Charge Discharge Properties Research Articles

Combinatorial Optimization of Grain Size and Domain Morphology Boosts the Energy Storage Performance in (Bi0.5Na0.5)TiO3-Based Dielectric Ceramics.

Lead-free dielectric ceramics exhibiting excellent energy storage capacity, long service life, and good safety have been considered to have immense prospects in next-generation pulsed power capacitors. However, it is still challenging to simultaneously achieve large recoverable energy density (Wrec), high efficiency (η), and excellent charge-discharge performance. Herein, we fabricated lead-free (1 - x)(Bi0.5Na0.5)TiO3-x(Sr0.7Bi0.1La0.1)TiO3 ((1 - x)BNT-xSBLT) dielectric ceramics, and a good balance between Wrec ∼ 4.15 J/cm3 and η ∼ 93.89% under 333 kV/cm, as well as superior charge-discharge properties (power density PD ∼ 185.42 MW/cm3, discharge energy density Wd ∼ 2.2 J/cm3, and discharge time t0.9 ∼ 53.8 ns under 250 kV/cm), was achieved in 0.6BNT-0.4SBLT ceramics. The good energy storage performance can be attributed to the synergistic contributions of significantly enhanced Eb caused by grain refinement and the large ΔP values induced by polar nanoregions (PNRs) under a high external electric field. Moreover, the 0.6BNT-0.4SBLT ceramics also present excellent temperature stability of energy storage properties (the variations of Wrec and η less than 0.45% and 0.14%, respectively) over a temperature range of 25-185 °C. These figures of merit make 0.6BNT-0.4SBLT ceramics the most promising candidate for energy storage capacitors in advanced pulse power systems.

Structure regulation and performance optimization mechanism of Sr0.7Bi0.2TiO3-based energy storage ceramics based on charged defect design engineering

The linear-like relaxor ferroelectric Sr0.7Bi0.2TiO3 with regulable microstructure offers a new platform to reveal the essential mechanism of energy storage properties improvement and develop advanced pulse capacitors. Herein, Li with relatively weak volatility accompanied by Bi was introduced in Sr0.7Bi0.2TiO3 to form a charged defect and increase the maximum polarization (Pmax) while avoiding the deterioration of dielectric breakdown strength (BDS). The occupation of Li and the formation of Li-Bi defect dipole polar were analyzed using first principle calculations. A unique local superlattice induced by the lattice distortion was first observed in related systems. The Pmax was enhanced due to the increased size and number of polar structures. The breakdown behaviour and local electric field distribution were analyzed using numerical simulation. The BDS was improved due to the decreased oxygen vacancies, high thermal conductivity and enhanced electrical insulation. The excellent and stable energy storage performance was achieved in different temperatures, frequencies and cycles. Meanwhile, the optimized sample possesses excellent and stable charge–discharge properties, especially fatigue resistance (105 cycles under 25 °C and 150 °C). After the process optimization, the sample shows a higher energy storage density of 3.44 J/cm3 with a high efficiency of 93.74 % at 345 kV/cm due to the further enhanced BDS. In this work, the performance improvement mechanism was studied in-depth, providing a new strategy for optimizing linear-like lead-free relaxor ferroelectric energy storage properties.

Stabilization of Cu2O catalyst via strong electronic interaction for selective electrocatalytic CO2 reduction to ethanol

