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Lithium ion capacitors provide both high energy and high power density. Li3V2O5//AC, which is based on Li3V2O5 nanospheres with fast kinetics reveals the potential for the application in high rate and long lifespan energy storage devices.

A hybrid protective layer containing a Li3N/Li–Bi alloy on the Li surface is constructed to guide dendrite-free Li deposition by accelerating Li+ transport and homogenizing Li plating/stripping behavior.

We propose an objective Mn-based competitive capacity evolution protocol and a recusing strategy for dead Mn-based Zn-ion batteries. The findings would provide new insights to understand the electrochemical behaviors more comprehensively.

Catalysts with two single-atom sites promote reversible conversion reactions between S and Li2S. The Co active site enhances the transformation kinetics of polysulfides upon charging, the Fe active site accelerates the transformation of Li2S to S8.

External photo-stimuli on heterojunctions commonly induce an electric potential gradient across the interface therein, such as photovoltaic effect, giving rise to various present-day technical devices. In contrast, in-plane potential gradient along the interface has been rarely observed. Here we show that scanning a light beam can induce a persistent in-plane photoelectric voltage along, instead of across, silicon-water interfaces. It is attributed to the following movement of a charge packet in the vicinity of the silicon surface, whose formation is driven by the light-induced potential change across the capacitive interface and a high permittivity of water with large polarity. Other polar liquids and hydrogel on silicon also allow the generation of the in-plane photovoltage, which is, however, negligible for nonpolar liquids. Based on the finding, a portable silicon-hydrogel array has been constructed for detecting the shadow path of a moving Cubaris. Our study opens a window for silicon-based photoelectronics through introducing semiconductor-water interfaces., Common photovoltaic effect is across the interface of heterojunctions. Here, the authors find that scanning a light beam can induce a persistent in-plane photoelectric voltage along silicon-water interfaces, due to the following movement of a charge packet in the vicinity of the silicon surface.

Sodium-ion hybrid capacitors (SICs) are attracting increasing attention due to their high energy/power superiority and potentially low cost. However, the sluggish sodium-ion diffusion in the bulk o...

Mesocrystals have received intense attention in the electrochemical energy storage field owing to their favourable electronic conductivity, high crystallinity and large specific surface area. However, a critical limitation to the wide applications of mesocrystals is the lack of a facile synthesis approach for high-performance mesocrystals. Here, we report a one-step self-assembly solvothermal method to prepare 3D hierarchical highly-ordered Nb3O7F nanowire cluster mesocrystals (denoted NOF-NCMs), of which the diameter of each nanowire is within 10 nm. Through kinetic analysis, NOF-NCMs can be confirmed to provide unique intercalation pseudocapacitance, enabling rapid charge transfer. When used as an anode material, the NOF-NCM electrode displays a high capacity of ∼356.7 mAh g−1 at 800 mA g−1, excellent rate performance and a long cycle life with ∼88.3% capacity retention after 3000 cycles. The improved electrochemical properties of NOF-NCMs are attributed to the unique highly-ordered nanowire cluster architectures. A lithium ion capacitor (LIC) is constructed by using well-prepared NOF-NCMs as an anode and commercial AC as a cathode. The NOF-NCMs//AC LIC can hold a maximum energy density of 74.5 W h kg−1 at 87.5 W kg−1, and has a long cycle lifespan with a 92.5% capacity retention after 3000 cycles and low self-discharge rate, demonstrating a bright candidate for applications in both high-energy and high-power electrochemical energy storage.

Fabrication of a stable dendrite-free Li metal anode that accommodates very large volume changes is urgently needed for the development of advanced lithium metal batteries. Herein, an integrated Li/TiN/carbon textile anode (LTNC) is fabricated in which lithium is hosted in a self-supported TiN nanorod array with high surface area, excellent electrical conductivity, and porous structure. The as-prepared LTNC anode achieves outstanding electrochemical performance with a low overpotential of 50 mV and stable cycling for 1000 h at 1 mA cm−2, 1 mA h cm−2, and even at a high current density of 10 mA cm−2 it shows highly stable performance with a low overpotential. When paired with a LiNi0.8Mn0.1Co0.1O2 cathode, the assembled cells display enhanced capacity retention of 85% after 500 cycles at 1C and improved coulombic efficiency. Furthermore, a high capacity of 2.3 mA h cm−2 with a capacity retention of 92% is maintained at 1 mA cm−2 after 100 cycles when the negative to positive electrode capacity ratio is only ∼3.5. This work indicates that the structural engineering of Li metal is highly applicable for lithium metal batteries with high rates and long cycle life.

