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Enabling the rechargeable lithium metal batteries (LMBs) is essential for exceeding the energy density of today's Lithium-ion batteries. However, practical challenges in almost all components of LMBs, of which the most serious issues are formation of Li dendrites and uncontrollable volume expansion of lithium metal anodes, hinder their practical applications. Traditional LMBs’ fabrication techniques have some limitations in controlling the geometry and structure of components, which compromises their performance. 3D printing is an ideal manufacturing technique that can increase the specific energy and power density of devices by precisely controlling their geometry and structure from nanoscale to macroscale without relying on any templates. In this work, we review recent advances of 3D printing in rechargeable LMBs in combination with their fundamental principles and representative printing techniques. Then we discuss the applications at component levels. Finally, we summarize the design rationales and practical challenges of 3D printed rechargeable LMBs and give our insights about future outlook of this emerging field.

The development of promising zinc anodes mainly suffers from their low plating/stripping coulombic efficiencies when using aqueous electrolyte, which are mainly associated with the interfacial formation of irreversible by-products. It is urgent to develop technologies that can solve this issue fundamentally. Herein, we report an artificial Sc2O3 protective film to construct a new class of interface for Zn anode. The density functional theory simulation and experimental results have proven that the interfacial side reaction was inhibited via a stratified adsorption effect between this artificial layer and Zn anode. Benefiting from this novel structure, the Sc2O3-coated Zn anode can run for more than 100 cycles without short circuit and exhibit low voltage hysteresis, and the coulombic efficiency increases by 1.2%. Importantly, it shows a good application prospect when matched with two of popular manganese-based and vanadium-based cathodes. The excellent electrochemical performance of the Sc2O3-coated Zn anode highlights the importance of rational design of anode materials and demonstrates a good way for developing high-performance Zn anodes with long lifespan and high efficiency.

Multifunctional mesoporous silica-based nanocarriers able to efficiently encapsulate drugs for stimuli-responsive release and display rapid biodegradation are highly desirable. In this work, we dope disulfide bonds and calcium into silica framework by one step method to obtain a redox and pH dual-responsive biodegradable mesoporous silica nanoparticle (BT-Ca-MSN) as a potential drug carrier for synergistic cancer therapy. TEM and ICP-OES are used to assess the biodegradation behavior of BT-Ca-MSN. The results show that BT-Ca-MSN can significantly biodegrade in a concurrent reductive and acidic environment due to the simultaneous disulfide bonds cleavage and Ca2+ release. In addition, BT-Ca-MSN shows efficient drug loading capacity and significant biodegradation-mediated drug release. Moreover, the in-vitro cytotoxicity indicates that BT-Ca-MSN can not only exhibit significant cancer cell killing effect without obvious toxicity on healthy cells via the way of released Ca2+-mediated apoptosis, but also can combine with its loaded doxorubicin hydrochloride for synergistic cancer therapy. This work demonstrates that BT-Ca-MSN is a promising platform as drug carrier, providing a paradigm to rationally design biodegradable silica-based carriers for highly efficient cancer therapy.

Ameliorating the interfacial issues of the zinc anode, particularly dendrite growth and electrode corrosion, is imperative for rechargeable zinc metal batteries. Herein, an electrochemical-inert li...

Noble metal-free electrocatalysts with high activity are highly desirable for the large-scale application of hydrogen evolution reaction (HER). Mo2C-based nanomaterials have been proved as a promising alternative to noble metal-based electrocatalysts owing to the Pt-resembled d-band density and optimal intermediates-adsorption properties. However, the aggregation and excessive growth of crystals often occur during their high-temperature synthesis procedure, leading to low catalytic utilization. In this study, the ultrafine Mo2C/Mo2N heterostructure with large surface and interface confined in the N-doped carbon nanofibers (N-CNFs) was obtained by a melamine-assisted method. The synergistic effect of Mo2C/Mo2N heterostructure and plenty active sites exposed on the surface of ultrafine nanocrystals improves the electrocatalytic activity. Meanwhile, the N-CNFs ensure fast charge transfer and high structural stability during reactions. Moreover, the in-situ synthesis method strengthens the interfacial coupling interactions between Mo2C/Mo2N heterostructure and N-CNFs, further enhancing the electronic conductivity and electrocatalytic activity. Owing to these advantages, Mo2C/Mo2N@N-CNFs exhibit excellent HER performance with a low overpotential of 75 mV at a current density of 10 mV cm−2 in alkaline solution, superior to the single phased Mo2C counterpart and recently reported Mo2C/Mo2N based catalysts. This study highlights a new effective strategy to design efficient electrocatalysts via integrating heterostructure, nanostructure and carbon modification.

Sodium superionic conductor (NASICON)-type compounds have been regarded as promising cathodes for sodium-ion batteries (SIBs) due to their favorable ionic conductivity and robust structural stability. However, their high cost and relatively low energy density restrict their further practical application, which can be tailored by widening the operating voltages with earth-abundant elements such as Mn. Here, we propose a rational strategy of infusing Mn element in NASICON frameworks with sufficiently mobile sodium ions that enhances the redox voltage and ionic migration activity. The optimized structure of Na3.5Mn0.5V1.5(PO4)3/C is achieved and investigated systematically to be a durable cathode (76.6% capacity retention over 5,000 cycles at 20 C) for SIBs, which exhibits high reversible capacity (113.1 mAh·g−1 at 0.5 C) with relatively low volume change (7.6%). Importantly, its high-areal-loading and temperature-resistant sodium ion storage properties are evaluated, and the full-cell configuration is demonstrated. This work indicates that this Na3.5Mn0.5V1.5(PO4)3/C composite could be a promising cathode candidate for SIBs.

