly properties. In this work, the bismuth sodium titanate-barium titanate-barium zirconate titanate [(0.94Bi 0 · 51 Na 0 · 47 TiO 3 -0.06BaTiO 3) -x BaZr 0.3 Ti 0 · 7 O 3 , abbreviated as BNBT-100 x BZT] relaxor ferroelectric ceramics were synthesized by the solid-state reaction technique. The microstructure, energy storage properties, and conductivity mechanism of BNBT-100 x BZT were analyzed as the barium zirconate titanate doping content changed. All BNBT-100 x BZT have a single perovskite structure by XRD. The BNBT-5BZT ceramics was found to be tetragonal by Rietveld refinement. Moreover, the doping of BZT is beneficial to optimize the breakdown strength (BDS). Owing to the higher BDS, an effective energy storage density of 1.457 J/cm3 was obtained under 122 kV/cm in BNBT-5BZT with an energy storage efficiency (η) of 81.9%. In addition, BNBT-5BZT has outstanding temperature and cycling stability. The results indicate that BNBT-5BZT ceramics is excellent candidates for energy storage devices. A new relaxor ferroelectric bismuth sodium titanate-barium titanate-barium zirconate titanate synthesized with a tetragonal phase shows an energy storage density of 1.457 J/cm3 at 122 kV/cm and energy storage efficiency of 81.9%. [Display omitted] [ABSTRACT FROM AUTHOR]

A series of lead-free (Bi 0·5 Na 0.5) 0.84 Sr 0·16 Ti 1- x (Y 0·5 Nb 0.5) x O 3 (abbreviated as BNST-100 x YN) relaxor ferroelectric ceramics were prepared by solid state reaction sintering. The micro morphology, dielectric properties, and energy storage properties of the ceramics with increasing doping content were systematically studied, and their conductive mechanism was also studied. The perovskite structure was not significantly changed with the addition of (Y 0·5 Nb 0.5)4+ complex ions, but it led to a certain amount of flake grains appear and element precipitation with increasing composition. And the larger dielectric breakdown strength (DBS) and lower remanent polarization (P r) were attained with the recoverable energy storage density (W rec) of ~1.0433 J/cm3 for x = 0.04 composition. In addition, it showed outstanding dielectric temperature stability and cycle stability. These results indicated that BNST-4YN ceramics are an excellent candidate for energy storage device and temperature-stable dielectric equipment. [ABSTRACT FROM AUTHOR]

Lead-free ceramics ((Bi0.5Na0.5)0.7(Sr0.7Bi0.2)0.3)1-xSmx)TiO3 (x = 0.0, 0.005, 0.01, 0.02, 0.03) with a novel phase boundary structure were successfully synthesized. All samples sintered well and shown pure perovskite structure. The doping of Sm3+ inhibits the grain growth and enhanced the relaxor properties. Besides, the activity of polar nanoregion (PNRs) is improved. Ferroelectric analysis showed that proper Sm3+ doping played a pegging role on the saturated polarized Pm, leading to a higher and slimmer P-E loop. As a result, a large energy storage density (~ 1.25 J/cm3) with high energy efficiency (~ 73%) were achieved at x = 0.005 under an electric field of 90 kV/cm. Further, the sample was found to have good temperature stability between room temperature and 110 °C. This study shows that ceramic material has great potential for the application of high-temperature stability energy storage capacitors. [ABSTRACT FROM AUTHOR]

(1- x)[0.94(Bi 0.5 Na 0.5)TiO 3 -0.06BaTiO 3 ]- x Ba(Sn 0.70 Nb 0.24)O 3 (abbreviated as BNTBT-100 x BSN) lead-free ceramics were fabricated with a relative density greater than 96 %, and the structure as well as performance were tested. BNTBT-100 x BSN ceramics are pseudo-cubic perovskite structure, with dense surface morphology. Doping BSN can effectively reduce the dielectric loss of ceramics and increase the relaxation properties to a certain extent. The randomly distributed ferroelectric phase was replaced by polar nano regions, thereby improving the electro-strain and energy storage performance of the system. The largest electro-strain and the corresponding normalized strain (d 33 *) reach ~ 0.43 % and 633 pm/V respectively in the BNTBT-1BSN ceramic. The largest effective energy storage density reaching ~ 1.28 J/cm3 was tested in BNTBT-2BSN. BNTBT-100 x BSN ceramics provide a feasible idea for the systematic research of lead-free ferroelectrics and improvements in electro-strain and energy storage applications. [ABSTRACT FROM AUTHOR]

Lead-free antiferroelectric (AFE) ceramic materials have attached increasing attention in application of high-power capacitors for the past few years, due to their high energy storage density and environmental protection. However, the related applications are seriously restricted because of the limited number of environment friendly AFE candidate materials, high cost and low energy storage efficiency. In this work, the A-site ion Sm3+ doped 0.88NaNbO 3 -0.12Sr 0·7 Bi 0·2 TiO 3 lead-free AFE P phase ceramics (0.88Na 1-3 x Sm x NbO 3 -0.12Sr 0·7 Bi 0·2 TiO 3 , abbreviated as NN-SBT-100 x Sm) were prepared and characterized. With the increase of Sm doping amount, a relaxor-like behavior was found in the dielectric-temperature curves of NN-SBT-100 x Sm, indicating the AFE orthorhombic P phase is gradually replaced by an AFE orthorhombic R phase. As a result, double-like and slim P - E curve with near-zero residual polarization and suppressed hysteresis loss was obtained at x > 0.01. More encouragingly, a good discharge energy storage density (W rec = 3.58 J/cm3) and a high efficiency (η = 82%) at a low electric field (E = 200 kV/cm) has been recorded simultaneously for NN-SBT-2Sm relaxor AFE ceramic, which are better than the other lead-free energy storage ceramics under the same E. In addition, the energy storage properties of NN-SBT-2Sm ceramics exhibit outstanding temperature and frequency stability. These results indicate that NN-SBT-2Sm relaxor AFE ceramic has a great practical value in pulse power capacitors. [ABSTRACT FROM AUTHOR]

