Specific Capacitance Retention Research Articles

One-Step Molten-Salt-Assisted Approach for Direct Preparation and Regeneration of LiNi0.6Co0.2Mn0.2O2 Cathode.

Single-crystal lithium-nickel-manganese-cobalt-oxide (SC-NMC) is attracting increasing attention due to its excellent structural stability. However, its practical production faces challenges associated with complex precursor preparation processes and severe lithium-nickel cation mixing at high temperatures, which restricts its widespread application. Here, a molten-salt-assisted method is proposed using low-melting-point carbonates. This method obviates the necessity for precursor processes and simplified the synthetic procedure for SC-NMC down to a single isothermal sintering step. Multiple characterizations indicate that the acquired SC-LiNi0.6Mn0.2Co0.2O2 (SC-622) exhibits favorable structural capability against intra-granular fracture and suppressive Li+/Ni2+ cation mixing. Consequently, the SC-622 exhibits superior electrochemical performance with a high initial specific capacity (174 mAhg-1 at 0.1C, 3.0-4.3V) and excellent capacity retention (87.5% after 300 cycles at 1C). Moreover, this molten-salt-assisted method exhibits its effectiveness in directly regenerating SC-622 from spent NMC materials. The recovered material delivered a capacity of 125.4 mAhg-1 and retained 99.4% of the initial capacity after 250 cycles at 1 C. This work highlights the importance of understanding the process-structure-property relationships and can broadly guide the synthesis of other SC Ni-rich cathode materials.

Recent Progress Using Graphene Oxide and Its Composites for Supercapacitor Applications: A Review

Supercapacitors are prospective energy storage devices for electronic devices due to their high power density, rapid charging and discharging, and extended cycle life. Materials with limited conductivity could have low charge-transfer ions, low rate capability, and low cycle stability, resulting in poor electrochemical performance. Enhancement of the device’s functionality can be achieved by controlling and designing the electrode materials. Graphene oxide (GO) has emerged as a promising material for the fabrication of supercapacitor devices on account of its remarkable physiochemical characteristics. The mechanical strength, surface area, and conductivity of GO are all quite excellent. These characteristics make it a promising material for use as electrodes, as they allow for the rapid storage and release of charges. To enhance the overall electrochemical performance, including conductivity, specific capacitance (Cs), cyclic stability, and capacitance retention, researchers concentrated their efforts on composite materials containing GO. Therefore, this review discusses the structural, morphological, and surface area characteristics of GO in composites with metal oxides, metal sulfides, metal chalcogenides, layered double hydroxides, metal–organic frameworks, and MXene for supercapacitor application. Furthermore, the organic and bacterial functionalization of GO is discussed. The electrochemical properties of GO and its composite structures are discussed according to the performance of three- and two-electrode systems. Finally, this review compares the performance of several composite types of GO to identify which is ideal. The development of these composite devices holds potential for use in energy storage applications. Because GO-modified materials embrace both electric double-layer capacitive and pseudocapacitive mechanisms, they often perform better than pristine by offering increased surface area, conductivity, and high rate capability. Additionally, the density functional theory (DFT) of GO-based electrode materials with geometrical structures and their characteristics for supercapacitors are addressed.

Comprehensive Study of Zr-Doped Ni-Rich Cathode Materials Upon Lithiation and Co-Precipitation Synthesis Steps.

Ni-rich layered oxides LiNi1-x-yMnxCoyO2 (NMC811, x = 0.1 and y = 0.1) are considered promising cathode materials in lithium-ion batteries (LiBs) due to their high energy density. However, those suffer a severe capacity loss upon cycling at high delithiated states. The loss of performance over time can be retarded by Zr doping. Herein, a small amount of Zr is added to NMC811 material via two alternative pathways: during the formation of the transition metal (TM) hydroxide precursor at the co-precipitation step (0.1%-Zr-cp) and during the lithiation at the solid-state synthesis step (0.1%-Zr-ss). In this work, the crystallographic Zr uptake in both 0.1%-Zr-ss and 0.1%-Zr-cp is determined and quantified through synchrotron X-ray diffraction and X-ray absorption spectroscopy. We prove that the inclusion of Zr in the TM site for 0.1%-Zr-cp leads to an improvement of both specific capacity (156 vs 149 mAh/g) and capacity retention (85 vs 82%) upon 100 cycles compared to 0.1%-Zr-ss where the Zr does not diffuse into the active material and forms only an extra phase separated from the NMC811 particles.