Lithium-ion batteries are a typical representative of energy storage system with high storage capacity and good cycle stability. However, the low specific capacity can not meet the storage capacity requirements for new generation of electronic products, which have limited their practical application. Herein, CoF 2 nanoparticles loaded on carbon fiber cloth (CoF 2 @CFC) as a flexible composite material prepared without binder or conductive agent is introduced as a cathode for lithium-ion batteries, which exhibit a high specific capacity of 330 mA h g −1 at 100 mA g −1 and have a stable specific capacity of 100 mA h g −1 at 1 A g −1 even after 1000 cycles. In addition, the flexibility of CoF 2 @CFC creates an application potential in the field of flexible electronic devices and wearable electronics.

High-capacity anode materials are widely studied for rechargeable batteries, which have the capability of storing more Li+ ions per formula. However, they normally experience large volume expansion and suffer inferior cycling stability. Herein, we propose pea-pod structured V2O3 yolk-shell microspheres@N, S co-doped carbon fiber network as an excellent anode material for lithium ion batteries. The prepared vanadium dioxide precursor is uniformly embedded into the carbon fibers by electrospinning treatment and further converted into V2O3 yolk-shell microspheres during the calcination process. The conductive carbon fiber framework which links V2O3 microspheres enhanced the electrical conductivity and structural stability significantly. Moreover, the co-doped N and S atoms derived from polymer could produce extrinsic defects, thereby improving Li+ diffusion and electrochemical active sites. When used as anodes for lithium ion batteries, the composite exhibits a high reversible capacity (793.7 mA h g−1 after 100 cycles at 100 mA g−1), excellent rate performance and cycle stability.

Germanium-based materials has been considered as a promising anode material for Li-ion batteries due to their high theoretical capacity. Herein, we reported a novel Ge/GeO 2 -Reduced graphene oxide (GG-RGO) microcubes via one-step recombination using sodium borohydride as reductant, followed by a calcination process in reducing atmosphere. During the recombination, the reduced graphene oxide coated GeO 2 nanoparticles self-assemble to form three-dimensional Ge shell/GeO 2 core cubic structure. RGO coated construction can relieve volume expansion, provide a large reactive area and reduce distance for lithium diffusion. Meanwhile, two-phase Ge/GeO 2 composite nanostructure can effectively increase specific capacity. Benefited from its unique three-dimensional structure, the Ge/GeO 2 -RGO composites exhibit high reversible capacity (1005 mAh g −1 at 100 mA g −1 ), good cycling stability (a high reversible capacity of 933 mAh g −1 after 50 cycles) and rate performance (740 mAh g −1 at 2000 mAh g −1 ).

MoSe2 has been attracting numerous attentions for energy storage and conversion applications due to its unique characteristics. However, the intrinsic low electric conductivity and sluggish reaction kinetics hinder its electrochemical performance. Herein, hierarchical mesoporous MoSe2@CoSe/N-doped carbon (N-C) composite was in situ fabricated from MoO3@Co-MOF precursor in selenium atmosphere. The incorporation of CoSe and N-C greatly enhanced the reaction kinetics and electronic conductivity of the composite. Moreover, the hierarchical mesoporous structure ensures fast Na+ diffusion and excellent structural stability upon cycling. As expected, the optimally structured composite showed superior electrochemical performance as an anode material in sodium-ion batteries, including a high specific capacity of 485 mA h g−1 at 0.1 A g−1 and good rate capability that it retains 91.4% of its 398 mA h g−1 initial capacity after 300 cycles at 2 A g−1. When paired with Na3V2(PO4)3/C, it also delivers a high reversible capacity of 345 mA h g−1 in full-cell configuration. In addition, as a catalyst, it also exhibits outstanding HER activity with a small overpotential of 64 mV and a Tafel slope of 53 mV dec−1.

Transition metal phosphides have been explored as promising active materials for sodium-ion batteries (SIBs) and hydrogen evolution reaction (HER) applications owing to their unique physical and chemical characteristics. However, they suffer from the drawbacks such as severe agglomeration, and sluggish reaction kinetics. Herein, bimetallic phosphides (Ni2P/ZnP4) embedded in P-doped carbon hierarchical microspheres are demonstrated with robust structural integrity, fast charge transfer, and abundant active sites. As expected, the optimally structured Ni2P/ZnP4 composite exhibits good electrochemical performance as an anode material in SIBs, including high specific capacity, good cycling stability and rate capability. Meanwhile, the Ni2P/ZnP4 composite also exhibits excellent electrocatalytic performance for HER with a small overpotential of 62 mV, a Tafel slope of 53 mV dec−1, as well as excellent stability.

Rechargeable aqueous zinc-ion batteries (ZIBs) with advantages of high safety and low-cost gradually show potential in large-scale energy storage/supply application. Yet the further development of aqueous ZIBs is hindered by finding suitable cathodes. Here we demonstrate that the chemical pre-intercalated transition metal ions (e.g. Fe2+, Co2+, Ni2+, Mn2+, Zn2+ and Cu2+, etc.) into the interlayer of V2O5, could effectively improve the electrochemical performance of aqueous ZIBs, in terms of high capacity, rate capability and long-term cycling stability, as well as excellent broad temperature adaptability. For instance, Cu2+-intercalated V2O5 cathode exhibits high capacity of 180 mA h g−1 after 10000 cycles at 10 A g−1 and 122 mA h g−1 after 3000 cycles at 20 A g−1. This universal strategy of pre-intercalated metal ions in the host materials is found to enable fast Zn2+ diffusion, enhanced electrical conductivity, and excellent structural reversibility, which can be applicable for other well-established aqueous ZIBs cathodes (i.e. MnO2), or other advanced battery systems.

