Search

Rechargeable lithium-metal batteries with a cell-level specific energy of >400 Wh kg-1 are highly desired for next-generation storage applications, yet the research has been retarded by poor electrolyte-electrode compatibility and rigorous safety concerns. We demonstrate that by simply formulating the composition of conventional electrolytes, a hybrid electrolyte was constructed to ensure high (electro)chemical and thermal stability with both the Li-metal anode and the nickel-rich layered oxide cathodes. By employing the new electrolyte, Li∥LiNi0.6 Co0.2 Mn0.2 O2 cells show favorable cycling and rate performance, and a 10 Ah Li∥LiNi0.8 Co0.1 Mn0.1 O2 pouch cell demonstrates a practical specific energy of >450 Wh kg-1 . Our findings shed light on reasonable design principles for electrolyte and electrode/electrolyte interfaces toward practical realization of high-energy rechargeable batteries.

Composite electrolytes composed of a nanoceramic and polymer have been widely studied because of their high ionic conductivity, good Li-ion transference number, and excellent machinability, whereas the intrinsic reason for the improvement of performance is ambiguous. Herein, we have designed a functional polymer skeleton with different types of nanofiller to reveal the superiority of fast ion conductors in composite electrolyte. Three types of ceramics with different dielectric constants and Li-ion transfer ability were selected to prepare composite electrolytes, the composition, structure, and electrochemical performances of which were systematically investigated. It was found that the addition of fast ion conductive ceramics could provide a high Li-ion transference ability and decreased diffusion barrier because the additional pathways existed in the ceramic, which are revealed by experiment and density functional theory calculations. Benefiting from the superiority of fast ion conductor, Li-metal batteries with this advanced composite electrolyte exhibit an impressive cycling stability and enable a dendrite-free Li surface after cycling. Our work enriches the understanding of the function of fast ion conductors in composite electrolyte and guides the design for other high-performance composite electrolytes in rechargeable solid batteries.

The necessity to explore high-efficiency and high-value utilization strategy for biomass-waste is desirable. Herein, the strategy for direct conversion biomass-waste (rice husks) to Si/C composite structure anode was built. The Si/C composite materials were successfully obtained via the typical thermal reduction with magnesium, and the Si nanoparticle was uniformly embedded in carbon frame, as revealed by Raman, X-ray diffraction (XRD) and transmission electron microscope (TEM) measurement. The carbon structure among rice husks was effectively used as a protective layer to accommodate the volume variation of Si anode during the repeated lithiation/delithiation process. Benefitting from the structure design, the batteries show a superior electrochemical stability with the capacity retention rate above 90% after 150 cycles at the charge/discharge rate of 0.5 C (1 C = 600 mAh/g), and hold a high charge capacity of 420.7 mAh/g at the rate of 3 C. Therefore, our finding not only provides a promising design strategy for directly conversion biomass-waste to electrochemical storage materials but broadens the high-efficiency utilization method for other biomass by-products.

A hybrid solid/liquid electrolyte with superior security facilitates the implementation of high-energy-density storage devices, but it suffers from inferior chemical compatibility with cathodes. Herein, an optimal lithium difluoro(oxalato)borate salt was introduced to build in situ an amorphous cathode electrolyte interphase (CEI) between Ni-rich cathodes and hybrid electrolyte. The CEI preserves the surface structure with high compatibility, leading to enhanced interfacial stability. Meanwhile, the space-charge layer can be prominently mitigated at the solid/solid interface via harmonized chemical potentials, acquiring promoted interfacial dynamics as revealed by COMSOL simulation. Consequently, the amorphous CEI integrates the bifunctionality to provide an excellent cycling stability, high Coulombic efficiency, and favorable rate capability in high-voltage Li-metal batteries, innovating the design philosophy of functional CEI strategy for future high-energy-density batteries.

The pursuit for batteries with high specific energy provokes the research of high-voltage/capacity cathode materials with superior stability and safety as the alternative for lithium iron phosphate. Herein, using the sol-gel method, a lithium vanadium phosphate with higher average discharge voltage (3.8 V, vs. Li+/Li) was obtained from a single source for Mg2+ and Cl− co-substitution and uniform carbon coating, and a nearly theoretical capacity (130.1 mA h g−1) and outstanding rate performance (25 C) are acquired together with splendid capacity retention (80%) after 650 cycles. This work reveals that the well-sized anion and cation substitution and uniform carbon coating are of both importance to accelerate kinetic performance in the context of nearly un-disturbed crystal structure for other analogue materials. It is anticipated that the electrochemistry comprehension will shed light on preparing cathode materials with high energy density in the future.