Dielectric ceramics for capacitors have attained significant attention in current time owing to their large power densities and fast charge/discharge rates. Lead-free [(Bi0.50Na0.40K0.10)0.94Ba0.06]1-xLaxTi0.975Ta0.025O3 (abbreviated as BNKBTT-100xLa) relaxor ceramics are prepared using mixed-oxide technique. All ceramics are revealed a pseudo-cubic structure using X-ray diffraction technique. The long-range order existing in BNKBTT-100xLa ceramics is found to reduce with increasing composition. As a result, a highly effective energy storage density (Wrec) ~ 1.558 J/cm3 and efficiency (η) ~ 88.46% is achieved in BNKBTT-2La ceramic. In addition, BNKBTT-2La composition is fatigue-free up to 105 cycles. Also, BNKBTT-4La ceramic exhibits a dielectric constant (ε') ~ 2281 near 150 °C with Δε'/ε'150 °C below 15% over a large range from 39 to 383 °C, showing an outstanding dielectric temperature stability. Therefore, BNKBTT-2La and BNKBTT-4La ceramics are outstanding for energy density and thermally stable dielectric permittivity, respectively, for the device applications. [ABSTRACT FROM AUTHOR]

In this study, (1- x)(0.66Bi 0.5 Na 0.5 TiO 3 –0.34Bi 0.2 Sr 0.7 TiO 3)– x K 0.5 Nd 0.5 TiO 3 (BNBST– x KNT) ceramics were designed and synthesized, and they present significantly enhanced dielectric temperature stability and energy storage properties. The BNBST–0.06KNT composition exhibits a remarkable dielectric stability, as reflected in its stable dielectric constant (△ ԑ / ԑ 150 °C < ±15%) over a broad temperature range (25–401 °C). BNBST–0.02KNT achieves a high energy storage density W rec = 1.2 J/cm3 under 110 kV/cm with an energy storage efficiency η of 76.9%, and the improved energy storage property originates from the improved breakdown field strength and decreased hysteresis behavior. The electrical conductivity and relaxation behaviors of BNBST– x KNT were also analyzed via impedance spectroscopy. [ABSTRACT FROM AUTHOR]

Lead-free perovskite materials for capacitors have been recognized worldwide attention in recent times with high storage energy density and efficiency. A series of (Bi0.50Na0.40K0.10)0.94Ba0.06Ti(1−x)(Al0.50Ta0.50)xO3 ceramics are synthesized using traditional mixed oxide route. All ceramics are in single-phase perovskite-like structure. At room temperature, high storage energy density, Wr ~ 1.67 J/cm3, and conversion efficiency, η ~ 81.46%, are perceived for x = 0.06 composition at 115 kV/cm. Temperature-dependent study obtains Wr ~ 1.21 J/cm3 and η ~ 84.96% at 80 °C with 80 kV/cm field. In addition, composition x = 0.06 is fatigue-free from 1 to 105 cycles measured at 80 kV/cm field. Furthermore, ceramic x = 0.04 is obtained a high bipolar strain ~ 0.31% at 80 kV/cm compared to other compositions. Hence, the compositions x = 0.06 for high energy density and x = 0.04 for strain might be useable in many electronic components. [ABSTRACT FROM AUTHOR]

The high storage energy density (W rec) and conversion efficiency (η) for lead-free ceramics have been attained significant interest in recent times for electronic devices. Enhanced W rec and stable fatigue properties are examined for lead-free 0.94Bi 0·50 (Na 0·78 K 0.22) 0.50 Ti 1- x (Al 0·50 Nb 0.50) x O 3 -0.06BaZrO 3 (for 0 ≤ x ≤ 0.05) ceramics, synthesized using the solid-state reaction method. Crystal structure and lattice dynamics are revealed by the X-ray diffraction and Raman scattering techniques. Highly compact ceramics is obtained with decreasing average grain size from 0.94 ± 0.23 μm (for x = 0) to 0.76 ± 0.31 μm (for x = 0.05) as a function of composition. A high W rec ~1.32 J/cm3 and η ~76.60% is achieved for x = 0.04 ceramic at room temperature with applied 95 kV/cm. In addition, W rec ~1.40 J/cm3 and η ~86% are perceived with a 90 kV/cm at 80 °C. Also, it is obtained as a fatigue-free property for x = 0.04 composition ceramic up to 105 cycles. Hence, this improvement in energy density performance and stable fatigue resistance for x = 0.04 dielectric ceramic is expected for practical applications in many electronic appliances. [ABSTRACT FROM AUTHOR]

Energy density and fatigue resistance properties were investigated for lead-free Na 0.46 Bi 0.46 Ba 0.05 La 0.02 Zr 0.03 Ti 0.97- x Sn x O 3 (for 0 ≤ x ≤ 0.15) ceramics, synthesized via solid-state reaction technique. Perovskite pseudo-cubic crystal structure was revealed for all ceramics using X-ray diffraction. Polarization and current density versus electric field were perceived and suggested the relaxor behavior with increasing composition. A high storage energy density ~1.58 J/cm3, and conversion efficiency ~71.7% at ~110 kV/cm applied field was obtained for x = 0.03 composition at room temperature. Energy storage density was revealed ~1.53 J/cm3, and efficiency ~88.6% at 110 °C with a 100 kV/cm applied field. In addition, ceramic x = 0.03 was fatigue-free from 1 to 105 cycles. Hence, the composition x = 0.03 might be applicable for high energy storage devices. [ABSTRACT FROM AUTHOR]

0.94(Bi 0.5 Na 0.5)(Y 0.5 Ta 0.5) x Ti 1- x O 3 -0.06BaTiO 3 lead-free piezoelectric ceramics were prepared by a conventional solid-state reaction method to study their excellent electro-strain properties and energy storage characteristics systematically. All ceramics exhibited a dense surface morphology. The introduction of (Y 0.5 Ta 0.5)4+ complex ions destroyed the long-range ferroelectric order, which reduced the T F-R to the operating temperature, resulting in an easier field-induced transition between relaxor and ferroelectric phase. Therefore, for x = 0.01 component attained unipolar strain of 0.37% under 52 kV/cm, and the corresponding normalized strain d 33 * was 708 pm/V. Besides, the destruction of the ferroelectric phase also induced a pinched hysteresis loop and the maximum storage density of 1.215 J/cm3 with the efficiency of 68.7% obtained at 98 kV/cm for BNYT30 ceramics. These all demonstrated that the doping of complex ions (Y 0.5 Ta 0.5)4+ made the BNT-BT an outstanding candidate for actuators and energy storage devices. [ABSTRACT FROM AUTHOR]

