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As an electrochemical energy storage material, transition metal layered double hydroxides (MLDHs) have attracted attention due to tunable two‐dimensional structure and low cost. In this study, NiMn‐LDH@MWCNT composites with hierarchical structure have been successfully synthesized with simple and economical one‐step hydrothermal method. The hierarchical structure of composites was formed by NiMn‐LDH nanosheets growing directly on multiwall carbon nanotubes (MWCNTs). This design not only can maintain excellent network conductive channels, but also increase active sites, enlarge specific surface area, and reduce internal resistance. Our results show that the NiMn‐LDH‐4 composite exhibits an excellent electrochemical performance with an ultrahigh specific capacitance of 1863 F g−1 at a current density of 1 A g−1 and 1164 F g−1 when the current density goes up 10 times. This may be attributed to the synergy effect of the hierarchical structure and introduction MWCNT. Moreover, the assembled NiMn‐LDH‐4//AC device can provide a relatively high specific energy density of 51.5 Wh kg−1 at a high energy density of 455.7 W kg−1 and possess great cycling stability (83.9 % capacitance retention after 5000 cycles). [ABSTRACT FROM AUTHOR]

In this work, honeycomb‐like Yb‐doped V2O5 ⋅ nH2O binder‐free thin film electrodes are synthesized via a simple and convenient sol‐gel method. Benefiting from the synergy of V2O5 ⋅ nH2O and rare‐earth metal ion Yb3+, thin‐layer honeycomb‐like morphology formed upon the introduction of Yb3+ into the V2O5 ⋅ nH2O, which markedly promotes the electrochemical performance of the V2O5 ⋅ H2O thin‐film electrode. After the condition optimization, 8 % Yb−V2O5 ⋅ H2O exhibits superior electrochemical performance with a specific capacitance of 703 F g−1 (at 1 A g−1) and outstanding cycling stability. Besides, owing to the ultra‐high conductivity of oxide super‐P (OSP) nanoparticles, the V2O5 ⋅ H2O@OSP‐4 binder‐free film electrode shows a high specific capacitance of 627 F g−1, which was prepared by the same simple sol‐gel strategy. The assembled 8 % Yb−V2O5 ⋅ nH2O//V2O5 ⋅ nH2O@OSP‐4 device delivers a high specific energy density and excellent cycling stability. This study may have certain inspirations for the fabrication of thin‐film electrodes for high‐efficiency energy storage systems. [ABSTRACT FROM AUTHOR]

• MP-VOPO 4 @rGO binder-free thin film electrode is first successfully synthesized. • The MP-VOPO 4 @rGO has more active sites and low internal resistance. • The dual strategy design enable accelerate ion diffusion and electron transfer. • The surface pseudocapacitive process is predominant in the total capacitance. Supercapacitors are being considered as promising electricity storage devices with green sustainable energy conversion. To efficiently develop and optimize pseudocapacitive material of vanadyl phosphate, herein, multiporous vanadyl phosphate/graphene (denoted as MP-VOPO 4 @rGO) is fabricated for the first time with phytic acid as a phosphorus source by extremely simple sol-gel and drop coating methods, and used as the free binder thin film electrode of supercapacitors. The smart combination of honeycomb-like architecture and graphene incorporation results in more active sites and low internal resistance, significantly improving energy storage performance. The effect of introducting polystyrene (denoted as PS) template and rGO on the performance of the nanocomposite is systematically analyzed by comparing the performance of the corresponding thin film electrodes. The MP-VOPO 4 @rGO thin film electrode delivers superior pseudocapacitive performance of 672 F g−1 at 1 A g−1 as well as a remarkable rate capability of 552 F g−1 at 5 A g−1, and it presents a remarkable longterm cycling stability, with a capacitance retention of 83.5% after 5000 cycles. Very interestingly, the results of surface capacitance contribution dominance clearly demonstrates its rapid capacitive response. In addition, based on MP-VOPO 4 @rGO thin film as positive and negative electrodes, the corresponding assembled symmetric supercapacitors exihibits outstanding energy density of 26.3 Wh kg−1 at power density of 249.9 W kg−1. This investigation can not only provide a versatile strategy to design other thin film electrode materials but also open up a new insight into the development of polyanion phosphate composites for next-generation high performance energy storage systems. [ABSTRACT FROM AUTHOR]

