High-power Energy Storage Devices Research Articles

High-Entropy Electrolyte Design for Low-Temperature Supercapacitors.

Supercapacitors (SCs) are high-power energy storage devices but often experience reduced electrochemical performance at low temperatures, especially below -30 °C, due to the high freezing points of conventional electrolytes. In this study, we introduce a novel high-entropy electrolyte (HEE) for supercapacitors that extends operational capabilities over a wide temperature range. The high entropy of the HEE results in an exceptionally low freezing point of -116 °C. With an increased number of solvent molecules in the cation solvation structures, the HEE exhibits high conductivity (3.9 mS cm⁻¹ at -50 °C) and low de-solvation energy (14.1 kJ mol⁻¹). When incorporated into a carbon-based SC, the HEE enables a capacitance retention of 58% at temperatures below -30 °C, compared to 25 °C, while conventional single-solvent electrolytes retain only 38%. Additionally, the HEE provides superior high-rate performance and excellent cycling stability, maintaining 88% capacitance after 15,000 cycles, compared to 73% with conventional electrolytes.

Excellent energy storage performance of Nd-modified lead-free AgNbO3 ceramics via triple collaborative optimization

Lead-free Dielectric capacitors that possess high power density as well as swift charging/discharging speed are in tremendous requirement in pulse/high power fields, but the lower recovery energy density and efficiency restrict their applications. Herein, via triple collaborative optimization, we designed Nd-modified AgNbO3 antiferroelectric ceramics with excellent energy storage performance. First, Nd3+ ions are smaller than Ag+ ions, which effectively inhibits cation displacements and the tilting of oxygen octahedra, leading to an optimized phase composition, the suppressed ferroelectricity and enhanced antiferroelectricity. Second, the valence of Nd3+ ions are higher than that of Ag+ ions, which help to lower the content of oxygen vacancies. Third, the random substitution of Nd3+, extrinsic ions, cause the chemical disorder, thus dwindling the grain size. Both of the latter could boost the breakdown field. Eventually, the synchronously boosted energy density of 7.16 J/cm3 and efficiency of 72 %, together with excellent frequency stability, temperature tolerance, ultrafast charging/discharging time of 45 ns and superhigh power density of 354.2 MW/cm3, are achieved in Ag0.91Nd0.03NbO3. All these merits manifest Nd- AgNbO3 as a promising candidate for lead-free high-power energy storage devices. Our work brings forward a good reference for developing the capabilities of antiferroelectric capacitors.

The role of polymer gel electrolyte infiltration for enhancement of capacitance and cycle stability

With the increasing application of electronic materials in various fields such as flexible electronic textiles, wearable and portable gadgets, aerospace and aircraft systems etc., the demand for clean high-power energy storage devices is also increasing rapidly. To date, the application of market available supercapacitors has not met the energy expectations in the range of market leading Li-ion batteries (LIBs) due to their unreliable mechanical flexibility, electrolyte leakage, low voltage application, low capacity, low cycle stability and moderate rate-capability. Inappropriate utilization of the maximum porosity of the electrode material and inefficient activities of the electrode/electrolyte interface are major challenges for present supercapacitor development. In this work, for the first time, the role of polymer gel electrolyte infiltration to improve the electrochemical performance of a supercapacitor has been explicitly studied and investigated. It has been observed that 1-Ethyl-3- Methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][TFSI] ionic liquid electrolyte embedded in Polypropylene Carbonate (PPC) and Polycarbonate (PC) polymer matrix polymer gel electrolyte (PGE) showed excellent supercapacitive performance at high voltage window 2.6 V by delivering maximum total capacitance of 5.81 F and maximum energy density 10.9 Wh kg-1 at 30 mA current (0.06 A g-1). Regular infiltration of the polymer gel electrolyte inside the electrode material is also observed during long cycle operation of 10,000 cycles. Infiltration of electrolyte ions into the pores of electrode materials plays a significant role in increasing capacitance and cycle Stability. These results highlight the potential of this novel high-voltage polymer gel electrolyte for future high-power energy storage device applications.

