High recoverable energy storage density and large energy efficiency simultaneously achieved in BaTiO3–Bi(Zn1/2Zr1/2)O3 relaxor ferroelectrics

Relaxor ferroelectrics have attracted much attention as electric energy storage materials for intermittent energy storage because of their high saturated polarization, near-zero remnant polarizations, and considerable dielectric breakdown strength (BDS). Despite the numerous efforts, the dielectric energy storage performance of relaxor ferroelectric ceramics is incomplete or unsatisfactory. The enhancement of recoverable energy storage density W_rec usually accompanies with the sacrifice of discharge-to-charge energy efficiency η; therefore, it is an important issue to achieve high recoverable W_rec and large efficiency η simultaneously. In this work, the (1-x)BaTiO₃-xBi(Zn_1/2Zr_1/2)O₃ (abbreviated as BT-100xBZZ, 0 ≤ x ≤ 0.20) ferroelectric ceramics were prepared using the conventional solid-state reaction method. The phase structure, microstructural morphology, dielectric and ferroelectric properties, relaxation behaviors, and energy storage properties of BT-BZZ ceramics were investigated in detail. X-ray powder diffraction, dielectric spectra, and ferroelectric properties confirm the transformation of tetragonal phase for normal ferroelectrics (BT) to pseudo-cubic phase for relaxor ferroelectrics (BT-8BZZ). A high recoverable energy storage density W_rec of 2.47 J/cm³ and a large energy efficiency η of 94.4% are simultaneously achieved in the composition of BT-12BZZ, which presents typical weakly coupled relaxor ferroelectric characteristics, with an activation energy E_a of 0.21 eV and a freezing temperature T_f of 139.7 K. Such excellent energy storage performance suggests that relaxor ferroelectric BT-12BZZ ceramics are promising dielectric energy storage materials for high-power pulsed capacitors.     

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 Sr_0·7Bi_0·2TiO₃ (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.     

High energy storage efficiency of NBT-SBT lead-free ferroelectric ceramics

Ceramic-based dielectrics have been widely used in pulsed power capacitors owing to their good mechanical and thermal properties. Bi_0.5Na_0.5TiO₃-based (NBT-based) solid solutions exhibit relatively high polarization, which is considered as a promising dielectric energy storage material. However, the high remnant polarization and low energy efficiency limit their application in dielectric capacitors. Herein, a typical relaxor ferroelectric Sr_0·7Bi_0·2TiO₃ (SBT) was introduced into the NBT system to strengthen the overall relaxor behavior, resulting in reduced remnant polarization. We prepared (1-x)NBT-xSBT (x = 0.35, 0.45, 0.55, and 0.65) ceramics by the conventional solid-phase reaction method and further investigated their microstructures, dielectric and energy storage properties. With the increase of SBT content, the size of the grains and the maximum dielectric constant gradually decreased, simultaneously. Furthermore, the dielectric shoulder corresponding to the maximum dielectric constant shifted to a lower temperature, indicating that the enhancement of polarization dynamics was a consequence of the domain refinement. As a result, the optimum property was identified in the 0.45NBT-0.55SBT sample with a high recoverable energy density of 1.34 J/cm³ and an outstanding energy efficiency of 96% at a low electric field of 100 kV/cm.     

Effects of annealing temperatures on energy storage performance of sol-gel derived (Ba0.95, Sr0.05) (Zr0.2, Ti0.8) O3 thin films

Dielectric polarization and breakdown strength of dielectrics generally show directly and inversely dependent upon their crystallization, respectively. Therefore, achieving the maximum energy storage density should be expected by controlling the crystallization. A serial of ferroelectric (Ba_0.95, Sr_0.05)(Zr_0.2, Ti_0.8)O₃ (BSZT) thin films were prepared by the sol-gel method. Effects of annealing temperatures on the microstructure, dielectric and energy storage performance of the films were investigated. The results indicate that BSZT thin films annealed at 600 °C for 30 min demonstrate the highest recoverable energy density and efficiency (50.5 J/cm³ and 91.9%). Such superior energy storage performance is attributed to an ultrahigh electric breakdown strength (6.65 MV/cm) induced by the dense amorphous-nanocrystalline microstructure. This work creates a new way for optimizing the energy storage performance of dielectric thin films via balancing their dielectric polarization and breakdown strength at appropriate heating processing temperature.     

