Improved Breakdown Strength in(Ba_(0.6)Sr_(0.4))_(0.85)Bi_(0.1)TiO_3 Ceramics with Addition of CaZrO_3 for Energy Storage Application

（Ba（0.6） Sr（0.4））（0.85） Bi（0.1） TiO3 ceramics doped with x wt%CaZrO3（x= 0-10） were synthesized by solid-state reaction method. The effects of CaZrO3 amount on the dielectric properties and structure of（Ba（0.6）Sr（0.4））（0.85） Bi（0.1） TiO3 ceramics were investigated. X-ray diffraction results indicated a pure cubic perovskite structure for all samples and that the lattice parameter increased till x=5 and then slightly decreased. A homogenous microstructure was observed with the addition of CaZrO3. Dielectric measurements revealed a relaxor-like characteristic for all samples and that the diffusivity γ reached the maximum value of 1.78 at x=5. With the addition of CaZrO3, the dielectric constant dependence on electric field was weakened, insulation resistivity enhanced and dielectric breakdown strength improved obviously and reached 19.9 k V/mm at x=7.5. In virtue of low dielectric loss（tan d〈0.001 5）, moderate dielectric constant（er 〉1 500） and high breakdown strength（Eb 〉17.5 k V/mm）, the CaZrO3 doped（Ba（0.6）Sr（0.4））0.85 Bi（0.1） TiO3 ceramic is a potential candidate material for high power electric applications.

Excellent thermal stability and high energy storage performances of BNT-based ceramics via phase-structure engineering

Herein,a novel strategy for regulating the phase structure was used to significantly enhance the recoverable energy storage density(Wrec)and the thermal stability via designing the(1-x)[(Bi_(0.5)Na_(0.5))_(0.7)Sr_(0.3)TiO_(3)]-xBiScO_(3)((1-x)BNST-xBS)relaxor ferroelectric ceramics.The incorporation of BS into BNST ceramics markedly increases the local micro-structure disorder,causing a high polarization and inhibiting polarization hysteresis for 0.95BNST-0.05BS ceramics,leading to a large Wrec of 5.41 J/cm^(3)with an ideal efficiency(h)of 78.5%.Meanwhile,transmission electron microscope(TEM)results further proved that the nano-domain structure and the tetragonal(P4bm)phase superlattice structure of 0.95BNST-0.05BS ceramics possess an excellent thermal stability(20-200℃).An outstanding Wrec value of 3.18×(1.00±0.03)J/cm^(3)and an h value of 74.500±0.025 are achieved under a temperature range from 20℃to 200℃.This work provides a promising method for phase-structure design that can make it possible to apply temperature-insensitive ceramic dielectrics with a high energy storage density in harsh environments.

Novel lead-free NaNbO_(3) -based relaxor antiferroelectric ceramics with ultrahigh energy storage density and high efficiency

The development of environmentally friendly ceramics for electrostatic energy storage has drawn growing interest due to the wide application in high power and/or pulsed power electronic systems.However,it is difficult to simultaneously achieve ultrahigh recoverable energy storage density(W rec>8 J/cm^(3))and high efficiency(η>80%),which restricts their application in the miniaturized,light weight and easy integrated electronic devices.Herein,the novel NaNbO_(3)-(Bi_(0.8)Sr_(0.2))(Fe_(0.9) Nb_(0.1))O_(3) relaxor antiferro-electric ceramics,which integrates the merits of antiferroelectrics and relaxors,are demonstrated to exhibit stabilized antiferroelectric phase and enhanced dielectric relaxor behavior.Of particular impor-tance is that the 0.88NN-0.12BSFN ceramic achieves giant electric breakdown strength E_(b)=98.3 kV/mm,ultrahigh W _(rec)=16.5 J/cm^(3) and high h=83.3%,as well as excellent frequency,cycling and thermal reliability simultaneously.The comprehensive energy storage performance of NN-BSFN not only out-performs state-of-the-art dielectric ceramics by comparison,but also displays outstanding potential for next-generation energy storage capacitors.