Boosting the electrochemical properties of MoO3/MnFe2O4/MXene for high-performance supercapacitor applications

The expanding population and extensive usage of energy-consuming sources are the main factors driving the interest of current researchers toward the development of extremely effective and useful electrode materials for high-power energy storage devices. A novel class of 2D transition metal carbides such as MXene has captured significant attention and has distinguished itself from other electrode materials because of its remarkable electrochemical characteristics. In this work, we have fabricated MoO3 and MnFe2O4 via a simple co-precipitation method. Further, we design multifunctional MoO3/MnFe2O4/MXene composite by the combination of MoO3/MnFe2O4 and MXene through the sonication route. SEM results confirmed the fabrication of nanorods of MoO3 and nanoparticles of MnFe2O4, sandwiched within the MXene sheets. As evident from CV profiles, at 10 mVs−1 MoO3/MnFe2O4@MXene showed a higher specific capacitance of 817 Fg−1 than other electrode materials mainly because of the combined effect of MoO3/MnFe2O4 and the conductive nature of MXene sheets. Furthermore, even after 10,000 cycles, MoO3/MnFe2O4/MXene demonstrated outstanding cyclic stability, maintaining 90.2 % retention of its initial specific capacitance. Furthermore, MoO3/MnFe2O4/MXene showed less solution resistance and charge transfer resistance than all other prepared materials. These findings suggest that the MoO3/MnFe2O4/MXene composite is a competent capacitive material in the supercapacitor research area.

Low Solvating Power of Acetonitrile Facilitates Ion Conduction: A Solvation-Conductivity Riddle.

Acetonitrile (AN) electrolyte solutions display uniquely high ionic conductivities, of which the rationale remains a long-standing puzzle. This research delves into the solution species and ion conduction behavior of 0.1 and 3.0 M LiTFSI AN and propylene carbonate (PC) solutions via Raman and dielectric relaxation spectroscopies. Notably, LiTFSI-AN contains a higher fraction of free solvent uncoordinated to Li ions than LiTFSI-PC, resulting in a lower viscosity of LiTFSI-AN and facilitating a higher level of ion conduction. The abundant free solvent in LiTFSI-AN is attributed to the lower Li-solvation power of AN, but despite this lower Li-solvation power, LiTFSI-AN exhibits a level of salt dissociation comparable to that of LiTFSI-PC, which is found to be enabled by TFSI anions loosely bound to Li ions. This work challenges the conventional notion that high solvating power is a prerequisite for high-conductivity solvents, suggesting an avenue to explore optimal solvents for high-power energy storage devices.

Improving the Energy Storage Performance of Barium Titanate-Based Ceramics through the Addition of ZnO-Bi2O3-SiO2 Glass

Lead-free ceramics with excellent energy storage performance are important for high-power energy storage devices. In this study, 0.9BaTiO3-0.1Bi(Mg2/3Nb1/3)O3 (BT-BMN) ceramics with x wt% ZnO-Bi2O3-SiO2 (ZBS) (x = 2, 4, 6, 8, 10) glass additives were fabricated using the solid-state reaction method. X-ray diffraction (XRD) analysis revealed that the ZBS glass-added ceramics exhibited a perovskite structure, with the maximum relative density achieved at x = 6. The average grain size reduced obviously as the glass additive wt% increased. Also, the dielectric constant decreased and the breakdown strength increased with increases in the glass additives. The optimal energy storage density of 1.39 J/cm3 with an energy storage efficiency of 78.3% was obtained at x = 6 due to high maximum polarization and enhanced breakdown strength. The results demonstrate that this material is a potential candidate for high-pulse-power energy storage devices.

Design of Hollow Porous P-NiCo2O4@Co3O4 Nanoarray and Its Alkaline Aqueous Zinc-Ion Battery Performance.