Sodium-ion batteries (SIBs) have attracted considerable attention for large-scale energy storage systems as a promising alternative to lithium-ion batteries (LIBs) due to the huge availability and low-cost. Yet the development of SIBs has been hindered by the low reversibility, sluggish ion diffusion, as well as large volume variations. Herein, we report an efficient hydrothermal method for fabricating hierarchical porous Na3V2(PO4)3/C (NVP/C) microspheres assembled from interconnected nanoflakes. The NVP nanocrystals are uniformly wrapped by N-doped carbon layer. As a half-cell cathode, the NVP/C porous microspheres exhibit superior rate capability (99.3 mA h g−1 at 100 C) and excellent cyclic stability (79.1% capacity retention over 10,000 cycles at 20 C). A full-cell configuration coupled with NVP/C cathode and SnS/C fibers anode exhibits an estimated practical energy density of 223 W h kg−1. The superior performance can be ascribed to the hierarchical porous micro/nano structure along with N-doped carbon encapsulation, which provide bicontinuous electron/ion pathways, large electrode-electrolyte contact area, as well as robust structural integrity. This work provides a promising approach for boosting the electrochemical performance of battery materials via the integration of hierarchical structure and heteroatoms doped carbon coating.

Aqueous zinc-ion batteries are largely restricted by the unsatisfactory performance of zinc (Zn) anodes, including their poor stability and irreversibility. In particular, the mechanism behind the electrochemical contrast caused by the surface crystal plane, which is a decisive factor of the electrochemical characteristics of the hostless Zn anode, is still relatively indistinct. Hence, new insight into a novel anode with a surface-preferred (002) crystal plane is provided. The interfacial reaction and morphology evolution are revealed by theoretical analysis and post-mortem/operando experimental techniques, indicating that Zn anodes with more exposed (002) basal planes exhibit free dendrites, no by-products, and weak hydrogen evolution, in sharp contrast to the (100) plane. These features benefit the Zn (002) anode by enabling a long cyclic life of more than 500 h and a high average coulombic efficiency of 97.71% for symmetric batteries, along with delivering long cycling stability and reversibility with life spans of over 2000 cycles for full batteries. This work provides new insights into the design of high-performance Zn anodes for large-scale energy storage and can potentially be applied to other metal anodes suffering from instability and irreversibility.

Highlights MoSe2/MoC/C multiphase boundaries boost ionic transfer kinetics.MoSe2 (5–10 nm) with rich edge sites is uniformly coated in N-doped framework.The obtained MoSe2 nanodots achieved ultralong cycle performance in LIBs and high capacity retention in full cell. Abstract Interface engineering has been widely explored to improve the electrochemical performances of composite electrodes, which governs the interface charge transfer, electron transportation, and structural stability. Herein, MoC is incorporated into MoSe2/C composite as an intermediate phase to alter the bridging between MoSe2- and nitrogen-doped three-dimensional (3D) carbon framework as MoSe2/MoC/N–C connection, which greatly improve the structural stability, electronic conductivity, and interfacial charge transfer. Moreover, the incorporation of MoC into the composites inhibits the overgrowth of MoSe2 nanosheets on the 3D carbon framework, producing much smaller MoSe2 nanodots. The obtained MoSe2 nanodots with fewer layers, rich edge sites, and heteroatom doping ensure the good kinetics to promote pseudo-capacitance contributions. Employing as anode material for lithium-ion batteries, it shows ultralong cycle life (with 90% capacity retention after 5000 cycles at 2 A g−1) and excellent rate capability. Moreover, the constructed LiFePO4//MoSe2/MoC/N–C full cell exhibits over 86% capacity retention at 2 A g−1 after 300 cycles. The results demonstrate the effectiveness of the interface engineering by incorporation of MoC as interface bridging intermediate to boost the lithium storage capability, which can be extended as a potential general strategy for the interface engineering of composite materials. Electronic supplementary material The online version of this article (10.1007/s40820-020-00511-4) contains supplementary material, which is available to authorized users.

As a promising conversion-type anode material, iron sulfide has been widely studied. However, due to its huge volume expansion during repeated lithiation/delithiation, iron sulfide tends to pulverize and form aggregates upon cycling, which greatly hinders its application in high performance lithium ion batteries as a durable anode material. Herein, a strategy for synthesizing and stabilizing iron sulfide nanosheets with a robust titanium oxide nanofiber interior support is proposed. The hierarchical nanostructured composite anode material was successfully synthesized by the electrospinning technique and subsequent sulfurization. The size of the iron sulfide nanosheets can be easily tuned by adjusting the composition of the reacting agents and/or the sulfurization temperature. Electrochemical results reveal that the composite delivers a reversible capacity of 591 mA h g−1 at a current density of 0.1 A g−1 after 100 cycles and exhibits excellent long-term cycling stability at 0.5 A g−1 and 1 A g−1 as well. Furthermore, when being paired with LiFePO4, the as-synthesized composite also delivers promising full-cell performance, showing its potential in serving as a competitive candidate anode material in lithium-ion batteries for power applications. Moreover, this method also opens up an avenue for modifying and improving other conversion-type anode materials.

