Recoverable Energy Storage Density Research Articles

Enhanced Energy Density and Efficiency in Lead‐Free Sodium Niobate‐Based Relaxor Antiferroelectric Ceramics for Electrostatic Energy Storage Application

AbstractAntiferroelectric ceramics are recently, a research hotspot for electrostatic energy storage because of their large electric‐field induced polarization. Lead‐free sodium niobate (NaNbO3)‐based ceramics are one of the emerging antiferroelectric counterparts. However, the unstable antiferroelectric phase seriously restricts the further improvement of energy density and efficiency. In this work, by introducing binary perovskite end‐member BiFeO3–BaTiO3 with lower tolerance factor and average electronegativity into NaNbO3 ceramics, the stablized antiferroelectric phase with improved relaxation characteristic is identified by slim double‐like polarization‐electric field (P–E) loops and four‐peak current–electric field (I–E) curves. Meanwhile, the antiferroelectric P to R phase transition is verified through Raman spectra, X‐ray diffraction (XRD) patterns, and dielectric performance. In particular, the enhanced electric breakdown strength Eb is achieved by synergic contributions from ultralow dielectric loss, reduced grain size, and so on. Consequently, the sample with optimized composition displays ultrahigh recoverable energy storage density (Wrec) of 14.5 J cm−3 and satisfied efficiency (η) of 83.9%, which shows the superiority in the state‐of‐the‐art dielectric ceramics. These results provide a feasible route by regulating the relationship between antiferroelectric structure and properties to explore high‐performance dielectrics for electrostatic energy storage applications.

Simultaneous excellent energy storage density and efficiency under applied low electric field for high entropy relaxor ferroelectric ceramics

Improving energy density and efficiency is a big problem at the present time for the utility of Pb-free dielectric capacitors. High entropy relaxor ferroelectric ceramics are the most hopeful materials to meet this challenge, which is due to their unique structure, single phase with complex composition, and significant lattice distortion. A high entropy relaxor ferroelectric ceramic, (Na0.2Bi0.2Ca0.2Sr0.2Ba0.2)TiO3 (NBCSBT) with pure-phase perovskite structure, has in the present study been successfully synthesized by using the solid-state technique. The energy storage properties, under different frequencies and temperatures, have been investigated in detail. The NBCSBT ceramic with a dense microstructure, exhibits relaxation behavior. A large recoverable energy storage density of 1.32 J/cm3, and a good energy storage efficiency of 91%, can be obtained under a low applied electric field (110 kV/cm). Moreover, moderate temperature endurance, in addition to an excellent frequency stability, is also obtained. These properties suggest that high entropy relaxor ferroelectric materials will be appealing for application in energy storage devices. It also offers a novel strategy for tuning energy storage performance.

(1-x)Bi0.5Na0.47Li0.03TiO3-xNaNbO3 lead-free ceramics with superior energy storage performances and good temperature stability

Dielectric capacitors show great potential in superior energy storage devices. However, the energy density of these capacitors is still inadequate to meet the requirement of energy storage applications. In this study, the Bi 0.5 Na 0.47 Li 0.03 TiO 3 - x NaNbO 3 (BNLT- x NN) ceramics were prepared via conventional solid-phase reaction. Results showed that NN can efficaciously enhance the breakdown strength ( E b ) and the relaxation behavior of the BNLT ceramic because of the broken ferroelectric long-range order. When x = 0.3, the maximum E b reached 350 kV/cm, at which the 0.7BNLT-0.3NN ceramic exhibited the high recoverable energy storage density ( W rec ) of 4.83 J/cm 3 and great efficiency ( η ) of 78.9%. The ceramic demonstrated good temperature stability at 20 °C-160 °C and excellent fatigue resistance. Additionally, the 0.7BNLT-0.3NN ceramic presented high power density ( P D ; ∼77.58 MW/cm 3 ), large current density ( C D ; ∼861.99 A/cm 2 ), and quite short discharge time ( t 0.9 ; ∼0.090 μs). These results indicated that the 0.7BNLT-0.3NN material has excellent energy storage properties and various application prospects.