Alkaline aqueous zinc-ion batteries possess a wider potential window than those in mildly acidic systems; they can achieve high energy density and are expected to become the next generation of energy storage devices. In this paper, a hollow porous P-NiCo2O4@Co3O4 nanoarray is obtained by ion etching and the calcination and phosphating of ZiF-67, which is directly grown on foam nickel substrate, as a precursor. It exhibits excellent performance as a cathode material for alkaline aqueous zinc-ion batteries. A high discharge specific capacity of 225.3 mAh g-1 is obtained at 1 A g-1 current density, and it remains 81.9% when the current density is increased to 10 A g-1. After one thousand cycles of charging and discharging at 3 A g-1 current density, the capacity retention rate is 88.8%. Even at an excellent power density of 25.5 kW kg-1, it maintains a high energy density of 304.5 Wh kg-1. It is a vital, promising high-power energy storage device for large-scale applications.

On the Viability of Lithium Bis(fluorosulfonyl)imide as Electrolyte Salt for Use in Lithium‐Ion Capacitors

AbstractLithium‐ion capacitors (LICs) represent promising high‐power energy storage devices, most commonly composed of a lithium‐ion intercalation anode (e. g., graphite or hard carbon), a supercapacitor activated carbon (AC) cathode, and an electrolyte with 1 M LiPF6 in carbonate solvents. LiPF6 is susceptible to hydrolysis, forming HF, which leads to challenges for disassembly and recycling, risks during hazardous events, and extensive energy consumption during production. Here, we report on the feasibility of replacing LiPF6 with the non‐hydrolysing salt LiFSI for use with AC electrodes. Based on voltage hold measurements in a half‐cell setup, good long‐term stability is achieved with an upper cut‐off voltage of 3.95 V vs. Li/Li+, potentially enabling cell voltages of ~3.8 V when combined with graphite or silicon‐based anodes (operating at ~0.1 V vs. Li/Li+) in LIC full cells. The lower cut‐off voltage was determined to be 2.15 V vs. Li/Li+. The systematic comparison of CV, leakage current analysis and capacity retention upon voltage hold highlights the importance of the latter method to provide a realistic assessment of the electrochemical stability window (ESW) of LiFSI on a commercial AC electrode. The morphological and surface‐chemical post‐mortem analysis of AC electrodes used with LiFSI revealed that the oxidation of the FSI anion, as evidenced by the presence of new S 2p and N 1s features in the XPS spectra, and an increasing number of oxygenated species on the AC were the main processes causing capacity fade at positive polarization.

Multi-scale synergic optimization strategy for dielectric energy storage ceramics

Dielectric capacitors, serving as the indispensable components in advanced high-power energy storage devices, have attracted ever increasing attention with the rapid development of science and technology. Among various dielectric capacitors, ceramic capacitors with perovskite structure show unique advantages in actual application, such as excellent adaptability in high temperature environments. And the optimization of their energy storage performances has become a hot research topic recently. This review presents the basic principles of energy storage in dielectric ceramics and introduces multi-scale synergic optimization strategies according to the key factors for superior energy storage performance. By summarizing the common points in numerous works, several universal modification strategies are reviewed and future research on fatigue fracture of ceramic capacitors under multi-field including but not limited to force, electric and thermal coupling conditions is also anticipated.

Ultrafastly activated needle coke as electrode material for supercapacitors

The uniform porous structure makes activated porous carbons (APCs) superior electrode material. Traditionally, APCs are produced by a combination of time-consuming high-temperature heat treatment and activation, with a production time of up to several hours. The produced APCs have relatively low specific surface area (SSA) and porosity. Therefore, the electrochemical performance is poor, which limits its application in high-power energy storage devices. Here, APCs materials are directly synthesized by a high temperature shock (HTS) strategy using needle coke as a precursor. The structure of as-prepared APC is characterized by XRD, SEM and Raman, and electrochemical tests confirmed its good electrochemical performance. In the two-electrode system, the supercapacitor with HTS-APC as the electrode material provides a high energy density of 35 ​Wh kg−1 and a high power density of 875 ​W ​kg−1 in EMIMBF4 ionic liquid. This work is instructive for the rapid synthesis of electrode materials, and also provides guidance for the large-scale application of porous carbon materials.