Optimizing the grain size and grain boundary morphology of (K,Na) NbO_(3)-based ceramics: Paving the way for ultrahigh energy storage capacitors

Relaxor dielectric ceramic capacitors are very attractive for high-power energy storage.However,the low breakdown strength severely restricts improvements to the energy storage density and practical application.Here,a strategy of designing small grain sizes and abundant amorphous grain boundaries is proposed to improve the energy storage properties under the guidance of phase field theory.0.925(K_(0.5)Na_(0.5))NbO_(3)-e0.075Bi(Zn_(2/3)(Ta_(0.5)Nb_(0.5))1/3)O_(3)(KNNe-BZTN)relaxor ferroelectric ceramic is taken as an example to verify our strategy.The grain sizes and grain boundaries of the KNNeBZTN ceramics are carefully controlled by the high-energy ball milling method and twoestep sintering strategy.Impedance analysis and diffusion reflectance spectra demonstrate that KNNeBZTN ceramics with a small grain size and abundant amorphous grain boundary exhibit a lower charge carrier concentration and higher band gap.As a consequence,the breakdown electric field of KNNeBZTN ceramics increases from 222 kV/cm to 317 kV/cm when the grain size is decreased from 410 nm to 200 nm,accompanied by a slightly degraded maximum polarization.KNNeBZTN ceramics with an average grain size of~250 nm and abundant amorphous grain boundaries exhibit optimum energy storage properties with a high recoverable energy density of 4.02 J/cm^(3) and a high energy efficiency of 87.4%.This successful local structural design opens up a new paradigm to improve the energy storage performance of other dielectric ceramic capacitors for electrical energy storage.

Enhanced energy-storage performance in BNT-based lead-free dielectric ceramics via introducing SrTi_(0.875)Nb_(0.1)O_(3)

Environmentally friendly lead-free ceramics capacitors,with outstanding power density,rapid charging/discharging rate,and superior stability,have been receiving increasing attention of late for their ability to meet the critical requirements of pulsed power devices in low-consumption systems.However,the relatively low energy storage capability must be urgently overcome.Herein,this work reports on leadfree SrTi_(0.875)Nb_(0.1)O_(3)(STN)replacement of(Bi_(0.47)La_(0.03)Na_(0.5))_(0.94)Ba_(0.06)TiO_(3)(BLNBT)ferroelectric ceramics with excellent energy storage performance.Improving relaxor behaviour and breakdown strength(Eb),decreasing grain size,and mitigating large polarization difference are conductive to the enhancement of comprehensive energy storage performances.The phase-field simulation methods are further analysized evolution process of electrical tree in the experimental breakdown.In particular,the 0.70BLNBT-0.30STN ceramic exhibit a large discharged energy density of 4.2 J/cm^(3) with an efficiency of 89.3%at room temperature under electric field of 380 kV/cm.Additionally,for practical applications,the BLNBT-based ceramics achieve a high power density(~62.3 MW/cm^(3))and fast discharged time(~148.8 ns)over broad temperature range(20-200℃).Therefore,this work can provide a simple and effective guideline paradigm for acquiring high-performance dielectric materials in low-consumption systems operating in a wide range of temperatures and long-term operations.

Structure,dielectric properties of low-temperature-sintering BaTiO3-based glass–ceramics for energy storage

The 0.85BaTiO3–0.15Bi(Mg_(2/3)Nb_(1/3))O_(3)(BTBMN)ceramics with low-melting-temperature B_(2)O_(3)–Na_(2)B_(4)O_(7)–Na_(2)SiO_(3)(BNN)glass addition were prepared by the solid state method.The composition of the glass–ceramics was BTBMN–x wt.%BNN(x=0,1,3,5,7,9,12,15;abbreviated as BG).The sintering characteristics,phase structure,microstructure,dielectric properties and energy storage properties were systematically investigated.The sintering temperature of BTBMN ceramics was greatly reduced by the addition of BNN glass.The second-phase BaTi(BO_(3)T_(2)was observed in the BG system until the glass content reached 15 wt.%.The addition of BNN glass significantly reduces the grain size of BTBMN ceramics.With the increase of BNN glass content,dielectric constant of BG glass–ceramics at 1 kHz gradually decreased,the maximum dielectric constant("mT of BG glass–ceramics gradually decreased,while the temperature corresponding to the maximum dielectric constant(T_(m)T increased,the ferroelectric relaxation behavior decreased and the temperature stability of the dielectric constant gradually improved.As the BNN glass content increased,the breakdown electric field strength(BDS)of BG glass–ceramics increased first and then decreased,and the polarization values reduced gradually,while the trend of energy storage performance is similar to BDS.When the BNN glass content was 3 wt.%,the energy storage properties of the BG glass–ceramics were optimal,and a recoverable energy storage density(Wrec)of 1.26 J/cm^(3)and an energy storage efficiency(η)of 80.9%were obtained at the electric field strength of 220 kV/cm.The results showed that BG glass–ceramics were promising for energy storage capacitors.