Medium electric field-induced ultrahigh polarization response and boosted energy-storage characteristics in BNT-based relaxor ferroelectric polycrystalline ceramics

Lead-free dielectric ceramics with a high recoverable energy-storage density (Wrec) and improved efficiency (η) are crucial for the development of pulse power capacitor devices. Although Wrec has been constantly improving, mainly via an increased breakdown electric field strength (Eb), a large driving electric field (>500 kV/cm) increases security risks and consequently increases insulating technology costs. In this work, we present a new (Bi0.5Na0.5)TiO3 (BNT)-based relaxor ferroelectric system, (1−x)(0.75Bi0.5Na0.4K0.1TiO3-0.25SrTiO3)-xBi(Mg0.5Ti0.5)O3 (BS-xBMT), with x ranging from 0.05 to 0.20. BMT disrupts both the A- and B-site long-range ferroelectric order of the ABO3 perovskite-structured BS matrix, induces polar nanoregions, and simultaneously increases Wrec and η. Aided by the viscous polymer process, the Eb with x = 0.15 increased to 270 kV/cm, and a maximum polarization (Pm) of 62 μC/cm2 was attained. A boosted Wrec of 4.82 J/cm3 and a high η of 84.9% were simultaneously obtained, together with good temperature stability from 30 to 140 °C. These results show that BNT-based dielectric ceramics with superior energy-storage properties can be obtained under a medium electric field.

Enhanced energy storage performances under moderate electric field in aliovalent A/B-site co-doped AgNbO3

Energy storage properties of Nd3+ and Hf4+ A/B-site co-doped AgNbO3 (Ag1-2xNdxNb1-xHfxO3, x = 0.005–0.02) ceramics were investigated. The introduction of Nd3+ and Hf4+ stabilizes the antiferroelectric phase and enhances the energy storage density. Besides, aliovalent doping of Nd3+ and Hf4+ increases the relaxor characteristic, leading to low energy storage loss in the polarization and high energy storage efficiency. Above the antipolar dipole freezing temperature (Tf), temperature-stable polarization is obtained, leading to a good temperature stability of energy storage properties. Ag0.97Nd0.015Nb0.985Hf0.015O3 exhibits excellent energy storage performances, with a recoverable energy storage density of 3.94 J/cm3 and energy storage efficiency of 64.0% under a moderate electric field of 235 kV/cm. The energy storage density increases with the temperature, and the energy storage efficiency maintains good temperature stability, with a variance of 11% in the range of 25 °C to 175 °C under an applied electric field of 200 kV/cm.

Enhanced moderate electric field dielectric energy storage performance in (Bi0.5Na0.5)TiO3-based lead-free ceramics

Lead-free relaxor ferroelectric ceramics were prepared using 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 (BNKT) as the matrix and Sr(Mg1/3Nb2/3)O3 (SMN) as the end-member. The structure and properties of the obtained ceramics were characterized. It was found that the ceramic with the composition of 0.85BNKT-0.15SMN has the best overall performance with the recoverable energy storage density of 3.50 J/cm3 and the efficiency of 86% at 300 kV/cm. The ceramic also exhibits excellent temperature and frequency stability. The current results suggest that 0.85BNKT-0.15SMN is promising for energy storage applications at low to moderate electric field.