Effectively boosted energy density in polymer/ceramic composites through area electron scattering and micro-regional electric displacement bridging

Dielectric electrostatic capacitors have drawn numerous attention due to the long service time and rapid charge-discharge rate. However, the enhancement of energy density is a significant challenge for elevating the energy capacity. Here, a polyvinylidene fluoride (PVDF) composite hybridly filled with anatase TiO2 1D nanowires and 2D nanosheets is investigated which possesses a high energy density. In the composite, electric displacement and breakdown strength are increased simultaneously via a synergetic effect of nanofillers with different dimensions. At the TiO2 loading of 8 vol% with the nanosheet/nanowire volume ratio of 5:1, the composite possesses a high Eb of 610.2 MV/m, realizing 39% enhancement from 440.3 MV/m of PVDF. A high D of 12.3 μC/cm2, superhigh energy density of 18 J/cm3 with high efficiency of 63% are also achieved in the composite at 600 MV/m, the displacement and energy density are higher than PVDF and its composites filled with pure 1D or 2D TiO2 nanofillers. The mechanism of the superior energy storage properties of the composite lies in micro-regional bridging of high electric displacement by nanowires and effective area electron scattering by large-area nanosheets. Thus, this study provides a method to prepare polymer/ceramic composites with superior electric properties for high-power energy storage device applications.

Enhanced Li-ion migration behavior in Li3V2O5 rock-salt anode via stepwise lattice tailoring

Electrode exploration with the appropriate equilibrium voltage and facile cation diffusion kinetics is the key enabler towards realizing the extreme power output of the battery formats. With the aid of the stepwise lattice tailoring, herein, we present an alternative fast-charging anode of the rock-salt lithium vanadium oxide. Specifically, the pre-insertion of polyaniline (PANI) molecules unlocks the basal plane of the layered V2O5 precursor, while subsequent Na+ doping at the octahedral sites could stabilize the lattice breathing and mitigate Li-ion diffusion barrier along the tetrahedron-octahedron-tetrahedron pathway, as confirmed by the operando X-ray diffraction and kinetics simulation. The Na0.6Li2.4V2O5@PANI//LiFePO4 full cell prototype (3 mAh cm−2) exhibits 82% capacity retention at 20 C for 2000 cycles, as well as the cycling endurance within a wider temperature range of 0-60°C. This stepwise lattice engineering strategy opens a fresh impetus of the electrode innovations for the high-power energy storage devices.

The Interactions between Zn Anode and Electrolytes in Aqueous Zn-Ion Batteries

Aqueous based Zn-ion batteries have gained significant interest in recent years for their potential to be a safe, low-cost, and high-power energy storage device. The past research efforts have been mainly focused on cathodes and the associated interfaces with electrolytes. The understanding on the Zn-anode and its interface with the electrolyte has been relatively lacking. Here in this presentation, we will report a systematic fundamental study on the Zn-anode/electrolyte interface, including the effect of pH and concentration of the electrolyte on chemical reactions and electrode kinetics at the Zn-anode surface. We expect the insights revealed from this study will facilitate the understanding of the potential issues associated with the Zn-anode and help the commercial development of ZIBs.

Cold-Starting All-Solid-State Batteries from Room Temperature by Thermally Modulated Current Collector in Sub-Minute.

All-solid-state batteries (ASSBs) show great potential as high-energy and high-power energy-storage devices but their attainable energy/power density at room temperature is severely reduced because of the sluggish kinetics of lithium-ion transport. Here a thermally modulated current collector (TMCC) is reported, which can rapidly cold-start ASSBs from room temperature to operating temperatures (70-90°C) in less than 1 min, and simultaneously enhance the transient peak power density by 15-fold compared to one without heating. This TMCC is prepared by integrating a uniform, ultrathin (≈200nm) nickel layer as a thermal modulator within an ultralight polymer-based current collector. By isolating the thermal modulator from the ion/electron pathway of ASSBs, it can provide fast, stable heat control yet does not interfere with regular battery operation. Moreover, this ultrathin (13.2µm) TMCC effectively shortens the heat-transfer pathway, minimizes heat losses, and mitigates the formation of local hot spots. The simulated heating energy consumption can be as low as ≈3.94% of the total battery energy. This TMCC design with good tunability opens new frontiers toward smart energy-storage devices in the future from the current collector perspective.