Polycrystalline (1- x)[(Na 0.5 Bi 0.5) 0.95 Ba 0.05 ] 0.98 La 0.02 TiO 3 - x K 0.5 Na 0.5 NbO 3 systems were prepared using the solid-state reaction technique. Modification of (Na 0.5 Bi 0.5) 0.95 Ba 0.05 ] 0.98 La 0.02 TiO 3 ceramic with a proper amount of K 0.5 Na 0.5 NbO 3 can effectively improve the temperature-stable of dielectric properties. A variation in dielectric constant is maintained smaller than ±5% from 80 to 300 °C accompanied with a low dielectric loss (≤0.04). The relaxor properties of the doped samples are significantly enhanced. A high energy storage density of 1.1 J/cm3 and efficiency ~80% at 90 kV/cm are achieved in the x = 0.05 composition. Hence, the as-prepared ceramics might be practical in dielectric constant which can work stably at a high temperature range and pulsed capacitors. [ABSTRACT FROM AUTHOR]

A NiCo-LDH/Mn 3 O 4 composite is synthesized on nickel foam substrate though a two-step electrodepositon process. The growth of Mn 3 O 4 nanoneedles on NiCo-LDH nanosheets can greatly reduce the transport pathway of electrons and ions. Meanwhile, abundant active sites for redox reactions are generated and the structural endurance together with chemical stability of material is improved, thus strongly enhancing the electrochemical characteristics. When measured in a typical three-electrode cell, NiCo-LDH/Mn 3 O 4 demonstrates a high specific capacity of 1.86 C cm−2 (1034.33 C g−1) at the current density of 1 mA cm−2, a superior rate capability of maintaining 76.88% at 20 mA cm−2 and 17.98% capacity loss after 5000 cycles. In addition, an all-solid-state hybrid supercapacitor device (HSC) is fabricated with NiCo-LDH/Mn 3 O 4 as the cathode and commercially-used active carbon as the anode, which delivers a superior energy density of 57.03 Wh kg−1 at the power density of 765.8 W kg−1 and maintains 20.98 Wh kg−1 even when the power density increases to 9681.6 W kg−1. Therefore, the satisfactory electrochemical property enables NiCo-LDH/Mn 3 O 4 to become a prospective electrode material in energy storage field. • We first synthesize a 3D partially-cladding NiCo-LDH/Mn 3 O 4 composite. • The integration of nanosheets and nanoneedles improves the stability. • We first define and use the curve of accumulative contribution versus potential. • The NiCo-LDH/Mn 3 O 4 //AC HSC device shows high energy density and power density. [ABSTRACT FROM AUTHOR]

The manganese oxides electrode material for electrochemical capacitor has been prepared with degreasing cotton as templates. The microstructure characterization figured that the constructed quasi-columnar formation is composed of manganese oxides nanoparticles after removal of template. The generated amorphous outlayer provides fast ion diffusion and improvement of structural stability. Consequently, electrochemical performance presented that 0.9 mg, 1.6 mg and 2.7 mg active material loaded on the pressed Ni foam have an excellent capacitance of 214, 189 and 154 F g−1, respectively. With constructed by manganese oxides and active carbon, an asymmetric device delivered an optimal specific energy of 38.4 Wh kg−1 at the specific power of 315 W kg−1. The quantitative experiments have further been performed to investigate the correlation of capacitive contribution and scan rates in detail. Unlabelled Image • Manganese oxides with quasi-columnar configuration for electrochemical capacitor was prepared by degreasing cotton as templates. • Amorphous outlayer provides fast ion diffusion and structural stability. • With manganese oxides and active carbon, an asymmetric device delivered an optimal specific energy of 38.4 Wh kg- 1 at the specific power of 315 W kg- 1. • Quantitative experiments performed to get the correlation of capacitive contribution and scan rates. [ABSTRACT FROM AUTHOR]

Abstract Nanoscale transition metal oxides and polyoxometalates attract great attention due to their short diffusion channel distance and reversible redox reaction. However, the inevitable agglomeration, shrinkage and volumetric expansion/shrinkage of nanomaterials seriously affect their electrochemical properties. Here, the 3D heterostructure CoWO 4 /Co 3 O 4 nanocone arrays are synthesized via a facile and efficient microwave hydrothermal method. The obtained CoWO 4 /Co 3 O 4 NCAs overcome these shortcomings and achieve high electrochemical performance. The electrochemical behaviors of as-prepared composites are investigated systematically, during which four pairs of redox peaks in cyclic voltammetry curve are observed and discussed in detail. The kinetic analysis of redox reaction is employed to confirm the redox pseudocapacitance mechanism (surface capacitance-dominated process) and intercalation pseudocapacitance mechanism (diffusion-controlled process) of charge storage, suggesting faradaic intercalation process of 3D heterostructure CoWO 4 /Co 3 O 4 NCAs (22% diffusion contribution at 0.8 mV s−1). The assembled solid-state hybrid supercapacitors further exhibit high energy density (45.6 Wh kg−1) and power density (7500 W kg−1 at 32.8 Wh kg−1) even at a super-high total loading mass of 23.1 mg of active materials. This work provides some meaningful and significant basis and foundation for the study of supercapacitors. Graphical abstract Image 1 Highlights • Four pairs of redox peaks were observed in CV curve and analyzed systematically. • The contribution of pseudocapacitive were quantified. • Solid-state supercapacitors exhibited a superior energy density at high loading mass. [ABSTRACT FROM AUTHOR]

A series of novel (1 − x)(0.94Na0.5Bi0.5TiO3-0.06BaTiO3)-xNa0.73Bi0.09NbO3 (BNT-BT-100xNBN) (x = 0-0.15) lead-free ceramics were fabricated by conventional solid state reaction method. The effects of NBN modification on the phase evolution, dielectric behavior, ferroelectric property and energy-storage performance were comprehensively investigated. All samples showed the pseudocubic structure and excessive dopants resulted in the secondary phase. The introduction of NBN resulted in deteriorative relaxor properties and maked two distinct dielectric anomalies smeared mutually. Therefore, the sample with x = 0.10 displayed a high permittivity (~ 1988) and low dielectric loss (< 0.02) in a broad temperature range of 25-337 °C. In addition, when x = 0.1, the optimal energy-storage density Wrec reached up to 1.56 J/cm3 with energy efficiency η = 92.5% at 120 kV/cm. The excellent thermal stability and fatigue resistance of sintered ceramics make it possible to be applied for practical dielectric capacitors. [ABSTRACT FROM AUTHOR]

