Significantly Enhanced Energy Storage Performance in High Hardness BKT-Based Ceramic via Defect Engineering and Relaxor Tuning

Abstract

Hybrid electric cars and pulsed power technologies have increased the demand for capacitors with high energy density, wide temperature stability, high operating voltage, and good mechanical qualities. In this work, (1 − x) (0.6Bi 0.5 K 0.5 TiO 3 -0.4BiFeO 3 )-x(Na 0.4 Sm 0.2 NbO 3 ) ((1 − x) (BKTBF)-xNSN) relaxor ceramics were prepared by constructing morphotropic phase boundary (MPB) combined with oxygen vacancy defect engineering. It is worth noting that the 0.6BKT-0.4BFO ceramics at MPB have a high P max ∼ 60 μC/cm 2 . The ultra-hard (H V = 10.7 GPa) BKTBFO-0.16NSN relaxor ferroelectric ceramic achieves a high W rec of 6.52 J/cm 3 , a working temperature of 20−120 °C, and a working frequency of 1−1000 Hz. Additionally, the BKTBFO-0.16NSN ceramic demonstrates comprehensive pulse charge−discharge performance (I max = 17.2 A, C D = 546.7 A/cm 2 , P D = 54.7 MW/cm 3 , and t 0.9 = 59 ns) and excellent stability (25−125 °C and 10 4 charge−discharge cycles). This study offers a novel approach for the practical implementation of high-performance pulse capacitors, which will undoubtedly stimulate further research and development of high-P max energy storage dielectrics (such as BNT, BKT, and BFO).

Chemical Framework to Design Linear-like Relaxors toward Capacitive Energy Storage

“…Encouragingly, a giant W rec of 17.3 J cm –3 , together with a high η of 88.5%, is realized under an E B of 78 kV mm –1 (Figure e). In comparison, the W rec in BKT-D1 exceeds the previously reported highest value in BKT-based systems, − ,− which was 7.6 J cm –3 in BKT-BT-NN, by more than double (Figure f and Table S3). Moreover, the energy storage properties well outperform other lead-free bulk ceramics, such as BT-based, BNT-based, NN-based, and AN-based RFEs (Figure S6).…”

“…The energy storage capacity of a dielectric material is determined by its polarization traits and breakdown strength ( E B ). Lead-free relaxor-ferroelectric (RFE) solid solutions exhibit desirable merits of large polarization ( P m ) and small hysteresis ( H ), making them the preferred option for high-performance dielectric capacitors. − Owing to the high chemical flexibility of perovskites that allow for various atomic combinations at both A- and B-sites, substantial lead-free RFEs have been explored to optimize energy-storage performance. − ,− Examples include BaTiO 3 (BT)-based, ,, Bi 0.5 K 0.5 TiO 3 (BKT)-based, − SrTiO 3 (ST)-based, , Bi 0.5 Na 0.5 TiO 3 (BNT)-based, ,,− (K,Na)­NbO 3 (KNN)-based, , NaNbO 3 (NN)-based, , and AgNbO 3 (AN)-based ,, relaxors, and their corresponding W rec in bulk ceramics has been significantly improved, with values typically ranging from 4 to 8 J cm –3 .…”

Breaking the Mutual Constraint between Polarization and Voltage Resistance with Nanograined High-Entropy Ceramic

“…It is evident that as the electric field increases from 60 to 260 kV/cm, the W d value shows a linear growth from 0.2281 to 1.549 J/cm 3 .The parameter τ 0.9 used to estimate the discharge time is determined to be 132 ns, demonstrating a relatively fast discharge speed. A comparison of the charge–discharge performance of the BKBSC-0.2Cu ceramic with those of other documented energy storage ceramics is shown in Figure (d). ,,,,− Clearly, the C D and P D of the BKBSC-0.2Cu ceramic are better than those of many reported lead-free dielectric ceramics.…”

“…These results indicate the immense energy storage capacity of the BKBSC-0.2Cu high-entropy ceramic. To comprehensively assess the energy storage capacity, we compared the various properties of recently published representative high-entropy ceramics, ,− BKT-based ceramics, BNT-based ceramics, KNN-based ceramics, and NN-based ceramic, as shown in Figure (e) (see Table S4 for details). It is clear that the BKBSC-0.2Cu ceramic exhibits superior characteristics in W rec , ε r , P max , E b , and η, especially in terms of maintaining a high breakdown electric field and high dielectric constants, which offer significant advantages compared to other ceramics.…”

Achieving Ultrahigh Energy Storage Performance for NaNbO3-Based Lead-Free Antiferroelectric Ceramics via the Coupling of the Stable Antiferroelectric R Phase and Nanodomain Engineering

“…Apparently, the larger Δ P (Δ P = P m – P r ) at the highest possible breakdown field strength ( E b ), the larger the W rec can be obtained. Dielectric ceramic capacitor materials, such as BaTiO 3 , SrTiO 3 , Bi 0.5 K 0.5 TiO 3 , and K 0.5 Na 0.5 NbO 3 with ultrahigh energy storage density, great temperature, frequency stability, and terrific mechanical strain properties, have caught the attention of researchers over the past decade. − For instance, Li et al reported a W rec = 6.52 J cm –3 with η = 70% under 425 kV cm –1 in 0.84­(0.6 Bi 0.5 K 0.5 TiO 3 -0.4BiFeO 3 )-0.16­(Na 0.4 Sm 0.2 NbO 3 ). Du et al achieved a W rec of 4.08 J cm –3 under 300 kV cm –1 by incorporating Bi­(Mg 2/3 Nb 1/3 )­O 3 into the K 0.5 Na 0.5 NbO 3 ceramic.…”