With the increasing demand for electrical energy storage, a new Mg−Li hybrid battery with Mg anode is regarded as a promising candidate because of low cost, high volumetric capacity, and dendrite‐free nature of the Mg anode. Nevertheless, the characteristics of low operation voltage and low energy density for Mg−Li hybrid batteries hinders their widespread application, owing to limited reversible cathodes. To overcome these issues, a highly reversible fast Li+ insertion cathode with high voltage is an effective strategy to realize high‐energy‐density Mg−Li hybrid batteries. Herein, we develop the 2 V high‐voltage spinel Li4Mn5O12 cathode material with unique nano‐/microspheres, using a novel low‐temperature method, offering a short Li‐diffusion path and sufficient transport channels for electrolyte penetration into the electrode. For the first time, we demonstrate the feasibility of the spinel Li4Mn5O12 nano‐/microspheres with hierarchical architecture as a cathode for 2 V hybrid Mg−Li batteries. It exhibits a reversible specific capacity of 155 mAh g−1 and a long discharge voltage platform exceeding 2.0 V (vs. Mg/Mg2+) coupled with high energy density of 326 Wh kg−1 at a current density of 0.1 C (1 C=163 mA g−1). Our results pave the way of constructing new hybrid Mg−Li batteries with high voltage and high energy density. [ABSTRACT FROM AUTHOR]

Enormous efforts have recently been devoted to exploiting high Faradaic redox active materials with ultrahigh energy density in new generation energy storage systems. In this study, a facile and cost‐effective solvothermal method was employed to synthesize high capacitance of rGO in situ encapsulating V2O5 microspheres (note as VrG). Benefiting from its unique hierarchical structure, large number of Faradaic redox active sites, and excellent electronic conductivity of rGO, the VrG composites can provide excellent pseudocapacitive performance with fast charge transfer and reaction kinetics between electrolyte and electrode material. Especially, the post‐optimized VrG‐5 demonstrates a remarkable discharge specific capacitance of 575 C g−1 at a current density of 1 A g−1 and an outstanding rate capability (48 % capacitance retention with the rate increasing 20 times), which is far better than the precursor component V2O5 under identical conditions. More importantly, the flexible VrG‐5//rGO asymmetric supercapacitors device can not only deliver excellent specific capacitance of 237 C g−1 and a high energy density of 46 Wh Kg−1, but also exhibit a superior mechanical flexibility under various bending angles and even 83 % capacitance retention after 5000 cycles under mechanical bending 180°, indicating its great potential application in the future flexible energy storage devices. [ABSTRACT FROM AUTHOR]

• The binder-free thin film electrodes were synthesized by sol-gel method. • The host material could be firmly riveted on the rGO or OAB surface. • The La-VOH@OAB exhibited an excellent rate capability (81.1% retention). • The assembled ASC devices showed an ultrahigh energy density of 56.3 Wh kg−1. In this work, multilayer networks lanthanum-doped V 2 O 5 · n H 2 O@OAB (noted as La-VOH@OAB) binder-free thin film positive electrode has been first successfully synthesized via a simple and economical sol-gel and drop-coating methods. Benefiting from its unique architecture and the favorable synergetic contributions for rare earth metal ions of La3+ and hydrophilic carbon of OAB, after the condition optimization, the 20%La-VOH@OAB-4 exhibits an excellent electrochemical performance with an ultrahigh specific capacitance of 612 F g−1 at a current density of 1 A g−1, good rate capability (81.1%, the current density increases tenfold) and outstanding cycling stability (90.4% capacitance retention over 2000 cycles). In addition, flexible Fe 2 O 3 @rGO binder-free thin film negative electrode prepared with the similarly facile strategy demonstrates a high specific capacitance of 366 F g−1 due to Fe 2 O 3 nanoparticles tightly anchored on the rGO surface. The assembled 20%La-VOH@OAB-4//Fe 2 O 3 @rGO ASCs device within a voltage window of 1.7 V delivers a relatively high specific energy density of 56.3 Wh kg−1 at a power density of 849.9 W kg−1 with exceptional cycling stability (81.3% capacitance retention after 5000 cycles), moreover, two ASCs devices in parallel can light up a red LED for 3 min, demonstrating its potential in practical applications. This work provides a certain reference for the fabrication of environmentally friendly thin film electrodes for developing high efficient energy storage systems. [ABSTRACT FROM AUTHOR]