Investigations on structural, dielectric, and impedance properties of ecofriendly Ho3+ / Nb5+ co-substituted Na0.5 Bi0.5TiO3

The lead-free, 0.5 mol% of Ho3+ substituted Na0.5 Bi0.5TiO3 (Na0.5Bi0.495Ho0.005TiO3) has been modified by Nb+5 substitution at the Ti-site to improve the relaxor nature and physical properties. Enhancement in relaxor characteristics was found through polarization loop and the bipolar strain studies. The slanted polarization loop showed slightly better recoverable energy storage density as compared to the square loop at the moderate electric field of ≈ 85 kV/cm. Maximum dielectric constant temperature (Tm) and depolarization temperature (Td) shifted towards the lower region with Nb5+ substitution along with decreased average grain size. The Cole-Cole plots portrayed the single semicircle for all the compositions at higher temperatures which confirms the Debye-type behavior due to the grain interiors. The decrement in the grain resistance with increase in temperature depicted the negative temperature coefficient of resistance (NTCR) behavior like the semiconductor materials. The 3 mol% of Nb5+ substituted composition exhibited improved insulating character at higher temperatures as compared to Na0.5Bi0.495Ho0.005TiO3. It is advantageous to use the material for high-temperature dielectric applications.

Enhanced energy storage in temperature stable Bi0.5Na0.5TiO3-modified BaTiO3-Bi(Zn2/3Nb1/3)O3 ceramics

Recently, BaTiO3-BiMeO3 ceramics have garnered focused research attention due to their outstanding performance, such as thermal stability, energy efficiency and rapid charge-discharge behavior, however, a lower recoverable energy storage density (Wrec) caused by a relatively low Pmax (<30 μC/cm2) mainly hinders practical applications. Herein, the energy density and thermal stability are improved by adding a tertiary component, i.e., Bi0.5Na0.5TiO3, into BaTiO3-BiMeO3, resulting in xBi0.5Na0.5TiO3-modified 0.88BaTiO3-0.12Bi(Zn2/3Nb1/3)O3 ceramics, with x = 0, 0.1, 0.2, 0.3 and 0.4, with superior dielectric properties and eco-friendly impact. Incorporating Bi0.5Na0.5TiO3 with a high saturation polarization and Curie temperature not only significantly enhances Pmax of BaTiO3-Bi(Zn2/3Nb1/3)O3 but also improves Curie temperature of (1-x)[0.88BaTiO3-0.12Bi(Zn2/3Nb1/3)O3]-xBi0.5Na0.5TiO3 system. Combined with complementary advantages, modified ceramics render a superior energy storage performance (ESP) with a high Wrec of 3.82 J/cm3, efficiency η of 94.4% and prominent temperature tolerance of 25–200 °C at x = 0.3. Moreover, this ceramic exhibit excellent pulse performance, realizing discharge energy storage density Wdis of 2.31 J/cm3 and t0.9 of 244 ns. Overall, the proposed strategy effectively improved comprehensive properties of BaTiO3-based ceramics, showing promise in next-generation pulse applications.

Enhancement of energy storage performance in NaNbO3 and Sm3+ modified BNT-based ceramics

Dielectric capacitors of excellent performance will possess high recoverable energystoragedensity (Wrec) and energy efficiency (η), and operate stably in extreme environments, such as at high temperature, high electric field intensity, and high frequency. In this study, lead-free relaxor ferroelectric(1-x)(0.85Bi0.5Na0.5TiO3–0.15Ba0.94Sm0.06TiO3) –xNaNbO3[(1-x)(BNT-BSmT)–xNN)] ceramics were prepared by a traditional solid phase sintering method to achieve excellent energy storage performance. The addition of Sm3+and NN locally disrupted the long-range ordered structure of the domain and inhibited grain growth due to limited grain boundary diffusion.The recoverable energy storage density and energy efficiency of the sample with an NN doping content ofx = 0.12 reached 2.42 J/cm3 and 81.18% at an applied electric field of 170 kV/cm, respectively. The efficiency remained stable (∼80%) at variable frequency (0.1–100 Hz) and temperature (20–140 °C). Furthermore, the0.88(0.85BNT–0.15BSmT)–0.12NN ceramic underwent rapid charge and discharge processes and achieved high power density (41.5 MV/cm3) at fast discharge rates (1.39 J/cm3). The new lead-free relaxor ferroelectric ceramics involved inthis study have great potential applications in the pulse capacitor field and a large temperature range.

