Charge Discharge Properties Research Articles

Boosting capacitive performance of lead-free relaxor ferroelectrics by introducing a linear dielectric

As an important core component used in high-power pulse electronic systems, dielectric ceramic capacitors have gained great interest because of their ultrahigh powder density (PD) and fast discharge speed (t0.9). However, inferior energy storage performance (ESP) greatly limits the development of energy storage devices with the requirement of miniaturization and integration. Herein, we propose a feasible approach to introduce linear dielectric CaTiO3 (CT) into (Bi0.5Na0.5)TiO3 (BNT) for the design of engineered relaxor ferroelectrics to tune ESP at the grain, domain, and macroscopic scales. The results demonstrate that introducing CT generates enhanced relaxor behavior with highly dynamic polar nanoregions, refines grain size, and suppresses dielectric loss, synergistically yielding increased breakdown strength, negligible remnant polarization, and a nearly linear polarization hysteresis loop. Consequently, superior ESP is achieved in BNT-0.3CT relaxor ferroelectric ceramics with a large energy density (∼5.65 J/cm3) and a high efficiency (∼88.1 %). Based on CT-induced merits, the excellent temperature/frequency/cycling stabilities and remarkable charge-discharge properties featuring a high PD of 200.4 MW/cm3, high discharge energy density of 2.27 J/cm3 and ultrashort t0.9 of 58 ns of the designed ceramics broaden the actual application prospects. This work demonstrates that introducing linear dielectric CT holds great promise for developing high-performance energy storage dielectrics.

Charge–discharge properties of LiMn 2 O 4 -group positive electrode active materials for lithium-ion batteries using high-throughput experimental screening and machine learning models

Charge–discharge properties of LiMn ₂ O ₄ -group positive electrode active materials for lithium-ion batteries using high-throughput experimental screening and machine learning models

Development of novel Co3+ doped LaMnO3 perovskite electrodes for supercapacitors and sensors: Mechanism of electrochemical energy storage and oxygen intercalation

LaMnO3 and La1-xCoxMnO3 (x = 0, 0.05, 0.2, 0.4) nanomaterials were prepared by the sol-gel method, and their structural and morphological properties were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. XRD results were validated using computational XRD pattern generated using density functional theory (DFT) calculations and found that they are in good agreement with each other. The estimated crystallite size from XRD and TEM is ∼23 nm for all synthesized undoped and doped materials. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanometric charge-discharge (GCD) properties of prepared electrodes were analyzed to study their capacitive performance and stability. An electrochemical sensor was developed for the detection of the paracetamol drug and analyzed using CV responses. These analyses showed La1-xCoxMnO3 are potential electrode materials with a high specific capacitance of 651.54 Fg−1 for x = 0.2 at the scan rate of 5 mVs−1 in 1 M KCl aqueous electrolyte for electrochemical supercapacitors and x = 0.05 for the development of an electrochemical sensor for paracetamol detection.

Improving electric-energy transmission performance of LixNi1-xO linear ceramic resistors by Li+/Ni3+ ion occupation regulation for pulsed power technology

Linear ceramic resistor receives extensive attention for its great advantages of fast energy transmission in pulsed power technology. However, the research about improving the linear current-voltage characteristics and pulsed charge-discharge speed of LixNi1-xO solid solution is rarely reported. Herein, we fabricated the LixNi1-xO linear ceramic resistors through a solid-phase reaction method, and the effects of the Li+ ion on the microstructure, current-voltage characteristics and pulsed charge-discharge properties were studied. Specifically, the electron holes exchange between divalent and trivalent nickel ions is enhanced by Li substitution, which contributed to the significantly decreasing in nonlinear coefficient (α) and resistivity. On a separate note, the rising edge of pulse charge-discharge is influenced by the linearity of LixNi1-xO ceramic resistors. The closer the nonlinear coefficient is to 1, the shorter the pulsed charge-discharge time is. Meanwhile, the defect dipoles induced by Li substitution may also contribute to the reduction of discharge time of LixNi1-xO linear ceramic resistors. As a result, the Li0.03Ni0.97O linear ceramic resistor with an excellent nonlinear coefficient of 1.03 exhibits extraordinary fast discharge speed (t0.9 = 94.8 ns) at 1.0 kV. The investigation on LixNi1-xO linear ceramic resistors suggests the potential of this material to be applied in the pulsed power system.