While cuprous oxide (Cu2O) remains the most efficient and viable electrocatalyst for the electrochemical conversion of CO2 to ethanol, its reduction to Cu during the catalytic CO2RR process poses a barrier to its industrial application. To address this challenge, we have reported a highly stable Cu2O-based catalyst by introducing pseudo-capacitive NiCo2O4 intermediate layers. The current densities observed on the surface of the prepared NF@NiCo2O4@Cu2O remained consistent over a 15-hour stability test, demonstrating excellent durability that exceeds that of the NF@Cu2O electrode by more than 200 %. Experimental characterization and DFT analysis indicate that the exceptional stability is primarily attributed to the pseudo-capacitive NiCo2O4 interlayer with cyclic charge–discharge properties, where NiCo2O4 can capture and eliminate accumulated reduced electrons around Cu2O under strong electronic interactions and release electrons through catalytic reduction to produce hydrogen. Furthermore, the NiCo2O4@Cu2O (111) heterostructure significantly reduces the Gibbs free energy (ΔG) required for C-C coupling of *CO intermediates compared to Cu2O (111). This mechanism establishes a cyclic charge–discharge process in order to prevent reduction of Cu2O into copper monomers. As a result, NF@NiCo2O4@Cu2O demonstrates a C2H5OH faradaic efficiency of 56.9 % at −0.5 V vs. RHE, surpassing many other Cu-based catalytic electrodes. This work provides new insights into studying strong electronic interaction structures to eliminate electron enrichment at the catalytic site for stabilizing catalysts and also offers an effective strategy for designing catalysts that maintain long-term stability in industrial applications.

Enhancing the electrochemical performance of Ni-doped CuCo2O4 electrode material through 2D layered sheets

Abstract In the present study, the structural and electrochemical properties on Ni–CuCo2O4 (0 ≤ x ≤ 10 %) was studied for the use of active electrode materials in asymmetric supercapacitors prepared by a simple hydrothermal process. The synthesized material’s morphology shows that the nanosheets are assembled with an average diameter of about 50 nm, and the X-ray diffraction results show the spinel cubic structure with the space group of Fd-3mz (No. 227). CuCo2O4 electrodes exhibit a high specific capacitance for the electrodes because of the abundant redox reactions of Co2+/Co3+ and Co3+/Co4+, and Ni at the Co site has displayed exceptional charge-discharge and cyclic stability properties. The electrochemical studies show that the Ni doped CuCo2O4 electrode has the highest pseudocapacitive nature, with ultra-specific capacitances of 803 F g−1, 889 F g−1, 924 F g−1, and 1,086 F g−1 at 1 A g−1 respectively for pure, 2, 6, and 10 % Ni doped CuCo2O4 electrodes. Further, the excellent rate capability with 82 % capacitance retention and 92.3 % Coulombic efficiency were realized after 1,000 cycles. Moreover, the M-H study at room temperature showed paramagnetic behaviour. Additionally, the electrochemical and magnetic characteristics of the CuCo2O4 system is expected to improve as the doping quantity of Ni increased. This study may pave the way for enhanced properties of Ni doped CuCo2O4 for futuristic hybrid devices applications.

Improved energy-storage and charge–discharge properties achieved in NaNbO3-Bi(Mg0.5Zr0.5)O3 ceramics

Improved energy-storage and charge–discharge properties achieved in NaNbO3-Bi(Mg0.5Zr0.5)O3 ceramics

Ultrahigh energy storage performance in BNT-based binary ceramic via relaxor design and grain engineering

Dielectric capacitors attract much attention for advanced electronic systems owing to their ultra-fast discharge rate and high power density. However, the low energy storage density (Wrec) and efficiency (η) severely limit their applications. Herein, Bi0.5Na0.5TiO3-K0.5Na0.5NbO3 binary ceramic is developed to obtain excellent energy storage performance with strong relaxor behavior, together with large polarization and distorted lattice calculated by first-principles calculations. The atomic-scale local structure analysis of 0.75Bi0.5Na0.5TiO3–0.25K0.5Na0.5NbO3 ceramic reveals distorted polarization distribution and small polar nanoregion related with the enhanced relaxation and low hysteresis. Finite element analysis demonstrates ultrafine grain and increased grain boundary density following hot-pressing sintering are crucial factors in significantly enhancing the breakdown strength (Eb). As a result, ultrahigh Wrec of 12.39 J/cm3 and η of 87.1 % are achieved at a superhigh Eb of 713 kV/cm. Encouragingly, excellent performance of temperature, frequency and fatigue stability at 400 kV/cm are obtained, and high power density of ∼ 306 MW/cm3 as well as fast discharge speed of ∼ 23.3 ns are also realized. This work proposes a simple binary design with strong relaxor behavior, and highlights the potential of grain engineering to achieve outstanding energy storage performance with great stability and excellent charge-discharge property for pulse power devices.