Energy storage is a vital issue to be solved for the efficient utilization of renewable energies such as solar, wind and tidal energy. In terms of rechargeable battery energy storage, magnesium has many advantages over lithium, such as low cost, environmental benignity and ease of operation. Therefore, rechargeable Mg batteries (RMBs) are considered as a promising green alternative to rechargeable lithium batteries for practical applications. Over the past few years, RMBs have made great progress, but there are also many problems. In this review, we summarize the latest developments of materials for RMBs from three main aspects: cathodes, electrolytes and anodes. The effects of cathode structures on Mg2+ ion migration kinetics are expounded; the properties and characteristics of various electrolytes for RMBs are briefly described; and the modification of metallic Mg and other types of anode materials are discussed comprehensively. In addition, the current challenges and several important guidelines for future progress of development of RMBs are also discussed.

The main aim of this work was to evaluate the feasibility of microalgae-assisted aquaculture and explore the relevant mechanisms. In this regard, our work explored the pollution problems in traditional aquaculture and studied the contribution of microalgae to eutrophication control, oxygen gas production and feed replacement. Besides, potential protection mechanisms of microalgae-assisted aquaculture were studied by bacterial community profile analysis and microscope observation. The results showed that microalgae performed well in nutrient assimilation and oxygen production, thus slowing down the eutrophication and preventing oxygen depletion in aquaculture. Study of the mechanisms revealed that microalgae-assisted aquaculture contained much fewer pathogens and a microalgal biofilm was formed to prevent the eutrophication caused by sludge degradation. It is expected that the findings in this work can support the further development of microalgae-assisted aquaculture and promote the industry upgrade.

A carbon sheet-decorated graphite felt electrode was synthesized by in situ polymerization and subsequent high-temperature calcination under an inert atmosphere. The resultant material brings an improved wettability, numerous defect sites, and abundant O, N and P elements as additional catalytic sites to elevate the reaction kinetics and efficiency of vanadium redox flow batteries (VRFBs). The unique CS modifier enriches electrolyte diffusion pathways, which even show a unique capillary flow. The GF@CS displays a high catalytic activity towards the VO2+/VO2+, V3+/VO2+ and V2+/V3+ oxidation-reduction couples and a reduced cathodic and anodic peak potential difference of 355 mV (vs. 564 mV for GF). The improvement to the electrode results in a GF@CS-based battery presenting an increased capacity of 20.8 Ah L−1 compared to 13.0 Ah L−1 of the GF-based battery and an increase in power density from 225 mA cm−2 to 300 mA cm−2. Furthermore, the battery exhibited a 74.79% energy efficiency (EE) at 150 mA cm−2, with no attenuation even at 300 cycles. GF@CS greatly elevates the reaction kinetics and efficiency of VRFBs.

Li-rich layered Li2MnO3 is of great attraction for high energy lithium ion batteries. However, its cycling is still needed for improvements. Here we report a hollow microsphere-structured xLi2MnO3·(1-x)LiNiO2 (x = 0.3–0.7) that is synthesized by using in-situ template-sacrificial strategy. Powder X-ray diffraction (XRD) and scanning electron microscope (SEM) characterizations prove that the xLi2MnO3·(1-x)LiNiO2 (x = 0.3–0.7) are based on monoclinic Li2MnO3 with α-NaFeO2 layered structure in which Li+ ions are orderly arranged in the transition metal layers, and the hollow-microspheres have diameters of ∼3 μm. Electrochemical results show that the optimal ratio of Li2MnO3/LiNiO2 is 0.6/0.4. As a consequence, the stabilized discharge capacity of 0.6Li2MnO3·0.4LiNiO2 (0.6LLMNO) is ∼210 mAh g−1 after the first few cycles. This shows that appropriate amount Ni substitution for Mn in Li2MnO3 helps to improve the specific capacity and cycling stability.

As high capacity cathodes, O3-type Na-based oxides always suffer from a series of monoclinic transitions upon sodiation/desodiation, mainly caused by Na+/vacancy ordering and Jahn–Teller (J−T) dist...

Despite significant advances in deep learning based object detection in recent years, training effective detectors in a small data regime remains an open challenge. This is very important since labelling training data for object detection is often very expensive and time-consuming. In this paper, we investigate the problem of few-shot object detection, where a detector has access to only limited amounts of annotated data. Based on the meta-learning principle, we propose a new meta-learning framework for object detection named "Meta-RCNN", which learns the ability to perform few-shot detection via meta-learning. Specifically, Meta-RCNN learns an object detector in an episodic learning paradigm on the (meta) training data. This learning scheme helps acquire a prior which enables Meta-RCNN to do few-shot detection on novel tasks. Built on top of the popular Faster RCNN detector, in Meta-RCNN, both the Region Proposal Network (RPN) and the object classification branch are meta-learned. The meta-trained RPN learns to provide class-specific proposals, while the object classifier learns to do few-shot classification. The novel loss objectives and learning strategy of Meta-RCNN can be trained in an end-to-end manner. We demonstrate the effectiveness of Meta-RCNN in few-shot detection on three datasets (Pascal-VOC, ImageNet-LOC and MSCOCO) with promising results.