Achieving ultrahigh energy storage performance in BiFeO3-BaTiO3 based lead free relaxors via a composition optimization strategy

The 0.63(1-x)Bi1.02FeO3-0.37BaTiO3-xBi(Zn2/3(Nb0.85Ta0.15)1/3)O3 (abbreviated BF-BT-xBZNT) high temperature dielectric ceramics were prepared via a two-step sintering (TTS) method. The appropriate medium permittivity achieved in the BF-BT-0.13BZNT ceramic is conducive to mitigating the polarization saturation and improving the breakdown field strength. The domain evolution behavior from piezoresponse force microscopy (PFM) reveals that the introduction of BZNT promotes the formation and switching of more nanodomains of BF-BT ceramics, facilitating the enhancement of energy storage efficiency. The excellent energy storage performance of total energy storage density (Wtot) of 6.06 J/cm3, recoverable energy storage density (Wrec) of 4.85 J/cm3 and a high energy storage efficiency (η) of 80% are simultaneously obtained under 410 kV/cm in the BF-BT-0.13BZNT ceramic. Meanwhile, the ceramic exhibits excellent thermal endurance (10–130 ℃), frequency (1–100 Hz) and fatigue (105 cycles) stability. The current work provides a promising strategy for designing high-performance dielectric energy storage materials which operate in harsh environments.

Insights into improved ferroelectric and electrocaloric performance of Ba0.85Ca0.15Ti0.9Zr0.1O3 thick films grown by the electrophoretic deposition

Lead-free Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCZT) bulk ceramics have recently gained attention as one of the attractive candidates for electrocaloric cooling due to their large heat absorption capacity induced by electro-structural phase transition near room temperature. However, adiabatic temperature change (ΔT) at room temperature in ceramics has been limited by their relatively low dielectric breakdown strength. Thick films, in this respect, possess the advantages of ceramics (volume) and thin films (thickness). In this work, a systematic ferroelectric and electrocaloric investigation of BCZT thick films, fabricated by electrophoretic deposition combined with laser annealing, has been carried out. Laser annealing at an optimized energy density of 398 W/cm2 has resulted in densely packed grain morphology with no compositional heterogeneities. Analysis of the scaling behavior of dynamic hysteresis revealed that ferroelectric domain reversal in BCZT/Pt has good stability and low energy consumption in the saturation region. The present thick films exhibited larger breakdown strength of 294 kV/cm and recoverable energy storage density of ∼7.3 J/cm3, at least five-fold enhancement compared to the bulk which is stable up to a 4 mm bending radius. The indirect electrocaloric measurements displayed parameters such as a ΔT and entropy change (ΔS) of 2.94 K and 3.1 J kg−1 K−1 respectively, for 205 kV/cm which are more than two orders increased compared to the bulk. Higher values of ΔT (1.9 K) at 25 °C, refrigerant capacity of 249 J/kg, and responsivity of 0.143 K mm/kV for BCZT/Pt film compared to relevant lead-free ferroelectric thick films elucidate the potential use of these films for solid-state refrigeration applications. The work also presents electrophoretic deposition with laser annealing as an alternative technique to widely studied tape-casting of thick films for electrocaloric studies.