Abstract: A new type of (0.7−x)Bi0.5Na0.5TiO3‐0.3Sr0.7Bi0.2TiO3‐xLaTi0.5Mg0.5O3 (LTM1000x, x = 0.0, 0.005, 0.01, 0.03, 0.05 wt%) lead‐free energy storage ceramic material was prepared by a combining ternary perovskite compounds, and the phase transition, dielectric, and energy storage characteristics were analyzed. It was found that the ceramic materials can achieve a stable dielectric property with a large dielectric constant in a wide temperature range with proper doping. The dielectric constant was stable at 2170 ± 15% in the temperature range of 35‐363°C at LTM05. In addition, the storage energy density was greatly improved to 1.32 J/cm3 with a high‐energy storage efficiency of 75% at the composition. More importantly, the energy storage density exhibited good temperature stability in the measurement range, which was maintained within 5% in the temperature range of 30‐110°C. Particularly, LTM05 show excellent fatigue resistance within 106 fatigue cycles. The results show that the ceramic material is a promising material for temperature‐stable energy storage. [ABSTRACT FROM AUTHOR]

Leed-free ferroelectric (1- x )(0.65Bi 0.5 Na 0.5 TiO 3 −0.35Bi 0.1 Sr 0.85 TiO 3 )- x KNbO 3 (BNBST- x KN) ceramics were prepared by the conventional solid state sintering method. The dielectric, ferroelectric and energy-storage properties were systematically investigated. Temperature dependent permittivity curves showed the relaxation properties of BNBST ceramics enhanced with the increase of KNbO 3 . BNBST-15KN exhibited a high permittivity of 3484 and low dielectric loss of 0.003 at 150 °C. Furthermore, Δ ε / ε 150 °C varied no more than 10% within the tmperature range of 30–297 °C, indicating an excellent dielectric temperature stability. The introduction of KNbO 3 gave rise to a large P m while P-E loops kept slim in shape. Therefore, the optimum energy-storage performance was realized in BNBST-15KN with an energy-storage density W rec of 1.32 J/cm 3 and energy-storage efficiency η of 82.5% at 95 kV/cm, accompanied with superior temperature stability and fatigue performance. The results demonstrated that BNBST- x KN system was a promising lead-free candidate for energy-storage applications. [ABSTRACT FROM AUTHOR]

High-performance ternary cobalt-based metal oxides, especially ZnCo 2 O 4 , have attracted increasing attention as promising electrode materials for supercapacitors. However, there are still great challenges for the as-reported ZnCo 2 O 4 materials, such as self-aggregation during repeated discharging-charging process and low packing density. To tackle the above issues, it is envisaged as an efficient strategy to combine the advantages of both hierarchical porous micro/nanostructures and self-supporting electrode to fabricate a free-standing hierarchical micro/nanostructured ZnCo 2 O 4 electrode. Herein we propose an efficient and simple synthetic strategy for the controllable synthesis of self-supporting hierarchical porous cactus-like ZnCo 2 O 4 material directly grown on Ni-foam using a facile hydrothermal method with post-calcination treatment. Furthermore, a growth mechanism is also proposed. The as-prepared cactus-like ZnCo 2 O 4 material possesses unique structural merits, such as hierarchical porous structures, large specific surface area, robust structural stability, and strong connections between the substrate and the ZnCo 2 O 4 active material. The unique cactus-like ZnCo 2 O 4 film electrode displayed excellent electrochemical performance, including a high specific capacity of 1115.7 F g−1 at 1 A g−1 and remarkable long cycle stability with 80.8% capacity retention after 30,000 cycles. A practical asymmetric supercapacitor (ASC) device was assembled using cactus-like ZnCo 2 O 4 and active carbon, which showed an excellent energy density of 35.4 Wh kg−1 at high power density of 160.1 W kg−1 and superior cycle stability (62.5% capacity retention after 30,000 cycles at 1 A g−1). All these results show that such hierarchical porous ZnCo 2 O 4 micro/nanostructured films are a promising candidate for high-performance supercapacitors for energy storage application. [Display omitted] • 3D hierarchical porous cactus-like ZnCo 2 O 4 film is grown on Ni foam. • A growth mechanism of the 3D cactus-like ZnCo 2 O 4 film is proposed. • The cactus-like ZnCo 2 O 4 electrode shows 80.8% capacitance retention after 30,000 cycles at 5 A g−1. • The ZnCo 2 O 4 @NF//AC asymmetric supercapacitor exhibits an excellent energy density and power density. [ABSTRACT FROM AUTHOR]

In order to hunt for the promising materials in energy-storage field, we prepared a series of compositions Bi 0.487 Na 0.427 K 0.06 Ba 0.026 TiO 3 - x CeO 2 (BNTC1000 x , x = 1.8, 2.2, 2.6, 3.0 wt%) by the solid–state reaction method. CeO 2 addition degraded the ferroelectricity of initial components and all these samples exhibited antiferroelectricity at room temperature. The optimum energy-storage density of 0.94 J/cm 3 was obtained at BNTC22 with the external electric field of 75 kV/cm. In addition, the energy-storage property not only possessed good temperature stability but also maintained high values over 0.81 J/cm 3 around 20–120 °C. These characteristics indicated that Bi 0.487 Na 0.427 K 0.06 Ba 0.026 TiO 3 - x CeO 2 system could be the promising lead-free materials for energy-storage capacitor application. The investigation on dielectric properties suggested that the dielectric relaxation behavior was involved in BNTC1000 x system and concerned with oxygen vacancy migration. [ABSTRACT FROM AUTHOR]

Large energy-storage density is observed in BaZrO (BZ)-modified 0.80BiNaTiO-0.20BiKTiO (BNBK) lead-free ferroelectric (FE) ceramics synthesized by conventional solid-state reaction. The energy-storage property of (1 − x)BNBK- xBZ has been investigated. Certain content of BZ can enhance the energy-storage property of BNBK by enhancing the breakdown strength. The largest energy-storage density W = 0.73 J/cm and efficiency of energy storage η = 0.75 at E = 70 kV/cm are achieved in the 0.96BNBK-0.04BZ, which is significantly higher than that of BNT-based and lead-containing FE materials reported. Its energy-storage density exhibits the superior thermal stability with temperature range of 30-100 °C. Those properties promise that the environmental friendly (1 − x)BNBK- xBZ ceramics are candidate for applications of energy-storage devices. [ABSTRACT FROM AUTHOR]