Improved interfacial stability of all-solid-state batteries using cation-anion co-doped glass electrolytes

The electrochemical performance of all-solid-state batteries needs to be improved by addressing the poor stability against the lithium metal anode and the high interfacial resistance at the cathode–solid electrolyte interface. Here, metal halide-doped Li7P2S8I–type (LPSI) solid electrolytes are synthesized that improve the electrochemical performance of all-solid-state batteries. The solid electrolytes exhibit a higher ionic conductivity value of 7.77 mS cm−1 than bare LPSI solid electrolytes of 3.96 mS cm−1, at room temperature. The metal halide-doped LPSI solid electrolyte is also stable against the lithium metal anode, with a calculated critical current density value of 1 mA cm−2. The fabricated all-solid-state battery shows high electrochemical performance with 99.2% specific capacity retention after 250 cycles at a 0.5 C rate. The results of post galvanostatic charge–discharge analysis confirms that the proposed metal halide-doped LPSI solid electrolyte exhibits improved interfacial stability compared to bare LPSI solid electrolytes.

Opening and Constructing Stable Lithium‐ion Channels within Polymer Electrolytes

Lithium‐ion batteries play an integral role in various aspects of daily life, yet there is a pressing need to enhance their safety and cycling stability. In this study, we have successfully developed a highly secure and flexible solid‐state polymer electrolyte (SPE) through the in‐situ polymerization of allyl acetoacetate (AAA) monomers. This SPE constructed an efficient Li+ transport channel inside and effectively improved the solid‐solid interface contact of solid‐state batteries to reduce interfacial impedance. Furthermore, it exhibited excellent thermal stability, an ionic conductivity of 3.82×10‐4 S cm‐1 at room temperature (RT), and a Li+ transport number (tLi+) of 0.66. The numerous oxygen vacancies on layered inorganic SiO2 created an excellent environment for TFSI‐ immobilization. Free Li+ migrated rapidly at the C=O equivalence site with the poly(allyl acetoacetate) (PAAA) matrix. Consequently, when cycled at 0.5 C and RT, it displayed an initial discharge specific capacity of 140.6 mAh g‐1 with a discharge specific capacity retention rate of 70% even after 500 cycles. Similarly, when cycled at a higher rate of 5 C, it demonstrated an initial discharge specific capacity of 132.3 mAh g‐1 while maintaining excellent cycling stability.

Starch Gel Electrolyte and its Interaction with Trivalent Aluminum for Aqueous Aluminum-Ion Batteries: Enhanced Low Temperature Electrochemical Performance.

This study explores trivalent Al interaction with aqueous starch gel in the presence of two different anions through salting effect. Salting-out nature of Al2(SO4)3·18H2O with starch gel causes precipitation of starch; this happens due to competitive anion-water complex formation over starch-water interaction, thereby reducing polymer solubility. Salting-in effect of AlCl3 with starch gel happens through Al3+ cation interaction with hydroxyl group of starch and increases polymer solubility, making gel electrolyte viable for battery applications. Prepared gel electrolyte exhibits ionic conductivity of 1.59mS cm-1 and a high tAl 3+ value of 0.77. The gel electrolyte's performance is studied using two different cathodes, the Al|MoO3 cell employing starch gel electrolyte achieves discharge capacity of 193mA h g-1 and Al|MnO2 cell achieves discharge capacity of 140mA h g-1 @0.1 A g-1 for first cycle. The diffusion coefficient of both cells using starch gel electrolyte is calculated and found to be 2.1×10-11cm2 s-1 for Al|MoO3 and 3.1×10-11 cm2 s-1 for Al|MnO2 cells. The Al|MoO3 cell at lower temperature shows improved electrochemical performance with a specific capacity retention of ≈87.8% over 90 cycles. This kind of aqueous gel electrolyte operating at low temperature broadens the application for next generation sustainable batteries.