Enhancement of Charge-Discharge Properties and Temperature Stability of (Ba0.975Na0.05)Ti0.99Nb0.01O3 Ceramic by Doping High-Entropy Oxide

A bidirectional optimization strategy was adopted to fabricate (1-x)(Ba0.975Na0.05)Ti0.99Nb0.01O3)-xBi(Zn0.2Mg0.2Al0.2Sn0.2Zr0.2)O3(abbreviated as (1-x)BNNT-xBZMASZ, x = 0.02–0.10) ceramics, aimed to improve the energy storage performance. X-ray diffraction results revealed that Bi2+ cations entered the A site and the multiple cations occupied the B site of BNNT, thereby decreased the remnant polarization intensity and refined the hysteresis loop. Scanning electron microscopy images showed uniform morphologies with clear grain boundaries of the ceramics, and the average size decreased with x increasing. The substitution of multiple cations at the B-site induced the splitting of macroscopic ferroelectric domains into smaller polar nanodomains, leading to the formation of high-dynamic polar nanoregions and accelerating the transition from BNNT to relaxor ferroelectrics, thus improving relaxation properties of the material. The excellent energy storage density (Wrec ∼ 2.80 J cm−3) and efficiency (∼90.0%) can be obtained under 200 kV cm−1. Moreover, the discharge-charge testing revealed excellent current density (∼589.5 A cm−2), high power density (∼20.63 MW cm−2), and extremely short discharge time (t0.9 ∼ 50.4 ns), along with exceptional temperature stability and cycling stability under the equivalent electric field of 120 kV cm−1. The 0.92BNNT-0.08BZMASZ ceramic offers a new approach to the design and an improvement of pulsed dielectric capacitor materials.

Structurally Regulated Design Strategy of Bi0.5Na0.5TiO3-Based Ceramics for High Energy-Storage Performance at a Low Electric Field.

Dielectric ceramic capacitors are prospective energy-storage devices for pulsed-power systems owing to their ultrafast charge-discharge speed. However, low energy-storage density makes them difficult to commercialize for high-pulse-power technology applications. Herein, we presented a structurally regulated design strategy to disrupt a long-range ferroelectric order, refined grains, and eventually achieve excellent comprehensive energy-storage performance in (1 - x) (0.7Bi0.5Na0.5TiO3-0.3SrTiO3)-x Sm(Zn2/3Nb1/3)O3 eco-friendly ceramics. A large Wrec of ∼7.43 ± 0.05 J/cm3 and a high η of ∼85 ± 0.5% of 0.96 (0.7Bi0.5Na0.5TiO3-0.3SrTiO3)-0.04 Sm(Zn2/3Nb1/3)O3 were obtained at a low electric field of 290 kV cm-1 with good energy-storage temperature (25-120 °C), frequency (1-100 Hz) stability, and charge-discharge properties (PD ∼ 74 ± 1 MW/cm3 and τ0.9 ∼ 159 ± 2 ns). This strategy inspires rational structurally regulated designs and aims to promote the development of eco-friendly 0.7Bi0.5Na0.5TiO3-based ceramics with excellent energy-storage characteristics.