Critical role of CuO doping on energy storage performance and electromechanical properties of Ba0.8Sr0.1Ca0.1Ti0.9Zr0.1O3 ceramics

CuO doped Ba_0.8Sr_0.1Ca_0.1Ti_0.95Zr_0.05O₃ (BSCTZ) ceramics were prepared by a modified mechano-chemical activation technique with the aim of improving energy storage properties for ceramic capacitor applications. CuO can effectively improve the microstructural characteristics along with a transformation of BSCTZ from classical ferroelectric to relaxor, which is the prime requirement for obtaining high discharge energy density and energy efficiency. The effect of CuO doping on the microstructural, ferroelectric, dielectric, and piezoelectric properties have been systematically studied. The study reveals that an appropriate amount of CuO doping can significantly enhance the morphological properties along with improvement in material density, which is very beneficial in a material for attaining improved energy storage performance. The BSCTZ sample with 3 mol% CuO doping has shown a highly dense microstructure, high saturation polarization (33.01 μC/cm²), low remnant polarization (6.74 μC/cm²), ultrahigh discharge energy density (1.81 J/cm³) and high energy efficiency (81.9%). The CuO doping in BSCTZ has also led to a slight improvement in breakdown strength and electromechanical properties compared to pure BSCTZ ceramics, which is mainly attributed to excellent density and optimum grain size of the material.     

Enhanced energy storage and breakdown strength in barium titanate zirconate solid solutions with niobates and tantalates

Lead-free relaxor compounds are considered as promising materials for the development of dielectric capacitors with a high energy storage density. This has stimulated many research groups around the world to search for the optimal composition and microstructure. In this paper, we report about two novel lead-free ceramic systems, (1-x)Ba(Ti_0.85Zr_0.15)O₃–(x)Bi(Zn_2/3Nb_1/3)O₃ (BTZ-BZNb) and (1-x)Ba(Ti_0.85Zr_0.15)O₃–(x)Bi(Zn_2/3Ta_1/3)O₃ (BTZ-BZTa), prepared by the solid-state method. Ba(Ti_0.85Zr_0.15)O₃ was chosen as starting compositions due to its ferroelectric-relaxor crossover behavior which combines slim hysteresis loops with high a maximum polarization. By substituting with niobates and tantalates, we have investigated their influence on the polarization, dielectric properties and energy storage performance. Moderate doping enhances the relaxor behavior of BTZ while maintaining a large polarizability, which is beneficial for a high recoverable energy density. The substitution with Nb seems to affect the lattice distortion more than Ta, which can be related to a lower degree of covalency of the Nb-O bonds. This effect does not affect the polarization behavior, and the niobate-doped materials achieve higher breakdown strength than the tantalate-doped materials. The breakdown strength is more influenced by the grain size distribution of the ceramics than by the substitution content and the band gap. Overall, the 6BZNb ceramic shows the most favorable energy storage properties with a high energy density of 1.53 J/cm³ at 244 kV/cm, a high energy efficiency of 91%, and a high breakdown strength of 239 kV/cm.     

Enhanced energy storage property achieved in Na0.5Bi0.5TiO3-based ferroelectric ceramics via composition design and grain size tuning

Dielectric energy storage capacitors have been explored to obtain excellent energy storage density along with high energy storage efficiency with the development of electronic devices. In this work, linear dielectric CaTi_0.5Zr_0.5O₃ is introduced into Bi_0.5Na_0.5TiO₃-NaNbO₃ matrix to form 0–3 type composites to vary the size and conductivity of the composite grain, which lead to ultra-high breakdown electric field of 410 kV/cm and the quasi-linear hysteresis loops. Meanwhile, linear dielectric does not change the characteristic of ferroelectric, and thus composites maintain high maximum polarization of 26.4 μC/cm². Integrating the advantages of linear dielectric and ferroelectric, an excellent recoverable energy density of 4.93 J/cm³ with an efficiency of 93.3% have been achieved in BNT-NN/7 wt%CZT ceramics. This work contributes to the development of dielectric energy storage capacitors for practical applications in pulsed power devices.     