The fundamental understanding of electrocatalytic reaction process is anticipated to guide electrode upgradation and acquirement of high-performance vanadium redox flow batteries (VRFBs). Herein, a carbon fiber prototype system with a heteroatom gradient distribution has been developed with enlarged interlayer spacing and a high graphitization that improve the electronic conductivity and accelerate the electrocatalytic reaction, and the mechanism by which gradient-distributed heteroatoms enhance vanadium redox reactions was elucidated with the assistance of density functional theory calculations. All these contributions endow the obtained electrode prominent redox reversibility and durability with only 1.7% decay in energy efficiency over 1000 cycles at 150 mA cm

The hierarchical electronic and ionic mixed conducting networks build in graphite felt electrodes possess excellent electrocatalytic activity and faster electronic and ionic conduction, resulting in an enhanced energy efficiency of vanadium redox flow batteries with durable life for 1000 cycles and a high discharge capacity of 10.1 A h L-1 at a current density of 350 mA cm-2.

A novel electrodeposited-hydrothermal method has been developed to fabricate high-density β-Na0.33V2O5 nanowire film on a metal current collector (Ti foil). The morphology, crystal structure, and the effects of deposition voltage, temperature and time on the prepared samples were tested and presented in detail. The thickness of the β-Na0.33V2O5 nanowire film was ∼10.5 μm under experimental conditions of 5 h time, 2.5 V voltage, and 90 °C temperature. When the β-Na0.33V2O5 nanowire film was coated with polypyrrole and served as a cathode of lithium-ion battery, it exhibited a high reversible discharge capacity of 269.9 mAh g−1 at a current density of 50 mA g−1. By contrast, the cycling behavior of this material is proved to be much better than the bare β-Na0.33V2O5 nanowire film. This research provides a new pathway to explore high tap density cathode materials for lithium-ion battery with enhanced electrochemical performance.

The rapid capacity decay caused by the poor contact and large polarization at the interface between the cathode and solid electrolytes is still a big challenge to overcome for high-power-density solid batteries. In this study, a superior Li+ conductive transition layer Li1.4Al0.4Ti1.6(PO4)3 is introduced to coat LiNi0.6Co0.2Mn0.2O2, as a model cathode, to mitigate polarization and enhance dynamic characteristics. The critical attribute for such superior dynamics is investigated by the atomic force microscopy with boundary potential analysis, revealing that the formed interfacial transition layer provides a gradual potential slope and sustain-released polarization, and endows the battery with improved cycling stability (90% after 100 cycles) and excellent rate capability (116 mA h g–1 at 2 C) at room temperature, which enlightens the comprehension of interface engineering in the future solid batteries systems.

In recent years, lithium batteries using conventional organic liquid electrolytes have been found to possess a series of safety concerns. Because of this, solid polymer electrolytes, benefiting from shape versatility, flexibility, low-weight and low processing costs, are being investigated as promising candidates to replace currently available organic liquid electrolytes in lithium batteries. However, the inferior ion diffusion and poor mechanical performance of these promising solid polymer electrolytes remain a challenge. To resolve these challenges and improve overall comprehensive performance, polymers are being coordinated with other components, including liquid electrolytes, polymers and inorganic fillers, to form polymer-based composite electrolytes. In this review, recent advancements in polymer-based composite electrolytes including polymer/liquid hybrid electrolytes, polymer/polymer coordinating electrolytes and polymer/inorganic composite electrolytes are reviewed; exploring the benefits, synergistic mechanisms, design methods, and developments and outlooks for each individual composite strategy. This review will also provide discussions aimed toward presenting perspectives for the strategic design of polymer-based composite electrolytes as well as building a foundation for the future research and development of high-performance solid polymer electrolytes.

A mild and simple synthesis process for large-scale vanadium redox flow batteries (VRFBs) energy storage systems is desirable. A graphite felt/MnO2 (GF-MNO) composite electrode with excellent electrocatalytic activity towards VO2+/VO2+ redox couples in a VRFB was synthesized by a one-step hydrothermal process. The resulting GF-MNO electrodes possess improved electrochemical kinetic reversibility of the vanadium redox reactions compared to pristine GF electrodes, and the corresponding energy efficiency and discharge capacity at 150 mA cm − 2 are increased by 12.5% and 40%, respectively. The discharge capacity is maintained at 4.8 A h L − 1 at the ultrahigh current density of 250 mA cm − 2. Above all, 80% of the energy efficiency of the GF-MNO composite electrodes is retained after 120 charge-discharge cycles at 150 mA cm − 2. Furthermore, these electrodes demonstrated that more evenly distributed catalytic active sites were obtained from the MnO2 particles under acidic conditions. The proposed synthetic route is facile, and the raw materials are low cost and environmentally friendly. Therefore, these novel GF-MNO electrodes hold great promise in large-scale vanadium redox flow battery energy storage systems.