A facile one-step approach to hierarchically assembled core-shell-like MnO2@MnO2 nanoarchitectures on carbon fibers： An efficient and flexible electrode material to enhance energy storage

Hierarchical core-shell-like MnO2 nanostructures （NSs） were used to anchor MnO2 hexagonal nanoplate arrays （HNPAs） on carbon cloth （CC） fibers. The NSs were prepared by a novel one-step electrochemical deposition method. Under an external cathodic voltage of -2.0 V for 30 min, hierarchical core-shell-like MnO2-NS-decorated MnO2 HNPAs （MnO2 NSs@MnO2 HNPAs） were uniformly grown on CC with reliable adhesion. The phase purity and morphological properties of the samples were characterized by various physicochemical techniques. At a constant external cathodic voltage, growth of MnO2 NSs@MnO2 HNPAs on CC was carried for different time periods. When utilized as a flexible, robust, and binder-free electrode for pseudocapacitors, the hierarchical core-shell-like MnO2 NSs@MnO2 HNPAs on CC showed clearly enhanced electrochemical properties in 1 M Na2SO4 electrolyte solution. The results indicate that the MnO2 NSs@MnO2 HNPAs on CC have a maximum specific capacitance of 244.54 F/g at a current density of 0.5 A/g with excellent cycling stability compared to that of bare MnO2 HNPAs on CC （112.1 F/g at 0.5 A/g current density）. We believe that the superior charge storage performance of the pseudocapacitive electrode can be mainly attributed to the hierarchical MnO2 NSs@MnO2 HNPAs building blocks that have a large specific surface area, offering additional electroactive sites for efficient electrochemical reactions. The facile and single-step approach to growth of hierarchical pseudocapacitive materials on textile based electrodes opens up the possibility for the fabrication of high-performance flexible energy storage devices.

Enhancing lithium-sulfur battery performance with In_(2)O_(3)-In_(2)S_(3)@NSC heterostructures:Synergistic effects of double barrier and catalytic transformation

The sluggish redox reaction kinetics of lithium polysulfides(LiPSs)are considered the main obstacle to the commercial application of lithium-sulfur(Li-S)batteries.To accelerate the conversion by catalysis and inhibit the shuttling of soluble LiPSs in Li-S batteries,a solution is proposed in this study.The solution involves fabrication of N,S co-doped carbon coated In_(2)O_(3)/In_(2)S_(3)heterostructure(In_(2)O_(3)-In_(2)S_(3)@NSC)as a multifunctional host material for the cathode.The In_(2)O_(3)-In_(2)S_(3)@NSC composite can reduce the Gibbs free energy for the conversion reactions of LiPSs,which results in superior performance.The synergy between different components in In_(2)O_(3)-In_(2)S_(3)@NSC and the unique 3D structure facilitate ion and electron transport in Li-S batteries.The In_(2)O_(3)-In_(2)S_(3)@NSC/Li 2 S 6 cathode exhibits excellent rate capacity,with a capacity of 599 mAh g−1 at 5.5 C,and good cycle stability,with a capacity of 436 mAh g^(−1)after 1000 cycles at 1 C.Overall,this study proposes a promising solution to improve the energy storage properties of Li-S batteries,which could potentially facilitate the commercialization of Li-S batteries.