• MoO 3 film is synthesized on carbon cloth through an electrodeposition process. • The electrochemical behaviors of as-made electrode are systematically exploded. • The ASSCs was assembled with MoO 3 as both cathode and anode. • The 2.0 V ASSCs device shows an energy density of 78 Wh kg−1 at 1 kW kg−1. Herein, a MoO 3 film is directly synthesized on carbon cloth through a simple electrodeposition procedure with an annealing treatment. The clingy MoO 3 film on carbon cloth fibers can speedily transfer electrons by virtue of the superior electrical conductivity of carbon cloth, while the outspread MoO 3 film in the gap between the adjacent carbon cloth fibers can provide abundant channels for the diffusion of Li+. The electrochemical properties of the as-fabricated MoO 3 electrode working as the cathode and anode materials are systematically studied, respectively. The specific capacitances of the MoO 3 electrode within the potential ranges of 0–1.0 V and of −1.0 to 0 V are 603 and 835 F g−1 at 1 A g−1, respectively. The CV kinetic analysis reveals the surface capacitance-dominated charge storage mechanism for the MoO 3 electrode under different potential windows. Moreover, the energy density of the as-assembled 2.0 V MoO 3 //MoO 3 aqueous symmetric supercapacitor device can reach up to 78 Wh kg−1 at 1 kW kg−1. Notably, this device exhibits a brilliant lifespan with 98% storage retention after 8000 CV scans at 150 mV s−1. The ease of preparation and outstanding energy storage capability make this newly-assembled aqueous symmetric supercapacitor a highly potential candidate for practical applications. [ABSTRACT FROM AUTHOR]

The enhancement of potential window can be identified as one of the effective pathways to boost the energy density of supercapacitors to break the limitation of practical applications. NiCo 2 O 4 nanosheet networks grown on carbon cloth are prepared via a facile cathodic electrodeposition process with a post-annealing procedure. A neutral electrolyte of mixing 2 M LiSO 4 and 0.1 M CoSO 4 is employed to enlarge the potential window of the as-prepared NiCo 2 O 4 /CC electrode to 0–1.2 V (vs SCE), while the corresponding potential window in alkaline electrolyte is merely 0–0.5 V. Moreover, the NiCo 2 O 4 /CC electrode shows an excellent cycling stability of maintaining 129.7% after 10,000 cycles in neutral electrolyte. The quantitative CV kinetic analysis is carried out to explore the charge storage mechanism, manifesting that capacitive contribution is estimated as high as 64.7–81.8% at the sweep rate of 3–10 mV s−1. Results demonstrate that this neutral electrolyte can greatly boost the electrochemical characteristics of the NiCo 2 O 4 electrode and also provide the possibility of achieving better characteristics in the field of energy storage when applied in other battery-type materials. Image 1 • NiCo 2 O 4 nanosheet networks were prepared on carbon cloth. • The electrochemical behaviors were exploded in different electrolyte. • The potential window was enlarged to 0–1.2 V (vs SCE) in neutral electrolyte. • The NiCo 2 O 4 /CC electrode shows an excellent cycling stability. • The charge storage mechanism is confirmed via the kinetic analysis. [ABSTRACT FROM AUTHOR]

With the rapid development of portable, foldable, and wearable intelligent electronic systems, there is an increasing demand for energy storage devices with enhanced flexibility, reduced weight, and high performance. Therefore, the configurations of modern electronics have developed from three-dimensional bulks or two-dimensional thin films to superflexible one-dimensional fibers. Fiber-shaped supercapacitors (FSCs) are widely favored by scholars because of their advantages including quick charge/discharge, high power density, excellent cycle stability, portability, light weight, outstanding flexibility, weavability and favourable compatibility with human body. The energy storage performance of FSCs heavily relies on the fiber electrode materials. Among various electrode materials, metal oxides are widely researched by virtue of earth abundance, low cost, ease of preparation, environmental benignity, tunable nanostructures, and more importantly, ultrahigh theoretical specific capacitance. This article firstly comprehensively reviews the main research progress in the current development and application of high-performance metal oxides based FSCs from the design of active materials, configuration of devices, and the investigation of energy storage properties investigation. Meanwhile, the main issues severely restricting the performance improvement of metal oxides based FSCs are discussed, and the corresponding ideas and the specific methods to address these issues are discussed. Secondly, the influences of different types of fiber-shaped substrates, electrolytes as well as assembly methods on the performance of metal oxides based FSCs are also discussed. Ultimately, a brief conclusion is made, accompanied by comments on the future technological development directions in the field of metal oxides based FSCs. [ABSTRACT FROM AUTHOR]

Developing high performance and pollution-free energy storage devices is crucial for the development of the energy industry. The Sm(Mg 0.5 Ti 0.5)O 3 -modified (Bi 0.5 Na 0.5) 0.7 Sr 0.3 TiO 3 ((1- x)BNST– x SMT, x = 0.00–0.15)) relaxor ceramics were synthesized by using a traditional solid-state sintering method. The phase structure, microstructure, dielectric spectrum, and energy storage properties were studied. The x = 0.10 sample obtained an energy storage density of 4.33 J/cm3 under an electric field of 290 kV/cm, while the energy storage efficiency reached 80 %. In addition, the variation of energy storage density remains within ±4 % and the energy storage efficiency is above 80 % at a frequency of 1–100 Hz and a temperature of 25–120 °C, respectively, indicating that the x = 0.10 sample has good stability in both temperature and frequency. The energy storage decreases slightly with increasing temperature and frequency, which originates from the migration of intrinsic charge carriers and the weakening of the interaction force between cations and anions. In addition, the x = 0.10 sample exhibits good fatigue resistance, with little change in the ferroelectric loop after 105 cycles. This performance advantage indicates that the (1- x)BNST- x SMT ceramic systems have great potential in the field of high energy storage. [ABSTRACT FROM AUTHOR]