Lithium-sulfur (Li-S) batteries show significant advantages for next-generation energy storage systems due to the high theoretical energy density and cost effectiveness. The main challenge for developing long-life and high-performance Li-S batteries is to simultaneously restrain the shuttle of soluble polysulfides while accelerating the redox kinetics of sulfur-related species during cell operation. Herein, a sandwich-type sulfur@Co/N-doped carbon (S@Co-NC) ternary composite is synthesized, combining in a simple way the advantages of synergetic physical and chemical confinement on sulfur-related species. A further electrochemical redox kinetic study confirms that the incorporated conductive Co mediators and doped N species serve as dual electrocatalysts, substantially accelerating the kinetics of the polysulfide redox reactions. By relieving the sluggishness of polysulfide redox reactions, the as-obtained sandwich-type S@Co-NC composite has significantly promoted electrochemical performance including enhanced rate capability, lower polarization and higher Coulombic efficiency. It delivers extremely high discharge capacity of 1401 mAh g−1 at 0.05 C with an area sulfur loading of 1.3 mg cm−2. More importantly, the ternary electrode retains a high rate capability of 694 mAh g−1 over extensive 600 cycles at 1 C, with nearly 100% Coulombic efficiency maintenance. These results suggest that the S@Co-NC ternary composite provides possibility of realizing the industrially practical Li-S batteries.

Summary The aspiration of employing metallic lithium (Li) as the anode is impeded by Li dendrites and unwanted redox shuttles in liquid electrolytes. In this study, a repellent used to safeguard the Li anode was demonstrated during the lithiation of a nanosized AlPO4 additive in an infiltrated quasi-solid electrolyte (i-QSE) containing a concentrated electrolyte in a poly(tri-acrylate) network. As a result of the infiltrated structure, the ion transfer number of i-QSE attained 0.79, and the activation energy was only 0.12 eV. Compared with the control counterpart, the repellent composed of Al-containing (oxy)fluorides played a vital role in stabilizing the interface and promoted the cycling durability of batteries (capacity retention >85% after 200 cycles) with a 1 C rate at an elevated temperature (55°C) without dendrite growth and by-product drifting. Such in situ generation of a repellent for a Li anode is a valid approach for metal-anode protection at the interface-engineering level.

The phosphorus and fluorine codoped graphite felt electrodes with prominent hydrophilicity present excellent electroactivity towards V2+/V3+ and VO2+/VO2+, elevate the discharging ability up to 250 mA cm−2 and dramatically extend the energy efficiency of vanadium redox flow batteries towards 1000 cycles with 0.003% reduction per cycle.

In order to obtain a safe, reliable, long-lived battery system without use of flammable, volatile, and relatively unstable organic liquid-based electrolytes, lithium garnet oxides with formulas Li7-xLa3Zr2-xTa x O12 (x=0.2-1) were synthesized by the solid state reaction method. Single cubic phases were observed in the composition x range between 0.2 and 1. The lattice parameters decreased with the addition of Ta due to the smaller ionic radius of Ta5+ compared with that of Zr4+, following the Vegard’s law. The total conductivity of the x = 0.3 composition is 6.03×10-5 S·cm-1 at room temperature with an activation energy of 0.30 eV. These lithium garnet oxides exhibit lithium ionic transport that is relevant to lithium battery application.

For the first time a three dimensional (3D) volume calculation model based on the total electrostatic potential (ESP) analysis and DFT calculations is applied to study the volume differences between hydrated multivalent vanadium ions (V2+, V3+, VO2+ and ) and charge-balancing ions (H3O+, and ) encountered in the electrolyte solutions of vanadium redox flow batteries (VRB). The calculated results indicate that radii of all charge-balancing ions are less than 3.01A and of all hydrated multivalent vanadium ions are greater than 3.78 A. The results of our calculations also suggest that cation exchange membranes (CEMs) with pore sizes ranging from 3.98 to 7.56 A and anion exchange membranes (AEMs) with pore sizes ranging from 6.02 to 7.56 A are suitable for the VRB application. These computational results agree very well with reported experimental results and provide valuable guidance for the selection and design of membranes on the molecular level for VRB applications.

