Retention Of Initial Capacitance Research Articles

Lithium-compound-coated graphite as an anode material for all-solid-state lithium batteries

We prepared 0.125 and 0.5 mol% LiAlO2-coated graphite powders and 0.125, 0.25, and 0.5 mol% LiGaO2-coated graphite powders by the solvothermal method. The samples had uniformly dispersed fine particles on the graphite surface, except for the 0.5 mol% LiGaO2-coated graphite powder, in which the graphite surface was partially coated with aggregates several micrometers in size. All-solid-state lithium batteries with Li3PS4 glass as a solid electrolyte were assembled to investigate the effect of the coating on the charge-discharge performance. Batteries containing 0.125 mol% LiAlO2 and LiGaO2-coated graphite powder showed a higher initial coulombic efficiency and capacity retention rate than those containing uncoated graphite powder.

A novel hierarchical core-shell structure of NiCo2O4@NiCo-LDH nanoarrays for higher-performance flexible all-solid-state supercapacitor electrode materials

In the present work a 3D hierarchical NiCo 2 O 4 @NiCo-LDH core-shell structure has been fabricated on activated carbon cloth through a facile hydrothermal strategy and an electrodeposition step. The core of the NiCo 2 O 4 nanowires forms the nanoarray backbone on carbon cloth while the shell of NiCo-LDH nanosheets extends the electrochemical active sites and generates mesoporous hierarchical channels to facilitate electron and ion transport. Therefore, with the optimized mass ratio of 1.9 between NiCo-LDH and NiCo 2 O 4 , such a core-shell structure enhanced the areal capacitance of the as-prepared NiCo 2 O 4 @NiCo-LDH electrode up to 6092 mF/cm 2 (or areal capacity of 0.846 mAh/cm 2 at 2 mA/cm 2 for the battery type pseudocapacitor) and obtain high specific capacitance of 1882 F/g under 1 A/cm 2 . The capacity retention rate can maintain 83.9 % after 5000 cycles at 30 mA/cm 2 . Furthermore, an all-solid-state asymmetric supercapacitor (ASC) was assembled using NiCo 2 O 4 @NiCo-LDH//activated carbon. Such an ASC exhibits a very high energy density of 49 Wh/kg at the power density of 750 W/kg and retains 30 Wh/kg at 7500 W/kg. The ASC shows its excellent cycling stability by keeping 83.3 % of initial capacity retention rate after 2000 cycles under 5 A/g. The assembled flexible all-solid-state supercapacitor with NiCo 2 O 4 @NiCo-LDH//activated carbon exhibits good mechanical stability and high specific capacity of 157 F/g under 1 A/g. The significantly improved electrochemical properties demonstrates the practical applications of the core-shell structure of NiCo 2 O 4 @NiCo-LDH on carbon cloth for novel ASC configuration design and development of next energy storage devices. • The unique NiCo 2 O 4 @NiCo-LDH cover-shell heterostructure greatly improve the electrochemical performance. • The NiCo 2 O 4 @NiCo-LDH//ACC electrode shows the high area capacitance of 6092 mF/cm 2 . • The NiCo 2 O 4 @NiCo-LDH//AC ASC device has good flexibility, high energy density and power density.

Amorphous S-doped NixCo3-xO4 for high-performance asymmetric supercapacitors

Amorphous S-doped NixCo3-xO4 materials were successfully synthesized using a facile co-precipitation method through changing additive in a mixed solution. As-prepared amorphous S-doped NixCo3-xO4 exhibit different Ni/Co ratio, O/S ratio, morphology and structure when a mixed solution including sodium dodecyl sulfate, without additive, or containing glycine. S-doped NixCo3-xO4 prepared with a mixed solution excluding additive (denoted as NixCo3-xO4-ySy-2) exhibits remarkable supercapacitive performance due to optimum Ni/Co ratio, minimum O/S ratio, proper morphology and structure. NixCo3-xO4-ySy-2 delivers a specific capacitance of 1335 F g−1 at 0.5 A g−1 and a ultra-high specific capacitance retention of 68.7% even at 16 A g−1, demonstrating high specific capacitance and good rate capability. Moreover, NixCo3-xO4-ySy-2 shows an initial specific capacitance retention of 80.8% after 2000 cycles, implying superior cycling stability. The assembled asymmetric supercapacitor (ASC) based on NixCo3-xO4-ySy-2 as the positive electrode and AC as the negative electrode achieves outstanding energy density of 31.87 Wh kg−1 at a power density of 900 W kg−1. The specific capacitance retention of the ASC is up to 90.2% after 2000 cycles, exhibiting excellent cycling stability. This study shows a promising electrode for supercapacitors device and provides an effective strategy for design of high-performance supercapacitor electrode materials.