Synthesis and Investigation of Electrochemical Studies on Thulium Tellurite (TmTeO3) for Supercapacitor Electrode Application

Thulium tellurite (TmTeO[Formula: see text] is synthesized by hydrothermal method. It exhibits nearly cuboid-shaped particles along with triangular particles. TmTeO3 is found to be monoclinic. The energy gap is 5.87 eV, the Urbach energy value is 0.287 eV and the refractive index is 1.881. The size of the particle is determined as 107 nm. Optical transitions between energy levels assign absorption and emission peaks. Tm, was found in the oxide matrix as Tellurite. Magnetic susceptibility between 20 K and 300 K decreases with temperature, reaches saturation and aligns all Thulium spins. M–H curve confirms paramagnetic nature at 300 K and feeble ferromagnetic nature at 77 K. Cyclic voltammogram and chronopotentiometry analysis exhibit pseudo-capacitive behavior. The potential window is 0.82. Specific capacitance is found to be 87 F/g. Chronopotentiometry analysis shows 55 F/g specific capacitance. Impedance analysis shows a pseudo-capacitive nature. TmTeO3 symmetrical supercapacitor device is fabricated with potential window of 1.52 V. A specific capacitance of 37.75F/g at 1 A/g, energy density 6.055Wh kg[Formula: see text] and power density 760.99W kg[Formula: see text] was achieved. Impedance analysis shows low series resistance of 2.567[Formula: see text] and charge transfer resistance of 0.473[Formula: see text]. Cyclic performance with 80% specific capacitance retention is observed after 5000 cycles. The TmTeO3 symmetric supercapacitor electrodes possess good electrochemical properties due to wider potential window, long cycle stability and notable energy density.

Ag nanocubes-decorated ammonium hydroxide-treated carbon nitride to improve photocatalytic H2O2 production and fuel cell performance

A novel photocatalyst is designed by surface modification and cocatalyst loading of graphitic carbon nitride (g-C3N4) with ammonium hydroxide and silver nanocubes (AgNCs), respectively. The synergistic effect of the modification in the intralayer of g-C3N4 and surface plasmon resonance (SPR) bands of AgNCs significantly enhances the migration and separation efficiency of photo-induced charge carriers. A nickel mesh coated with photocatalyst and the carbon paper loaded with pristine g–C3N4–mixed iron phthalocyanine (FeIIPc) used as the photoanode and cathode, respectively, are constructed for the self-powered photoelectrochemical cell, which exhibits the maximum power density of 0.74 mW cm−2. The AHCN/AgNCs-based cell reveals approximately a 3.1-times enhancement in maximum power density compared with the pristine g–C3N4–based cell. In addition, the photocatalytically generated H2O2 (chemical energy) can be stored in water, and then used as fuel by the connection of two electrodes in the dark. After the fuel cell is operated for 12 h, the specific capacitance retention rate still maintains as high as 57.2 %, which is the greatest retention rate in comparison with the previously reported H2O2 fuel cell systems. Our work offers a feasible opinion on how to improve the visible light utilization of semiconductors by tuning the intralayer properties and loading plasmonic metal.

3D Architecting triple gradient graphene-based fiber electrode for high-performance asymmetric supercapacitors

High-performance fibrous architectures and controllable fabrication methods for active nanomaterials are fundamental in the development of fiber-based supercapacitors (FSCs). Herein, we rationally designed a triple gradient structured fibrous electrode based on three-dimensional (3D) architectural approach with Ni3S2 nanoflakes (Ni3S2 NFs) in situ growth on Ni-coated graphene fiber (Ni3S2-NiGFs) for highly energy-dense asymmetric supercapacitors. Remarkably, the Ni-metal coating imparted the Ni3S2-NiGFs exceptional electrical conductivity (619.8 S cm−1), mechanical strength (335.0 MPa), and flexibility without significantly compromising its density. Moreover, the unique 3D interconnected ultrathin Ni3S2 NFs significantly increase the contact area between the electrode and the electrolyte solution, providing abundant redox activity to facilitate ion transport and accumulation. Therefore, the fibrous electrode showcased a remarkable areal specific capacitance of 1387.6 mF cm−2 at 3 mA cm−2 in 3 M KOHaq electrolyte, while its asymmetric FSCs delivered an impressive areal energy density of 15.6 μW h cm−2 at power density of 1.0 mW cm−2 along with durable cycle life (86.7 % of the initial specific capacitance retention over 10,000 cycles). In summary, the featured work provides a facile but robust electrode design to realize highly energy-dense flexible energy storage devices for next-generation wearable industries.