Obtaining high breakdown strength and excellent charge–discharge properties in bismuth ferrite-based lead-free relaxor ferroelectric ceramics

Obtaining high breakdown strength and excellent charge–discharge properties in bismuth ferrite-based lead-free relaxor ferroelectric ceramics

Comparative study of different lithium salts as electrolyte additives of Li/SiOx–Si–C half-cells for lithium sulfur batteries

Silicon oxide and its derivatives (SiOx, 0 < x < 2) are drawing significant interest as electrode material for Li-ion and Li–S batteries owing to their unique properties of high specific capacity, low working potential, high abundance, and environmental friendliness. In-depth research is done on the effects of electrolyte additives on the electrochemical and interfacial characteristics of SiOx-based anodes for Li–S batteries. Two different electrolyte additives namely lithium bis (fluorosulfonyl imide) (LiFSI) and lithium bis (oxalatoborate) (LiBOB) were incorporated in the supporting electrolyte containing 1 M lithium bis (trifluoromethanesulfonyl imide) (LiTFSI) in tetraethylene glycol dimethyl ether (TEGDME): 1,3 dioxolane (DOL) in the ratio of 1:1 (v/v). The Li/SiOx–Si–C 2032-type half-cells were assembled, and their charge–discharge properties were explored at 0.1 C-rate. Surface morphology and electrochemical impedance investigations of the electrode materials have been performed after cycling. The interfacial properties of SiOx-based electrodes were examined by FTIR and XPS. Among the electrolytes studied LiFSI-added electrolytes offer superior charge–discharge properties, which was attributed to the formation of a stable solid electrolyte interphase (SEI) layer on the electrode surface. The surface chemistry studies revealed the formation of Li2CO3 and ROCO2Li peaks on the lithium metal surface. The formation of Li2CO3 and ROCO2Li compounds are identified on lithium surface by XPS data and complemented by NMR analysis.

Simultaneously achieving high energy storage and charge-discharge performance by Nd-doped Sr0.7Bi0.2TiO3 lead-free relaxor ferroelectric ceramics

Dielectric capacitors have been extensively studied in electronic and power systems based on their high power density and ultra-fast discharge rates. In this study, the dielectric, energy storage and charge-discharge properties of Sr0.7Bi0.2TiO3-based lead-free relaxor ferroelectric ceramic were investigated. The dielectric breakdown strength was significantly improved by introducing the rare earth element Nd, which was attributed to the rise in resistivity and large band gap. The results show that Sr0.7Bi0.15Nd0.05TiO3 obtain a high recoverable energy storage density of 2.34 J/cm3 with high efficiency of 92%. In addition, pulsed charge-discharge tests demonstrated that Sr0.7Bi0.15Nd0.05TiO3 possesses a high power density of 73.5 MW/cm3, a short discharge period of 0.1 μs, and a pulsed discharge energy density of 2.0 J/cm3. Meanwhile, the energy storage performance of Sr0.7Bi0.15Nd0.05TiO3 exhibits excellent stability of temperature, frequency and cycling. This work provides a systematic study and a new strategy for enhancing the performance of SBT ceramics.

Evolving energy-storage performances during temperature-induced antiferroelectric P–R phase transition in NaNbO3-based lead-free ceramics

Temperature-driven antiferroelectric (AFE) P to AFE R phase transition in MnO2-doped 0.90NaNbO3-0.10CaTiO3 ceramics was investigated through polarization-field response, energy-storage and charge-discharge properties as well as ex/in-situ multiscale structure characterization. Both room-temperature AFE P and high-temperature AFE R phases show double polarization-electric field hysteresis loops, indicating a reversible field-driven AFE to ferroelectric (FE) phase transition. An abnormal variation of critical fields for the AFE-FE and FE-AFE phase transition and a faster polarization-field response contribute to the reduced polarization hysteresis for both AFE P and R phases but an obviously expanded linear polarization-field response only for AFE R phase, being responsible for a two-time significant enhancement in energy-storage properties from P phase to P–R phase boundary and then to R phase. The variation of unit cell anisotropy and domain morphology with temperature was found to play crucial roles in the modulated field-driven phase transition behavior and polarization-field response on heating.