Accepted Manuscript version. The Published Journal Article is available on Journal of Solid State Chemistry, Volume 310, article number 123006 (DOI: https://doi.org/10.1016/j.jssc.2022.123006). Supplementary data available free of charge on the article webpage. © 2022. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/

Lithium ion capacitors combine the complementary advantageous characteristics of batteries and supercapacitors are expected to deliver both high energy and high power density. However, this technology suffers from the kinetics imbalance between battery electrode and capacitive electrode. Here, two dimensional T-Nb2O5/N-doped carbon nanosheets with a well-continuous ionic/electronic conducting network demonstrate superior rate capability of 142.3 mA h g−1 at 20 C (1 C = 200 mA g−1). A majority of charge storage in the T-Nb2O5/N-doped carbon nanosheets was proved to be intercalation pseudocapacitive processes by kinetic analysis, enabling fast charge storage performance. A lithium ion capacitor is based upon these T-Nb2O5/N-doped carbon nanosheets was successfully fabricated, demonstrating high energy density (70.3 W h kg−1) and high power density (16,014 W kg−1).

The development of suitable anode materials is far from satisfactory and is a major scientific challenge for a competitive sodium-ion battery technology. Metal sulfides have demonstrated encouraging results, but still suffer from sluggish kinetics and severe capacity decay associated with the phase change. Herein we show that rational electrode design, that is, building efficient electron/ion mixed-conducting networks, can overcome the problems resulting from conversion reactions. A general strategy for the preparation of hierarchical carbon-coated metal sulfide (MS⊂C) spheres through thermal sulfurization of metal glycerate has been developed. We demonstrate the concept by synthesizing highly uniform hierarchical carbon coated vanadium sulfide (V2 S3 ⊂C) spheres, which exhibit a highly reversibly sodium storage capacity of 777 mAh g-1 at 100 mA g-1 , excellent rate capability (410 mAh g-1 at 4000 mA g-1 ), and impressive cycling ability.

The lithium metal anode is regarded as ideal for high-energy rechargeable batteries. Unfortunately, the uncontrolled lithium dendritic growth and the infinite volume expansion upon cycling result in low Coulombic efficiency, fast capacity decay and safety issues. Herein, a mismatch electrical-conductivity framework has been designed as a stable host to regulate lithium deposition behaviour. Due to the ionic conductivity of the lithiophilic layer and the electron conductivity of hollow carbon nanofibres (HCF), lithium metal is preferentially deposited into and encapsulated by the HCF, resulting in greatly improved electrochemical performance. The heat generation upon lithium storage and release in the Al2O3 coated HCF (A–HCF) during cycling is lower compared to the plating/stripping on copper foil. The A-HCF electrodes show high Coulombic efficiency (97%) upon 500 cycles employing a conventional, alkyl carbonate-based electrolyte, demonstrating improved reversibility of Li plating/stripping. Complete cells assembled employing LiNi0.8Co0.1Mn0.1O2 (NMC811)-based positive electrodes exhibit high capacity retention (94%) after 120 cycles at 1 C, delivering a high energy density (363 Wh per kg of NMC811). Even upon cycling at 5 C rate, the cells, employing less than three times excess lithium, deliver a very high capacity (133 mAh per g of NMC811) for 50 cycles.