Composition-dependent xBa(Zr0.2Ti0.8)O3-(1-x)(Ba0.7Ca0.3)TiO3 bulk ceramics for high energy storage applications

This work reports the composition dependent microstructure, dielectric, ferroelectric and energy storage properties, and the phase transitions sequence of lead free xBa(Zr_0.2Ti_0.8)O₃-(1-x)(Ba_0.7Ca_0.3)TiO₃ [xBZT-(1-x)BCT] ceramics, with x?=?0.4, 0.5 and 0.6, prepared by solid state reaction method. The XRD and Raman scattering results confirm the coexistence of rhombohedral and tetragonal phases at room temperature (RT). The temperature dependence of Raman scattering spectra, dielectric permittivity and polarization points a first phase transition from ferroelectric rhombohedral phase to ferroelectric tetragonal phase at a temperature (T_R-T) of 40?°C and a second phase transition from ferroelectric tetragonal phase - paraelectric pseudocubic phase at a temperature (T_T-C) of 110?°C. The dielectric analysis suggests that the phase transition at T_T-C is of diffusive type and the BZT-BCT ceramics are a relaxor type ferroelectric materials. The composition induced variation in the temperature dependence of dielectric losses was correlated with full width half maxima (FWHM) of A₁, E(LO) Raman mode. The saturation polarization (P_s) ≈8.3?μC/cm² and coercive fields ≈2.9?kV/cm were found to be optimum at composition x?=?0.6 and is attributed to grain size effect. It is also shown that BZT-BCT ceramics exhibit a fatigue free response up to 10⁵ cycles. The effect of a.c. electric field amplitude and temperature on energy storage density and storage efficiency is also discussed. The presence of high T_T-C (110?°C), a high dielectric constant (ε_r ≈?12,285) with low dielectric loss (0.03), good polarization (P_s ≈?8.3?μC/cm²) and large recoverable energy density (W?=?121?mJ/cm³) with an energy storage efficiency (η) of 70% at an electric field of 25?kV/cm in 0.6BZT-0.4BCT ceramics make them suitable candidates for energy storage capacitor applications.     

Lead-free BaTiO3-Bi0.5Na0.5TiO3-Na0.73Bi0.09NbO3 relaxor ferroelectric ceramics for high energy storage

A series of (1-x)(0.65BaTiO₃-0.35Bi_0.5Na_0.5TiO₃)-xNa_0.73Bi_0.09NbO₃ ((1-x)BBNT-xNBN) (x = 0–0.14) ceramics were designed and fabricated using the conventional solid-state sintering method. The microstructure, dielectric property, relaxor behavior and energy storage property were systematically investigated. X-ray diffraction results reveal a pure perovskite structure and dielectric measurements exhibit a relaxor behavior for the (1-x)BBNT-xNBN ceramics. The slim polarization electric field (P-E) loops were observed in the samples with x ≥ 0.02 and the addition of Na_0.73Bi_0.09NbO₃ (NBN) could decrease the remnant polarization (P_r) of the (1-x)BBNT-xNBN ceramics obviously. The sample with x = 0.08 exhibits the highest energy storage density of 1.70 J/cm³ and the energy storage efficiency of 82% at 172 kV/cm owing to its submicron grain size and high relative density. These results show that the (1-x)BBNT-xNBN ceramics may be promising lead-free materials for high energy storage density capacitors.     

Breakdown field enhancement and energy storage performance in four-layered Aurivillius films

In dielectric capacitors, ferroelectric thin films with slim polarisation electric (P-E) hysteresis loops, which are mainly characterised by small residual polarisation (P_r) and large saturation polarisation (P_s) are expected to obtain high recoverable energy density (U_r) and efficiency (η). However, a lower breakdown in ferroelectric thin films usually impedes this result. Here, through the co-doping of La³⁺ and Pr³⁺ ions, a larger U_r of 54.27 J/cm³ and high η of 85.6% were obtained in four-layered Aurivillius phase ferroelectric thin films capacitors due to the enhanced breakdown electric field. The doped films annealed at relatively low temperatures showed similar energy storage properties compared with those of the prototype and higher energy storage efficiency compared with that of higher annealing films. In addition, the obtained thin film shows excellent energy storage properties in a wide frequency range, fatigue durability and good thermal stability. These results indicated that four-layered Aurivillius films are promising candidate materials for dielectric energy storage capacitors. The co-doping of double ions was an effective way to improve energy storage performance.     