Molybdenum selenide (MoSe2), a promising anode material for sodium ion batteries (SIBs), has generated intensive scientific interest due to its high theoretical capacity and favorable conversion kinetics. Nevertheless, its practical applications are seriously restricted by the volume variation, inferior structural stability and dissolved poly-selenides. Herein, we report dual carbon protected MoSe2 (MoSe2@NC@rGO) and the intrinsic mechanism for its enhanced sodium storage performance. Organic–inorganic hybrid Mo3O10(C2H10N2) (MoOx-EDA) is used as a self-sacrificing precursor. The synthesis process involves self-assembly of MoOx-EDA with functionalized graphene oxide (GO) and subsequent thermal selenization. The dual protection carbon layers can block the poly-selenide shuttling, promote electron transfer and buffer the huge volume change. When evaluated as an anode material for SIBs, the optimized MoSe2@NC@rGO-200 electrode delivers a high reversible specific capacity of 447 mA h g−1 at 100 mA g−1 and maintains an appreciable capacity of 281 mA h g−1 at 5 A g−1. Moreover, a capacity of 360 mA h g−1 is retained after 200 cycles at 1 A g−1 with no obvious capacity decay. A full-battery configuration coupled with the Na3V2(PO4)2/C cathode exhibits an average operating potential of 1.8 V and good cycling performance. Such a dual carbon-confined approach can also be extended to other electrode materials with large volume swelling.

Owing to their high cost and safety hazards, and the low abundance of Li in natural resources, the future of Li-ion batteries is becoming difficult. To replace Li-ion batteries, aqueous multivalent ion batteries are considered to be a worthwhile choice. In particular, aqueous zinc ion batteries are becoming an attractive option due to the natural abundance and unique properties of zinc. However, as for the Li-ion battery, the Zn-ion battery also has its own inadequacies in terms of cathodes. Finding a suitable cathode material for Zn-ion batteries with adequate structural stability and high capacity is an uphill task for researchers. This review presents the recent developments of various cathode materials in zinc ion batteries and their effectiveness towards the advancement of Zn-ion batteries. Based on the collected literature, various strategies adopted for enhancing the performance of Zn-ion batteries are also briefly discussed in this review. Furthermore, the explicit progress and future perspectives of Zn-ion batteries are also discussed.

Homogeneous copper incorporated nickel sulfide (NS) nanosheets were realized via an in situ ion exchange method and one-pot hydrothermal process. Nickel foam (NF) and copper foam (CF) were used as metal sources for the co-formation of Cu1.8S–Ni3S2 in the presence of thiourea. As a result of the Cu incorporation, the NF-supported Ni3S2 nanosheets exhibited improved electronic conductivity with higher electrochemical surface area (ECSA). When evaluated as electrode materials for supercapacitors, the as-obtained active materials demonstrated high specific capacitance (1686 F g−1 at 1 A g−1) with excellent cycling performance (95.39% capacitive retention after 10 000 cycles), which may be attributed to the unique structural features as well as the synergistic effect of localized copper species with Ni3S2 nanosheets.

Tin-based oxides are considered to be promising candidates for lithium-ion battery anode materials due to their high theoretical capacities. However, the low conductivity and drastic volume expansion/contraction during the reaction with Li+ ions greatly limit their practical applications. Herein, we have successfully grown vertically aligned Sn3O4 nanoflakes on the carbon fiber cloth substrate by a hydrothermal method, referred to as Sn3O4@CFC. As a binder-free flexible anode for LIBs, this composite can not only accommodate the structural strain upon cycling, but also improve the electrical conductivity. As a consequence, the Sn3O4@CFC electrode manifests high specific capacity and good cycling stability. It exhibits a high specific capacity of around 1500 mA h g−1 at 100 mA g−1, superior rate capability (835.6 mA h g−1 at a high current density up to 2000 mA g−1) and good cyclic stability with 66.2% capacity retention over 200 cycles at 1000 mA g−1.

We report the engineering of the interplanar spacing of ammonium vanadates to achieve the optimal electrochemical performance as cathodes for aqueous zinc-ion batteries (ZIBs) and provide insights into the origin of the enhanced electrochemical behaviors. The NH4V4O10 compound, with the largest interplanar spacing (9.8 A) and high diffusion coefficient, exhibits high energy density (374.3 W h kg−1) and power density (9000 W kg−1) as well as superior long-term cycling performance (a discharge capacity of 255.5 mA h g−1 can be maintained after 1000 cycles at 10 A g−1). With the merits of impressive energy density and long cycle life, the NH4V4O10 might be a new promising cathode for aqueous ZIBs for grid energy storage applications. This work provides a direction for choosing or designing the ideal high-performance cathode for aqueous ZIBs and other advanced battery systems.

Nb2O5 has attracted increasing attention as anode materials for lithium ion batteries (LIBs) because of its high safety and good structural stability. However, its electrochemical properties are controlled by the poor electronic conductivity and low ion diffusivity. In this work, we report the preparation of Nb2O5/carbon nanocomposites overcomes these issues by a facile solvothermal method with subsequent calcination. The Nb2O5 nanoparticles are homogeneously distributed in a carbon matrix derived from carbon quantum dots. As anode materials for lithium ion batteries, the as-prepared Nb2O5/carbon nanocomposites exhibit high capacity, good rate capability and cyclic stability. The Nb2O5/carbon nanocomposites can deliver a stable capacity of 385 mA h g−1 after 100 cycles at 0.1 A g−1. A specific capacity of 240 mA h g−1 is maintained even after 600 cycles at 1 A g−1. The composite electrode exhibits improved electrochemical performance than pure Nb2O5 electrode. With the homogeneous distribution of the Nb2O5 in a carbon matrix derived from carbon quantum dots, the aggregation of Nb2O5 during cycles can be prevented and the electronic conductivity of Nb2O5 can be enhanced.