Anhydrous Fast Proton Transport Boosted by the Hydrogen Bond Network in a Dense Oxide-Ion Array of α-MoO3.

Developing high-power battery chemistry is an urgent task to buffer fluctuating renewable energies and achieve a sustainable and flexible power supply. Owing to the small size of the proton and its ultrahigh mobility in water via the Grotthuss mechanism, aqueous proton batteries are an attractive candidate for high-power energy storage devices. Grotthuss proton transfer is ultrafast owing to the hydrogen-bonded networks of water molecules. In this work, similar continuous hydrogen bond networks in a dense oxide-ion array of solid α-MoO3 are discovered, which facilitate the anhydrous proton transport even without structural water. The fast proton transfer and accumulation that occurs during (de)intercalation in α-MoO3 is unveiled using both experiments and first-principles calculations. Coupled with a zinc anode and a superconcentrated Zn2+ /H+ electrolyte, the proton-transport mechanism in anhydrous hydrogen-bonded networks realizes an aqueous MoO3 -Zn battery with large capacity, long life, and fast charge-discharge abilities.

Material Optimization Engineering toward xLiFePO4·yLi3V2(PO4)3 Composites in Application-Oriented Li-Ion Batteries.

The development of LiFePO4 (LFP) in high-power energy storage devices is hampered by its slow Li-ion diffusion kinetics. Constructing the composite electrode materials with vanadium substitution is a scientific endeavor to boost LFP’s power capacity. Herein, a series of xLiFePO4·yLi3V2(PO4)3 (xLFP·yLVP) composites were fabricated using a simple spray-drying approach. We propose that 5LFP·LVP is the optimal choice for Li-ion battery promotion, owning to its excellent Li-ion storage capacity (material energy density of 413.6 W·h·kg−1), strong machining capability (compacted density of 1.82 g·cm−3) and lower raw material cost consumption. Furthermore, the 5LFP·LVP||LTO Li-ion pouch cell also presents prominent energy storage capability. After 300 cycles of a constant current test at 400 mA, 75% of the initial capacity (379.1 mA·h) is achieved, with around 100% of Coulombic efficiency. A capacity retention of 60.3% is displayed for the 300th cycle when discharging at 1200 mA, with the capacity fading by 0.15% per cycle. This prototype provides a valid and scientific attempt to accelerate the development of xLFP·yLVP composites in application-oriented Li-ion batteries.

High-Performance PbZrO3-based antiferroelectric multilayer capacitors based on multiple enhancement strategy

Antiferroelectric (AFE) materials are thought to be one of the most promising candidates for energy storage application owing to their large polarization difference between maximum polarization and remanent polarization originating from unique electric field-induced phase transition, but the large polarization hysteresis leads to an inferior energy efficiency, which restricts their applications in advanced pulsed power devices. Herein, we propose a multiple enhancement strategy of composition and structural modification to solve this problem. The (Pb0.875La0.05Sr0.05)(Zr0.695Ti0.005Sn0.3)O3 (PLSZTS) antiferroelectric ceramic and corresponding multilayer ceramic capacitor (MLCC) are fabricated. A low hysteresis is obtained via composition optimization. Moreover, multilayer ceramic constructing improves significantly breakdown strength (BDS) due to decreased thickness of dielectric layer. An ultrahigh recoverable energy density (Wdis) of 19.9 J/cm3, together with a high energy efficiency (η) of 96.4% are achieved synchronously at an electric field of 85 kV/mm. In addition, the studied MLCCs also possess outstanding discharge energy storage properties with a high discharge energy density (Wdis) of 15.4 J/cm3 and a large power density (PD) of 170.5 MW/cm3, a wide temperature range of 20–120 °C, and strong fatigue endurance after 3000 cycles. The present research results not only offer a potential candidate for high-power energy storage devices, but also, more importantly, develop a universal approach for optimizing the overall energy storage performance.