High energy storage performance in BaTiO3-based lead-free relaxors via multi-dimensional collaborative design

The application of advanced pulse power capacitors strongly depends on the fabrication of high-performance energy storage ceramics. However, the low recoverable energy storage density (W_rec) and energy efficiency (η) become the key links limiting the development of energy storage capacitors. In this work, a high W_rec of ～5.57 J cm^?3 and a large η of ～85.6% are simultaneously realized in BaTiO₃-based relaxor ceramics via multi-dimensional collaborative design, which are mainly attributed to the ferroelectric-relaxor transition, enhanced polarization, improved breakdown electric field, and delayed polarization saturation. Furthermore, the excellent temperature stability (ΔW_rec < ± 5%, 25–140 °C), frequency stability (ΔW_rec < ± 5%, 1–200 Hz), and outstanding charge/discharge performance (current density ～1583.3 A cm^?2, power density ～190.0 MW cm^?3) with good thermal stability are also achieved. It is encouraging that this work demonstrates that multi-dimensional collaborative design is a good strategy to develop new high-performance lead-free materials used in advanced dielectric capacitors.     

Enhanced energy storage performance in bismuth layer-structured BaBi2Me2O9 (Me = Nb and Ta) relaxor ferroelectric ceramics

Bismuth layer-structured BaBi₂Nb₂O₉ (BBN) and BaBi₂Ta₂O₉ (BBT) relaxor ferroelectric ceramics were explored as potential energy storage materials. Remarkable energy storage performances were obtained in both BBN and BBT ceramics, featured by large recoverable energy storage density (~0.84 J/cm³ and ~0.68 J/cm³) and high energy storage efficiency (~90% and ~94%), respectively. Furthermore, both the two ceramics exhibit good thermal and frequency stabilities. Delightedly, both the BBN and BBT ceramics can complete the discharge process within 0.15 μs, resulting in ultrahigh current density of 195 A/cm² and 234 A/cm² and excellent power density of 10.74 MW/cm³ and 12.89 MW/cm³, respectively. The obtained results suggest that BaBi₂Nb₂O₉ and BaBi₂Ta₂O₉ ceramics could have a promising future in energy storage applications. This study also demonstrates that the bismuth layer-structured relaxor ferroelectric ceramic can be considered as a novel potential lead-free energy storage materials, in addition to the widely studied pervoskite-structured relaxor ferroelectric ceramics.     

Enhanced energy storage performance of eco-friendly BNT-based relaxor ferroelectric ceramics via polarization mismatch-reestablishment and viscous polymer process

In this work, we synthesized a novel and eco-friendly relaxor ferroelectric system, i.e., (1?x)(0.8Bi_0.5Na_0.4K_0.1TiO₃-0.2SrTiO₃)-xNaNbO₃ (BS-xNN) ceramics with x = 0.1–0.4 based on a solid state reaction technique. The structural, microstructural, dielectric as well as ferroelectric characteristics of BS-xNN ceramics were comprehensively examined. According to our findings, the Ti–O coupling reduces as the NN content increases, while the Nb–O coupling strengthens, leading in a nano-scale polarization mismatch-reestablishment process that enhances energy storage performance. Because of the reduction in thickness and porosity, the viscous polymer process significantly increases the breakdown strength of ceramic samples. More crucially, at 260 kV/cm, 0.6BS-0.4NN ceramics have an ultrahigh recoverable energy storage density W_rec of 4.44 J/cm³ and a high energy storage efficiency η of 81.8%. Furthermore, thermal stability of energy storage performance is also identified across a wide temperature range of 30 °C from 140 °C at 215 kV/cm. The higher performance of energy storage not only indicates the feasibility of our technique, but also serves as a model for the manufacturing of high-quality dielectric ceramics with a wide range of industrial applications.     

