Ultrahigh Energy Storage Research Articles

Synergistic optimization of antiferroelectric ceramics with superior energy storage properties via phase structure engineering

Dielectric capacitors with high energy storage density and high efficiency exhibit potential applications in lightweight, miniaturized microelectronic devices. Here, (Pb, La)(Zr, Sn)O3 (PLZS) based ceramics with Ba substitution were selected and studied with in-situ Raman spectra and in-situ synchrotron X-ray diffraction. Results show that the room temperature phase structure consists of two coexisting antiferroelectric phases of OI and OII (O refers to orthorhombic), and between them the latter possesses lower forward phase-switching electric field (EAF) and should be the origin of FE(I). Meanwhile, Polarization-electric field (P-E) loops and Raman spectrum under variable temperature reveal optimal Ba content of 0.02. Suitable Ba substitution forms balanced coexisting structure and therefore achieves ultrahigh recoverable energy storage density (Wrec) of 12.8 J/cm3 and simultaneously high energy storage efficiency (η) of 84.2% under an electric field of 450 kV/cm. Extremely short discharge period of 51.6 ns and high Wrec support ultrahigh power density (PD) of 327 MW/cm3 and high discharge current density (Ddis) of 1815 A/cm2. Reasonable phase structure design after clarifying the relationship between structure and performance shows guiding significance, and the improved ultra-high Wrec and PD enhance the possibility of applications of antiferroelectric ceramics in pulsed power capacitor.

Simultaneously with large energy density and high efficiency achieved in NaNbO3-based relaxor ferroelectric ceramics

Dielectric capacitors are in urgent need of miniaturized and lightweight products. The new lead-free NaNbO3-based ferroelectric ceramic material is a good choice owing to its high energy storage density, superior charge/discharge performance and decent frequency/temperature stability. In this work, a novel lead-free relaxor ferroelectric ceramic, (1-x)NaNbO3-xBa(Mg1/3Nb2/3)O3 [(1-x)NN-xBMN, x = 0.18, 0.20, 0.22 and 0.24], was designed and prepared via a local random field strategy. The impedance analysis demonstrates that the introduction of BMN could enhance the insulation ability and breakdown strength of the (1-x)NN-xBMN ceramic. Finally, the excellent energy storage performances with simultaneously ultrahigh energy storage density (Wst～4.04 J/cm3), recoverable energy storage density (Wrec～3.51 J/cm3), efficiency (η～87 %) and fatigue endurance (number of cycles: 5000) are obtained in the 0.78NN-0.22BMN ceramic. In addition, excellent frequency (1～100 Hz) and temperature stability (20～140 °C) can also be observed in the 0.78NN-0.22BMN ceramic. It is crucial that the ceramic shows extremely short charge-discharge time (t0.9～45 ns), tremendous current density (CD～680 A/cm2), giant power density (PD～47.6 MW/cm3) and excellent temperature stability (30～150 °C). These results indicate that 0.78NN-0.22BMN ceramic is a promising dielectric capacitor material.

Ultrahigh energy storage density and charge‐discharge performance in novel sodium bismuth titanate‐based ceramics

AbstractLead‐free ferroelectric ceramics are very suitable for electrostatic energy storage capacitors due to their outstanding characteristics of high charge‐discharge speed, high power density, and environmental friendliness. Herein, a novel material system as (1−x)Na0.5Bi0.5TiO3‐xCaZr0.5Ti0.5O3 (NBT‐CZT, x = 0, 0.05, 0.10, 0.12, 0.15, and 0.20) was designed and prepared for dielectric energy storage ceramics. It demonstrated that the CZT additives induced a phase transition for the NBT ceramics, from ferroelectric to relaxor ferroelectric. In particular, extremely high stored energy storage density (6.92 and 5.37 J/cm3), high recoverable energy storage density (4.77 and 4.37 J/cm3), and moderate efficiency (69.0% and 81.4%) were achieved in both the samples of x = 0.12 and x = 0.15, respectively. The ceramics exhibited excellent stability of energy storage performance covering a wide temperature (25°C–200°C) and frequency (0.5–50 Hz) range, and also fatigue cycles up to 105. Additionally, the NBT‐CZT ceramics had a fast discharge speed (t0.9 < 100 ns) and high power density (24.2 MW/cm3, E = 100 kV/cm, x = 0.15), and the charge‐discharge process remained stable even when the measured temperature was up to 160°C. Therefore, the NBT‐CZT ceramics have the potential to be utilized in electrostatic energy storage applications.