Cycling Stability of a 2D Pristine MOF Supercapacitors

AbstractTwo‐dimensional (2D) metal–organic frameworks (MOFs) have been a worldwide research interest due to their potential application in supercapacitors. Herein, a cobalt‐based layered MOF ([Co2(μ‐SO4)(Hppza)2(H2O)3]n, namely, SEU‐1; H2ppza=3‐(pyridin‐4‐yl)‐1H‐pyrazole‐5‐carboxylic acid) has been synthesized via a one‐step solvothermal method. Single X‐ray diffraction analysis shows that the SEU‐1 exhibits a (3,3,4)‐connected 2D structure with a Schläfli symbol of (62 ⋅ 8)(63)(64 ⋅ 8 ⋅ 10). Variable‐temperature magnetic susceptibility data display that antiferromagnetic interactions between two CoII ions exist in SEU‐1. The supercapacitive performance has been evaluated in the three‐electrode system. Its maximum specific capacitance is 145.5 F g−1 at 1 A g−1, along with the specific capacitance retention of 92.7 % at the current density of 5 A g−1 after 6000 cycles in 3 M KOH solution. These results demonstrate that SEU‐1 is a good candidate for electrode material for electrochemical energy storage.

Investigating the electrochemical performance of Mn3O4/MoMn2P12 mixed-phase catalyst on MWCNT for high specific energy supercapacitors and HER/OER reactions

A versatile Mn/MoMn hybrid oxide/phosphide composite (MnO/MoMnP) supported on MWCNT is synthesized using hydrothermal method and in-situ phosphorization methods. This composite serves as a catalyst for supercapacitors and oxygen and hydrogen evolution reactions (OER/HER) in electrochemical water splitting. XRD analysis confirmed the presence of mixed-phase of Mn3O4 and MoMn2P12. Electrochemical tests revealed exceptional charge storage performance for MnO/MoMnP/MWCNT, with a high specific capacitance(436 F g−1 at 1 A g−1) and impressive capacitance retention (96.51 % for 5000 cycles at 15 A g−1). This performance surpasses that of bare MnO/MoMnP by 50 %. Furthermore, we assembled a MnO/MoMnP/MWCNT//MWCNT device, that achieved a remarkable energy density of 128.11 W h kg−1 at an ultra-high-power density of 1920 W kg−1, along with excellent cycling stability (92.5 % for 5000 cycles). Moreover, the MnO/MoMnP/MWCNT composite exhibited a remarkable bifunctional electro catalytic activity for OER and HER, with low overpotentials of 335 and 430 mV at 10 mA cm−2 in 1 M KOH solution. These results highlight MnO/MoMnP/MWCNT as a promising and efficient alternative catalyst for future applications in supercapacitors and water electrolysis.

Copper/cobalt metal-organic framework composites for advanced anode material of lithium-ion battery