Enhanced energy storage properties under low electric fields in (Bi0.5Na0.5)TiO3-based relaxor ferroelectrics via a synergistic optimization strategy

Lead-free dielectric ceramics with high energy storage performance (ESP) are strongly desired for pulse power capacitor applications. However, low recoverable energy storage density (Wrec) under low electric fields seriously hinders their applications in miniatured and integrated electronic devices. In this work, we adopted a synergism strategy to develop (Bi0.5Na0.5)0.7Sr0.3Ti(1-x)(Al0.5Nb0.5)xO3 (BNST-xAN) ceramics with substantially enhanced low-field ESP through combining composition design and tape-casting approaches. Complex-ion substitution of (Al0.5Nb0.5)4+ for Ti4+ shifted the temperature of maximum dielectric constant towards room temperature direction, made relaxor behavior stronger and promoted formation of highly dynamic nanodomains, thus reducing the remanent polarization. Besides, refined submicron grains and improved densification behavior were achieved in those ceramics fabricated by tape casting, further increasing the breakdown strength. Consequently, a large Wrec of 4.30 J/cm3 was achieved at a low electric field of 230 kV/cm at x = 0.10, which is superior to previously reported lead-free energy storage ceramics under low electric fields. Moreover, our ceramics exhibited brilliant thermal endurance (20–140 °C) and frequency stability (0.2–200 Hz) together with fast discharge speed. These characteristics suggest the great potential of the BNST-0.10AN ceramic for low-field and high-performance energy storage capacitor applications.

Enhanced energy-storage performance in silver niobate-based dielectric ceramics sintered at low temperature

Silver niobate (AgNbO3, AN) dielectric ceramics and their antiferroelectric behavior have attracted increasing attention for their potential applications in energy-storage capacitors. However, AN’s inferior dielectric breakdown strength, recoverable energy storage density, and efficiency have limited its application. In this work, a combination of chemical composition design and liquid-phase sintering was considered for the fabrication of highly insulated and desensitized AN-based ceramics for enhancing Eb, Wrec, and η of AN. We design and prepare (1 − x)AgNbO3-x(Sr0.7Bi0.2)HfO3 (AN-100xSBH, x = 0.00–0.06) ceramics with the addition of 1 mol% BaCu(B2O5) (BCB) as a sintering aid to realize this. It is found that highly desensitized ceramics can be formed at 1000–1030 °C over the course of 2 h. The electrical property characterization results indicate that the AFE state and Eb are significantly enhanced with increasing SBH concentration. High Wrec and η values of 6.1 J/cm3 and 73%, respectively, under an applied field of 330 kV/cm are achieved in the AN-5.5SBH ceramic. Meanwhile, the AN-5.5SBH ceramic shows excellent thermal stability over a wide temperature range (25–120 °C) under an externally applied field of 290 kV/cm, in which the fluctuations of Wrec and η are 3.8% and 1.5%, respectively. These results provide an effective method for obtaining AN-based ceramics with excellent electrical properties under a lower sintering temperature than that required for pure AN ceramics. This method could be further generalized to develop new lead-free energy-storage dielectric materials.

Energy storage and charge-discharge performance of B-site doped NBT-based lead-free ceramics

Dielectric ceramic materials with high energy-storage density and excellent charge-discharge performance are desirable for use in dielectric capacitors. In this study, (Na 0.5 Bi 0.5 ) 0.75 Sr 0.25 TiO 3 – x Nb 2 O 5 (denoted as NBSTN x ) lead-free ceramics were prepared by a solid-state reaction method. Polarization-electric field hysteresis loops ( P–E loops) reflected the energy storage characteristics of the NBSTN x ceramics. Introducing Nb into a pure NBST ceramic can reduce the large remnant polarization ( P r ) and make the P–E loops slimmer. Through repeated trials and calculations, the maximum recoverable energy-storage density ( W rec ~ 3.25 J/cm 3 ) and energy storage efficiency ( η ~ 74.5%) were achieved for the NBSTN 0.03 ceramic at 140 kV/cm. We also tested the stability performance of the NBSTN x ceramics, where the NBSTN 0.03 ceramic exhibited the highest thermal stability (30–100 °C) and frequency stability (10–1000 Hz). The NBSTN 0.03 ceramic also had a fast discharge rate (<300 ns) and a good discharge energy-storage density ( W d ~ 1.80 J/cm 3 ). Therefore, the NBSTN 0.03 ceramic with a good energy-storage density and charge-discharge performance has excellent application prospects for practical dielectric capacitors. • A strategy incorporating B-site doping to enhance energy storage performance. • A relatively high W rec of 3.25 J/cm 3 and η of 74.5%. • Sample with 0.03 mol Nb doping shows relatively good temperature and frequency stability.