High-efficiency energy storage in Nd-doped (1-x)BiFeO3–xBaTiO3 relaxor ferroelectric ceramics

Dielectric capacitors as energy storage electronics have drawn much attention due to ultrahigh power densities with quick charging and discharging rates. In this report, A-site Nd-doped (1-x)BiFeO₃-xBaTiO₃ (x = 0.2–0.45) relaxor ferroelectric ceramics with superior storage efficiencies were prepared with 0.1 wt% MnO₂ additive. Energy-storage efficiency (η) increases from 63.7% to 89% at 190 kV/cm as BaTiO₃ increases accompanied by recoverable energy densities (W_rec) in the range of 2.5–2.7 J/cm³. The energy-storage performance persists thermally stable up to 125 °C. The superior storage efficiency is associated with growth of the cubic Pm-3m symmetry and the core-shell structure with increasing BaTiO₃ content. The formation of nanocluster/nanomosaic structure also plays an essential role as a barrier in suppressing the long-range polarization order. This work provides a design of binary rare-earth doped BiFeO₃–BaTiO₃ dielectric ceramics for thermally stable and high-efficiency electrical energy storage.     

Effect of Sr(Zn1/3Nb2/3)O3 modification on the energy storage performance of BaTiO3 ceramics

Lead-free (1-x)BaTiO₃-xSr(Zn_1/3Nb_2/3)O₃ (abbreviated as BT-xSZN, x = 0–0.08) relaxor ferroelectric ceramics were prepared using the traditional solid phase technology, and the effects of SZN modification on their phase structures, microstructures, dielectric performance, ferroelectricity and energy storage performance were studied in detail. A pure perovskite phase was observed in the BT-xSZN ceramics. The BT-based ceramics modified by SZN exhibited refined grain size. As the SZN content was increased, the breakdown strength initially increased and then decreased, and the ferroelectric loops gradually became ‘slim’. The BT-xSZN (x = 0.07) ceramics demonstrated a favourable energy storage performance with high recoverable energy density (W_rec = ~1.45 J/cm³) and energy storage efficiency (η = ~83.12%) at 260 kV/cm. Results indicate that the energy storage performance of BaTiO₃ ceramics modified by SZN can be remarkably improved, widening their applications in energy storage at low temperatures.     

Simultaneously achieving high energy storage density and efficiency under low electric field in BiFeO3-based lead-free relaxor ferroelectric ceramics

BiFeO₃-BaTiO₃-based relaxor ferroelectric ceramic has attracted increasing attention for energy storage applications. However, simultaneously achieving high recoverable energy storage density (W_rec) and efficiency (η) under low electric field has been a longstanding drawback for their practical applications. Herein, a novel relaxor ferroelectric material was designed by introducing (Sr_0.7Bi_0.2)TiO₃ (SBT) into the composition 0.67BiFeO₃-0.33BaTiO₃ (BF-BT-xSBT). A large W_rec of ∼2.40 J/cm³ and a high η of ∼90.4 % were simultaneously realized under a low electric field of 180 kV/cm, which is superior to that of most previously reported lead-free ceramics. Moreover, moderate temperature endurance and excellent frequency stability were also obtained. More importantly, this ceramic has a large discharge current density (∼289.18 A/cm²), a discharge power density (∼14.46 MW/cm³) and short discharge time (<0.25 μs). These results not only demonstrate superior potential in BF-BT-SBT ceramics, but also offer a new design to tune the energy storage performance of lead-free relaxor ferroelectric ceramics.     

Impact of fatigue behavior on energy storage performance in dielectric thin-film capacitors

The polarization hysteresis loops and the dynamics of domain switching in ferroelectric Pb(Zr_0.52Ti_0.48)O₃ (PZT), antiferroelectric PbZrO₃ (PZ) and relaxor-ferroelectric Pb_0.9La_0.1(Zr_0.52Ti_0.48)O₃ (PLZT) thin films deposited on Pt/Ti/SiO₂/Si substrates were investigated under various bipolar electric fields during repetitive switching cycles. Fatigue behavior was observed in PZT thin films and was accelerated at higher bipolar electric fields. Degradation of energy storage performance observed in PZ thin films corresponds to the appearance of a ferroelectric state just under a high bipolar electric field, which could be related to the nonuniform strain buildup in some regions within bulk PZ. Meanwhile, PLZT thin films demonstrated fatigue-free in both polarization and energy storage performance and independent bipolar electric fields, which are probably related to the highly dynamic polar nanodomains. More importantly, PLZT thin films also exhibited excellent recoverable energy-storage density and energy efficiency, extracted from the polarization hysteresis loops, making them promising dielectric capacitors for energy-storage applications.     