Novel NaNbO3–Sr0.7Bi0·2TiO3 lead-free dielectric ceramics with excellent energy storage properties

NaNbO3 (NN) is considered to be one of the most prospective lead-free antiferroelectric energy storage materials due to the merits of low cost, nontoxicity, and low density. Nevertheless, the electric field-induced ferroelectric phase remains dominant after the removal of the electric field, resulting in large residual polarization, which prevents NN ceramics from obtaining superior energy storage performance. In this work, the relaxor ferroelectric Sr0·7Bi0·2TiO3 (SBT) was chosen to partially replace the NN ceramics, and the introduction of the nanodomain of the relaxor ferroelectric hinders the generation of field-induced ferroelectric phases, allowing the material to combine the large polarization strength of the relaxor ferroelectric with the near-zero residual polarization of the antiferroelectric. Large recoverable energy storage density (4.5 J cm−3) and ultra-high energy storage efficiency (90.3%) were gained in NN-20SBT under an electric field of 288 kV cm−1. Furthermore, superior temperature (25–120 °C) and frequency (1–500 Hz) stabilities were acquired. These performances demonstrate that NN-20SBT ceramics are potential candidates as dielectric materials for high energy storage density pulsed power capacitors.

Ultrahigh and field-independent energy storage efficiency of (1-x)(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3-xBi(Mg0.5Ti0.5)O3 ceramics

Relaxor ferroelectrics are attracting an increasing interest in the application of pulse power systems due to their excellent energy storage performance. In this paper, the (1-x)(Ba0·85Ca0.15)(Zr0·1Ti0.9)O3-xBi(Mg0·5Ti0.5)O3 ((1-x)BCZT-xBMT, x ≤ 0.2) relaxor ceramics are prepared by the solid state method. The influence of BMT on the microstructure, dielectric and energy storage properties of the prepared ceramics is investigated. The XRD results show that the peak intensity of impurities (Bi2O3, TiO2 and Ba2Bi4Ti5O18) is gradually stronger than that of BCZT phase with x increasing. Meanwhile, the grain size of (1-x)BCZT-xBMT ceramics gradually increases on account of the appearance of impurities Bi2O3. Influenced by the impurities and BMT, the dielectric constant of prepared ceramics gradually decreases with x increasing. A large Wrec value of 0.65 J/cm3 with an ultrahigh η value of 97.89% is achieved at x = 0.15 due to the high breakdown strength and slim P-E hysteresis loop. Meanwhile, the η is insensitive to the electric field. The ultrahigh η leads to lesser energy loss during the charge and discharge process. It makes the 0.85BCZT-0.15BMT ceramic more attractive in the application of pulse power systems.

Giant energy storage density in lead-free dielectric thin films deposited on Si wafers with an artificial dead-layer