A co-doping strategy to achieve high energy storage performance in BiFeO3-based ceramics

In this work, (Bi0.65-0.65xBa0.35-0.35xNdx)(Fe0.65-0.65xTi0.35-0.35xNbx)O3+x (abbreviated as: BFBT-xNN, x = 0, 0.04, 0.08 and 0.12) ceramics were fabricated through a solid-state reaction method, aiming to obtain high-performance capacitor materials. BFBT ceramics have attracted increasing attention as potential energy storage materials because of their excellent dielectric and ferroelectric properties. However, two handicaps limit the large improvement of their energy storage performance (ESP). One is the large hysteresis of their polarization (P)-electric field (E) loops; the other is the low dielectric breakdown strength (Eb), which has a close correlation with the inevitable defects present in BF-based ceramics. Herein, we designed a co-doping strategy to overcome the two handicaps in order to achieve high ESP in BFBT ceramics. In this strategy, the trivalent rare earth Nd3+ ions and high valence Nb5+ ions are simultaneously introduced at the perovskite A- and B-sites of BFBT ceramics, which is called NN co-doping. The NN co-doping enhances the relaxor properties of BFBT ceramics due to the enhanced composition and charge fluctuations and promotes the formation of the Bi-rich phases, which contribute to the appearance of a slim P-E loop. Meanwhile, the Eb of BFBT ceramics is enhanced, which is ascribed to the significantly decreased oxygen vacancy concentration, the reduced grain size and the Bi-rich phases. Benefitting from these factors, a high recoverable energy storage density (Wrec) of 3.64 J/cm3 and energy storage efficiency (η) of 88% are simultaneously obtained under an enhanced Eb of 330 kV/cm in BFBT-0.08NN ceramics. Moreover, the ESP of BFBT-0.08NN ceramics shows good thermal stability (30–150 °C) and charge-discharge properties. These results indicate that BFBT-0.08NN ceramics could be a promising capacitor material.

PPy@MWCNT Nanocomposite for Supercapacitor Applications

Polypyrrole (PPy) is a potential electrode material for supercapacitors due to its properties suchas high conductivity and chemical stability. However, additional additives can be used to further improvethe capacity values and energy storage performance of PPy. Multi-walled carbon nanotubes (MWCNT) arenanomaterials with properties such as high surface area, excellent conductivity and mechanical strength,and can improve supercapacitor performance when integrated into the PPy matrix. In this study, synthesis,characterization and performance analysis were performed to evaluate the potential of PPy and MWCNTdoped PPy in supercapacitor applications. PPy and MWCNT doped PPy were characterized using analyticaltechniques such as XRD (X-ray diffraction) analysis and SEM (scanning electron microscopy) imaging.XRD analysis was used to determine the crystal structures and crystal sizes of the material and showed thatthe crystal structures of PPy and MWCNT doped PPy were preserved. SEM imaging was used to examinethe surface morphology of the material and it was observed that it has a homogeneous surface structure.Supercapacitor performance was evaluated using electrochemical characterization methods. PPy andMWCNT doped PPy samples exhibited high capacitance values and fast charge-discharge properties. Theintegration of the MWCNT additive into the PPy matrix allowed the electrode to maintain its chemicalstability while increasing the surface area. These results show that PPy and MWCNT doped PPy have thepotential to provide more efficient energy storage in supercapacitors.

Secondary‐Phase‐Induced Charge–Discharge Performance Enhancement of Co‐Free High Entropy Spinel Oxide Electrodes for Li‐Ion Batteries