Transition metal dichalcogenides (TMDs) have attracted increasing attention for rechargeable batteries because of its high theoretical capacity. However, its real application is limited by the intrinsic low electron conductivity and inferior structural stability. Herein, we report the fabrication of one-dimensional (1D) MoSe2/C nanorods composite from organic-inorganic hybrid Mo3O10(C2H10N2) (named as MoOx-EDA) with subsequent selenization and carbon coating process. As anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), the carbon-encapsulated composite exhibited enhanced Li+/Na+ storage properties compared to MoSe2 nanorods, including good cycling stability and high rate capability. A specific capacity of 835 mA h g−1 can be obtained at a current density of 200 mA g−1 for the MoSe2/C electrode in LIBs, which retained 755 mA h g−1 after 200 cycles. Moreover, a reversible Na+ storage capacity of 404 mA h g−1 can be remained after 100 cycles at a current density of 200 mA g−1. The good electrochemical performances of the MoSe2/C nanorod composites can be attributed to the bicontinuous electron/ion pathways, low charge transfer resistance, and robust structure stability.

Tin sulfides have attracted great attentions as sodium-batteries anode materials due to the remarkable high theoretical capacity, but their application is vastly limited by the poor rate capability and cycle stability. In this report, we constructed a double carbon-coated structure of carbon-coated tin (II) sulfide nanoflakes anchored on reduced graphene sheets (C@SnS-rGO) by a one-pot solvothermal synthesis with a subsequent annealing process. The carbon layer deposited on the surface of nanoflakes and the rGO sheet substrate combined into a framework which can enhance the electric conductivity and structural stability. Moreover, the carbon skeleton is doped with nitrogen and sulfur atoms which can increase the active sites and surface-capacitive effect of the as-prepared composite. As anode materials for sodium-ion batteries, the C@SnS-rGO composite electrode exhibits high capacity, good rate capability and cycling stability. The superior electrochemical performances are attributed to the improved electronic conductivity and good structural stability of the composite electrode.

Three-dimensional (3D) nanostructures are commonly endowed with numerous active sites, large specific surface area, and good mechanical strength, which make them as an efficient candidate for energy storage and conversion. Herein, by considering the advantages of 3D nanostructures, we successfully fabricated carbon-coated nickel sulfide on a nickel foam (C@NS@NF) with a unique 3D treelike superstructure via a two-step hydrothermal process. By virtue of its hierarchical superstructures, 3D treelike architecture, and carbon shell encapsulation, the as-fabricated carbon-coated Ni3S2 can be directly served as binder-free bifunctional electrodes for supercapacitor and hydrogen evolution reaction, where high specific areal capacitance (6.086 F cm-2 at 10 mA cm-2) for supercapacitors and low overpotential (92 mV at 10 mA cm-2) for the electrocatalyst have been demonstrated. These inspiring results of this material make it as a potential candidate for energy storage and conversion.

Niobium pentoxide (Nb2O5) has been extensively studied as anode materials for lithium ion batteries (LIBs) due to its good rate performance and safety advantages. However, the intrinsic low electronic conductivity has largely restricted its practical application. In this work, we report the construction of mesoporous T-Nb2O5 nanofibers by electrospinning followed by heat treatment in air. The interconnected mesoporous structure ensures a high surface area with easy electrolyte penetration. When used as anodes for LIBs, the mesoporous Nb2O5 electrode delivers a high reversible specific capacity of 238 mA h g−1 after 1,000 cycles at a current density of 1 A g−1 within a voltage range of 0.01–3.0 V. Even at a higher discharge cut-off voltage window of 1.0–3.0 V, it still possesses a high reversible capacity of 166 mA h g−1 after 200 cycles. Moreover, the porous Nb2O5 electrode also exhibits excellent rate capability. The enhanced electrochemical performances are attributed to the synergistic effects of porous nanofiber structure and unique crystal structure of T-Nb2O5, which has endowed this material a large electrode-electrolyte contact area with improved electronic conductivity.

Although current high-energy-density lithium-ion batteries (LIBs) have taken over the commercial rechargeable battery market, increasing concerns about limited lithium resources, high cost, and insecurity of organic electrolyte scale-up limit their further development. Rechargeable aqueous zinc-ion batteries (ZIBs), an alternative battery chemistry, have paved the way not only for realizing environmentally benign and safe energy storage devices but also for reducing the manufacturing costs of next-generation batteries. This Review underscores recent advances in aqueous ZIBs; these include the design of a highly reversible Zn anode, optimization of the electrolyte, and a wide range of cathode materials and their energy storage mechanisms. We also present recent advanced techniques that aim at overcoming the current issues in aqueous ZIB systems. This Review on the future perspectives and research directions will provide a guide for future aqueous ZIB study.

Three-dimensional heterogeneous nanocomposites exhibit eminent cycling stability and rate capability as electrode materials for lithium-ion batteries. In this work, the composites of MoS2 nanosheets uniformly coated TiO2 nanowire arrays are fabricated by a glucose-assisted hydrothermal approach. The usage of glucose can be favorable to the uniform growth of MoS2 morphology. As anode materials for lithium ion batteries, the composites exhibit good specific capacity, cycling stability and rate capacity. The enhanced electrochemical properties are attributed to uniformity of composites since the uniform composites can effectively integrate the good cycling stability of TiO2 nanowire arrays and high capacity of MoS2 nanosheets. The gentle synthesis procedure and excellent electrochemical properties make TiO2 nanowire@MoS2 nanosheet arrays promising in high-performance lithium-ion batteries.