Titanium carbide@Poly (3,4-propylenedioxythiophene) composite as electrode for asymmetric flexible supercapacitors

In this paper, the composite of Ti3C2Tx and poly (3,4-propylenedioxythiophene) (PProDOT) is prepared via a simple in-situ chemical oxidative polymerization. The optimum ratio of Ti3C2Tx@PProDOT composite with an outstanding capacitance of 462 C g−1 (462 F g−1) at 1 A g−1 is obtained by adjusting the mass ratio of Ti3C2Tx and ProDOT. The asymmetric flexible supercapacitor with Ti3C2Tx@PProDOT (1:10)//AC exhibits the gravimetric capacity of 238 C g−1 at 1 A g−1, and the retention of initial capacity remains at 79.6% after 10,000 cycles. Meanwhile, the asymmetrical supercapacitor displays an energy density of 48.6 Wh kg−1 at a power density of 729.6 W kg−1. The improvement of these properties stems from that the PProDOT effectively inhibits the stacking of Ti3C2Tx sheets, which is advantageous to shortening the transport path of ions and promoting electron transport as well as the rapid redox reactions. Therefore, these characteristics enhance the electrochemical performance of composites.

Significantly promoting the energy storage performance of hierarchically porous carbon by introducing antimonene nanosheets

• Preparing a new electrode material Sb@HPC by mixing HPC and antimonene. • The specific capacitance of the Sb@HPC is about 3 times that of HPC. • The introduction of antimonene does not sacrifice the rate performance of HPC. Increasing the capacitance and cycle life of electrode materials while maintaining a high rate in supercapacitors is still a challenge. Herein, we report a new electrode material Sb@HPC prepared by mixing hierarchically porous carbon (HPC) with a high specific surface area of 2810.1 m 2 g −1 and antimonene nanosheets. In a three-electrode system, the specific capacitance of the Sb@HPC (1138 F g −1 at 2 A g −1 ) is about 3 times that of HPC (420 F g −1 at 2 A g −1 ). Besides, when the current density increases from 2 to 10 A g −1 , the Sb@HPC delivers a high rate capability with 70.8 % initial capacitance retention, which is comparable with that of the HPC (70.0 %). Most importantly, the specific capacitance retention of the Sb@HPC can reach up to 100 % after the cyclic test at 10 A g −1 , which is much higher than that of the HPC (50 %). These results reveal the introduction of antimonene nanosheets improves the specific capacitance and cyclic performance of the HPC without the degradation of rate performance. This work provides a reference for the improvement of specific capacitance and cycle life of other electrode materials.

Decorating cobalt selenide nanoparticles on polypyrrole nanowires as nanocomposite electrodes for hybrid supercapacitors

• PPy@Co 0.85 Se nanocomposites are fabricated by a two-step electrochemical method. • Dispersed Co 0.85 Se nanoparticles are decorated on PPy nanowires growing on Ni foam. • PPy@Co 0.85 Se electrodes demonstrate improved rate capacities and cyclic stability. • The improved charge storage property arises from structural merits of nanocomposites. Cobalt selenide electrode materials for hybrid supercapacitors (HSCs) still suffer from the unsatisfactory rate performance and cyclic stability thanks to their limited electrical conductivity and poor structural stability. To address these issues, we here report on the construction of polypyrrole (PPy)@Co 0.85 Se nanocomposites that grow on Ni foam by a two-step electrochemical synthesis method. In such nanocomposites, well dispersed Co 0.85 Se nanoparticles are decorated on conductive PPy nanowires, which are featured by enhanced electrical conductivity, rich electroactive sites, easy adsorption/desorption and diffusion of electrolyte ions, and good mechanical stability. As a result, the obtained PPy@Co 0.85 Se nanocomposites give a maximum specific capacity of 827 C g −1 at 1 A/g, a capacity retention of 67 % at 20 A/g, and an initial capacity retention of 93 % after 5000 cycles at 10 A/g. Furthermore, a two-electrode HSC device is assembled with PPy@Co 0.85 Se as the positive electrode, which demonstrates an energy density of 51.9 Wh kg −1 at a power density of 812 W kg −1 as well as an initial capacity retention of 96 % after 5000 cycles at 5 A/g. These results showcase a great potential for future application of the synthesized PPy@Co 0.85 Se nanocomposites in HSCs, and our work may provide an efficient strategy for engineering other metal selenide-based electrode materials for HSCs.