Ferroelectric ceramics have good piezoelectric and ferroelectric properties and can be used for energy storage equipment and actuators. Nevertheless, current research on dielectric capacitors has only focused on the energy storage density, but ignored efficiency. Moreover, conventional piezoelectric materials have a large strain hysteresis. In this work, (Al 0.5 Nb 0.5)4+ (AN) complex ions doped 0.7Bi 0.5 Na 0.5 TiO 3 -0.3Ba 0.3 Sr 0.7 TiO 3 (BNBST) ceramics were prepared. Doping AN destroyed the long-range ordered ferroelectric domains and generated polar nano regions, resulting in a gradual thinning and inclination of polarization hysteresis loops and an increase in relaxor degree. For BNBST-3AN ceramics, a W rec of 1.52 J/cm3 and a η of 92.1% were achieved at 150 kV/cm. Meanwhile, BNBST-3AN ceramics had good energy storage temperature stability and cycling performance. The AN doping reduced the strain hysteresis in BNBST ceramics. BNBST-2AN ceramics exhibited a longitudinal electrostrictive coefficient Q 33 ∼ 0.0292 m4/C2 and a field-induced strain of 0.25% with low strain hysteresis (6.67%). Furthermore, BNBST-4AN ceramics had superior dielectric temperature stability from 24 to 270 °C. All results show that BNBST-100 x AN ceramics have great promise for energy storage devices and actuators. [ABSTRACT FROM AUTHOR]

Transition metal oxide nanostructures are one of current investigation focuses for energy storage applications. We herein report a novel template-free electrochemical approach to fabricate Ni(OH) 2 /NiO/Ni composite nanotube array films on the nickel substrate. The inner diameter of the composite nanotubes can be effectively tuned by tailoring the concentration of Cu 2+ in the precursor solutions. The as-constructed composite nanotube array film electrode, which is fabricated by the electrochemical approach using the 0.1 M Cu 2+ containing precursor solution, delivers the specific capacitance of 1070 F g −1 at the current density of 15 A g −1 after 10,000 charge–discharge cycles. The specific capacitance of the cycled electrode at 150 A g −1 is as much as 79.3% of that at 15 A g −1 , demonstrating its excellent rate capability. The cycled electrode presents a high specific energy density of 31.4 Wh kg −1 at a larger power density of 11.1 kW kg −1 . The excellent pseudocapacitive performance of the Ni(OH) 2 /NiO/Ni composite nanotube array electrodes can be attributed to their unique structure characteristics. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectrics are promising candidates for energy storage equipment due to their excellent energy-storage properties. Lead-free (1- x)Bi 0.38 Na 0.38 Sr 0.24 TiO 3 - x BaSnO 3 (abbreviated as BNST-100 x BS) relaxor ceramics were synthesized by a traditional solid-phase sintering method. The influences of the addition of BaSnO 3 dopants for the energy storage and dielectric temperature-stable properties of BNST-100 x BS ceramics were systemically investigated. All samples exhibited a typical pseudo-cubic symmetry structure and obtained the dense microstructure. The ergodic relaxor behavior of all ceramics was observed and revealed a trend of increase as a function of composition. All samples showed a single grain conduction mechanism and the activation energy decreased with the addition of composition. It is related to the generation of oxygen vacancies induced by the defect dipoles. BNST-2.5BS ceramic exhibited an outstanding recoverable energy density of ~1.42 J/cm3 with the corresponding efficiency of ~79.7% at 115 kV/cm field. In addition, excellent temperature-stable permittivity (43–255 °C) was obtained for BNST-7.5BS ceramic. Hence, BNST-2.5BS ceramic revealed excellent energy density properties and BNST-7.5BS exhibited outstanding temperature-stable dielectric permittivity, which was beneficial to use in energy storage equipment and other device applications. [ABSTRACT FROM AUTHOR]

A series of novel Bi 0.38 Na 0.38 Sr 0.24 Ti (1- x) (Mn 1/3 Nb 2/3) x O 3 lead-free ceramics (BNST-100 x MN) were designed and fabricated. The dielectric, ferroelectric, energy-storage, electrostrain properties, and impedance performance of these materials were systematically investigated. A large strain response under low driving electric field was obtained that benefits from the enhanced relaxor-to-ferroelectric phase transition. The optimum piezoelectric stain coefficient d 33 * of 930 pm/V (under 40 kV/cm) was achieved in BNST-1MN composition. The substitution by MN dopant gave rise to a homogeneous micro-morphology with small grains that gave rise to an enhanced high breakdown strength (BDS). Slim and slanted ferroelectric hysteresis was obtained by introducing a larger amount of MN, and hence the BNST-2MN ceramic exhibits a high energy-storage density of 1.30 J/cm3 at 110 kV/cm, accompanied with an excellent fatigue-free behavior. The dielectric response exhibited a stable high temperature dielectric property with low dielectric loss. These results indicate that BNST-100 x MN ceramics are promising candidates for the actuator and energy storage applications. [ABSTRACT FROM AUTHOR]

The Na 0.325 Bi 0.395 Sr 0.245□0.035 TiO 3 + x % MnCO 3 (NBST-100 x Mn) lead-free ceramic samples had been fabricated by solid-state reaction method. Microstructure and electrical properties with the addition of MnCO 3 had been studied in detail. The NBST-4Mn showed a low hysteresis behavior with the maximum electrostrictive coefficient (Q) of 0.0294 m4/C2 and the recoverable energy storage density (W rec) of 1.3 J/cm3 at 95 kV/cm. In addition, the electrostrictive effect and energy storage ability presented outstanding temperature stability and fatigue resistance, which indicated a promising lead-free ceramic for high precise actuator. [ABSTRACT FROM AUTHOR]

Abstract Leed-free ferroelectric (1-x)(0.72Bi 0.5 Na 0.5 TiO 3 -0.28Bi 0.2 Sr 0.7□0.1 TiO 3)-xLa (NBST-xLa; x = 0, 0.5%, 1.5%, 2%) ceramics were synthesized using a conventional solid-state reaction method and the effect of La-doping on the microstructure and electrical properties was investigated. The introduction of La could reduce the grain size and improve the porosity of NBST ceramics. Temperature-dependent dielectric permittivity illustrated that the relaxation properties of NBST-xLa ceramics changed parabolically with the increase of La content. The introduction of La gave rise to a large dielectric breakdown strength and maximum polarization when x = 0.5%, which was attributed to the variation of the microstructure and the relaxation properties of NBST-xLa ceramics, respectively. The optimum effective energy storage density of 1.2 J/cm3 at 90 kV/cm was achieved when x = 0.5%. These results indicated that NBST-0.5%La ceramic may provide a practical perspective for energy storage ceramics research. Highlights • La-doped ceramics were synthesized using a solid-state reaction method. • The introduction of La gave rise to a large DBS and P max. • NBST-0.5%La possessed the optimum effective energy storage density. [ABSTRACT FROM AUTHOR]