Realizing high energy density and superior charge-discharge characteristics in NN-10BT-based ceramics

The low recoverable energy storage density (Wrec) of bulk ceramics has long limited their miniaturization and lightweight development. Here, we designed the (1-x)(0.90NaNbO3-0.10BaTiO3)-xNa0.2Bi0.4La0.2TiO3 (NN-10BT-xNBLT) ceramics. With the introduction of NBLT, the dielectric breakdown strength (BDS) of NN-10BT-based ceramics increased from 174.8 kV/cm to 289.1 kV/cm. A promising finding is that the NN-10BT-15NBLT ceramic has an ultrahigh energy storage density W of 3.42 J/cm3 and a large energy storage efficiency η of 78.9%, as well as excellent frequency and thermal stability. The NN-10BT-15NBLT ceramic, on the other hand, has an outstanding current density CD of 1021.21 A/cm2 together with a high power density PD of 102.12 MW/cm3 at 200 kV/cm. Most importantly, the variation of charge-discharge properties (CD and PD) is only −7.8% after 104 cycles, suggesting that the capacitor has potential practical application significance.

Boosting Energy Storage Performance of Lead‐Free Ceramics via Layered Structure Optimization Strategy

Owing to the current global scenario of environmental pollution and the energy crisis, the development of new dielectrics using lead-free ceramics for application in advanced electronic and energy storage systems is essential because of the high power density and excellent stability of such ceramics. Unfortunately, most of them have low breakdown strength and/or low maximum polarization, resulting in low energy density and efficiency. To overcome this limitation here, lead-free ceramics comprising a layered structure are designed and fabricated. By optimizing the distribution of the layered structure, a large maximum polarization and high applied electric field (>500kV cm-1 ) can be achieved; these result in an ultrahigh recoverable energy storage density (≈7 J cm-3 ) and near ideal energy storage efficiency (≈95%). Furthermore, the energy storage performance without obvious deterioration over a broad range of operating frequencies (1-100Hz), working temperatures (30-160°C), and fatigue cycles (1-104 ). In addition, the prepared ceramics exhibit extremely high discharge energy density (4.52 J cm-3 ) and power density (405.50 MW cm-3 ). Here, the results demonstrate that the strategy of layered structure design and optimization is promising for enhancing the energy storage performance of lead-free ceramics.

Designing Barium Titanate Ceramics with High Energy Storage and Mechanical Properties

Designing the fine-grained ceramics with high recoverable energy storage density and excellent mechanical performance, still presents great challenges. Because the ceramics with large pore size and low relative density were obtained by the traditional sintering method, they always exhibit small breakdown strength and poor mechanical properties, which limits the miniaturization and operation of devices in harsh environments. In this paper, we designed the barium titanate ceramics (BT) ceramics with grain size of 252 nm and relative density of 0.92 can be obtained via co-sintering of two sizes of BT particles at 1000 °C for 10 h. The cubic phase BT particles with 80 nm are doped in the tetragonal phase BT particles with 200 nm to obtain tetragonal phase fine-grained BT ceramics. When doped with 80 nm BT particles, the sintering of 200 nm BT particles is promoted. The enhanced sinterability is due to the phase transformation and metastability, which act as sintering aids. The obtained BT ceramics with nanodomains, high energy storage and mechanical properties. The discharge energy density is of 0.81 J/cm3, and the Vickers hardness is 1.75 GPa.