Achieving ultrahigh energy density and efficiency simultaneously in (Na, K)NbO3-based lead-free relaxor ferroelectrics via a collaborative design

Relaxor ferroelectrics have garnered enormous attention for their great application potential in pulsed power energy-storage capacitors, while simultaneously achieving large recoverable energy density (Wrec) and high efficiency (η) remains a formidable challenge. Through collaboratively controlling multiscale structure via a combination of composition design and processing improvement, polar nanodomains with multiple local symmetries were engineered in ultrafine grains, enabling significantly reduced polarization hysteresis, delayed saturation polarization, maintained high polarization, and enhanced breakdown strength. As a result, an excellent comprehensive energy-storage performance of Wrec ∼11.8 J/cm3 and η ∼88.7 % is achieved in the (Na, K)NbO3-based spark-plasma-sintered lead-free ceramics, together with stable charge-discharge properties of power density ∼176.3 MW/cm3, discharge energy density ∼3.2 J/cm3, and discharge time ∼43 ns over a wide temperature range of 20–140 °C. The studied ceramic demonstrates great advantages in advanced capacitive energy-storage applications.

Inherent Behavior of Electrode Materials of Lithium-Ion Batteries.

For independency from the fossil fuels and to save environment, we need to move toward the green energies, which requires better energy storage devices, especially for usage in electric vehicles. Li-ion and beyond-lithium insertion batteries are promising to this aim. However, they suffer from some inherent limitations which must be understood to allow their development and pave the way to find suitable energy storage alternatives. It is found that each positive or negative electrode material (cathode or anode) of the intercalation batteries has its own behavioral (charge-discharge) properties. The modification of preparation parameters (composition, loading density, porosity, particle size, etc.) may improve some aspects of the electrode performance, but cannot change the intrinsic property of the electrode itself. Accordingly, these properties are called as the "inherent behavior characteristics" of the active material. It is concluded that the behavior of a specific electrode substance, even following different preparation routes, depends only on diffusion mechanisms. This work shows that the inherent electrode properties can be visualized by representation of current density vs. capacity.

Synthesis of Nano-electrolytic Manganese Dioxide for Alkaline Batteries Mediated by Organic Additives

This article discusses the impact of adding organic additives like glycine (GLY), sucrose (SUC), and saccharine (SACCH) on the electrical characteristics and microstructure of electrolytic manganese dioxide (EMD), which is made from an acidic aqueous sulphate solution. The structure and chemistry of EMD were ascertained by means of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). To assess the material's potential for use in alkaline batteries, its charge-discharge properties were ascertained. It was found that the majority of MnO2 in all the EMD samples was in the γ-phase, which is electrochemically active and useful for energy storage applications. When glycine, sucrose, and saccharine were added to the solution as organic additives, the electrochemical deposition of manganese dioxide (MnO2) resulted in an increase in current efficiency and a decrease in energy consumption. The SEM images demonstrated that when EMD was deposited with an additive, small grain sizes and discrete particles free of agglomeration were formed, but large grain sizes were obtained in the absence of additives. Charge-discharge characteristics suggested that the additions improve the ability of MnO2 structure to store energy. This suggested that the additions may have an impact on the morphology and size of the particles, and consequently, the electrochemical activities of the material that was electrodeposited. In the case of the additives examined in this paper, the outcome was the creation of a material with possible use in battery technology.

Achieving high energy storage density and efficiency in (Na0.5Bi0.5)TiO3-based lead-free ceramics

Due to the demands of miniaturization, weight reduction and green development for electronic devices, development of lead-free dielectric ceramic capacitors with high recoverable energy density (Wrec) and energy storage efficiency (η) attracts much attention. To this end, (1-x)[0.75(Na0.5Bi0.5)TiO3-0.25SrTiO3]-xNdNbO4 (abbreviated as: NBST-xNN) ceramics were fabricated through a solid-state reaction method. After adding NN, the non-perovskite phase of Bi2Ti2O7 (BTO) with low dielectric constant (εr) and loss (tan δ) is generated. Finite element software (COMSOL) was used to explore the influence of the BTO phase on breakdown strength (Eb). The simulation result indicates that the BTO phase with a low εr concentrates a larger local electric field (LEF), and thus weakens the LEF loading in the main perovskite phase, which is beneficial for enhancing Eb. Moreover, NN doping significantly decreases the oxygen vacancy concentration in NBST ceramics, which plays a key role in improving Eb. On the other hand, as NN content increases, the hysteresis of the polarization (P)-electric field (E) loops is substantially suppressed, and the polarization saturation is delayed, which can be ascribed to the appearance of the BTO phase having a linear dielectric characteristic and to the enhanced fluctuations of composition and charge by NN doping. Benefitting from the above factors, the optimal energy storage performance (ESP) with a Wrec of 4.14 J/cm3 and an η of 90 % is obtained in NBST-0.08NN ceramics. Meanwhile, the ESP of NBST-0.08NN ceramics shows good charge-discharge properties and thermal stability. In conclusion, these results demonstrate that NBST-0.08NN ceramics are promising candidates as environment-friendly dielectric capacitor materials.