For the development of high-performance sodium and aqueous zinc ion batteries, the exploitation of suitable cathode materials is urgently needed. In this work, pilotaxitic Na1.1V3O7.9 nanoribbons/graphene (Na1.1V3O7.9@rGO) have been prepared. As cathode for sodium ion battery, the Na1.1V3O7.9@rGO delivers high capacities at different rates. Stable capacity of 84.8 mA h g−1 is obtained at 1 A g−1 after 500 cycles, corresponding to a low capacity fading rate of 0.015% per cycle. The ex-situ XRD and TEM results demonstrate good structural stability of Na1.1V3O7.9@rGO. Most importantly, the layered structure of Na1.1V3O7.9@rGO is firstly employed as cathode for aqueous zinc ion battery. This composite can deliver a high capacity of ~ 220 mA h g−1 at 300 mA g−1, as well as good cyclic stability, which suggests the sodium vanadates may be a good cathode candidate for aqueous zinc ion battery.

Synthesis of cathode materials with high rates and long cycle life is critical to meet the demands of high-power lithium-ion battery applications. Batteries that can work at extreme low temperature conditions are also urgently needed. Herein, we report the rational design and synthesis of a novel lithium vanadium phosphate/carbon (Li3V2(PO4)3/C) nanocomposite with a thin-layer amorphous carbon shell (∼4 nm) coating and a mesoporous KB carbon matrix. As expected, the Li3V2(PO4)3/C nanocomposite demonstrates an excellent high-rate and long-term cycling performance as well as broad temperature adaptability. Even at a high rate of 16C, a high capacity of 102 mA h g–1 can be achieved. Importantly, the capacity retention is 99% after 1000 cycles and 94% after 2000 cycles when cycled at a rate of 6 C at room temperature in a voltage range of 3–4.3 V. Importantly, this nanocomposite can cycle at −30 °C for 500 cycles with a stable capacity. The excellent rate capability, stable cycling performance, and broad temp...

Developing rechargeable sodium ion batteries (SIBs) with fast charge/discharge rate, high energy and power density, and long lifespan is still a significant challenge. Na3V2(PO4)3 (NVP) is regarded as one of the most potential SIBs cathodes due to its high theoretical capacity and stable sodium superionic conductor (NASICON) structure. However, the general NVP exhibits inferior electron conductivity due to the two separated [VO6] octahedral arrangement, which limits its widespread applications. Here, we present a design of hierarchical porous carbon-coated NVP nanoflakes via a facile molten hydrocarbon-assisted, solid-state reaction strategy, in which span 80 acts as surfactant and carbon source. The formation mechanism of this hierarchical open structure constructed by uniform nanoflakes was investigated by a heating-rate controlled experiment, which indicated that heating rates play an important role in morphology and structure of the final products. When used as SIBs cathode, the hierarchical porous carbon-coated NVP nanoflakes electrodes exhibited high reversible capacity of 114.2 mA h g−1 at 0.5 C, high rate capacity of 87.7 mA h g−1 at 100 C and excellent cyclic stability up to 10,000 cycles with only 0.0048% per cycling capacity fading, indicating the good sodium storage performances. This work demonstrates that the unique hierarchically porous flaky structure is favorable for improving the cyclability and rate capability in energy storage applications.

Ni2P2O7-based composites grown on conductive substrate can efficiently promote the electrical transport during the electrochemical reactions in supercapacitors. However, Ni2P2O7 nanoarrays are easily peeled off from the substrate upon repeated electrochemical reaction. Herein, Ni2P2O7 nanoarrays grown on Ni foam with surficially decorated C3N4 thin nanosheets are achieved by a hydrothermal and in situ calcination strategy. The decorated C3N4 nanosheet network on the surface fully covers both Ni2P2O7 and Ni foam and efficiently prevents Ni2P2O7 nanoarrays from peeling off during the charge and discharge cycles. The optimized composites exhibit high pseudocapacitance and greatly enhanced cycling stability. The assembled asymmetric supercapacitor shows favorable specific capacitance and stability as energy storage devices. Such a strategy for fabricating C3N4-modified Ni2P2O7 nanoarrays is feasible and efficient, and can be therefore extended for constructing other electrodes with high capacitance and excell...

Na3V2(PO4)3 (NVP) is considered as a promising cathode material in Sodium-ion batteries (SIBs). However, the intrinsically poor electronic conductivity greatly limits its electrochemical performances and practical applications. Herein, a solid-state annealing process using a facile surfactant-assisted method has been developed to fabricate a three-dimensional (3D) Na3V2(PO4)3/C (NVP/C) composite with hierarchical nanoflake-assembled structure. Sodium oleate functions both as sodium and carbon sources. Moreover, it dictates the preferential growth of nanocrystal as a surfactant. This flaky structure coated by carbon can ensure the excellent electrochemical performances of the NVP/C composite, such as high reversible capacity (103.4 mA h g−1 at 1 C), excellent rate capability (68.3 mA h g−1 at a rate up to 20 C) and good cycling stability (a capacity retention of 78.2% after 2000 cycles at 10 C).