High-performance lead-free thin-film capacitors deposited on the silicon (Si) wafers with large energy storage density ( W ) and high reliability are strongly attractive in the modern electrical and electronic devices. Here, an ultrahigh W was achieved in the Ba 0.3 Sr 0.7 Zr 0.18 Ti 0.82 O 3 (BSZT) relaxor ferroelectric thin films deposited on the Si wafers with the help of an ultrathin Ca 0.2 Zr 0.8 O 1.8 (CSZ) artificial “dead-layer” simultaneously possessing high resistivity, wide band gap and high permittivity among linear dielectrics. As the CSZ was implanted, the W of the Ba 0.3 Sr 0.7 Zr 0.18 Ti 0.82 O 3 (BSZT) thin films was greatly increased from 64.9 J/cm 3 to 89.4 J/cm 3 , which is comparable to the best W of thin film deposited on expensive single crystal substrates, and is the largest one reported so far than those of lead-free thin films deposited on the Si wafers, and even for lead thin films. Due to the formation of ultrahigh electrons injection barrier (3.92 eV) between the interface of the CSZ dead layer and the Au top electrode, the Schottky emission of the BSZT thin films under high electric field and at high temperatures was effective suppressed, which is responsible for the greatly improved dielectric breakdown strength and thermal stability. Moreover, the fatigue endurance was also enhanced. It is concluded that the implantation of the CSZ artificial dead-layer could be used as a universal-simple-effective strategy to improve the electrical performances of ferroelectric materials working in the harsh environment of high electric field. With the help of an ultrathin Ca 0.2 Zr 0.8 O 1.8 artificial “dead-layer”, the energy storage properties of the BSZT thin films was greatly improved. The implantation of the new artificial dead-layer could be used as a universal-simple-effective strategy to improve the electrical performances of ferroelectric materials working in the high electric field. • High quality lead-free thin films deposited on Si wafers were obtained. • An ultrahigh energy storage density ( W ) on Si wafers ~ 89 J/cm 3 was achieved. • Artificial Dead-layer implantation benefits the enhancement of W and DBS. • Artificial Dead-layer implantation benefits the improvement of thermal stability and fatigue endurance. • High electrons injection barrier can suppress Schottky Emission.

Ultrahigh Energy Storage Characteristics of Sodium Niobate-Based Ceramics by Introducing a Local Random Field

Lead-free ceramic capacitors are widely applied for novel pulse power supply systems owing to their environmental friendliness, high power density and fast charge/discharge characteristics. Neverth...

Boosting up the capacitive energy storage performances of lead-free ceramics via grain engineering for pulse power applications

Exploring high-performance ceramics has been a great challenge for advanced electronic devices due to their limited capacitive energy storage densities in high-voltage pulse applications. The refinement of the microstructures can considerably optimize energy storage performances of dielectric ceramics by tailoring dielectric breakdown. Here, two-step sintering was employed to refine the microstructures of the lead-free 2.0 mol% Mn-doped 0.55 (0.94Na0.5Bi0.5TiO3-0.06BaTiO3)-0.45SrTiO3 bulk ceramics to offer the possibility of increasing energy storage performances. Compared with conventional sintering, fine grains by two-step sintering can be obtained, resulting in the obviously enhanced dielectric breakdown due to the increased fraction of grain boundary and the suppressed movement of domain walls. An ultrahigh charge energy storage density of 2.98 J/cm3 with a moderate efficiency (η) of 73.1% can be achieved at 28 kV/mm, accompanying with excellent temperature insensitivity in a wide range from 30 to 180 °C compared with the previous Na0.5Bi0.5TiO3-based derivatives. This work presented here strongly indicates that two-step sintering is a promising way to optimize the microstructural morphology and electrical performances of dielectric ceramics.

Energy storage and dielectric properties of a novel Bi1.5MgNb1.5O7-Bi2Mg2/3Nb4/3O7 thin film

Lead-free Bi1.5MgNb1.5O7-Bi2Mg2/3Nb4/3O7 (BMN1.5-BMN2) thin films have been deposited on Pt/Ti/SiO2/Si substrates by RF magnetron sputtering. A very low loss tangent of ~0.005 with a high dielectric constant of 158 is achieved in a BMN1.5-BMN2 thin film annealed in an oxygen pressure of 0.03 MPa. The BMN1.5-BMN2 thin film possesses superior energy storage properties due to its slim P-E loops, large maximum polarization (Pmax~36.97 μC/cm2) and high charge storage density (Pmax-Pr~32.25 μC/cm2), with an energy storage density of 40.59 J/cm3 and an energy conversion efficiency of 61.67% at 2.91 MV/cm. The energy storage density is superior to other the reference ferroelectric thin films. In addition, the BMN1.5-BMN2 thin film exhibits a large power density of 16.34 MW/cm3 due to the low dielectric loss. More importantly, BMN1.5-BMN2 as a new system provides new ideas for the design of lead-free linear dielectrics with ultrahigh energy storage density, indicating it is a very promising candidate for electrostatic energy storage capacitors.