Optimization of VOSO4@C cathode materials with CNT and GO for lithium-ion batteries

VOSO 4 is a promising cathode material for lithium-ion batteries owing to its polyanionic structure and the polyvalency of vanadium. In this study, carbon nanotubes (CNTs) and graphene oxide (GO) were adopted for modifying the microstructure and improving the overall performance of VOSO 4 . Before the chemical synthesis of VOSO 4 , the CNTs were firstly combined with precursor and CNT-VOSO 4 @C was formed via a one-step chemical synthesis. The results showed that CNTs could improve the charge–discharge performance of the VOSO 4 @C. The initial discharge specific capacity of CNT-VOSO 4 @C was up to 151.6 mAh·g −1 at 0.05 C, and even at 1 C the capacity could reach 66.06 mAh·g −1 . The discharge–capacity retention rate is 100% after a long circulation. Secondly, CNTs and GO were composited with the synthesized VOSO 4 @C and the obtained composites VOSO 4 @C-CNT and VOSO 4 @C-GO exhibited good electrochemical properties with initial discharge specific capacities of 135.7 and 141.8 mAh·g −1 at 0.05 C, respectively. This may be attributed to the high specific surface areas and conductivities of CNTs and GO. When grinding the composites, CNTs and GO are uniformly distributed among the particles, forming bridges between the particles, that can increase the electrical conductivity between the particles and reduce the volume expansion of electrode materials. CNT-VOSO 4 @C exhibits the best modification effect. This study proposes a feasible approach for applying VOSO 4 in lithium-ion batteries, particularly under weak currents. • CNT and GO act as bridges between the VOSO 4 @C particles. • CNT-VOSO 4 @C has the best initial discharge capacity and capacity retention rate. • This work provides a feasible approach for applying VOSO 4 in lithium-ion battery, especially at weak currents.

Nickel phosphide nanoparticles decorated on polypyrrole nanowires as battery-type electrodes for hybrid supercapacitors

Metal phosphides as electrode materials for hybrid supercapacitors (HSCs) still face many challenges, such as insufficient electroactive sites, sluggish reaction kinetics, and low structural stability. To resolve these problems, we here integrate nickel phosphide (NiP) with polypyrrole (PPy) to construct PPy@NiP nanocomposites using a two-step electrochemical approach. Such nanocomposites are composed of amorphous NiP nanoparticles decorated on PPy nanowires. They are featured by increased amount of electroactive sites, enhanced electrical conductivity and electrolyte diffusion rate, and improved structural stability compared to the pure NiP particles. As a result, the PPy@NiP nanocomposites as HSC electrodes yield specific capacities of up to 364 mAh g−1 at 3 A g−1 and 159 mAh g−1 at 20 A g−1 as well as a 91% initial capacity retention over 5000 cycles at 10 A g−1. Their charge storage performance is superior to that of the pure NiP electrode. Furthermore, the fabricated PPy@NiP-based HSC device demonstrates an energy density of 57.3 Wh kg−1 at 798 W kg−1. This strategy for constructing PPy@NiP electrodes may be extended to other metal phosphide-based electrodes with enhanced charge storage performance for HSCs.