Highlights A green water-in-salt electrolyte was developed using lithium acetate as solute with a wide electrochemical stability window of 2.8 V.Molecular dynamics simulation confirmed the nature of water-in-salt electrolyte, where hydrogen bonds of water–water were disrupted and ionic interactions became stronger than dilute solution.Nb18W16O93-based lithium-ion capacitors delivered unexceptionable stability over 50,000 cycles. Electronic supplementary material The online version of this article (10.1007/s40820-020-00508-z) contains supplementary material, which is available to authorized users., Aqueous hybrid supercapacitors are attracting increasing attention due to their potential low cost, high safety and eco-friendliness. However, the narrow operating potential window of aqueous electrolyte and the lack of suitable negative electrode materials seriously hinder its future applications. Here, we explore high concentrated lithium acetate with high ionic conductivity of 65.5 mS cm−1 as a green “water-in-salt” electrolyte, providing wide voltage window up to 2.8 V. It facilitates the reversible function of niobium tungsten oxide, Nb18W16O93, that otherwise only operations in organic electrolytes previously. The Nb18W16O93 with lithium-ion intercalation pseudocapacitive behavior exhibits excellent rate performance, high areal capacity, and ultra-long cycling stability. An aqueous lithium-ion hybrid capacitor is developed by using Nb18W16O93 as negative electrode combined with graphene as positive electrode in lithium acetate-based “water-in-salt” electrolyte, delivering a high energy density of 41.9 W kg−1, high power density of 20,000 W kg−1 and unexceptionable stability of 50,000 cycles. Electronic supplementary material The online version of this article (10.1007/s40820-020-00508-z) contains supplementary material, which is available to authorized users.

Nickel cobalt sulfur is attracting more attention due to its great electrical conductivity and high specific capacitance for faraday pseudo-capacitors. Here, by evaporation-induced drying, heterostructure NiS2/NiCo2S4 nanosheets on self-supporting substrate of nitrogen-doped single-walled carbon nanotubes sponge (NSCS) are obtained with the sponge volume significantly being reduced. With the electrode film thickness being 80 μm, the as-prepared heterostructure NiS2/NiCo2S4/NSCS electrode shows outstanding areal/gravimetric/volumetric capacitance of 10.5 F cm−2/2905 F g−1/1307.2 F cm−3 at 1 A g−1. With the increase of current density from 1 to 60 A g−1, the current retention rate maintains at 61%. When the active material loading is increased to 14 mg cm−2, the gravimetric capacitance can still maintain at 1725 F g−1, indicating the high ratio performance. After 10,000 cycles, the capacity retention still remains 83% at current density of 10 A g−1. In addition, an asymmetric supercapacitor (ASC) delivers have high gravimetric/volumetric energy density of 58.1 W h kg−1/52.3 W h L−1 with excellent cycle stability after 20,000 cycles. Therefore, the electrode material with high loading and high rate performance can be realized by this method.

Hybrid ion capacitors (HICs) based on insertion reactions have attracted considerable attention due to their energy density being much higher than that of the electrical double-layer capacitors (EDLCs). However, the development of hybrid ion capacitors with high energy density at high power density is a big challenge due to the mismatch of charge storage capacities and electrode kinetics between the battery-type anode and capacitor-type cathode. In this work, N and O dual doped carbon nanofibers (N,O-CNFs) were combined with carbon nanotubes (CNTs) to compose a complex carbon anode. N,O dual doping effectively tuned the functional group and surface activity of the CNFs while the integration of CNTs increased the extent of graphitization and electrical conductivity. The carbon cathode with high specific surface area and high capacity was obtained by the activation of CNFs (A-CNFs). Finally, a hybrid sodium ion capacitor was constructed by the double carbon electrode, which showed a superior electrochemical capacitive performance. The as-assembled HIC device delivers a maximum energy density of 59.2 W h kg−1 at a power density of 275 W kg−1, with a high energy density of 38.7 W h kg−1 at a power density of 5500 W kg−1.

Sodium-ion batteries (SIB) are regarded as the most promising competitors to lithium-ion batteries in spite of expected electrochemical disadvantages. Here a “cross-linking” strategy is proposed to mitigate the typical SIB problems. We present a SIB full battery that exhibits a working potential of 3.3 V and an energy density of 180 Wh kg–1 with good cycle life. The anode is composed of cross-linking hollow carbon sheet encapsulated CuP2 nanoparticles (CHCS-CuP2) and a cathode of carbon coated Na3V2(PO4)2F3 (C-NVPF). For the preparation of the CHCS-CuP2 nanocomposites, we develop an in situ phosphorization approach, which is superior to mechanical mixing. Such CHCS-CuP2 nanocomposites deliver a high reversible capacity of 451 mAh g–1 at 80 mA g–1, showing an excellent capacity retention ratio of 91% in 200 cycles together with good rate capability and stable cycling performance. Post mortem analysis reveals that the cross-linking hollow carbon sheet structure as well as the initially formed SEI layers are...