In this paper, two new types of metal-organic frameworks (MOFs) materials, namely Cu-IM and Co-MOF, have been successfully applied to the anode of lithium-ion batteries with LiPF6 (EC: DMC = 1:1, volume) electrolyte additive. Cu-IM and Co-MOF employed imidazole (IM) and 2-methylimidazole (2-MeIM) as organic ligands, respectively. The results revealed the synthesized MOFs exhibited high initial discharge specific capacities (Cu-IM: 1964.5 mAh g−1, Co-MOF: 1423.3 mAh g−1) as well as low internal resistances (Cu-IM: 146 Ω; Co-MOF: 236 Ω). To alleviate the issue of capacity decay in single MOFs, we attempted the dual-MOFs materials through the rational design of interfacial/surface properties and microstructure. Compared to Cu-IM, the prepared Cu-IM/Co-MOF composites have a higher specific surface area and pore volume. Furthermore, the charge transfer resistance of Cu-IM/Co-MOF composites (141 Ω) was lower than that of Cu-IM and Co-MOF respectively. After a heat treatment to Cu-IM/Co-MOF composites, the electrochemical performance of obtained Cu-IM/Co-MOF 250 dual-MOFs composites have been significantly improved. The Cu-IM/Co-MOF 250 dual-MOFs composites demonstrated excellent cycling stability and high discharge specific capacities at various current densities. The composites displayed stable discharge specific capacity retention of 834 mAh g−1 (50 mA g−1, 75 cycles), 710.5 mAh g−1 (200 mA g−1, 50 cycles), and 392.5 mAh g−1 (500 mA g−1, 50 cycles), highlighting their promising performance for energy storage applications. The synthesized Cu-IM/Co-MOF 250 dual-MOFs composites demonstrates exceptional cycling performance and rate capability, implying that it has the promising prospects as anode material for lithium-ion batteries.

Largely improved cycling stability of CoV2O6 supercapacitor electrode synthesized by deep eutectic solvent

Transition metal oxides composed of cobalt-based and vanadate configurations are widely used in supercapacitor electrodes due to the abundant nature of the various elements and their outstanding electrochemical performance. However, redox and ion intercalation mechanisms are involved between the electrodes and electrolyte, which inevitably lead to large differences in capacity retention and long-term cycling ability of synthetic electrodes by different preparation methods. In this work, the CoV2O6 electrode with a capacity of 194.0 C g−1 and a capacitance retention of 122.2 % after performing 100,000 cycles was synthesized by using deep eutectic solvent. In addition, the underlying mechanism of its excellent cycling stability was systematically studied. It was demonstrated that the continuous growth of particles on the electrode surface could lead to the formation of a stable polyhedron structure. More specifically, the generation of the CoOOH phase with strong reversibility on the electrode surface is considered the key to attaining the long cycling life of the CoV2O6 electrode. A hybrid supercapacitor (CoV2O6//AC HSC) was assembled for the evaluation of practical applications. It delivers a specific capacity of 119.3 C g−1 as well as a rate capability with 92.3 % capacity retention and good cycling durability, and the energy density of the HSC can reach up to a high energy density of 20.6 W h kg−1 at 373.4 W kg−1. A new cobalt vanadate electrode synthesis method was proposed here to examine the changes in the specific capacity and capacitance retention after performing ultra-long cycles, which provide a solid experimental basis for the development of supercapacitors for practical applications.

Alternative inner filling and outer surface coating of BNNT by Tungsten(VI) oxide for supercapacitor electrode

The motivation behind this research is to address the need for advanced energy storage materials by exploring the selective filling and coating of boron nitride nanotube (BNNT) with tungsten(VI) oxide (WO3) to enhance the pseudocapacitive performance. In this study, we present a novel synthesis method that allows precise control over the extent of filling and coating, aiming to create tailored hybrid structures. Morphological and structural analysis confirm the filling and coating of BNNT by WO3. Inner filling and outer surface coating of BNNT by WO3 significantly impact on the electrochemical properties. The filling of WO3 within the BNNT can enhance the stability of the system, whereas outer surface coating of BNNT by WO3 improves the capacitive performances. The role of BNNT influences both these phenomena by acting as electrolyte transportation channel as well as stabilizing the WO3. In three electrode study, WO3 coated BNNT showed the maximum specific capacitance of 856 F/g at 1 A/g. An asymmetric supercapacitor device using WO3 coated BNNT as positive electrode revealed the maximum specific capacitance of 137 F/g at 2 A/g current density with an improved energy density of 52 W h/kg. The WO3 coated BNNT-based asymmetric supercapacitor device also showed ∼81 % specific capacitance retention after the completion of 10,000 GCD cycles, whereas WO3 filled BNNT-based supercapacitor device demonstrated better stability (∼94 % specific capacitance retention) due to the filling and stabilization of pseudocapacitive WO3 by BNNT.