High power density & energy density Li-ion battery with aluminum foam enhanced electrode: Fabrication and simulation

Compared with aluminum foil (Al foil), the three-dimensional (3D) aluminum foam (Al foam) has the characteristics of 3D interconnected metal wires and through-hole structure with high specific surface area, which exhibits great potential for application in high-power energy storage devices. In this work, 3D Al foam-based and Al foil-based cathode sheets were fabricated and assembled into pouch cells. In-situ XRD was employed to analyze the electrochemical reaction behavior of the two types of porous electrodes. The 3D Al foam-based cathode demonstrated faster electron transfer and lithium-ion diffusion as compared to the Al foil-based electrode, which is helpful for a uniform electrochemical reaction and decreases the electrochemical polarization. Electrochemical simulations and porous electrode models were built to understand these phenomena. The Al foam-based LiFePO4 batteries exhibit much better power and energy performance than Al foil-based LiFePO4 battery. The power density of the Al foam pouch cells is 7.0–7.7 kW/L when the energy density is 230–367 Wh/L, which is the highest power and energy density among reported Al foam-based devices. The new findings open up opportunities for the development of high-power and high-energy-density commercial batteries.

Biomass-Derived Graphene-Based Materials Embedded with Onion-Like Carbons for High Power Supercapacitors

We report a facile method to produce composites of hierarchically porous graphene-based materials embedded with onion-like carbons (Gr-OLCs) for high power density supercapacitors. Gr-OLCs were produced from the mixture of glucose, thiourea, and ammonium chloride, through stepwise reactions including a condensation reaction, subsequent blow into three-dimensional (3D) structure, and carbonization process. Owing to its high surface area, hierarchical pore distribution, and interconnected carbon networks embedded with onion-like carbons, this carbon showed high specific capacitance of 140 F g−1 even at a high current density of 64 A g−1. Interconnected carbon networks and hierarchical pore structrues served to facilitate the movement of electrolyte ions within the electrode and provide an efficient pathway for the movement of charge carriers, resulting in an exceptionally high power density of 1,737 kW kg−1 with an energy density of 30 Wh kg−1 at current density of 256 A g−1. Studies on the complex capacitance revealed that a supercapacitor with these carbon electrodes exhibited stable energy storage features with minimal capacitive loss, achieving both high power and energy densities. This work provides a new type of carbon-based electrode materials that can meet the requirements for high power energy storage devices.

Construction of vertically aligned Ni-Co-Mo hybrid oxides nanosheet array for high-performance hybrid supercapacitors

Multi-metal oxide materials have gained increasing attention due to their superior electrochemical performance for supercapacitors. In this work, Ni-Co-Mo oxides composite materials (NiCoMo/NF) are synthesized and anchored on Ni foam in the form of vertically aligned nanosheet arrays using a two-step hydrothermal method. It has confirmed that good electrochemical performance stems from a synergic interaction effect between the hybrid Ni-Co-Mo composite materials and the co-existence of Ni-Co and Co-Mo oxide, which can be attributed to a unique nanostructure in the hybrid Ni-Co-Mo composite materials and Ni-Co/Co-Mo oxide intersections with each other. The NiCoMo/NF binder-free electrode shows an enhanced specific capacitance of 1837.7 F g−1(3.31 F cm−2) at a current density of 1 A g−1 and maintains capacitance retention of 81.2% after 6000 cycles at 5 A g−1. Meanwhile, the fabricated hybrid capacitor achieves high specific energy of 41.1 W h kg−1. The results indicate that NiCoMo/NF has the potential for application in supercapacitors. Moreover, our work provides a practical approach for fabrication of multi-metal oxide materials and hold promise for high-power energy storage devices.