An alternative way to design excellent energy-storage properties in Na0.5Bi0.5TiO3-based lead-free system by constructing relaxor dielectric composites

With growing concerns over environmental protection, lead-free dielectric ceramic capacitors are attracting much attention. In this work, a series of novel (1-x) Na0.5Bi0.5TiO3-x Ba5LaTi3Ta7O30 ((1-x)NBT-xBLTT) dielectric composite ceramics were fabricated by a traditional solid‐state method. All the samples possess a compact microstructure with refined grain morphology with increasing BLTT content, and tend to exhibit a diphase dielectric composite as x reaches up to 0.05. Furthermore, the addition of BLTT enhances the dielectric relaxor behavior of NBT-based ceramics, such that the x = 0.15 composite ceramic exhibits a typical feature of relaxor ferroelectrics. As a result, a high recoverable energy-storage density of Wrec~3.67 J/cm3, an ultrahigh energy-storage efficiency of η~97.3%, and a high power density of PD~333 MW/cm3 can be simultaneously obtained in the x = 0.15 relaxor composite ceramic. This study provides an alternative way to design excellent energy-storage performances in NBT-based compositions through constructing dielectric relaxor composites via introducing non-polar tungsten bronze oxides.

Electrocaloric and energy storage properties of sol-gel derived lanthanum doped PZT thick films

Electrocaloric effect has been investigated in lanthanum doped lead zirconium titanate (PLZT) thick films for potential application in cooling devices. Modified sol gel technique has been used for the preparation of PLZT thick films. Dielectric constant has been enhanced from 497 to 1048 with minimum dielectric losses varying from 0.04 to 0.07 measured at 1 MHz with increase in La doping from 2% to 6%, respectively. The maximum and remnant polarizations have been observed to vary from 23 μC/cm2 to 62 μC/cm2 and from 18 μC/cm2 to 49 μC/cm2 with increase in the lanthanum doping level from 2% to 6%, respectively, measured at 20 Hz frequency. The recoverable energy storage density of 1.05 J/cm3 and an efficiency of 21% has been obtained for 2% lanthanum doping. The electrocaloric temperature change (ΔT) of 4.26K has been measured at 310K with an electrocaloric efficiency of 0.28 × 10−6 Km/V in the 6% La doped PZT film. These properties indicate that PZT thick films with 6% La doping have potential for application in cooling devices.

Enhanced energy storage performance and temperature stability achieved by a synergic effect in Nd3+/Ga3+ co-doped (Na0.5Bi0.5)TiO3 -based ceramics

(1-x)(0.75(Na0.5Bi0.5)TiO3-0.25SrTiO3)-xNdGaO3 ceramics (NBST-xNG, x = 0–0.06) were fabricated through a solid-state reaction method. High-valent Nd3+ ions enter the perovskite A-site to occupy Bi vacancies resulting from the volatilization of Bi, inhibiting the formation of oxygen vacancies and contributing to an enhanced breakdown electric field (Eb). Low-valent Ga3+ ions enter the B-site to substitute for Ti4+ ions, resulting in the formation of random electric fields (REFs) at the B-site due to co-occupying hetero-valence ions of Ga3+/Ti4+, which significantly reduces ferroelectric hysteresis. Therefore, a synergic effect of A- and B-sites co-doping was realized in NBST-xNG ceramics. Benefitting from this synergic effect, an enhanced recoverable energy storage density (Wrec) of 2.88 J/cm3 and an efficiency (η) of 83% are simultaneously obtained in NBST-0.04NG ceramics under a moderate electric field (E) of 200 kV/cm. Compared with most NBT-based ceramics, the values of (η vs Wrec/E2) for NBST-0.04NG ceramics show an obvious advantage, indicating excellent potential for application as an energy storage material. Moreover, Wrec and η of NBST-0.04NG ceramics exhibit excellent temperature stability from 30 °C to 200 °C due to the enhanced correlation strength of polar nanoregions (PNRs) and local structural stability. This work provides a potential strategy to improve the energy storage performance of NBT-based ceramics via the synergic effect of A- and B-site co-doping.