Nanoparticle-based electrode materials have sparked enormous excitement in the sodium-ion battery community because of potentially fast transport kinetics. However, they may suffer from many challenging static and dynamic problems, such as agglomeration of nanoparticles, high contact resistance, volume change, and instability of solid electrolyte interphase. Herein, we develop inter-connected 2D carbon nanosheets in which ultrasmall 0D Sb nanodots are embedded homogenously through a previously unexplored “top-down” strategy. Starting from the laminar structure K3Sb3P2O14, H3Sb3P2O14 nanosheets are exfoliated by ion exchange and then serve as templates for the synthesis of carbon sheets and Sb nanodots. Such combination of multi-dimensional and multi-scale nanostructures in the electrode materials lead to excellent electron/ion transport kinetics and pronounced integrity of the electrode structure on cycling, providing a promising pathway for developing advanced electrode materials in terms of reversibility, rate capability and cycle life.

Biomass-based porous carbons as electrode materials in asymmetric Li-ion capacitors (LICs) have shown broad prospect application. In this work, one kind of copper hyperaccumulator-elsholtzia splendens was selected as biomass source to synthesize micro-/nanoporous carbons to be used as both anode and cathodefor LICs due to the need of waste disposal. On the basis of separate charge storage mechanisms of anode and cathode in this system, corresponding strategies were adopted to rationally optimize the microstructure of micro-/nanoporous carbons to promote their electrochemical performance. Electrochemical tests showed that hierarchical porous carbon microsphere (PECS) anode exhibited an excellent rate capability (215.6 mA h g−1 at 2 A g-1) and a long lifespan (87.1% capacity retention over 1000 cycles). Carbon cathode with an ultrahigh specific surface area of 2819 m2 g-1 revealed a high specific capacity of 90.9 mA h g−1 at 5 A g-1. Benefiting from the high rate capability of anode and the high specific capacity of cathode, the as-assembled LIC delivered a high energy density of 129.4 W h kg−1 and 51.9 W h kg−1 at a power density of 205.5 W kg−1 and 10.3 kW kg−1.

The current insertion anode chemistries are approaching their capacity limits; thus, alloying reaction anode materials with high theoretical specific capacity are investigated as potential alternatives for lithium-ion batteries. However, their performance is far from being satisfactory because of the large volume change and severe capacity decay that occurs upon lithium alloying and dealloying processes. To address these problems, we propose and demonstrate a versatile strategy that makes use of the electronic reaction confinement via the synthesis of ultrasmall Ge nanoparticles (10 nm) uniformly confined in a matrix of larger spherical carbon particles (Ge⊂C spheres). This architecture provides free pathways for electron transport and Li+ diffusion, allowing for the alloying reaction of the Ge nanoparticles. The thickness change of electrodes containing such a material, monitored byan in situ electrochemical dilatometer, is rather limited and reversible, confirming the excellent mechanical integrity of the confined electrode. As a result, these electrodes exhibit high reversible capacity (1310 mAh g-1, 0.1C) and very impressive cycling ability (92% after 1000 cycles at 2C). A prototype device employing such an alloying electrode material in combination with LiNi0.8Mn0.1Co0.1O2 offers a high energy density of 250 Wh kg-1.

International audience; Low-Pt based nanocrystals demonstrate potential as highly active catalysts for the oxygen reduction reaction (ORR), but they suffer from undesirable structural degradation. Therefore, it is highly challenging to optimize their surface and interfacial structures to tune their catalytic properties for both activity and stability. Here core–shell Cu/FePtCu nanoparticles with a face-centered-tetragonal phase are prepared by a facile one–pot polyol method at 320 °C. The optimized core–shell Fe45Pt35Cu20 catalyst with Pt-enriched surface exhibits 0.5 A/mgPt mass activity, which is a factor of 4 better than that of commercial Pt/C (0.13 A/mgPt). In addition, the current density of the catalyst drops only 3.0% after 1000 cycles, which is much better than Pt/C (34.2% decay). Using aberration-corrected scanning transmission electron microscopy and atomically resolved elemental mapping, the morphology and structure evolving between the FePtCu alloy and core–shell Cu/FePtCu could clearly be explained. This work demonstrates that an ordered and core–shell FePtCu catalyst is highly promising for ORR and other electrochemical processes.