Three-dimensional (3D) binary oxides with hierarchical porous nanostructures are attracting increasing attentions as electrode materials in energy storage and conversion systems because of their structural superiority which not only create desired electronic and ion transport channels but also possess better structural mechanical stability. Herein, unusual 3D hierarchical MnCo2O4 porous dumbbells have been synthesized by a facile solvothermal method combined with a following heat treatment in air. The as-obtained MnCo2O4 dumbbells are composed of tightly stacked nanorods and show a large specific surface area of 41.30 m2 g–1 with a pore size distribution of 2–10 nm. As an anode material for lithium-ion batteries (LIBs), the MnCo2O4 dumbbell electrode exhibits high reversible capacity and good rate capability, where a stable reversible capacity of 955 mA h g–1 can be maintained after 180 cycles at 200 mA g–1. Even at a high current density of 2000 mA g–1, the electrode can still deliver a specific capacity...

Layered transition metal dichalcogenides (TMDs) such as molybdenum diselenides (MoSe2) have raised much research interest for its excellent electrochemical and catalytic properties. In this study, a new nanocomplex (MoSe2/HPCFs) was constructed by anchoring MoSe2 nanosheets onto nitric-acid modified Polyacrylonitrile carbon nanofibers (HPCFs) via one pot hydrothermal treatment, followed by calcination. To target issues triggered by energy storage, lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) and hydrogen evolution reactions (HER) were deployed to comprehensively assess the electrochemical and electrocatalytic performances of the binder-free MoSe2/HPCFs electrodes. When investigated as anode material for LIBs and SIBs, the MoSe2/HPCFs electrodes delivered initial discharge capacities of 862.7 and 586.6 mA h g−1, respectively, at a current density of 0.1 A g−1. The MoSe2/HPCFs electrodes also displayed outstanding electrocatalytic activity in HER, requiring only 106 mV of overpotential to reach a current density of 10 mA cm−2, all the while having a small Tafel slope of 61 mV dec−1. This study’s findings suggest that the synergistic combination of HPCFs fibers and MoSe2 nanosheets could significantly enhance the electrochemical and electrocatalytic performances of Li-ion/Na-ion batteries and HER, which could provide a feasible and easy solution in designing high-performance flexible devices for energy storage and conversion.

Polypyrrole and sulfur derived hollow carbon nanofibers co-doped with nitrogen/sulfur are synthesized and applied as the anode for Na-ion batteries (NIBs). Successful doping of hollow carbon nanofiber with nitrogen and sulfur is confirmed by X-ray photoelectron spectroscopy, scanning and tunneling electron microscopy. Further analysis certifies that sulfur doping has a significant impact in improving the elecctrochemical performance of the carbon-based anodes for NIBs. The obtained N-doped hollow carbon nanofiber and N/S co-doped hollow carbon nanofiber exhibit similar morphologies but different electrochemical behavior. As expected, the N/S co-doped hollow carbon nanofiber anode exhibits enhanced electrochemical performance, including high specific capacity, outstanding long-term stability, and good rate stability.

Heterogeneous structures with binary chemical compositions could achieve unique chemical properties by modification of the components and interface engineering. Meanwhile, hollow microspheres with complex interiors have been extensively studied in energy storage and conversion systems due to their possibility of adjusting the electrochemical performances. In this work, we report the reliable preparation of heterogeneous (NiO)x(NiS)1−x (0 ≤ x ≤ 1) multi-shelled hollow microspheres derived from carbon sphere@nickel precursor templates. The structural evolution of the multiple shells is carefully studied. Moreover, the effect of sulfurization extent of the (NiO)x(NiS)1−x compounds on the electrochemical performance is also explored. As electrode materials for supercapacitors, the heterogeneous (NiO)0.1(NiS)0.9 multi-shelled hollow microspheres exhibit the best electrochemical performances among a series of nickel oxide/sulfide compounds. The (NiO)0.1(NiS)0.9 sample can deliver a high specific capacitance of 1063 F g−1 at 2 A g−1. Even at a high current density of 50 A g−1, the electrode can still retain a high specific capacitance of 486 F g−1 after 10 000 cycles. Furthermore, a (NiO)0.1(NiS)0.9‖active carbon asymmetric supercapacitor (ASC) exhibits a specific capacitance of 58.5 F g−1 at 2 A g−1 in 2 M KOH solution. The superior electrochemical performances can be attributed to the careful composition regulation and the stable multi-shelled structure.

Transition metal oxides have been extensively studied as anode materials for lithium ion batteries due to their high capacity. However, the intrinsically low electronic conductivity and large volume changes upon repeated cycles are the obstacles for obtaining their high electrochemical properties. In this work, we report the novel construction of uniform Ni/MnO porous microspheres by an in situ conversion from their solvothermally synthesized precursor composites (xNiCO3·yMnCO3). The structures of the precursor composites can be controlled by the solvothermal duration and solution compositions. During the high-temperature annealing process, the precursor composites were transferred into Ni and MnO composite and porous structure was created by the decomposition of the carbonate materials. As an anode material for lithium-ion battery, the porous Ni/MnO electrode demonstrates high reversible capacity of 700.6 mA h g−1 after 250 cycles. Moreover, the Ni/MnO microspheres exhibit excellent rate capacity. The exceptional electrochemical performances are attributed to the homogeneous distribution of nickel nanoparticles within the MnO microspheres and porous structures throughout the whole microspheres, which can improve the electronic conductivity of the electrode materials and keep the structural integrity upon repeated cycles.