The fast-ionic-conducting ceramic electrolyte is promising for next-generation high-energy-density Li-metal batteries, yet its application suffers from the high interfacial resistance and poor interfacial stability. In this study, the compatible solid-state electrolyte was designed by coating Li1.4Al0.4Ti1.6(PO4)3 (LATP) with polyacrylonitrile (PAN) and polyethylene oxide (PEO) oppositely to satisfy deliberately the disparate interface demands. Wherein, the upper PAN constructs soft-contact with LiNi0.6Mn0.2Co0.2O2, and the lower PEO protects LATP from being reduced, guaranteeing high-voltage tolerance and improved stability toward Li-metal anode performed in one ceramic. Moreover, the core function of LATP is amplified to guide homogeneous ions distribution and hence suppresses the formation of a space-charge layer across interfaces, uncovered by the COMSOL Multiphysics concentration field simulation. Thus, such a bifunctional modified ceramic electrolyte integrates the respective superiority to render Li-metal batteries with excellent cycling stability (89% after 120 cycles), high Coulombic efficiency (exceeding 99.5% per cycle), and a dendrite-free Li anode at 60 °C, which represents an overall design of ceramic interface engineering for future practical solid battery systems.

We, for the first time, demonstrate a facile preparation of N, O dual-doped carbon felt (CF) as electrodes in all-vanadium redox flow batteries (VRFB). N2 and O2 plasma was employed to treat the CF, introducing nitrogen and oxygen atoms doped into the carbon felt to result in the improved electrocatalytic activity and enhanced interaction of CF-electrolyte during the battery operation. The energy efficiency of the as-assembled VRFB is improved from 65% (pristine) to 78% (doped) at a current density of 50 mA cm-2 with excellent cycling stability.

Soluble starch-functionalized graphene oxide composite (GO-starch) was prepared by a facile esterification reaction. And the composite was used as a novel adsorbent for the removal of Cd(II) from aqueous solution. The chemical composition and morphology of the GO-starch was investigated by fourier transform infrared spectroscopy, scanning electron microscopy and Raman spectroscopy. To evaluate the effects of the adsorption of Cd(II) by GO-starch, batch adsorption studies were performed to optimize the major parameters such as contact time, pH, initial concentration and temperature. The maximum uptake capacity of Cd(II) was 43.20 mg/g under the optimal conditions. Furthermore, the adsorption kinetics, isotherms and thermodynamics of Cd(II) on GO-starch were also investigated. The experimental data indicated that the adsorption kinetics and adsorption isotherms of Cd(II) on GO-starch were well fitted by pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The adsorption thermodynamic parameters were calculated as ΔG 0 0 and ΔS 0 > 0, respectively. The thermodynamic parameters indicated that the adsorption process was endothermic, feasible and spontaneous. Due to its high adsorption capacity for Cd(II), the GO-starch might have considerable potential for the aqueous removal of metal ions. Soluble starch-functionalized graphene oxide composite (GO-starch) was prepared and used as a novel adsorbent for the aqueous removal of Cd(II). The chemical composition and morphology of the GO-starch was characterized by fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Raman spectroscopy. Batch adsorption experiments were performed to optimize the major parameters such as contact time, pH, initial concentration and temperature. The maximum uptake capacity of Cd(II) was 43.20 mg/g under the optimal conditions. The adsorption kinetics and adsorption isotherms were well fitted by pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The adsorption thermodynamic parameters were ΔG 0 0 and ΔS 0 > 0, indicating that the Cd(II) adsorption process was spontaneous, endothermic and feasible.

The development of a three-dimensionally flexible, large-surface area, high-conductivity electrode is important to improve the low conductivity and utilization of active materials and restrict the shuttle of long-chain polysulfides in Li–polysulfide batteries. Herein, we constructed an integrated three-dimensional carbon nanotube forest/carbon cloth electrode with heteroatom doping and high electrical conductivity. The as-constructed electrode provides strong trapping on the polysulfide species and fast charge transfer. Therefore, the Li–polysulfide batteries with as-constructed electrodes achieved high specific capacities of ∼1200 and ∼800 mA h g–1 at 0.1 and 1 C, respectively. After 300 cycles at 0.5 C, a specific capacity of 623 mA h g–1 was retained.

Notably, many significant breakthroughs for a new generation of supercapacitors have been reported in recent years, related to theoretical understanding, material synthesis and device designs. Herein, we summarize the state-of-the-art progress toward mechanisms, new materials, and novel device designs for supercapacitors. Firstly, fundamental understanding of the mechanism is mainly focused on the relationship between the structural properties of electrode materials and their electrochemical performances based on some in situ characterization techniques and simulations. Secondly, some emerging electrode materials are discussed, including metal–organic frameworks (MOFs), covalent organic frameworks (COFs), MXenes, metal nitrides, black phosphorus, LaMnO3, and RbAg4I5/graphite. Thirdly, the device innovations for the next generation of supercapacitors are provided successively, mainly emphasizing flow supercapacitors, alternating current (AC) line-filtering supercapacitors, redox electrolyte enhanced supercapacitors, metal ion hybrid supercapacitors, micro-supercapacitors (fiber, plane and three-dimensional) and multifunctional supercapacitors including electrochromic supercapacitors, self-healing supercapacitors, piezoelectric supercapacitors, shape-memory supercapacitors, thermal self-protective supercapacitors, thermal self-charging supercapacitors, and photo self-charging supercapacitors. Finally, the future developments and key technical challenges are highlighted regarding further research in this thriving field.