Cu7S4 superionic with liquid-like mobility of copper ions for high-performance room-temperature rechargeable magnesium batteries

Rechargeable magnesium batteries (RMBs) are promising energy storage systems due to their high volumetric capacity, good safety, and abundant resources. However, it is still a great challenge to develop high-performance cathode materials for RMBs owing to the strong Coulombic interaction between the highly polarized Mg2+ and lattice anions of hosts. Herein, Cu7S4 superionic nanoparticles are prepared by in situ reduction method and used as a durable cathode material for RMBs. The small size of Cu7S4 is beneficial for the full contact between active materials and electrolytes and meanwhile greatly shortens Mg2+ diffusion length, leading to rapid kinetics of Mg2+ participation in electrochemical reaction. Moreover, the high mobility of copper ion in Cu7S4 superionic can enhance the capacitive contribution, improving the rate and long-term performance. Benefiting from these advantages, at room temperature, Cu7S4 superionic cathode delivers high reversible capacity of ∼211.8 mAh/g at 100 mA/g, high rate capability with the capacity up to 134 mAh/g at 500 mA/g, and a long cycling lifespan with initial capacity retention of 71.6% after 500 cycles at 500 mA/g. This work offers an avenue for developing high-performance cathode materials for RMBs.

Suitable polysulfides adsorption and conversion on MoSe2@g-C3N4 interlayer for advanced lithium-sulfur batteries

The shuttle effect of lithium polysulfides (LiPS) and sluggish redox kinetic still restrict the commercial application of lithium-sulfur batteries (LSBs). Developing the modified functional separators that block the migration of LiPS and accelerate the LiPS conversion is an effective method to solve both problems. Here we report a MoSe2@g-C3N4 composite material with the merits of strong adsorption in g-C3N4 and appropriate migration in MoSe2 for LiPS simultaneously achieved on the surface. g-C3N4 has strong adsorption for LiPS while MoSe2 with a low migration barrier of LiPS and improves their conversion into solid-state Li2S. The excellent wettability of MoSe2@g-C3N4 facilitates electrolyte migration and improves the electrochemical performance. With a MoSe2@g-C3N4 interlayer delivered 2.2 times increase initial capacity than that with a conventional polypropylene (PP) separator at 0.5C, and a low-capacity decay per cycle of 0.09 % was achieved at 0.5C after 500 cycles. It showed the best rate capability of 564.2 mA h g−1 at 3C. Even under the high sulfur loadings of 3.2 and 4.0 mg cm−2, showing high initial capacity and decent capacity retention. This project provides a novel insight into designing the functional separators with the g-C3N4 substrate composites for stable LSBs.

Si1–xGex anode synthesis on plastic films for flexible rechargeable batteries

SiGe is a promising anode material for replacing graphite in next generation thin-film batteries owing to its high theoretical charge/discharge capacity. Metal-induced layer exchange (LE) is a unique technique used for the low-temperature synthesis of SiGe layers on arbitrary substrates. Here, we demonstrate the synthesis of Si1−xGex (x = 0–1) layers on plastic films using Al-induced LE. The resulting SiGe layers exhibited high electrical conductivity (up to 1200 S cm−1), reflecting the self-organized doping effect of LE. Moreover, the Si1−xGex layer synthesized by the same process was adopted as the anode for the lithium-ion battery. All Si1−xGex anodes showed clear charge/discharge operation and high coulombic efficiency (≥ 97%) after 100 cycles. While the discharge capacities almost reflected the theoretical values at each x at 0.1 C, the capacity degradation with increasing current rate strongly depended on x. Si-rich samples exhibited high initial capacity and low capacity retention, while Ge-rich samples showed contrasting characteristics. In particular, the Si1−xGex layers with x ≥ 0.8 showed excellent current rate performance owing to their high electrical conductivity and low volume expansion, maintaining a high capacity (> 500 mAh g–1) even at a high current rate (10 C). Thus, we revealed the relationship between SiGe composition and anode characteristics for the SiGe layers formed by LE at low temperatures. These results will pave the way for the next generation of flexible batteries based on SiGe anodes.