Microstructure induced ultra-high energy storage density coupled with rapid discharge properties in lead-free Ba0.9Ca0.1Ti0.9Zr0.1O3–SrNb2O6 ceramics

Novel lead-free (1-x)Ba0·9Ca0·1Ti0·9Zr0·1O3-xSrNb2O6 ceramics were synthesized via a two-step high energy ball milling process. The evolution of microstructural properties, phase transformation, and energy storage characteristics was comprehensively investigated to assess the applicability of material in multi-layered ceramic capacitors. The substitution of SrNb2O6 (SNO) in Ba0·9Ca0·1Ti0·9Zr0·1O3 (BTCZ) has resulted in substantial improvement in materials density along with a small increase in the grain size of the synthesized ceramic. A thorough microstructural investigation indicates an excellent dispersibility and compatibility between BTCZ and SNO phases. With an increase in SNO substitution, a transition from typical ferroelectric to relaxor ferroelectric has been observed, which has led to a significantly slimmer ferroelectric loop along with frequency dispersive dielectric properties. The optimized composition (i.e., x = 0.10) exhibits an ultra-high recoverable energy density of 2.68 J/cm3 along with a moderately high energy efficiency of 83.4%. Further, SNO substituted samples have also shown an enhancement in breakdown strength. The improvement in energy storage performance and breakdown strength of SNO substituted BTCZ composites are mainly attributed to relatively homogeneous grain morphology, optimum grain size, microstructural density, and improved grain boundary interface.

Achieving ultrahigh energy storage density in NaNbO3–Bi(Ni0.5Zr0.5)O3 solid solution by enhancing the breakdown electric field

Developing high-energy storage materials is essential for the miniaturization and integration of electronic components. Traditional dielectric ceramics have drawbacks such as low energy storage and complex composition. One of the most effective methods to enhance the energy storage characteristics of dielectrics is to increase their breakdown field strength. In this study, lead-free (1-x)NaNbO3-xBi(Ni0.5Zr0.5)O3 [(1-x)NN-xBNZ] ceramics with high recoverable energy storage density (Wrec) were fabricated by secondary solid-state sintering method. The BNZ was integrated into the NN as a secondary component to restrict the growth of grain and enhance the breakdown field strength. Ultimately, an excellent Wrec of 4.90 J/cm3 and an ultrahigh breakdown field strength (Eb) of 500 kV/cm were obtained for the 0.88NN-0.12BNZ ceramic, which is related to the non-equivalent substitution of the B site. In addition, the sample remained notably stable at the test temperatures ranging from 20 °C to 120 °C and frequencies ranging from 10 Hz to 100 Hz. Excellent charge-discharge performances with high power density (PD = 41.2 MW/cm3) and a large current density (CD = 588.9 A/cm2), as well as an ultrafast discharge speed (60 ns) were obtained. All the aforementioned properties are potential conditions for high performance energy storage electronic ceramics.