Electrochemical capacitors are playing increasing roles in our daily life but their low energy densities limit their wide applications. The appearance of Li-ion capacitors (LICs) is regarded as the beginning of a new era of increased energy densities in the field of electrochemical capacitors. However, it is a great challenge to find a suitable anode material with superior electrochemical performance. In addition, the intrinsic instability of the liquid electrolytes used in LICs can easily result in leakage of the electrolyte and causes a serious safety issue. Here, a quasi-solid-state LIC is fabricated by applying Li3VO4/carbon nanofibers as the anode and electrochemically-exfoliated graphene sheets as the cathode in a gel polymer electrolyte. It achieves an energy density of 110 W h kg−1 and a good cycling performance. Our results demonstrate that quasi-solid-state LICs provide a key system acting as a bridge between conventional Li-ion batteries and supercapacitors, while meeting the high safety demands of electronic devices.

Anode materials with high capacity for aqueous rechargeable lithium batteries (ARLBs) are very rarely reported. Here we found that a dual core–shell structured MWCNTs@S@PPy nanocomposite prepared by us shows excellent electrochemical performance. Its initial discharge capacity in a saturated LiAc aqueous electrolyte is very high, which is up to 481 mA h g−1 based on the weight of the composite and 879 mA h g−1 based on the sulfur content. It shows excellent rate capability. When nanotube LiMn2O4 is used as a cathode, the assembled ARLB can deliver an energy density of 110 Wh kg−1 based on two electrodes and show excellent cycling. These results show great promise for the practical application of ARLBs.

In this paper, a flow frame with multi-distribution channels is designed. The electrolyte flow distribution in the graphite felt electrode is simulated to be uniform at some degree with the tool of a commercial computational fluid dynamics (CFD) package of Star-CCM+. A 5 kW-class vanadium redox flow battery (VRB) stack composed of 40 single cells is assembled. The electrochemical performance of the VRB stack is investigated. Under the applied current density of 60 mA cm−2 during the charge and discharge processes, the current and energy efficiencies are delivered to be 93.9 and 80.8 %, respectively. A higher average output power of 7.2 kW can be achieved at the current density of 80 mA cm−2 with a lower energy efficiency of 78.4 %. The studies of kW-class VRB stack can be beneficial to the development of large-scale energy storage.

The lithium (Li) metal battery reveals appealing merits in energy density but suffers from problems of dendrite growth and low coulombic efficiency before its applications. The ether electrolytes entitle Li metal batteries with more smooth Li stripping/deposition but narrow electrochemical stability in contrast to carbonate electrolyte. circumventing this contradictory, a lithium fluoride-nitride mixed ionic conducting interphase was embedded on lithium surface via formulated fluorine-rich carbonate and cyclophosphonitrile, which renders a dendrite-free plating/stripping over 2200 h and extend the electrochuemcial window of ether electrolyte to 4.5 V with the assistance of experiments and calculating simulations, ensuring LiCoO2 to operate efficiently over 200 cycles with nearly no capacity decay.

LiNixCoyMnzO2 (LNCM)-layered materials are considered the most promising cathode for high-energy lithium ion batteries, but suffer from poor rate capability and short lifecycle. In addition, the LiNi1/3Co1/3Mn1/3O2 (NCM 111) is considered one of the most widely used LNCM cathodes because of its high energy density and good safety. Herein, a kind of NCM 111 with semi-closed structure was designed by controlling the amount of urea, which possesses high rate capability and long lifespan, exhibiting 140.9 mAh&middot, g&minus, 1 at 0.85 A&middot, 1 and 114.3 mAh&middot, 1 at 1.70 A&middot, 1, respectively. The semi-closed structure is conducive to the infiltration of electrolytes and fast lithium ion-transfer inside the electrode material, thus improving the rate performance of the battery. Our work may provide an effective strategy for designing layered-cathode materials with high rate capability.

Catalytic efficiency is a crucial index for electrodes in flow batteries, and tremendous efforts have been devoted to exploring catalysts with as many reaction zones as possible. Nevertheless, the space between the reaction sites, especially for interstitial space utilization, is usually ignored and challengeable to exploit owing to the balance between the catalytic efficiency and structural stability. Herein, a three-dimensional conducting network was constructed via a nitrogen-rich carbon film-bridged graphite felt framework (GF@N-C) to maximize its electrocatalytic effectiveness toward redox species. As the electrode, GF@N-C exhibits a superior rate constant and catalytic efficiency at 370 mA cm

The uncontrolled growth of Li dendrites upon cycling might result in low coulombic efficiency and severe safety hazards. Herein, a lithiophilic binary lithium-aluminum alloy layer, which was generated through an in situ electrochemical process, was utilized to guide the uniform metallic Li nucleation and growth, free from the formation of dendrites. Moreover, the formed LiAl alloy layer can function as a Li reservoir to compensate the irreversible Li loss, enabling long-term stability. The protected Li electrode shows superior cycling over 1700 h in a Li|Li symmetric cell.