Anti-ferroelectric materials with large saturated polarization, small remnant polarization, and moderate breakdown strength are receiving increasing attention for modern high-power electrical systems. Here we demonstrated that by incorporating CaZrO 3 into NaNbO 3 ceramics, the antiferroelectricity in NaNbO 3 -CaZrO 3 solid solutions could be stabilized at room temperature. The effects of phase constitution and microstructure on the dielectric properties, electrical breakdown strength, and energy storage properties of the NaNbO 3 -CaZrO 3 ceramics were investigated. Ferroelectric and antiferroelectric phase coexistence in the NaNbO3-CaZrO 3 was confirmed by XRD and TEM analyses. With increasing CaZrO 3 content, the grain size was reduced, and the dielectric breakdown strength was improved. Therefore, a high energy density of 0.55 J/cm 3 and efficiency of 63% was obtained in the NaNbO 3 -0.04CaZrO 3 ceramics. These lead-free NaNbO 3 -CaZrO 3 antiferroelectrics with good electrical energy storage can be exploited for high-power storage devices. [ABSTRACT FROM AUTHOR]

A series of (1- x )(0.7Bi 0.5 Na 0.5 TiO 3 -0.3Bi 0.2 Sr 0.7 TiO 3 )- x NaNbO 3 (BNT-BST-100 x NN) lead-free ceramics were fabricated using conventional solid-state reaction technique. The phase behavior, microstructure, dielectric, ac impedance and energy-storage properties of the sintered ceramics were systematically investigated. XRD patterns and surface SEM micrographs revealed the introduction of NaNbO 3 didn't change the perovskite structure of BNT-BST at low doping level. The NaNbO 3 doping gave rise to slimmer P - E loops and thus gained enhanced energy storage properties. Therefore, a maximum energy storage density of 1.03 J/cm 3 was achieved at 85 kV/cm at x = 0.01 via increasing the dielectric breakdown strength (DBS). Temperature-dependent dielectric permittivity illustrated the enhanced relaxor characteristics, implying the long-rang ferroelectric order was further damaged due to the introduction of NaNbO 3 . The results above indicate the sintered ternary ceramics can be a promising lead-free candidate for energy storage capacitors. [ABSTRACT FROM AUTHOR]

(1- x )BiTi 0.5 Zn 0.5 O 3 -x(0.935Bi 0.5 Na 0.5 TiO 3 -0.065BaTiO 3 ) (abbreviated as BTZx) lead-free ceramics were prepared by using a conventional solid state reaction method and their composition and temperature dependent energy-storage properties were investigated. The addition of BiTi 0.5 Zn 0.5 O 3 sharply decreased the content of ferroelectric phase, leading to lowered remanent polarization and coercive field. A large energy storage density (W) of 1.04 J cm −3 was achieved at 95 kV cm −1 for BTZ0.916. In the high temperature region, the remanent polarization was suppressed, while maximum polarization still maintained at a high level. Significantly enhanced W of ~0.952 J cm −3 at 80 kV cm −1 was obtained with a relatively high efficiency of ~0.8, making these materials attractive in energy storage applications. [ABSTRACT FROM AUTHOR]

The development of lead-free ceramics with high energy storage density is critical due to the human health and environmental hazards of lead and the demand to miniaturize and integrate electronic devices. Nevertheless, the high applied electric field limits their use in integrated circuits. In this work, (1- x) Bi 0.5 (Na 0.82 K 0.18) 0.5 Ti 0.99 (Y 0.5 Nb 0.5) 0.01 O 3 - x NaNbO 3 (BNKTYN-100 x NN) ceramics were prepared, and excellent energy storage properties were obtained. It has revealed that NaNbO 3 dopant reduces remanent polarization and increases relaxor degree. BNKTYN-9NN ceramics has high energy storage density (W rec =1.6 J/cm3) and responsivity (ξ = W rec / E = 145.5 J/(kV•m2)) under 110 kV/cm. Meanwhile, good temperature stability (20–120 °C) and fatigue resistance (105 cycles) were also obtained in BNKTYN-9NN ceramics. In addition, doping NaNbO 3 suppresses the dielectric anomaly peak, and BNKTYN-9NN ceramics has excellent temperature-stable dielectric permittivity from 53° to 447°C. These results suggest that BNKTYN-100 x NN ceramics are promising for energy storage equipment. • Using antiferroelectric NaNbO 3 to improve the energy storage performance of Bi 0.5 (Na 0.82 K 0.18) 0.5 TiO 3 -based ceramics. • A high W rec of 1.6 J/cm3 and η of 73.1 % at a lower electric field of 110 kV/cm were obtained in the x = 0.09 composition. • BNKTYN-9NN ceramics has outstanding dielectric temperature stability from 53 °C to 447 °C. [ABSTRACT FROM AUTHOR]

Lead-free (1- x)[(Bi 0.5 Na 0.5) 0.94 Ba 0.06 TiO 3 ]- x AgNbO 3 (abbreviated as BNTBT-100 x AN) ceramics were fabricated using a conventional solid-phase reaction technique. The effect of the antiferroelectric AgNbO 3 dopants for fatigue resistance, energy-storage density, temperature-stable permittivity, and conductivity mechanism was systematically investigated. The addition of AgNbO 3 led to the decrease of remnant polarization and the increase of dielectric breakdown strength, a large effective energy-storage density of ~1.27 J/cm3 corresponding to the conversion efficiency of ~ 77.5% for BNTBT-5AN ceramic were attained under applied 105 kV/cm field. Meanwhile, it exhibited an outstanding fatigue-resistant performance at 70 kV/cm fixed field up to 105 cycles accompanied with excellent temperature-stable properties in the temperature range of 30 °C ~ 120 °C. Besides, BNTBT-5AN sample has also obtained outstanding temperature-stable permittivity, which was associated with the enhancement of the ergodic relaxor domain structure. A little variance of dielectric content (Δ ε' / ε' 150 °C ≤ ± 15%) was acquired from 40 °C to 387 °C with a small tangent loss (tan δ ≤ 0.05) between 50 °C and 461 °C. Hence, it revealed that the high energy storage properties and excellent dielectric temperature stability for BNTBT-5AN ceramic were conducive to its better applications in electronic equipment. • A large effective energy-storage density of ~ 1.27 J/cm3 corresponding to the conversion efficiency of ~ 77.5% for x = 0.05 composition were attained under applied 105 kV/cm field. • BNTBT-5AN ceramic has also obtained outstanding temperature-stable permittivity, which was associated with the enhancement of the ergodic relaxor domain structure. • A little variance of dielectric content (Δ ε' / ε' 150 °C ≤ ± 15%) was acquired from 40 to 387 °C with a small tangent less (tan δ ≤ 0.05) between 50 °C and 461 °C for BNTBT-5AN ceramic. [ABSTRACT FROM AUTHOR]