Controlled synthesis of a high-performance α-NiS/Ni3S4 hybrid by a binary synergy of sulfur sources for supercapacitor

Nickel sulfide possesses ultra-high theoretical energy storage capacity. Though it is easily obtained, it is very difficult to exert its intrinsic strong capacity. In this work, a new strategy based on a binary synergy of sulfur sources is introduced. By regulating the molar ratio of two sulfur sources, a high-performance α-NiS/Ni3S4 binary hybrid is successfully synthesized. Interestingly, it is found that changing the molar ratio of two sulfur sources in hydrothermal process can efficiently regulate the components of product but cannot visibly affect its morphology. The electrochemical results indicate that this strategy is highly effective for improving the performance of nickel sulfide. As a result, a highest specific capacity of 214.9 mAh g−1 at 2 A g−1 was reached. In addition, the fabricated S3//rGO hybrid supercapacitor displays a highest energy density of 41.9 Wh kg−1 at a power density of 799.0 kW kg−1. Moreover, the device delivers an excellent cycle stability with 103% capacity retention rate after 10,000 cycles. These findings open a new avenue for the controlled synthesis of high-performance nickel sulfides or other metal sulfides.

Fabrication of three-dimensionally heterostructured rGO/WO3·0.5H2O@Cu2S electrodes for high-energy solid-state pouch-type asymmetric supercapacitor

Advanced nanostructured electrodes containing more electroactive sites are essential to develop the high rate performance supercapacitors (SCs). Herein, we engineered two-dimensional (2D) reduced graphene oxide (rGO) on the diamond-like cubic tungsten oxide (WO3·0.5H2O), which was further decorated with the plant-like monoclinic copper sulfide (Cu2S) to form a three-dimensionally (3D) heterostructured rGO/WO3·0.5H2O@Cu2S electrode using a simple two-step hydrothermal method. This electrode exhibited a 1.5-fold higher areal capacitance of 545.6 mF cm−2 (974.4 F g−1) over the WO3·0.5H2O based electrode in the redox active Na2SO4:K4[Fe(CN)6] electrolyte. Meanwhile, the asymmetric pouch-type solid-state supercapacitor (APSC) was successfully operated at a high potential of 2 V with an excellent areal capacitance of 235.4 mF cm−2 (269 F g−1) at 5 mV s−1, an energy density of 32.6 μWh cm−2 (37.3 Wh kg−1), cycling stability of 88% over 10,000 rapid charging/discharging cycles and a short relaxation time of 0.084 s at a frequency of 11.9 Hz. In addition, the density functional theory (DFT) simulations were used to explore the origin of the superb performance. It is found that the nanosheet-state graphene at the interface of WO3·0.5H2O and Cu2S could create the fast-electronic pathway, shorten the diffusion distance and give structural reliability. This novel strategy is expected to offer an effective way to develop new-generation supercapacitors with ultra-high energy storage ability.

Metal Ti quantum chain-inlaid 2D NaSn2(PO4)3/H-doped hard carbon hybrid electrodes with ultrahigh energy storage density

We report the development of a new hybrid electrode that allows for a reinforcing combination of different energy storage mechanisms, providing enhanced energy and power densities. This hybrid electrode is composed of chain-like metal titanium (zero valency state) quantum dots (<10 nm), two-dimension NaSn2(PO4)3 layer and H-doped hard carbon layer, and possesses unique sandwich and hierarchically meso-macroporous structures. These chain-like quantum dots are inlaid on the edge of ultra-thin NaSn2(PO4)3 nanosheets by using a convenient and economic method, enhancing its conductivity. This design takes advantage of the unique properties of each component and nanostructure, resulting in synergistic effects to improve the charge transfer and energy storage. The hybrid electrode not only shows high capacity, outstanding rate performance and long cycling stability, but also matches well with porous Na3V2(PO4)3 cathode. Remarkably, the Na/Li mixed-ion full battery exhibits significant improvements on the energy and power densities (555 Wh Kg−1/804 W Kg−1 at 1C). Detailed charge storage mechanism investigation reveals that the prelithiation reduces the pseudocapacitive of hybrid electrode and increases its battery behavior, resulting in an ultrahigh energy storage density. Our findings demonstrate that this hybrid electrode is a new potential candidate for high-performance mixed-ion batteries.