Metal-Doped NASICON/Polymer Composite Solid Electrolyte for Lithium Titania Anode in Lithium-Ion Batteries.

This study reports five types of metal-doped (Co, Cu, Sn, V, and Zr) NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP)/polymer composite solid electrolytes (CSEs) enabling Li4Ti5O12 (LTO) anodes to have high rate capability and excellent cycling performance. The high Li+-conductivity LATP samples are successfully synthesized through a modified sol-gel method followed by thermal calcination. We find that the cation dopants clearly influence the substitution of Al for Ti, with the type of dopant serving as a crucial factor in determining the ionic conductivity and interfacial resistance of the solid electrolyte. The CSE containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and Sn-LATP shows an ionic conductivity of 1.88 × 10-4 S cm-1 at ambient temperature. The optimum conductivity can be attributed to alterations in the lattice parameters and Li+ transport pathways owing to Sn doping. The solid-state cell equipped with the LTO-supported CSE containing Sn-LATP fillers demonstrates both excellent high rate capability at 5 C (with a capacity retention of 86% compared to the value measured at 0.2 C) and superior cycling stability, maintaining high Coulombic efficiency (>99.0%) over 510 cycles. These findings indicate that the proposed CSE is highly promising for use in solid-state lithium batteries with desirable charge-discharge properties and high durability.

Innovative Design of BNKT-xSLZT Ceramics: Maximizing the Polarization Difference for Enhanced Energy Storage.

Lead-free relaxor ferroelectric ceramics with outstanding energy-storage (ES) density (Wrec) and high ES efficiency (η) are crucial for advanced pulse-power capacitors. This study introduces a strategic approach to maximizing the polarization difference (ΔP) by inducing a transition from the ferroelectric phase to the ergodic relaxor (ER) phase. By employing this strategy, a series of ceramics, (1 - x)(Bi0.5Na0.4K0.1)TiO3-x(Sr0.85La0.1)(Zr0.5Ti0.5)O3 (BNKT-xSLZT), with varying SLZT content (x = 0.05, 0.10, 0.15, and 0.20), were designed. The addition of SLZT enhances cationic disorder, induces vacancies at A sites, and disrupts long-range ferroelectric order, facilitating the formation of polar nanoregions and enhancing relaxor ferroelectric behavior. Furthermore, a viscous polymer process (VPP) technology is employed to optimize the ceramics' structure, aiming to increase the breakdown strength (Eb) and enhance ΔP. Ultimately, enhanced ES performance is demonstrated in BNKT-0.15SLZTVPP, achieving a remarkable Wrec of 6.85 J/cm3 and η of 84% under 470 kV/cm. This composition demonstrates excellent stability with minimal variations in Wrec (3.0%) and η (4.4%) over the temperature range of 20-110 °C. Additionally, BNKT-0.15SLZTVPP exhibits exceptional pulse charge-discharge properties, featuring a high discharge density of 3.72 J/cm3, a large power density of 164.2 MW/cm3, and a short discharge time (t0.9) of 193 ns under 300 kV/cm. The study validates the practicality of BNKT-0.15SLZTVPP for pulse capacitors and underscores the potential to enhance ES performance through A-site donor doping and VPP technology. This work provides a comprehensive understanding of the interplay among composition, structure, and ES properties in lead-free relaxor dielectric ceramics, laying the groundwork for innovative advancements in the field.