Microalgae Derived Nano Carbon-Sulfur Composite Cathodes for Sulfur Batteries

Nano porous carbon and sulfur composites were prepared using microalgae as carbon precorsors by the melt diffusion method. Initially, nano porous carbon materials were synthesized by the hydrothermal method, followed by the chemical activation method with and without ferrocene as catalyst. Therefore, we have two types of porous carbon samples, the first sample was denoted as NPC (preparation with ferrocene) and the other one is PC (preparation without ferrocene) Brunauer–Emmett–Teller analysis indicated that the surface area and total pore volume (at P/P o) of NPC samples were lower than those of the PC samples. The NPC and PC samples were then mixed with sulfur to obtain NPC-S and PC-S composites. Those composites were then utilized as cathode materials for Lithium Sulfur Battery. The NPC-S samples with a sulfur content of 76.7 wt.% exhibited a higher initial specific capacity and better cycle retention than those of the PC-S. Optimized sulfur content for NPC-S was investigated to handle the shuttle effect problem. improved electrochemical performance is attributed to the increased conductivity of the NPC-S samples and optimized sulfur loading content, which effectively confined lithium polysulfide intermediates.

Introducing a Bio-Degradable Binder for Aqueous Production of NMC111 Cathodes

The LiNixMn1-x-yCoyO2 (NMC) is a widely used cathode material in lithium-ion batteries (LIBs) due to its high capacity. By enabling water-based cathode processing, the cost and environmental impact of LIBs will be reduced substantially. However, the water compatibility of Ni-containing materials has been problematic due to lithium (Li)-leaching, corrosion of the aluminium (Al) current collector, and lack of aqueous dissoluble binders. For the first time, we demonstrated that NMC111 cathodes with comparable specific capacities to the standard polyvinylidene fluoride/N-methyl-2-pyrrolidone (PVDF/NMP)-processed cathodes can be formulated in water using lignin as binder material. Rheology measurements revealed that less solvent is needed to obtain the same slurry viscosity when replacing the NMP solvent with water. Cycling voltammetry and differential scanning calorimetry revealed that lignin is electrochemically inactive between 2.5-4.5 V and thermally stable up to 152 oC, respectively. Drying the cathode coatings at 50 oC allowed for a controlled evaporation rate as surface cracks and binder migration detected using scanning electron microscopy diminished. The lignin binder provided strong cohesion forces to the carbon black (CB) and the NMC111 particles, and the use of carbon(C)-coated Al-foil (C-Al) further increased the coating's mechanical strength. Scratch tests revealed that calendaring magnified the nature of the initial mechanical strength, intensifying a poor adhesion of the coating to the Al-foil and strong cohesion between the particles. While calendering and pore removal improved the rate performance for PVDF-cathodes (85:10:5 wt % NMC:CB:binder), the rate capability of lignin-cathodes (80:11:9 wt %) decreased with lower porosity (from 53 to 0 %) and higher mass loading (9.7 mg/cm2). Particle deformation and extensive pore-blocking at high carbon contents created a Li+-transfer barrier across the cathode/electrolyte surface, decreasing the rate performance. Cathodes using a CMC/lignin-binder mix (2:7 wt% ratio) and C-Al foil (75 % capacity retention) electrochemically outperformed those with the commercial CMC/SBR mix and plain Al-foil (35 % capacity retention) at a high C-rate (5 C). Of all the aqueous produced cathodes, the uncalendered with pure lignin-binder, C-Al foil, dried at 50 oC, and a mass loading of 7.4 mg/cm2 showed the highest capacity retention at 5 C (60 %). Additionally, the lignin-cathodes have poor electrolyte wetting abilities and need longer exposure time before cycling and additional formation cycles compared to the PVDF-cathodes. Lignin-cathodes with the smallest lignin/CB matrix (90:5:5 wt% NMC:CB:binder) wetted for 35 days with 5 formation cycles at C/10 showed similar initial discharge capacity and capacity retention (154 mAh/g and 89 %) as 85:10:5 PVDF-based cathodes (153 mAh/g and 93 %) after 100 cycles at C/2.