Fatigue‐Free Aurivillius Phase Ferroelectric Thin Films with Ultrahigh Energy Storage Performance

AbstractDielectric capacitors have become a key enabling technology for electronics and electrical systems. Although great strides have been made in the development of ferroelectric ceramic and thin films for capacitors, much less attention has been given to preventing polarization fatigue, while improving the energy density, of ferroelectrics. Here superior capacitive properties and outstanding stability are reported over 107 charge/discharge cycles and a wide temperature range of −60 to 200 °C of ferroelectric Aurivillius phase Bi3.25La0.75Ti3O12‐BiFeO3 (BLT‐BFO), which represents one of the best capacitive performances recorded for the ferroelectric materials. The modification of BLT thin films with BFO overcomes the constraints of ferroelectric Aurivillius compounds and presents an unprecedented combination of the ideal features including improved polarization, reduced ferroelectric hysteresis, and lowered leakage current for high‐energy‐density capacitors. Given the lead‐free and fatigue‐free nature of this Aurivillius phase ferroelectric, this work unveils a new approach towards high‐performance eco‐friendly ferroelectric materials for electrical energy storage applications.

Effective Strategy to Achieve Excellent Energy Storage Properties in Lead-Free BaTiO3-Based Bulk Ceramics.

Although extensive studies have been done on lead-free dielectric ceramics to achieve excellent dielectric behaviors and good energy storage performance, the major problem of low energy density has not been solved so far. Here, we report on designing the crossover relaxor ferroelectrics (CRFE), a crossover region between the normal ferroelectrics and relaxor ferroelectrics, as a solution to overcome the low energy density. CRFE exhibits smaller free energy and lower defect density in the modified Landau theory, which helps to obtain ultrahigh energy density and efficiency. The (1-x)Ba0.65Sr0.35TiO3-xBi(Mg2/3Nb1/3)O3 ((1-x)BST-xBMN) (x = 0, 0.08, 0.1, 0.18, 0.2) ceramic was synthesized by a solid-state reaction method. The solid solutions exhibit dielectric frequency dispersion, which suggests typical relaxor characteristics with the increasing BMN content. The crossover ferroelectrics of 0.9BST-0.1BMN ceramic possesses a high energy storage efficiency (η) of 85.71%, a high energy storage density (W) of 3.90 J/cm3, and an ultrahigh recoverable energy storage density (Wrec) of 3.34 J/cm3 under a dielectric breakdown strength of 400 kV/cm and is superior to other lead-free BaTiO3 (BT)-based energy storage ceramics. It also exhibits strong thermal stability in the temperature range from 25 to 150 °C under an electric field of 300 kV/cm, with the fluctuations below 3% and with the energy storage density and energy efficiency at about 2.8 J/cm3 and 82.93%, respectively. The enhanced recoverable energy density and breakdown strength of BT-based materials with significantly high energy efficiency make it a promising candidate to meet the wide requirements for high power applications.

Ultrahigh energy storage performance and fast charge-discharge capability in Dy- modified SrTiO3 linear ceramics with high optical transmissivity by defect and interface engineering

The excellent energy storage and pulse charge-discharge performance ceramics with high temperature stability and optical transmissivity are competitive for the development of electronic devices. In this work, comprehensive improved performances are simultaneously realized in DyxSr1-xTiO3 (DST) ceramics through defect and interface engineering. Meanwhile, increased high insulation grain boundary and reduced carrier mobility promote the increase of grain boundary resistance, and the increase of grain resistance primarily originates from the fact that DyTi' can easily attract oxygen vacancy, forming defect dipoles and restraining the movement of oxygen vacancies. Additionally, the relative density of ceramics is increased by sintering in O2 and doping Dy ions. Hence, x = 0.008 ceramics exhibit high coverable energy storage density of 4.00 J/cm3, high energy storage efficiency of 89.49%, excellent frequency (1Hz-1 kHz) and temperature stability (20-120 °C) and transmittance of >60% are achieved at 510 kV/cm at 0.2 mm. Furthermore, x = 0.008 ceramics possess the prominent current density of 420.1 A/cm2 and the prominent power density of 19.2 MW/cm3. Meanwhile, the short discharge rate of 20 ns and excellent stability of temperature (20-120 °C) are also achieved, suggesting that it is one candidate with strong potential for the application of lead-free high power capacitors.