Polycrystalline phases engineered in-situ in polyaniline-graphene composite evoluting an exceptional stability and high charge storage capacity: An EIS investigative approach to evaluate material's stability

Development of electroactive materials exhibiting high performance with superior stability is crucial in the field of supercapacitors and battery research. We report on synthesis of highly stable composite of semi-polycrystalline polyaniline and graphene (SPani-graphene) and its application in supercapacitor electrodes. The electrochemical behavior and device performance of the electrodes were investigated through cyclic voltammetry (CV), galvanostatic charge-discharge GCD) and electrochemical impedance spectroscopy (EIS) in a 3-electrode and a 2-electrode (device) cell configurations, repectively. The cell specific capacitance (Cell Csp) achieved from the 2-electrode symmetric cell configuration was 525.5 F g−1 at 0.1 A g−1 using polymer gel electrolyte (PGE). The PGE in this work is xanthan gum jellied in 1 M aq. Na2SO4. The maximum energy density and power density achieved from the device was 46.7 Wh kg−1 and 16.16 kW kg−1, respectively, at 0.4 A g−1. Furthermore, the device exhibits an excellent retention of cell specific capacitance and coulombic efficiency of 97 % and 94 %, respectively, over 10,000 continuous GCD cycles, indicating an excellent rate capability as well as a promising power management. To investigate the material's electrochemical durability, a detailed EIS study has been carried out using both, 3-electrode, and 2-electrode cell configurations, before and after long cycling test (over 10,000 continuous GCD cycles). Our thorough experimentation delivers satisfactory results and has been explained in detail in the manuscript. Hereby, we propose that the EIS technique can be adopted for investigating materials' electrochemical stability, in addition to long CV and GCD cycles in the field of supercapacitors and battery research.

Environmentally friendly additives for crystal surface modulation and suppression of dendrites for aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) as promising energy storage devices provide synergistic advantages of high safety, low cost and high energy density. However, it has been observed that underestimated but not negligible dendrites of Zn and H2 production affect battery performance and limit applications of AZIBs. In this work, a functional electrolyte strategy is reported by adding polyhydroxy chlorinated organic compound-sucralose (SCL), which can improve the lifetime of battery. A combination of experimental and theoretical research reveals that SCL could induce the deposition behavior of Zn2+, i.e. the preferential deposition of Zn2+ on the (002) crystal plane, which is conducive to suppress dendrite formation. In the presence of 0.5 mA cm−2 and 1.0 mAh cm−2, compared with pure ZnSO4 electrolyte, the electrolyte with SCL significantly improves the cycle lifespan of Zn||Zn symmetrical cells (3200 h compared to 125 h). To validate the feasibility of SCL, we assemble Zn||MnO2 full cells, which exhibit excellent specific capacity (149 mAh g−1) and capacity retention (89 %) over 2000 cycles at 1.0 A g−1.

Investigating the energy storage mechanism of modified PEDOT:PSS for enhanced electrochemical performance

In this study, first principles calculations are performed to investigate the relevant energy storage mechanisms of PEDOT:PSS membranes and WO3/MnO2. The calculation results indicate that the modified PEDOT:PSS reduces the interaction force between cation and inorganic material lattice, weakens the adsorption energy, and accelerates the electrochemical reaction kinetics. Simultaneously, the prepared composite material exhibits a higher state density and more energy orbitals. The cations of the electrolyte can be stored in the s and p orbitals of the material, leading to significant hybridization of electron clouds in these orbitals and improving the conductivity of the material. Based on the above calculation results, a WO3/MnO2 self-healing electrochromic energy storage device is prepared. The device has a high specific capacitance (10.81 mF cm−2) and excellent cycle retention performance (97% retention rate after 1000 cycles), which ensures its efficient energy storage and reliable durability. Furthermore, the device has the self-healing capability to restore most of its functions even in the event of damage, ensuring its long-term utilization.