Salt template tuning morphology and porosity of biomass-derived N-doped porous carbon with high redox-activation for efficient energy storage

In this work, N-doped porous carbon with effective Faraday reaction activation is fabricated by pyrolysis of egg white in air at high temperature using a mixed KCl and NaCl salt sealing strategy. The mechanism of the morphology and pores affecting the redox reaction are discussed in depth and the morphology and porosity of the carbon product are regulated by adding different amounts of saturated NaCl salt solution to egg white before cooking in a water bath. The increasing amounts of saturated NaCl salt solution added to egg white can enable more salt particles to penetrate into carbon framework at high temperature due to the interaction between water molecules and salt particles, leading to the achievement of N-doped porous carbon with thin sheet and mesopore structure. The sheets and mesopores can accelerate the reaction kinetics involved with fast Faraday reaction and diffusion-controlled process by providing more electron and ion transfer expressways, producing the effective Faraday effects of carbon electrodes. Therefore, explored the supercapacitor applications, as-synthesized N-doped porous carbon is exhibited a superb three-electrode specific capacitance of 304 F g−1 at 1 A g −1. The symmetrical surpercapacitors are also displayed a high specific capacitance of 248 F g−1 at 1 A g −1 and a good cycling stability with 98.7% of initial capacitance retention rate undergoing 15 000 cycles at 2.5 A g−1. This work has fundamental merits for the use of the sustainable abandoned eggs and concentrated protein solution feedstocks to prepare carbon electrode materials and further expands the application field of the salt sealing technique.

Ultrathin graphene@NiCo2S4@Ni-Mo layered double hydroxide with a 3D hierarchical flowers structure as a high performance positive electrode for hybrid supercapacitor

This study presents three-dimensional flower-like spheres composed of NiCo2S4@Ni-Mo layered double hydroxide (LDH) nanocomposites, which are grown in situ on reduced graphene oxide (RGO). The RGO@NiCo2S4@NiMo-LDH nanocomposites exhibit remarkable electrochemical properties and have a specific capacitance of 1346 F g−1 at the current density of 1 A g−1. In addition, using RGO@NiCo2S4 @NiMo-LDH hybrid nanosheets and activated carbon (AC) as the positive and negative electrodes, the asymmetric supercapacitor device was successfully assembled, and it showed a significant energy density of 59.38 Wh kg−1 at a power density of 808.19 W kg−1, with good cycle stability. The initial capacity retention rate is 80 % after 10,000 cycles. These results demonstrate the great potential of the synthesized RGO@NiCo2S4@NiMo-LDH composite for the development of high-performance electrode materials for supercapacitors.

Ni embedded carbon nanofibers/ Ni-Al LDHs with multicomponent synergy for hybrid supercapacitor electrodes

Preparation of multi-component composites is an effective strategy to obtain novel and highly efficient electrode materials. Herein, to achieve the synergistic effect of compositions and microstructures, hybrid materials made of Ni embedded carbon nanofibers/Ni-Al layered double hydroxides (Ni-Al LDH) were prepared in this work. Ni embedded carbon nanofibers were first fabricated ingeniously via the combination of electrospinning and thermal treatment, which provided a great number of active sites and increased the space for ion transportation. Subsequently, we combined Ni embedded carbon nanofibers with a nanostructured Ni-Al LDH via a hydrothermal process. It was reasoned that Ni embedded carbon nanofibers could help optimize microstructures of Ni-Al LDH, which could alleviate the aggregation problem and improve the rate performance of Ni-Al LDH. A series of composites were made and evaluated. It was found out that, the 3 % Ni embedded carbon nanofibers/ Ni-Al-LDH (3 %-Ni-CNA) electrode achieved an outstanding specific capacity of 1228.2 C g−1 at 1 A g−1, an excellent rate performance of 68.1 % of initial capacity even at 20 A g−1,and a long-cycle lifetime with 88.6 % of initial capacity retention after 10,000 cycles at 8 A g−1. In addition, an asymmetric supercapacitor device based on 3 %-Ni-CNA and AC was constructed and demonstrated a high energy density of 74.9 W h kg−1 at 800 W kg−1 It is noteworthy that the capacity of the device achieved 91.4 % retention after 10,000 cycles at 6 A g−1. Hence, the 3 %-Ni-CNA could be an ideal material for the hybrid supercapacitors and other energy storage applications. At the same time, it provides a novel mentality for improving the electrical conductivity of electrodes and constructing nanomaterials with heterostructures