Linear-like NaNbO3-based Lead-free Relaxor Antiferroelectric Ceramics with Excellent Energy-storage and Charge-discharge Properties

Linear-like NaNbO₃-based Lead-free Relaxor Antiferroelectric Ceramics with Excellent Energy-storage and Charge-discharge Properties

Synthesis, Electrochemical Properties and Crystal and Electronic Structure Changes in Charge/Discharge Process of Spinel Type Cathode-Materials Mg1.33-Y(V1.67-x+yMnx)O4 for Magnesium Secondary Batteries

Attention has therefore focused on rechargeable batteries using multivalent cations, which are expected to offer even higher energy densities than lithium ion batteries. One topic that has attracted attention is rechargeable batteries using Mg as a carrier. The advantage of using Mg is that it has a low electrode potential with a high capacity.Although previous research into Mg rechargeable battery cathode materials started with a report by Aurbach1) et al., and included chevrel compounds, these have had problems in terms of battery voltage and cycle properties. In spinel-type Mg1+yCo2-x-yMnxO4, charge and discharge capacities were reported to increase by substituting Mn2). V is thought to have high reversibility due to having a broad mixed atomic valence. The authors synthesized Mg1.33V1.57Ni0.1O4, and reported that the discharge capacity after 14 cycles was 160 mAh/g and the capacity retention rate was high3). Furthermore, the authors investigated the spinel solid solution αMgCo1.5Mn0.5O4-(1-α)Mg(Mg0.33V1.57Ni0.1)O4 as a new cathode material and evaluated its battery properties, and as a result found that the initial discharge capacity at α = 0.3 was 180 mAh/g with the discharge capacity maintained after 60 cycles4 ). However, the substitution products need to be investigated in order to improve the discharge potential of the Mg-V system and enhance the cycle properties.The present study investigated the synthesis of a new spinel type cathode material Mg1.33-y(V1.67-x+yMnx)O4 by substituting Mn into Mg1.33V1.67O4 and different Mg content in order to increase the charge-discharge capacity and improve the cycle properties. The crystal and electronic structures and charge-discharge properties depending on the amount of Mn substitution and Mg content, and the structural changes accompanying charging and discharging.Mg1.33-y(V1.67-x+yMnx)O4 was synthesized by a solid -phase method under high vacuum atmosphere. The product was assigned to the spinel structure with space group Fd-3m from the powder X-ray diffraction. Synthesized materials of uniform composition were confirmed from elemental mapping by STEM-EDS. Charge and discharge cycle tests showed that the deliverable discharge capacity depends on the cycle number, Mn composition, and working temperature. The charge and discharge cycle tests showed the discharge capacity increased with repeated cycles. Mg1.33V1.57Mn0.1O4 showed the largest discharge capacity of 256 mAh/g at 13th cycles while the initial capacity was only 73 mAh/g at 90°C. The local structure was analyzed based on EXAFS spectra at the V K-edge for the pristine and electrode materials, and the results suggested that Mg1.33V1.57Mn0.1O4 had the smallest lattice distortion due to Mn at 16d sites, and XAFS spectra at the V K-edge indicated the significant change in the oxidation state of V during the charge/discharge cycles. The particularly stable crystal structure and large contribution of charge compensation by V may jointly contribute to the superior charge-discharge property of Mg1.33V1.57Mn0.1O4 5).Moreover, we investigated the different Mg, Mn content sample. Mg1.25(V1.55Mn0.2)O4 showed an increase in capacity from the first discharge capacity 71mAh/g to 199mAh/g after 34 cycles at 90℃ (Fig.1). The change in crystal structure due to charging and discharging was investigated. Focusing on the magnitude of M(16d)-O6 octahedral strain, the strain after 10th discharge is significantly reduced, so it is considered that the structure was stabilized by repeating the cycles and contributed to the improvement of the cycles characteristics. The electronic structure was analyzed by MEM, which showed that the electron density between the 16d-32e sites was higher and the covalent bond was higher than that of the diffusion sites after charge and discharge. From this, it is considered that the host structure was stabilized by charge and discharge, which contributed to the increase in charge and discharge capacity. From the result of XANES, it revealed that V is trivalent to tetravalent and Mn is divalent. Furthermore, from the results of EXAFS, it was clarified that the amount of reduction was larger in Mg1.25(V1.55Mn0.2)O4, especially in charge and discharge, because the amount of change in the distance between V and O was larger. Acknowledgements This work was supported by JST ALCA-SPRING Grant Number JPMJAC1301, Japan.We are deeply grateful for the cooperation of Dr. T. Honma and Dr. H. Ofuchi of JASRI for the XAFS analyses (SPring-8, BL14B2), Dr. K. Osaka of JASRI for the measurement of the synchrotron X-ray diffraction (SPring-8, BL19B2). References 1) D. Aurbach, et al., Adv. Mater., 19, 4260 (2007).2) Y. Idemoto, et al., J. Power Sources, 482, 228920 (2021).3) Y. Idemoto, et al., J. Power Sources, 455, 227962 (2020).4) Y. Idemoto, et al, Electrochemistry, 90(2), 027002(2022).5) Y. Idemoto, et al, J. Electroanal. Chem., 928, 1107064 (2023). Figure 1