Reportedly, Li4Ti5O12 could provide the novel characteristics of both Li+ insertion and Na+ insertion. In this work, we firstly take advantage of this unique feature and use lithium/sodium mixed organic solvent as electrolyte for evaluating the electrochemical performance of as-synthesized Li4Ti5O12 nano-microspheres (LTO MS). As a result, the potential window of LTO MS is broadened, leading to full utilization of Li4Ti5O12. In addition, the difference between insertion potentials of Li+ and Na+ inserting into LTO MS is applied to reasonably intercept the potential windows of LTO MS, ensuring its remarkable cycling stability and high rate property. Therefore, LTO MS using lithium/sodium mixed electrolyte (LTO MS-L/SIB system) can provide a broadened potential window of 0.4–2.5 V, leading to a high specific capacity without sacrificing rate performance and cycling stability. We also systemically analyze the charge storage mechanism of LTO MS-L/SIB by ex-situ XRD technologies. For the first time, the lithium-sodium hybrid ion capacitor (LTO MS//PSC L/SIC) is constructed with LTO MS as anode, peanut shell derived carbon (PSC) as cathode, and lithium-sodium mixed organic solvent as electrolyte. Compared with the as-constructed lithium ion capacitors (LTO MS//PSC LIC) and sodium ion capacitors (LTO MS//PSC SIC), LTO MS//PSC L/SIC device provides the highest gravimetric energy density of ~65.3 Wh kg−1, a remarkable cycling stability, and an ultra-low self-discharge rate.

Carbon materials are widely used as anodes of supercapacitors due to the long cycling stability, but the low capacitance results in low energy density of the supercapacitor device in aqueous solution, greatly limiting the application field of the supercapacitor. Here, the spiral low-crystalline Ni(OH)2 supported on self-standing layered film structure of N-doped graphene/carbon nanotubes film (NCF) is reported. The prepared flexible film electrode of low-crystalline Ni(OH)2/NCF is functioned as cathode directly, presenting high gravimetric capacitance (GC) and areal capacitance of 2130[Formula: see text]F[Formula: see text]g[Formula: see text] (2[Formula: see text]A[Formula: see text]g[Formula: see text]) and 2.88[Formula: see text]F[Formula: see text]cm[Formula: see text] (1[Formula: see text]A[Formula: see text]g[Formula: see text]). Also, this self-standing electrode film shows ultra-long cycle life, retaining 111.4% of initial capacitance after 30 000 circles at large current densities (20[Formula: see text]A[Formula: see text]g[Formula: see text]) and almost 0% fade before 10 000 circles. Moreover, Ni(OH)2/NCF and activated polyaniline derived carbon (APDC) have been assembled into an asymmetric supercapacitor, exhibiting a high gravimetric energy density of 60[Formula: see text]Wh[Formula: see text]kg[Formula: see text] at 800[Formula: see text]W[Formula: see text]kg[Formula: see text], suggesting that the obtained electrode has a good prospect application in long cycling stability with high energy density of supercapacitor devices.

High-performance electrical double-layer capacitors (EDLCs) require carbon electrode materials with high specific surface area, short ion-diffusion pathways, and outstanding electrical conductivity. Herein, a general approach combing the molten-salt method and chemical activation to prepare N-doped carbon nanosheets with high surface area (654 m2 g−1) and adjustable porous structure is presented. Owing to their structural features, the N-doped carbon nanosheets exhibited superior capacitive performance, demonstrated by a maximum capacitance of 243 F g−1 (area-normalized capacitance up to 37 μF cm−2) at a current density of 0.5 A g−1 in aqueous electrolyte, high rate capability (179 F g−1 at 20 A g−1), and excellent cycle stability. This method provides a new route to prepare porous and heteroatom-doped carbon nanosheets for high-performance EDLCs, which could also be extended to other polymer precursors and even waste biomass.

Recently, hybrid ion capacitors which combine the characteristics of batteries and supercapacitors have gained great interests for large-scale energy storage applications. Here, we demonstrated a new hybrid sodium ion capacitor configuration, utilizing the niobium pentoxide (Nb2O5) and peanut shell carbon (PSC) as the anode and cathode materials, respectively. The advanced architecture of self-assembled Nb2O5 nanosheets with exceptional sodium ion storage property was obtained by carefully controlling reaction kinetics. A key finding is that the growth mechanism is demonstrated to be a process from one-dimensional nanorods to three-dimensional nanocubes, and further to two-dimensional nanosheets. The resulting Nb2O5 nanosheets//PSC hybrid capacitors deliver an exceptionally high energy density (43.2 Wh kg–1) and high power density (5760 W kg–1) based on the active materials, with a long and stable cycle life (capacity retention: ∼80% at 1280 mA g–1 after 3000 cycles).