Electrostatic energy storage performances of La(Ni2/3Ta1/3)O3-modified Na0.5Bi0.5TiO3 lead-free ceramics

Ceramic capacitors with high electrostatic energy storage performances have captured much research interest in latest years. Sodium bismuth titanate (Na_0.5Bi_0.5TiO₃)-based ferroelectric ceramics show great potential due to their environment-friendly composition, high polarization, and excellent relaxor properties. However, the nonergodic relaxor state of Na_0.5Bi_0.5TiO₃-based ceramics hampers the decrement of remanent polarization, leading to poor energy storage performance. Herein, the (1 − x)Na_0.5Bi_0.5TiO₃–xLa(Ni_2/3Ta_1/3)O₃ ceramics were designed to generate the transformation between nonergodic and ergodic relaxor state. As a result, the ceramics exhibit improved dielectric relaxation, slim polarization–electric field loops, and flattened current–electric field curves due to highly dynamic polar nanoregions. Particularly, the 0.85Na_0.5Bi_0.5TiO₃–0.15La(Ni_2/3Ta_1/3)O₃ ceramics show large breakdown electric field E_b (345 kV/cm), high recoverable energy density W_rec (3.6 J/cm³), and efficiency η (80.6%), revealing potential applications in electrostatic energy storage.     

Improved energy storage properties of Sr(Zr0.8Nb0.16)O3-doped Bi0.47Na0.47Ba0.06TiO3 ceramics with excellent temperature/frequency stability

Lead-free perovskite dielectric materials for capacitors have received wide concern in recent years, but their energy storage density and efficiency still cannot meet the growing application demand for practical applications. In this work, we prepared a lead-free relaxor ferroelectric ceramic of (1-x)Bi_0.47Na_0.47Ba_0.06TiO₃-xSr(Zr_0.8Nb_0.16)O₃, which was synthesized via a normal solid-state route. The microstructure, dielectric properties and energy storage behavior of the ceramics were explored. The ceramics can be well sintered and situated in the region where rhombohedral and tetragonal phases coexist. The addition of Sr(Zr_0.8Nb_0.16)O₃ (SZN) significantly extends the dielectric-temperature plateau between T_s and T_m and reduces the remnant polarization P_r, but the large saturation polarization P_s is still maintained. Besides, the doping of SZN enhances the relaxation of the material and increases the dielectric breakdown strength (DBS) from 50 kV/cm (x = 0) to 100 kV/cm (x = 0.04 and 0.06). Therefore, the ceramic with x = 0.06 exhibits a high discharging efficiency (η) of 71.1% and energy density (W) of 1.56 J/cm³ at 100 kV/cm and shows the superior thermal stability with the changes in recoverable energy density (W_rec) and η of less than 10% and 30% at the temperature range of 25–180 °C and the excellent frequency stability with the variations of W_rec and η of less than 1.8% and 1% at the frequency range of 10 Hz–100 Hz.     

Enhanced breakdown strength and energy storage density in a new BiFeO3-based ternary lead-free relaxor ferroelectric ceramic

A new ternary lead-free relaxor ferroelectric ceramic of (0.67-x)BiFeO₃-0.33(Ba_0.8Sr_0.2)TiO₃-xLa(Mg_2/3Nb_1/3)O₃+y wt.% MnO₂+z wt.% BaCu(B₂O₅) (BF-BST-xLMN+y wt.% MnO₂+z wt.% BCB) was prepared by a solid-state reaction method. The substitution of LMN for BF was believed to induce a typical dielectric relaxation behavior owing to the increased random fields. After co-doping MnO₂ and BCB, a significant decrease in the conductivity and grain size was simultaneously realized, resulting in obviously enhanced dielectric breakdown strength and energy-storage performances at room temperature. A high recoverable energy storage density W˜3.38 J/cm³ and an acceptable energy storage efficiency η˜59% were achieved in the composition with x = 0.06, y = 0.1 and z = 2 under a measuring electric field of 23 kV/mm. In addition, the energy-storage performance is quite stable against both frequency (0.1 Hz–100 Hz) and temperature (30–170 °C), suggesting that BF-BST-xLMN+y wt.% MnO₂+z wt.% BCB lead-free relaxor ferroelectric ceramics might be a promising dielectric material for high-power pulsed capacitors.