Electrospun Perovskite Nanofiber/Poly(vinylidene fluoride-cohexafluoropropylene) Quasi-Solid-State for Lithium-Metal Batteries

Solid-state lithium-metal batteries (SSLMBs) with a composite solid electrolyte (CSE) have great potential for achieving both high energy density and high safety and are thus promising next-generation energy storage devices. Nevertheless, the key bottleneck issues are a high electrode/electrolyte interface resistance and the limited Li+ conductivity of the solid electrolyte. A free-standing CSE consisting of Li0.33La0.557TiO3 (LLTO) nanofibers, poly(vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is developed for room-temperature SSLMB applications. First, the calcination temperature for the electrospun LLTO precursor is optimized. The effects of the LLTO filler fraction and the morphology (spherical vs. fibrous) on CSE conductivity are examined. Furthermore, a succinonitrile interlayer (SNI), which is composed of succinonitrile, fluoroethylene carbonate, and LiTFSI, is developed to lower the high interfacial impedance. Compared to a conventional ester-based interlayer (EBI), SNI effectively decreases the Li//CSE interfacial resistance and suppresses unfavorable interfacial side reactions. The derived LiF- and CF x -rich protective layer on the Li electrode surface prevents the accumulation of dead Li and the excessive formation of SEI. Importantly, the dehydrofluorination reactions of PVDF-HFP are adequately mitigated, and a highly conductive and stable Li//CSE interface is achieved owing to SNI. Accordingly, both Li//CSE@SNI//Li and Li//CSE@SNI//LiFePO4 cells exhibit superior charge-discharge properties and cyclability to those of an EBI counterpart. A simple and low-cost interface modification strategy to enhance the performance of SSLMBs is proposed in this paper.

High-Voltage Graphite//LiNi0.5Mn1.5O4 Full Cell with Bis(fluorosulfonyl)Imide and bis(trifluoromethyl)Sulfonylimide Ionic Liquid Electrolytes