AbstractHigh entropy oxide (HEO) has emerged as a new class of anode material for Li‐ion batteries (LIBs) by offering infinite possibilities to tailor the charge–discharge properties. While the advantages of single‐phase HEO anodes are realized, the effects of a secondary phase are overlooked. In this study, two kinds of Co‐free HEOs are prepared, containing Cr, Mn, Fe, Ni, and Zn, for use as LIB anodes. One is a plain cubic‐structure high entropy spinel oxide HESO (C) prepared using a solvothermal method. The other HESO (C+T) contains an extra secondary phase of tetragonal spinel oxide and is prepared using a hydrothermal method. It is demonstrated that the secondary tetragonal spinel phase introduces phase boundaries and defects/oxygen vacancies within HESO (C+T), which improve the redox kinetics and reversibility during electrode lithiation/delithiation. Density functional theory calculation is performed to assess the phase stability of cubic spinel, tetragonal spinel, and rock‐salt structures, and validate the cycling stability of the electrodes upon charging–discharging. The secondary‐phase‐induced rate capability and cyclability enhancement of HEO electrodes are for the first time demonstrated. A HESO (C+T)||LiNi0.8Co0.1Mn0.1O2 full cell is assembled and evaluated, showing a promising gravimetric energy density of ≈610 Wh kg−1 based on electrode‐active materials.

Excellent energy storage properties realized in novel BaTiO3-based lead-free ceramics by regulating relaxation behavior

BaTiO3(BT) has attracted extensive attention among advanced lead-free ferroelectric materials due to its unique dielectric and ferroelectric properties. However, the enormous remanent polarization and coercive field severely impede the improvement of its energy storage capabilities. Here, the BaTiO3Bi(Zn0.5Hf0.5)O3 (BT-BZH) ceramics with high breakdown field strength and remarkable relaxation characteristics can be obtained by introducing the composite component BZH in BT to regulate the phase structure and grain size of the ceramics. The findings demonstrate that the improvement of energy storage performance is related to the increase of relaxation behavior. A large energy storage density (Wrec∼3.62 J/cm3) along with superior energy storage efficiency (η∼88.5%) is achieved in 0.88BT-0.12BZH relaxor ceramics only at 240 kV/cm. In addition, the sample suggests superior thermal stability and frequency stability within 25–115 °C and 1–500 Hz, respectively. Furthermore, the outstanding charge-discharge properties with an ultrafast discharge time (100 ns), large discharged energy density (1.2 J/cm3), impressive current density (519.4 A/cm2) and power density (31.1 MW/cm3) under the electric field of 120 kV/cm are achieved in studied ceramics. The excellent energy storage performance of BT-BZH ceramics provides a promising platform for the application of lead-free energy-storage materials.

Improved capacitive energy storage in sodium niobate-based relaxor antiferroelectric ceramics

Ceramic-based dielectric capacitors have become an attractive issue due to their wide applications in current pulsed-/high-power electronic devices. Antiferroelectric ceramics generally exhibit ultrahigh energy density owing to their giant polarization activated by antiferroelectric–ferroelectric phase transition under a high electric field but suffer from large hysteresis, meanwhile giving rise to low efficiency. Herein, by introducing perovskite compound Sr(Fe0.5Ta0.5)O3 into an antiferroelectric NaNbO3 matrix, a stabilized antiferroelectric phase and an improved relaxor behavior are observed. That is, relaxor antiferroelectric ceramics are constructed. Accordingly, a double polarization–electric field (P–E) loop becomes slimmer with increasing incorporation of dopants, leading to an ultrahigh recoverable energy density of 11.5 J/cm3, an energy storage efficiency of 86.2%, outstanding frequency/cycling/thermal reliability, and charge–discharge properties in 0.90NaNbO3-0.10Sr(Fe0.5Ta0.5)O3 ceramics. This work reveals that inducing the relaxor behavior in antiferroelectric materials is an effective route to improve their capacitive energy storage.

Tailoring relaxor P4bm+P21ma phases in BNT-based ceramics for enhancing comprehensive energy storage properties

Tailoring relaxor phase is an effective strategy to enhance energy-storage properties (ESP) for Bi0.5Na0.5TiO3 (BNT)-based ceramics. Herein, we incorporate Na0.91Bi0.09Nb0.94Mg0.06O3 (NBNM) into BNT matrix to form a solid solution of BNT-xNBNM with x = 0.1–0.4. Rietveld refinements reveal that the composition with x = 0.3 has 46% relaxor tetragonal P4bm phase and 54% relaxor orthorhombic P21ma one, thus exhibiting a large normalized energy-storage density (Wrec/E = 0.015 J kV−1 cm−2) and a high efficiency (η = 87%) at 370 kV cm−1. The optimized composition also presents superior temperature stability with a variation of <±5% in the range of 20 °C–150 °C, outstanding frequency reliability with a variation of <±4% in the range of 5 Hz–500 Hz and excellent charge-discharge properties (discharge rate of 76 ns, current density of 1032 A cm−2 and power density of 129 MW cm−3 at 250 kV cm−1). The results demonstrate a successful strategy to design high performance Pb-free relaxor ferroelectrics for pulsed power capacitor applications.