• 3D NiCoFe-LDH nanosheet assembled nanospheres/nanoflowers are fabricated on carbon cloth via an electrodeposition method. • The growth pattern of NiCoFe-LDH nanosheet assembled nanospheres/nanoflowers on carbon cloth has been investigated. • NiCoFe-LDH electrode containing appropriate amount of Fe element delivers superior electrochemical properties. • The NiCoFe-LDH//AC HSC device shows high energy density and power density. [Display omitted] Although layered double hydroxides (LDHs), especially NiCo-based LDHs, have been verified to be a type of potential cathode material for supercapacitors with high specific capacity and electric conductivity, their lifespan and rate performance are still not satisfactory. Herein, a series of 3D NiCoFe-LDH samples with different molar ratio of Ni/Co/Fe are successfully fabricated on carbon cloth via an electrodeposition method. It is found that NiCoFe-LDH nanosheet assembled nanospheres/nanoflowers electrode delivers high specific capacity, electrical conductivity, and more importantly, more superior rate performance as well as cycle stability than pristine NiCo-LDH electrode without Fe introduction. Moreover, the as-assembled hybrid supercapacitor device with NiCoFe-LDH and activated carbon as the cathode and anode respectively displays a wide voltage window (0–1.5 V), large specific energy (65 W h kg−1 at the specific power of 83 W kg−1) together with an ultrahigh cycle stability (26% capacity increment after 5000 cycles). With the merits of ease to fabricate and outstanding energy storage property, the newly assembled hybrid supercapacitor delivers great potential for practical application in the near future. [ABSTRACT FROM AUTHOR]

• Successfully developed a facile route to synthesize core-shell Bi@NC nanorods. • Core-shell Bi@NC nanorods were firstly applied as anode for MIBs. • Micropores in carbon matrix mitigate the large volume change of inner core Bi. • Excellent Mg storage performance, especially in rate performance. The rechargeable magnesium batteries are potentially applicable in large-scale energy storage systems because of the low costs and rich sources. But the alternative anodes for magnesium ion batteries have not been fully developed. In this work, a novel bismuth-carbon composite with bismuth nanorods anchored in nitrogen-doped mesoporous carbon matrix (Bi@NC), was prepared as anode for magnesium ion batteries by carbonizing the dopamine-coated bismuth metal precursors. The matrix facilitated the magnesiation/de-magnesiation of bismuth due to its highly electronic conductive network. Moreover, it restrained the aggregation of bismuth nanorods and serves as a buffer layer to alleviate the mechanical strain of bismuth nanorods upon magnesium insertion/extraction. As the anode for magnesium ion batteries, the Bi@NC core-shell nanorods delivered a reversible capacity of 360 mAh g−1 at the current density of 100 mA g−1, and 87 % of the initial capacity was achieved after 100 cycles. The standout rate performance is 275 mAh g−1 at the current density of 1 A g−1. Such a good electrochemical property demonstrated the great application potential of Bi@NC as anode in magnesium ion batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

Lithium-ion batteries and supercapacitors represent the predominant electrochemical power sources and energy storage devices. High-capacity and long-life electrode materials are essential for the next-generation lithium-ion batteries (LIBs) and supercapacitors (SCs) with high power density and high energy density. Herein, FeCo-Nx doped hollow shelled polyhedrons excessively covered with a 3D network of carbon nanotubes (FeCo–N x @CNTs) have been successfully developed and investigated as one of the most promising materials for lithium-ion batteries and supercapacitors. We developed a self-template strategy to synthesize a series of FeCo–N x @CNTs via one step carbonization process of Fe doped ZIF-67 MOF. Such a FeCo-Nx doped 3D network of carbon nanotubes effectively tolerates the volume strain and prevents the metal nanoparticles aggregation. In the interim, the 3D network of porous N-doped carbon nanotubes agrees fast electron transport to accomplish remarkably excellent rate capability. Consequently, the FeCo–N x @CNTs-1.5 shows excellent electrochemical activity for Li-ion hopping in LIBs and SCs. Additionally, this effort also unveils the synergistic effect of the iron doping on the Li-ion storage capability. Image 1 • FeCo-Nx doped hollow shelled polyhedrons excessively covered with 3D network of carbon nanotubes. • A self-template strategy to synthesize a series of FeCo–N x @CNTs was developed. • The 3D framework of carbon nanotubes on hollow shell polyhedron allow fast reversible reaction. • CNTs provides numerous channels for Li-ions hopping and fast kinetics. • FeCo–N x @CNTs-1.5 shows excellent electrochemical activity for Li-ion hopping in LIB and SC. [ABSTRACT FROM AUTHOR]