The 0.94Bi 0.5 Na 0.5 TiO 3 –0.06BaTiO 3 (BNBT6) introduced by CaZrO 3 (CZ) lead-free ferroelectric ceramics are successfully fabricated by conventional solid state reaction. The influence of CZ substitution on the phase transition, microstructure, dielectric, ferroelectric, and energy storage properties of (1 − x)BNBT6-xCZ ceramics are systematically investigated. The energy-storage density 0.7 J/cm 3 under the electric field 70 kV/cm is obtained in the 0.97BNBT6-0.03CZ. In addition, its energy-storage property exhibits thermal stability at the temperature range of 30–130 °C. [ABSTRACT FROM AUTHOR]

• 3D NiCoFe-LDH nanosheet assembled nanospheres/nanoflowers are fabricated on carbon cloth via an electrodeposition method. • The growth pattern of NiCoFe-LDH nanosheet assembled nanospheres/nanoflowers on carbon cloth has been investigated. • NiCoFe-LDH electrode containing appropriate amount of Fe element delivers superior electrochemical properties. • The NiCoFe-LDH//AC HSC device shows high energy density and power density. [Display omitted] Although layered double hydroxides (LDHs), especially NiCo-based LDHs, have been verified to be a type of potential cathode material for supercapacitors with high specific capacity and electric conductivity, their lifespan and rate performance are still not satisfactory. Herein, a series of 3D NiCoFe-LDH samples with different molar ratio of Ni/Co/Fe are successfully fabricated on carbon cloth via an electrodeposition method. It is found that NiCoFe-LDH nanosheet assembled nanospheres/nanoflowers electrode delivers high specific capacity, electrical conductivity, and more importantly, more superior rate performance as well as cycle stability than pristine NiCo-LDH electrode without Fe introduction. Moreover, the as-assembled hybrid supercapacitor device with NiCoFe-LDH and activated carbon as the cathode and anode respectively displays a wide voltage window (0–1.5 V), large specific energy (65 W h kg−1 at the specific power of 83 W kg−1) together with an ultrahigh cycle stability (26% capacity increment after 5000 cycles). With the merits of ease to fabricate and outstanding energy storage property, the newly assembled hybrid supercapacitor delivers great potential for practical application in the near future. [ABSTRACT FROM AUTHOR]

• The doping of Li+ ion has an obvious influence on the strain and energy storage performance. • The TEM image and XPS spectra of O 1s for BNKTT-100xLi ceramics demonstrate the existence of PNRs and oxygen vacancies. • The maximum bipolar strain (S = 0.462%) and unipolar strain (S u = 0.443%) for x = 0.025 sample were obtained under 80 kV/cm, and its unipolar strain achieved 0.573% at 100 °C. • BNKTT-15Li ceramic exhibited outstanding energy storage performance with a recoverable energy density of 1.29 J/cm3 under applied 130 kV/cm field. The conventional solid reaction was used to synthesize (Na 0.8- x K 0.2 Li x) 0.5 Bi 0.5 Ti 0.985 Ta 0.015 O 3 (abbreviated as BNKTT-100 x Li) lead-free perovskite ceramics. The influences of Li+ ion doping for the relaxation mechanism and piezoelectric performances of all ceramics were systematically investigated. All ceramics exhibited a single perovskite structure, accompanied with a dense surface morphology and uniform element distributions. AC impedance spectroscopy showed the single grain conduction mechanism for all samples. The maximum bipolar strain (S = 0.462%) and unipolar strain (S u = 0.443%) for x = 0.025 sample were obtained under 80 kV/cm, and its unipolar strain achieved 0.573% at 100 °C. BNKTT-15Li ceramic exhibited outstanding energy storage performance with a recoverable energy density of 1.29 J/cm3 under applied 130 kV/cm field. It suggested that the excellent electro-strain and energy-storage properties for BNKTT-100 x Li ceramics could be widely applicable to electronic equipment. [ABSTRACT FROM AUTHOR]

• In the present work, oxygen vacancies are introduced into V 2 O 5 lattice for high performing aqueous zinc-ion battery. • The battery reaches an ultra-long cyclic duration of 620 h at 0.2 A g−1 without any significant capacity fading. • The oxygen-deficient V 2 O 5 possesses significantly higher specific capacity and better cyclic stability than pristine V 2 O 5. [Display omitted] Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted considerable attention for large-scale energy storage systems due to their high energy density, low cost, and inherent safety. However, ZIBs suffer from limited cyclic stability with the use of the current cathode materials (such as V 2 O 5) due to the strong electrostatic ion–lattice interactions with the diffusing divalent Zn2+, usually leading to a limited cyclic duration (<400 h). Herein, oxygen vacancies are introduced into V 2 O 5 lattice to promote Zn2+ diffusion kinetic, thus enhancing the storage capacity and Zn2+ (de)intercalation processes, so as to high reversibility. In this work, the oxygen-deficient V 2 O 5 displays improvements in electrochemical performances over the pristine V 2 O 5. The as-assembled Zn//oxygen-deficient V 2 O 5 battery shows an impressive stability of 90% capacity retention over 1000 cycles as compared to Zn//pristine V 2 O 5 with 59% capacity retention over 680 cycles at a current density of 2 A g−1. It is also able to attain a high reversible specific capacity of approximately 406 mAh g−1 at 0.1 A g−1, which is 33% higher as compared to the capacity of pristine V 2 O 5 (307 mAh g−1). More importantly, the Zn//oxygen-deficient V 2 O 5 battery reaches an ultra-long cyclic duration of 620 h at 0.2 A g−1 without any significant capacity fading, which is, to the best of our knowledge, one of the best cyclic performance reported for V 2 O 5 system. Thus, based on these encouraging results, harnessing oxygen vacancies in V 2 O 5 may help to further enhance the electrochemical performance of the cathodes towards high performing ZIBs. [ABSTRACT FROM AUTHOR]