Zn2+ doped Ni3(NO3)2(OH)4 nanoflower spheres for electrochemical applications

In this present work, Ni3(NO3)2(OH)4 doped with Zn2+ ions are prepared by a solvothermal method using Ni(NO3)2·6H2O, Zn(NO3)2·6H2O, C16H33(CH3)3NBr (CTAB) and C2H5OH as raw materials. Characterization methods such as X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) are used to analyze the materials. Cyclic voltammetry (CV) and galvanostatic charge–discharge curves (GCD) are employed to compare the electrochemical performance of materials with different doping amounts. The electrochemical test results show that doping with Zn2+ significantly enhances the poor electrical conductivity of Ni3(NO3)2(OH)4. Electrochemical tests reveal that the doping amount of 0.4 mmol has the best electrochemical performance with a mass-specific capacitance of 1832 F·g−1 at a current density of 1 A·g−1 in the three-electrode system which is much higher than that of undoping sample (771 F·g−1). Additionally, the assembled NiZn-0.4//AC asymmetric supercapacitor device (ASC) has an energy density of 61.9 Wh·kg−1 at a power density of 747.8 W·kg−1. The Coulombic efficiency retention of the ASC device remains at 98 % after 2000 galvanostatic charge–discharge circles, and the specific capacitance retention is 91 % of the initial value. The doping of Zn2+ provides a valuable approach for enhancing the conductivity and specific capacitance of nickel-based supercapacitor electrode materials.

A free-standing ZnO@NiCo2O4 nanofilm for supercapacitors and zinc-ion batteries with high-rate performance and high energy density

Transition metal oxides are promising candidates for high-performance electrode materials due to their high conductivity and abundant active sites. Nevertheless, its low energy density and poor rate performance limit its application in energy storage devices. Herein, a free-standing ZnO@NiCo2O4-4 nanofilm was sythesised through simple hydrothermal method. This novel material exhibited excellent electrochemical properties as a result of the synergistic effect of ZnO and NiCo2O4. Specially, the ZnO@NiCo2O4-4 electrode a high specific capacitance of 812.5 F g−1 at 1 A g−1 with remarkable rate performance delivers (615.8 F g−1 even at 10 A g−1). The as-prepared ZnO@NiCo2O4-4//AC supercapacitor exhibits a large energy density of 48.8 W h kg−1 at a power density of 375 W kg−1, and the specific capacitance retention rate of the device maintains 82% after 5000 cycles at 3 A g−1. Furthermore, the assembled ZnO@NiCo2O4-4//Zn zinc ion battery can deliver a high specific capacity of 71 mA h g−1. This work offers important guidance for preparing transition metal oxide nanofilms with excellent performance for supercapacitors and zinc-ion batteries.

A Thiol Branched 3D Network Quasi Solid-State Polymer Electrolyte Reinforced by Covalent Organic Frameworks for Lithium Metal Batteries.

Quasi solid-state polymer electrolytes (QSPEs) are particularly attractive due to their high ionic conductivity and excellent safety for lithium metal batteries (LMBs). However, it is still a great challenge for QSPEs to achieve strong mechanical strength and high electrochemical performance simultaneously. Herein, a QSPE (SCOF-PEP-PEA) using a covalent organic framework (COF) containing abundant allyl groups (SCOF) as a rigid porous filler as well as a cross-linker to reinforce the polymer network is reported. Benefitting from the unique 3D nanonetwork structure and abundant lithiophilic functional groups, SCOF-PEP-PEA QSPE exhibits high ionic conductivity (4.0 × 10-4 S cm-1) and high lithium-ion transference number (0.82) at room temperature. Moreover, SCOF-PEP-PEA QSPE displays much improved mechanical strength compared to PEP-PEA QSPE (AFM Young's modulus: 453 vs 36MPa). As a result, the Li/LFP full cell with SCOF-PEP-PEA QSPE shows great rate performance of 141 mAh g-1 at 1C and delivers a high specific capacity retention of 92% after 220 cycles at 0.5 C (60 °C). This work provides a new strategy to design and prepare high-performance QSPEs with COFs as porous organic filler, and further expand the application of COFs for energy storage applications.