Graphene is known to suffer from severe aggregation and incomplete recovery of a π–π conjugated system during the reduction process from graphene oxide. Here we report that these issues can be addressed by using a modified molten salt system. The advantages of the molten salt for reducing graphene show in three aspects: (i) prevent restacking; (ii) restore the conjugated network; (iii) serve as reaction medium for KNO 3 activation and nitrogen doping. The molten-salt method-derived graphene (MNG) displays a highly sp 2 –hybrid constitution, nitrogen doping and hierarchically porous structure. With this design, the MNG–based supercapacitor manifests outstanding specific capacitance (234 F g −1 and 130 F g −1 in 6 M KOH and EMIMBF 4 electrolyte, respectively), high power density, combined with excellent cycling stability and low self-discharge rate. The facile and scalable features of this strategy will be helpful for the rational design of functionalized graphene-based materials for diverse applications.

Flexible energy storage devices are critical components for emerging flexible and wearable electronics. Improving the electrochemical performance of flexible energy storage devices depends largely on development of novel electrode architectures and new systems. Here, a new class of flexible energy storage device called flexible sodium-ion pseudocapacitors is developed based on 3D-flexible Na2Ti3O7 nanosheet arrays/carbon textiles (NTO/CT) as anode and flexible reduced graphene oxide film (GFs) as cathode without metal current collectors or conducting additives. The NTO/CT anode with advanced electrode architectures is fabricated by directly growing Na2Ti3O7 nanosheet arrays on carbon textiles with robust adhesion through a simple hydrothermal process. The flexible GF//NTO/CT configuration achieves a high energy density of 55 Wh kg−1 and high power density of 3000 W kg−1. Taking the fully packaged flexible sodium-ion pseudocapacitors into consideration, the maximum practical volumetric energy density and power density reach up to 1.3 mWh cm−3 and 70 mW cm−3, respectively. In addition, the flexible GF//NTO/CT device demonstrates a stable electrochemical performances with almost 100% capacitance retention under harsh mechanical deformation.

The three-dimensional porous Li3V2(PO4)3/nitrogen-doped reduced graphene oxide (LVP/N-RGO) composite was prepared by a facile one-pot hydrothermal method and evaluated as cathode material for lithium-ion batteries. It is clearly seen that the novel porous structure of the as-prepared LVP/N-RGO significantly facilitates electron transfer and lithium-ion diffusion, as well as markedly restrains the agglomeration of Li3V2(PO4)3 (LVP) nanoparticles. The introduction of N atom also has positive influence on the conductivity of RGO, which improves the kinetics of electrochemical reaction during the charge and discharge cycles. It can be found that the resultant LVP/N-RGO composite exhibits superior rate properties (92 mA h g−1 at 30 C) and outstanding cycle performance (122 mA h g−1 after 300 cycles at 5 C), indicating that nitrogen-doped RGO could be used to improve the electrochemical properties of LVP cathodes for high-power lithium-ion battery application.

Metal–organic framework (MOF)-derived carbon materials exhibit large surface areas, but dominant micropore characteristics and uncontrollable dimensions. Herein, we propose a self-sacrificial template-directed synthesis method to engineer the porous structure and dimensions of MOF-derived carbon materials. A porous zinc oxide (ZnO) nanosheet solid is selected as the self-sacrificial template and two-dimensional (2D) nanostructure-directing agent to prepare 2D ZIF-8-derived carbon nanosheets (ZCNs). The as-prepared ZCN materials exhibit a large surface area with hierarchical porosity. These intriguing features render ZCN materials advanced electrode materials for electrochemical energy-storage devices, demonstrating large ion-accessible surface area and high ion-/electron-transport rates. This self-sacrificial template-directed synthesis method offers new avenues for rational engineering of the porous structure and dimensions of MOF-derived porous carbon materials, thus exploiting their full potential for electrochemical energy-storage devices.