Interfacial problems, including interfacial stability and contact issues, severely plague the practical application of Li metal anodes. Here we report an interfacial regulation strategy that stabilizes the Li metal-gel electrolyte interface through in situ constructing a stable solid electrolyte interphase (SEI) layer. By stabilizing the interface of Li metal anodes, the gel electrolyte enables dendrite-free morphology and high plating/stripping efficiency. A systematic analysis further confirms that the formed SEI layer is responsible for homogeneous deposition and stable cycling performance. Benefiting from the interfacial stability between electrodes and electrolytes, the lifespan of Li metal batteries is extended.

Vanadium redox flow batteries (VRFBs) are receiving increasing interest in energy storage fields because of their safety and versatility. However, the electrocatalytic activity of the electrode is a pivotal factor that still restricts the power and cycling capabilities of VRFBs. Here, a hierarchical carbon micro/nanonetwork (HCN) electrode codoped with nitrogen and phosphorus is prepared for application in VRFBs by cross‐linking polymerization of aniline and physic acid, and subsequent pyrolysis on graphite felt. Due to the hierarchical electron pathways and abundant heteroatom active sites, the HCN exhibits superior electrocatalysis toward the vanadium redox couples and imparts the VRFBs with an outstanding energy efficiency and extraordinary stability after 2000 cycles at 250 mA cm−2 and a discharge capacity of 10.5 mA h mL−1 at an extra‐large current density of 400 mA cm−2. Such a micro/nanostructure design will force the advancement of durable and high‐power VRFBs and other electrochemical energy storage devices.

Highly catalytic electrodes play a vital role in exploiting the capability of vanadium redox flow batteries (VRFBs), but they suffer from a tedious synthesis process and ambiguous interaction mechanisms for catalytic sites. Herein, a facile urea pyrolysis process was applied to prepare graphitic carbon nitride-modified graphite felt (GF@CN), and by the virtue of a density functional theory-assisted calculation, the electron-rich pyridinic nitrogen atom of CN granules is demonstrated as the adsorption center for redox species and plays the key role in improving the performance of VRFBs, with 800 cycles and an energy efficiency of 75% at 150 mA cm–2. Such experimental and computational collaborative investigations guide a realizable and cost-effective solution for other high-power flow batteries.

Electrochemical capacitors are becoming promising energy conversion/storage and power output devices. However, high cost and low energy density are two serious disadvantages. By integrating the advantages of Li-/Na-ion batteries and electrochemical capacitors, Li-/Na-ion capacitors have been explored recently. Al is very cheap and is the most abundant metal element on the earth. There are few reports on Al-ion capacitors due to the challenges in finding a suitable anode with large capacitance and good rate performance. Here, the feasibility of assembling an Al-ion capacitor with good electrochemical performance is demonstrated. The Al-ion capacitor is assembled by using a composite of MoO3 nanotubes coated by a conductive polypyrrole (PPy@MoO3) as an anode, which functions via a redox intercalation/deintercalation of Al3+ ions in aqueous solution. It delivers a capacitance of 693 F g−1, about 3 times higher than that of electrode materials for sodium-ion capacitors in aqueous solution. Combined with an activated carbon (AC) cathode, the Al-ion capacitor presents an energy density of 30 W h kg−1 and an excellent cycling life with 93% capacitance retention after 1800 cycles. This finding provides another energy storage device with low cost and promotes the application of capacitors.

Nanotechnology has opened up new frontiers in materials science and engineering in the past several decades. Considerable efforts on nanostructured electrode materials have been made in recent years to fulfill the future requirements of electrochemical energy storage. Compared to bulk materials, most of these nanostructured electrode materials improve the thermodynamic and kinetic properties of electrochemical reactions for achieving high energy and power densities. Here we briefly review the state-of-the-art research activities in the area of nanostructured positive electrode materials for post-lithium ion batteries, including Li–S batteries, Li–Se batteries, aqueous rechargeable lithium batteries, Li–O2 batteries, Na-ion batteries, Mg-ion batteries and Al-ion batteries. These future rechargeable battery systems may offer increased energy densities, reduced cost, and more environmental benignity. A particular focus is directed to the design principles of these nanostructured positive electrode materials and how nanostructuring influences electrochemical performance. Moreover, the recent achievements in nanostructured positive electrode materials for some of the latest emerging rechargeable batteries are also summarized, such as Zn-ion batteries, F- and Cl-ion batteries, Na–, K– and Al–S batteries, Na– and K–O2 batteries, Li–CO2 batteries, novel Zn–air batteries, and hybrid redox flow batteries. To facilitate further research and development, some future research trends and directions are finally discussed.