The Dual-Site Adsorption and High Redox Activity Enabled by Hybrid Organic-Inorganic Vanadyl Ethylene Glycolate for High-Rate and Long-Durability Lithium-Sulfur Batteries.

Transition metal oxides (TMOs) have attracted considerable attention owing to their strong anchoring ability and natural abundance. However, their single-site adsorption toward sulfur (S) species significantly lowers the possibility of S species reacting with Li+ in the electrolyte and increases the reaction barrier. This study investigates molecular modification by coupling the TMO structure with Li+ conductive polymer ligands, and vanadyl ethylene glycolate (VEG) is successfully synthesized by introducing organic ligands into the VOx crystal structure. In addition to the strong interaction between the VOx and lithium polysulfides via the V-S bond, the groups in the VEG polymer ligands can reversibly couple/decouple with Li+ in the electrolyte. Such dual-site adsorption enables a smooth dynamic adsorption-diffusion process. Accordingly, the VEG-based Li-S cells exhibit excellent rate reversibility, cyclic stability, and a long cycle life without the addition of conducting agents. Encouragingly, the VEG-based cells also exhibit close and excellent capacity decays of 0.081%, 0.078%, and 0.095% at 0, 25, and 50 °C (1 C for 200 cycles), respectively. This work provides a novel approach for developing advanced catalysts that can realize Li-S batteries with long-term durability, fast charge-discharge properties, and applications in a wide temperature range.

Structure Effect on Pseudocapacitive Properties of A2LaMn2O7 (A = Ca, Sr)

Herein, the effect of structure on pseudocapacitive properties in alkaline conditions is demonstrated through the investigation of isoelectronic oxides Ca2LaMn2O7 and Sr2LaMn2O7, where the difference in ionic radii of Ca2+ and Sr2+ leads to a change in structure and lattice symmetry, resulting in an orthorhombic Cmcm structure for the former and a tetragonal I4/mmm structure for the latter. While calcium and strontium do not make a direct contribution to the near‐surface faradaic processes that are essential to the pseudocapacitive properties, their effect on the structure leads to a change in the oxygen intercalation process and the associated pseudocapacitive energy storage. It is shown that Sr2LaMn2O7 has a significantly greater specific capacitance than Ca2LaMn2O7. In addition, the former shows a considerably higher‐energy density compared to the latter. Furthermore, these materials show highly stable energy‐storage properties, and retain their specific capacitance over 10 000 cycles of charge–discharge in a symmetric pseudocapacitive cell. Importantly, these findings show the structure–property relationships, where a change in the structure and lattice symmetry can result in a significant change in pseudocapacitive charge–discharge properties in isoelectronic systems.

In situ induced growth strategy of Co2P nanocrystals encapsulated into stable 3D carbon network as a bifunctional electrocatalyst for Zn-air battery

Rational design of inexpensive and robust carbon-based bifunctional catalysts is of considerable interest for practical application of rechargeable Zn-air battery (ZAB) technology. Herein, a facile in-situ induced growth strategy is developed to construct Co2P nanocrystals encapsulated into a stable 3D carbon nanotube-modified graphene network (Co2P@NPCNG). Specifically, cobalt tetranitrophthalocyanine (CoPc(NO2)4) is employed not only as the coupling agent to form and complex Co2P nanocrystals with graphene, but also as the inducer to catalyze the graphitization of melamine to grow the uniform Co2P nanocrystal-encapsulated CNTs on graphene in situ. Encouragingly, the as-synthesized Co2P@NPCNG exhibits favorable bifunctional oxygen electrocatalytic activity, fast reaction kinetics and excellent stability. Impressively, both liquid ZAB and all-solid-state ZABs used Co2P@NPCNG as air-cathode catalysts display considerable open-circuit voltage, charge-discharge property and long lifetime. Significantly, density functional theory (DFT) calculations demonstrate that the superior properties of Co2P@NPCNG originate to the synergetic contributions between the stable configuration of 3D conductive carbon network and high metallic density of Co2P. This work may provide feasible and facile avenues to strategically construct high-efficient 3D carbon-based bifunctional electrocatalysts for portable and even wearable devices.