Monoclinic MgF 2 and C co-coated Li 3 V 2 (PO 4 ) 3 (LVP) has been investigated as long life cathode of lithium-ion battery. The X-ray diffraction (XRD) results reveal that MgF 2 modification has not changed the structure of LVP/C. The high resolution transmission electron microscopy (HRTEM) shows that the thickness of the uniform amorphous hybrid coating is about 10 nm. The research shows that the novel co-coating significantly enhanced the electrochemical performance of LVP cathode material, which is attributed to synergistic effect between MgF 2 and C coating. MgF 2 layer can restrain the dissolution of V element and enhance the structural stability of LVP in the electrolyte. Meanwhile, the presence of the carbon coating enhances the electron conductivity. The electrochemical impedance spectroscopy (EIS) further demonstrates that the hybrid coating is beneficial for structural stability of LVP/C during cycling. In conclusion, it can be speculated that the hybrid coating of MgF 2 and C should be an effective strategy to enhance the electrochemical performance of LVP.

Lithium ion capacitors (LICs), which have high energy density and power density and benefit from the combination of the merits of batteries and supercapacitors, have been attracted tremendous attention. The sluggish faradaic battery anode is a big challenge for the development of high-performance LICs. In this study, an Nb2O5/ordered mesoporous carbon (CMK-3) nanocomposite has been synthesized via the nanocasting technology using CMK-3 as the hard template and NbCl5 as the precursor. The Nb2O5/CMK-3 electrode exhibits significantly enhanced electrochemical performance in terms of specific capacity, rate capability and cyclic stability when compared with bulk Nb2O5. Furthermore, a high performance LIC composed of the Nb2O5/CMK-3 nanocomposite as the anode and activated carbon derived from peanut shell as the cathode was constructed, which exhibits a high energy density of 43.9 W h kg−1 (at a power density of 87.5 W kg−1) and high power density of 8750 W kg−1 (at an energy density of 24.4 W h kg−1). Such outstanding performance mainly stems from the synergic effects between the mesoporous carbon matrices and the well-dispersed active material nanoparticles, which increase electronic conductivity and the reactivity of Nb2O5.

To improve the energy density of supercapacitors, a new type of electrode material with high electrochemical activity and favorable morphology is extremely desired. Ternary metal sulfides with higher electrochemical capacity and activity than mono-metal sulfides hold great promise in the field of energy storage devices. Herein, an advanced electrode composed of zinc cobalt sulfide nanosheets supported on sandwich-like nitrogen-doped graphene/carbon nanotubes (NGN/CNTs) film has been successfully fabricated through a two-step synthesis. Benefiting from the characteristic features and 3D electrode architectures, the Zn0.76Co0.24S electrode exhibits a high specific capacitance of 2484 F g−1 at 2 A g−1 and excellent cycling stability (almost no capacitance fading after 10 000 cycles at 30 A g−1). This creative nanostructure design of ternary transition metal sulfides could provide a promising prospect for application in energy storage devices. Moreover, an asymmetric supercapacitor was also fabricated by using Zn0.76Co0.24S/NGN/CNTs film as the positive electrode and NGN/CNTs film as the negative electrode, exhibiting a high energy density of 50.2 W h kg−1 at 387.5 W kg−1 and superior cycling stability of 100% initial capacity retention over 2000 cycles. This creative nanostructure design could provide a promising new way to develop high-performance supercapacitors and shed new light on configuring carbon-based ternary transition metal sulfide electrode materials in energy storage and conversion devices.

Mixed-valence vanadium oxide (VOx)/ordered mesoporous carbon (CMK-3) composite (VOC) were synthesized through a facile liquid-phase method followed by calcination. The microstructures of the composite were characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption, X-ray photoelectron spectra (XPS), scanning election microscopy (SEM) and transmission election microscopy (TEM). The relevant results showed that vanadium oxide nanoparticles with mixed valence were successfully embedded in mesoporous channels in the conductive matrix and dispersed on the CMK-3 surface to form the interwoven composite. The introduction of the CMK-3 framework not only improves electron transfer but also prevents the structure collapsing during cycling. As expected, the composite exhibits excellent electrochemical properties. It delivered a specific capacitance of 257 F g−1 at 0.5 A g−1 and maintained 77.3% at 8 A g−1 in 5 M LiNO3. After 5000 cycles, the capacitance only decreased 20%.