The demand for clean and renewable energy has promoted the rapid development of state-of-the-art energy storage electrochemical systems. Vanadium redox flow batteries attract much more attentions due to low cost and high security, unfortunately the low catalytic activity of electrodes for vanadium ion redox process is the main barrier to achieve a high efficiency. This work proposes a novel composite electrode derived from Bacillus mycoides to overcome the dilemma between high degree of graphitization and uniform heteroatom doping. Consequently, this composite electrode simultaneously achieves rapid charge migration and high electrocatalytic activity and enhances the vanadium ion redox reaction on porous lamellar carbon (PLC) materials. Compared with the pristine electrode, the potential polarization for V(IV)/V(V) and V(II)/V(III) redox couples on PLC electrode decrease by 254 mV and 278 mV, respectively. Moreover, a high stability for cycling continuously for over 1000 cycles at a high current density of 200 mA cm−2 and a high energy efficiency can be realized based on PLC electrode. This work not only paves the way to achieve high energy efficiency of vanadium redox flow batteries, but also provides a feasible and novel way to design carbon materials with high catalytic activity and high electronic conductivity.

In this work, a novel activated carbon containing graphene composite was developed using a fast, simple, and green ultrasonic-assisted method. Graphene is more likely a framework which provides support for activated carbon (AC) particles to form hierarchical microstructure of carbon composite. Scanning electron microscope (SEM), transmission electron microscope (TEM), Brunauer–Emmett–Teller (BET) surface area measurement, thermogravimetric analysis (TGA), Raman spectra analysis, XRD, and XPS were used to analyze the morphology and surface structure of the composite. The electrochemical properties of the supercapacitor electrode based on the as-prepared carbon composite were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), charge/discharge, and cycling performance measurements. It exhibited better electrochemical performance including higher specific capacitance (284 F g−1 at a current density of 0.5 A g−1), better rate behavior (70.7% retention), and more stable cycling performance (no capacitance fading even after 2000 cycles). It is easier for us to find that the composite produced by our method was superior to pristine AC in terms of electrochemical performance due to the unique conductive network between graphene and AC.

The Li metal anode has long been considered as one of the most ideal anodes due to its high energy density. However, safety concerns, low efficiency, and huge volume change are severe hurdles to the practical application of Li metal anodes, especially in the case of high areal capacity. Here it is shown that that graphitized carbon fibers (GCF) electrode can serve as a multifunctional 3D current collector to enhance the Li storage capacity. The GCF electrode can store a huge amount of Li via intercalation and electrodeposition reactions. The as-obtained anode can deliver an areal capacity as high as 8 mA h cm-2 and exhibits no obvious dendritic formation. In addition, the enlarged surface area and porous framework of the GCF electrode result in lower local current density and mitigate high volume change during cycling. Thus, the Li composite anode displays low voltage hysteresis, high plating/stripping efficiency, and long lifespan. The multifunctional 3D current collector promisingly provides a new strategy for promoting the cycling lifespan of high areal capacity Li anodes.

Water splitting is considered to be a very promising alternative to greenly produce hydrogen, and the key to optimizing this process is the development of suitable electrocatalysts. Here, a sacrificial-counter-electrode method to synthesize a MoS x /carbon nanotubes/Pt catalyst (0.55 wt% Pt loading) is developed, which exhibits a low overpotential of 25 mV at a current density of 10 mA cm-2, a low Tafel slope of 27 mV dec-1, and excellent stability under acidic conditions. The theory calculations and experimental results confirm the high hydrogen evolution activity that is likely due to the fact that the S atoms in MoS x can be substituted with O atoms during a potential cycling process when using Pt as a counter-electrode, where the O atoms act as bridges between the catalytic PtO x particles and the MoS x support to generate a MoS x -O-PtO x structure, allowing the Pt atoms to donate more electrons thus facilitating the hydrogen evolution reaction process.

A composite electrode composed of reduced graphene oxide-graphite felt (rGO-GF) with excellent electrocatalytic redox reversibility toward V2+/V3+ and VO2+/VO2+ redox couples in vanadium batteries was fabricated by a facile hydrothermal method. Compared with the pristine graphite felt (GF) electrode, the rGO-GF composite electrode possesses abundant oxygen functional groups, high electron conductivity, and outstanding stability. Its corresponding energy efficiency and discharge capacity are significantly increased by 20% and 300%, respectively, at a high current density of 150 mA cm−2. Moreover, a discharge capacity of 20 A h L−1 is obtained with a higher voltage efficiency (74.5%) and energy efficiency (72.0%), even at a large current density of 200 mA cm−2. The prepared rGO-GF composite electrode holds great promise as a high-performance electrode for vanadium redox flow battery (VRFB).