Room-temperature ionic liquids (ILs) are a promising type of lithium-ion battery (LIB) electrolyte owing to their wide electrochemical stability windows, high thermal stability, non-volatility, and environmental friendliness. Particularly, bis(fluorosulfonyl)imide (FSI−)-based ILs are appealing due to their high ionic conductivity, low viscosity, and excellent anode compatibility. Nevertheless, the strong corrosivity of FSI− toward the Al current collector at high operating potential is a major concern and needs to be addressed. Three strategies have been adopted in this work to overcome this limitation. The effects of IL composition on the electrochemical properties of the LiNi0.5Mn1.5O4 (LNMO) cathode and graphite anode are investigated. First, Li+ fractions are modulated in the N-propyl-N-methylpyrrolidinium−FSI (PMP−FSI) IL. We find that simply increasing the LiFSI concentration (even to 3.2 m) in the PMP−FSI IL electrolyte cannot effectively inhibit Al corrosion, leading to a low charge-discharge Coulombic efficiency (CE) of the LNMO electrode. Second, increasing the bis(trifluoromethyl)sulfonylimide (TFSI−)/FSI− molar ratio leads to a reduced rate capability of the LNMO cathode and a unsatisfactory compatibility with the graphite anode. Finally, we propose a Li+/TFSI−/FSI− modulation concept to optimize the IL electrolyte. The optimal 2.4 m LiTFSI/PMP−FSI IL electrolyte minimizes the corrosion current of the Al substrate at 5 V. Moreover, the relatively high Li+ and FSI− content ensures superior charge-discharge properties of both the LNMO and graphite electrodes. A high reversible capacity of approximately 135 mAh g–1 at 0.1 C based on LNMO is verified for a graphite//LNMO full cell. This cell is able to retain ~85% of its initial capacity after 200 cycles. The obtained experimental results can guide the development of IL electrolytes for high-reliability LIBs.

Energy‐storage properties of (0.7Bi0.65Na0.35Fe0.3Ti0.7O3–0.3Sr0.85Bi0.1TiO3)–NaTaO3 relaxor under low electric fields

AbstractCurrently, the energy‐storage properties of dielectric ceramic capacitors have aroused wide attention; however, most materials exhibiting excellent energy‐storage properties are based on high electric fields, which increase the cost of insulation technology. Herein, the energy‐storage and charge–discharge properties of (1 − x)(0.7Bi0.65Na0.35Fe0.3Ti0.7O3–0.3Sr0.85Bi0.1TiO3)–xNaTaO3 (x = 0.03–0.18, abbreviated as 100xNT) ceramics are investigated. 9NT achieves superior energy‐storage properties under a low electric field of 210 kV/cm, with an energy‐storage density (Wrec) of 3.44 J/cm3 and efficiency (η) of 86.6%. The energy‐storage properties exhibit excellent frequency stability in 3–100 Hz as well as temperature stability between 25 and 175°C. Furthermore, the charge–discharge performance features a high‐power density (PD = 67.04 MW/cm3), and an ultrafast discharge speed (t0.9 = 52 ns). This work paves a new way to explore energy‐storage competitive materials under low electric fields.

Significantly enhanced energy-storage properties in NaNbO3-based relaxor ferroelectric ceramics via introducing a wide band-gap linear dielectric

The achievement of simultaneous high energy-storage density and efficiency is a long-standing challenge for dielectric ceramics. Herein, a wide band-gap lead-free ceramic of NaNbO3–BaZrO3 featuring polar nanoregions with a rhombohedral local symmetry, as evidenced by piezoresponse force microscopy and transmission electron microscopy, were reported to exhibit a giant energy-storage density of ∼5.0 J/cm3 and a high efficiency of ∼85 % as well as excellent charge-discharge properties simultaneously. Enhanced breakdown strength from a synergistic effect of wider band gap and decreased grain size provides a prerequisite for improving energy-storage performance. Meanwhile, the substitution of linear dielectric BaZrO3 can not only adjust the low-temperature ferroelectric rhombohedral phase of NaNbO3 into near room temperature, but also significantly reduce the FE domain size owing to the increased local random fields. Therefore, suppressed polarization hysteresis and delayed polarization saturation can be observed with increasing BaZrO3 content, leading to the significantly enhanced overall energy-storage properties.