Effect of Sn Addition on Anode Properties of SiO&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt; in Sodium-Ion Batteries

Our group has investigated the properties of lithium-ion battery anodes fabricated using Sn/SiOx (SiOx is a mixed phase of Si clusters and amorphous SiO2 matrix). The addition of Sn improves the conductivity of the SiO2 matrix, while the formation of the Li+-conductive Li2Si2O5 phase in the SiO2 matrix improves Si utilization. The charge–discharge cycle life is also extended. In this study, Sn-doped SiOx has been used to fabricate the anode of a sodium-ion battery, and its charge–discharge properties are evaluated. The addition of 3 wt% Sn to SiOx improves the cycle property, as revealed by charge–discharge tests. X-ray diffraction analysis confirmed that the Na+-conductive Na2Si2O5 phase is formed during the charging and discharging processes. These results indicate that adding Sn improves the electronic conductivity of SiO2, and Na2Si2O5 facilitated the movement of Na in the SiO2 matrix. Thus, the utilization of Si is enhanced, and a high discharge capacity is achieved.

Concentration shift experiment with an electrode of active material for precise electrochemical analysis.

To precisely evaluate the electrochemical properties of a battery of active material, we proposed a "concentration shift experiment" using single-particle electrochemical measurement (SPEM) and a diluted electrode sheet (DES). SPEM can be used for information, such as the charge-discharge and resistance properties of only the active material (extremely dilute condition: ≈0). DES consists of concentrations varying from 1% to 100% of the active material (LiCoO2) and inactive material (α-Al2O3), electrically conductive additive and binder polymer onto an Al current collector. The resistance components derived from the LiCoO2 single particles were measured and calculated. Their apparent activation energy (Ea) was 27 kJ mol-1, which is relatively low compared with the applied-type sheet electrode (30-60 kJ mol-1). Simple electric/ionic conductive route was analyzed using SPEM cell, and the fundamental LiCoO2 originated Ea could be calculated. Resistance components attributed to LiCoO2 were also measured and extracted by alternating current impedance measurements using DES. The resistance non-linearly decreased with LiCoO2 concentration, and the percolation and inhomogeneity of LiCoO2 particles were suspected. The planful isolation of an active material particle should be critical for the overall information on an electrode particle.

Superior Energy and Power Density Realized in Pb(Hf 1- x Ti x )O 3 System at Low Electric Field

The development of antiferroelectric materials with large energy density and fast discharge speed makes dielectric capacitors possess great prospects for applications in pulsed power technology. Here, the PbHfO 3 -based ceramics with compositions of Pb(Hf 1- x Ti x )O 3 (PHT, 0.01 ≤ x ≤ 0.05) were synthesized, and their antiferroelectricity and phase transition behavior were studied. According to the tests of x-ray diffraction, dielectric spectrum, and polarization–electric field hysteresis loops, PHT ceramics gradually transition from an orthorhombic symmetric antiferroelectric phase to a hexagonal symmetric ferroelectric phase at room temperature as Ti 4+ concentration increases. The forward phase switching field of antiferroelectric to ferroelectric phase transition can be markedly regulated by the introduction of Ti 4+ , and the optimal energy storage performance was obtained in Pb(Hf 0.98 Ti 0.02 )O 3 ceramics with a large recoverable energy storage density of W rec ~ 4.15 J/cm 3 and efficiency of η ~ 65.3% only at a low electric field of 190 kV/cm. Furthermore, the outstanding charge–discharge properties with an ultrafast discharge time (71 ns), remarkable discharged energy density (2.84 J/cm 3 ), impressive current density (1,190 A/cm 2 ), and ultrahigh power density (101 MW/cm 3 ) at a low electric field of 170 kV/cm were obtained in studied ceramics. The excellent energy storage performance of PHT ceramics provides a promising platform for the application of dielectric capacitors.