Ultrahigh-Energy Storage Properties of (PbCa)ZrO3 Antiferroelectric Thin Films via Constructing a Pyrochlore Nanocrystalline Structure.

In recent years, antiferroelectric materials have been attracting considerable attention as energy storage capacitors due to their potential applications in pulsed power systems. In this work, antiferroelectric Pb0.88Ca0.12ZrO3 (PCZ) thin films were prepared via chemical solution deposition and annealed using rapid thermal annealing. The microstructures of PCZ thin films were controlled via annealing temperature, and the effects of microstructures on electric properties and energy storage performance were systematically studied. Our results indicate that PCZ thin films annealed at 550 °C crystallized into a nanocrystalline structure of the pyrochlore phase, while also displaying the highest recoverable energy density and efficiency (91.3 J/cm3 and 85.3%). We attribute the ultrahigh energy storage properties mainly to dramatic improvements in the electric breakdown strength caused by the dense nanocrystalline structure. The findings reported herein help to elucidate the relationship between energy storage performance and thin-film microstructure, thereby providing an effective way for improving the energy storage performance of antiferroelectric thin films.

Simultaneously achieved high energy storage density and efficiency in sol-gel-derived amorphous Mn-doped SrTiO3 thin films

Recently, dielectric energy storage capacitors obtain extensive attention and become a research hotspot owing to the high power density and ultrafast charge/discharge speed, while their applications are limited because of low energy storage density. Here, 1% Mn doped SrTiO3 (ST) thin films with different microstructure were prepared by modulating annealing temperature to optimize the energy storage performance. The X-ray diffraction analysis shows that the ST thin films annealed below 600 °C are amorphous structure while the thin film annealed at 700 °C is polycrystalline. The dielectric properties of amorphous ST thin films show outstanding frequency stability, electric field stability and temperature stability. The electric breakdown strength and discharge energy storage density of the thin films improve first, and then reduce with the annealing temperature. The optimal energy storage performance is obtained in ST thin film annealed at 550 °C: an ultrahigh discharge energy storage density of 53.9 J/cm3 with high efficiency of 77.2% at 4.541 MV/cm. It reveals that amorphous ST thin film is promising as dielectric energy storage devices in pulse power fields.

Design on polarization distribution in all-organic polymer hybrids for high density energy storage

Polymer-based dielectric capacitors have attracted increasing attention in advanced electronics and pulsed power systems due to their high power density and ultrafast charge–discharge speed. However, most of recent achievements focus on polymer-based nanocomposites employing high-k inorganic nanofillers, generating mismatched filler/matrix interfaces that need careful modification. Herein, all-organic hybrid polymers have been explored to achieve ultrahigh energy storage density. Ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) with large polarization was introduced into poly(vinylidene fluoride) (PVDF) with smaller polarization forming blend films, and next sandwich structures constructed by PVDF and P(VDF-TrFE)/PVDF blend films were elaborately designed. A high discharge energy density (Ue) of 23.6 J/cm3 at 636 MV/m has been achieved in 30/70 (volume ratio) P(VDF-TrFE)/PVDF blend film, which is 55% and 130% higher than that of PVDF and P(VDF-TrFE), respectively. Further, by designing sandwich structured all-organic films with 50/50 (volume ratio) P(VDF-TrFE)/PVDF blend film as middle layer to provide high electric displacement and PVDF as two outer layers to withstand high electric field, high Ue = 20–24 J/cm3 and charge–discharge efficiency (>65%) have been achieved. In-depth understanding on the microscopic mechanism for achieving high Ue is gained via finite element analysis showing that the volume fraction of ferroelectric phase in the hybrid system and the mesoscopic layer/layer interfaces are crucial. This work thus provides a promising alternative strategy for high-density energy storage via all-organic films design.