Three-dimensional activated graphite paper for high-performance supercapacitors

Developing electrodes with both high specific capacity and high rate performance is critical for high-performance supercapacitors. Three-dimensional current collector is essential for achieving high specific capacity and high rate capability because it can not only significantly improve active materials' mass loading and uniformity, but also largely benefit the charge transfer. Herein, a simple electrochemical-assisted method is developed to activate graphite paper under room temperature. The activated graphite paper (AGP) features both low structural defects and an open structure with partially exfoliated graphite sheets anchoring on the base of graphite paper. After hybridizing NiCo layered double hydroxide (NiCo-LDH), the obtained sample (AGP@NiCo-LDH) presents a high specific capacity of 875 C g−1 at 1A g−1 and excellent rate capability (87.3% capacitance retention at 20 A g−1). Furthermore, the assembled asymmetric supercapacitor based on AGP@NiCo-LDH shows a high energy density of 27.56 Wh kg−1 at a power density of 16.0 kW kg−1 and excellent cycling stability (94.4% of the initial capacitance retention at 10 A g−1 over 5000 cycles).

Facile Synthesis of Nitrogen/Sulfur Co-doped Three-Dimensional Holey Graphene Hydrogels for High Supercapacitive Performance

Heteroatom-doped holey graphene hydrogels (HGHs) have attracted great interest owing to their remarkable porous structure, superior electrochemical performances, and prospective applications for supercapacitors. Herein, a simple and scalable approach to synthesize nitrogen, sulfur co-doped three-dimensional HGHs is developed using (NH4)2S2O8 as the pore-making agent and N, S sources by a one-step hydrothermal reaction. In a 6 M KOH electrolyte, the optimized HGH-based asymmetric supercapacitor exhibits an exceptionally high specific capacitance of 354 F g–1 at 1 A g–1, an excellent rate capability of 299 F g–1 at 100 A g–1, and outstanding cycle stability (104% of initial capacity retention at 5 A g–1 after 10,000 cycles). Additionally, the assembled HGH electrode supercapacitor possesses a high energy density of 21.14 Wh kg–1 (449.95 W kg–1) in a 1 M Na2SO4 electrolyte. The N, S heteroatom doping and hierarchical pore structure are ascribed to the superior electrochemical performance of HGHs. Therefore, the convenient and efficient method in the present work provides new ways into the preparation of heteroatom-doped HGHs for high-performance supercapacitors.

High-performance complementary electrochromic energy storage device based on tungsten trioxide and manganese dioxide films

In this work, we have selected a representative pseudocapacitive material of manganese dioxide (MnO2) film as the complementing electrode of tungsten trioxide (WO3) film to construct a smart electrochromic energy storage device (EESD), with the aim to simultaneously provide the optical modulation and energy storage performance. WO3 and MnO2 films have been respectively synthesized via simple hydrothermal and electrodeposition methods to achieve desirable matched performance. For the constructed EESD, an obvious optical contrast (38.63% at 633 nm), fast switching times (tb/tc = 9.37/5.19 s), high coloration efficiency (85.36 cm2·C−1), satisfactory specific capacitance (10.69 mF·cm−2 at the discharge current density of 0.1 mA·cm−2) as well as excellent cycle stability (initial capacitance retention rate of 95.90% after 1000 charge/discharge cycles) have been derived. After charging, the obtained EESD could light up an LED bulb or an LCD screen, showing high promising application prospect in energy storage.

RETRACTED: Oxygen vacancy induced high specific capacitance in Sr2CoSbO6

Sr2CoSbO6, a double perovskite compound known to have oxide ion vacancies, is not well explored for its electrical properties. In the present article, we study the effect of the aliovalent doping of Na+ at Sr site in Sr2CoSbO6 on their electrochemical performance. The X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) techniques confirm the phase formation and reveal particle-like morphologies for all the samples. The cyclic voltammetry study reveals the specific capacitance increases with increasing Na concentration and a specific capacitance value of 228 F/g is obtained for the maximum dopant composition. Excellent cycling stability of 92% of initial capacitance retention even after 2000 continuous cycles at a high scan rate of 100 mVs-1 in an aqueous 1 M KOH electrolyte solution and a 98% of coulombic efficiency at a current density of 1 A/g is observed. These values suggest that the Na doped Sr2CoSbO6 can find application as supercapacitors material.