Antimony (Sb) has been intensively investigated as a promising anode material for sodium ion batteries (SIBs) in recent years. However, bulk Sb particles usually suffer from excessive volume expansion thus leading to dramatic capacity decay after cycling. To address this issue, Sb has been uniformly decorated on Polyacrylonitrile (PAN) derived carbon nanofibers (PCFs) via a simple chemical deposition strategy to form a one-dimensional (1D) core-shell nanostructure of Sb@PCFs. PCFs were first derived from electrospun PAN fibers and treated with subsequent calcination. The PCFs constructed an interwoven carbon network were later employed for Sb deposition, which can effectively alleviate aggregation or further cracking of Sb nanoparticles occurred in electrochemical kinetic process. The as-obtained Sb@PCFs nanocomposites demonstrated excellent cycling stability with good rate performances. This carefully designed core-shell nanostructure of antimony nanoparticles wrapped PCFs are responsible for good electrochemical Na-ion storage. Moreover, the 1D nanostructure manage to pave pathways for fast ions transfer during charge-discharge, which could extra contribute to the enhanced SIBs performances.

Flexible hybrid electrodes with high electronic conductivity and porosity have attracted great attention for energy storage and conversion systems. Herein, we report the fabrication of a porous graphitic carbon wrapped MnO/Ni microsphere network (MnO/Ni/CNF) by a combined solvothermal and electrospinning method followed by stabilization and carbonization processes. Carbon nanofibers which link porous MnO/Ni/C microspheres function as both a 3D conductive network and a current collector for the flexible composite electrode. Meanwhile, the porous MnO/Ni microspheres are coated with porous graphene-like carbon layers, further improving the electronic conductivity and facilitating the electrolyte penetration. When directly utilized as an anode material for LIBs, the MnO/Ni/CNF electrode exhibits excellent electrochemical performances, including high reversible capacity, good cycle stability and rate capability. The as-prepared flexible electrode delivers a capacity of 534.5 mA h g−1 at 200 mA g−1 after 100 cycles (based on the whole electrode mass) and possesses a capacity retention of 95.7% even after long-term 600 cycles at 1 A g−1, suggesting its promising applicability in lithium ion batteries as a flexible binder-free anode.

As a complement or alternative to lithium ion batteries, development of high-performance sodium ion batteries with long cycle life is urgent. Here, nitrogen doped urchin-like MoS2/C hollow structures are successfully synthesized by using Mo-MOFs as the precursors with a facile sulfuration process. The nanocomposites that contain carbon and nitrogen elements possess good electronic conductivity as well as expanded interlayer, which are beneficial for electron transportation and ion diffusion. The hierarchical hollow structure is able to accommodate volume change during discharge/charge. When applied as anode for sodium-ion batteries, the N-doped MoS2/C anode exhibits good rate capability and outstanding cycling performance. It delivers a high initial discharge capacity of 972 mA h g−1 at 100 mA g−1. The discharge capacity can achieve 242 mA h g−1 even at 5000 mA g−1. Importantly, long-term cycling test shows that the capacity maintains a considerable capacity of 128 mA h g−1 after 5000 cycles at 2 A g−1, with a capacity fading rate of 0.036% per cycle.

Doping of N atoms into the carbonacous materials can generate extrinsic defects and more active sites, improve electrode wettability and also broaden the interlayer distance of carbon, hence promote Na storage capacity and high rate capability. Herein, we report the nitrogen-doped carbon nanosheets materials (PPyCs) obtained from pyrolysis of Polypyrrole coated graphene oxides. The pyrolysis temperature plays an important role on the electrochemical performance of PPyCs. With thermal treatment at 400, 600 and 800 °C, PPyCs have different content of N doping, and the doped N shows different existential forms. The PPyCs thermal treated at 600 °C (PPyC-600) exhibit a reversible capacity of 388.8 mA h g −1 at a current density of 100 mA g −1 , and even at a high current density of 10 A g −1 , high capacity of 198.6 mA h g −1 is maintained after 10,000 cycles, demonstrating outstanding cyclic stability, and high-rate capability. Furthermore, the assembled NVP/PPyC-600 full-cell demonstrates a high capacity of 122.2 mA h g −1 at a current density of 100 mA g −1 after 100 cycles, indicating the practical application of PPyCs nanosheets anode in sodium ion batteries.

Tin-based nanomaterials have been extensively explored as high-capacity anode materials for lithium ion batteries (LIBs). However, the large volume changes upon repeated cycling always cause the pulverization of the electrode materials. Herein, we report the fabrication of uniform SnS2@C hollow microspheres from hydrothermally prepared SnO2@C hollow microspheres by a solid-state sulfurization process. The as-prepared hollow SnS2@C microspheres with unique carbon shell, as electrodes in LIBs, exhibit high reversible capacity of 814 mA h g−1 at a current density of 100 mA g−1, good cycling performance ( 783 mA h g−1 for 200 cycles maintained with an average degradation rate of 0.02% per cycle) and remarkable rate capability (reversible capabilities of 433 mA h g−1 at 2 C ). The hollow space could serve as extra space for volume expansion during the charge-discharge cycling, while the carbon shell can ensure the structural integrity of the microspheres. The preeminent electrochemical performances of the SnS2@C electrodes demonstrate their promising application as anode materials in the next-generation LIBs.

Na-ion batteries (NIBs) and Na-ion capacitors (NICs) have tremendous potential in many large-scale energy storage applications. Here, NIBs based on TiO2 nanorods/carbon fiber cloth (TiO2/CFC) flexible anode materials are introduced. The as-prepared flexible anode exhibited a notable rate performance and high specific capacity of 148.7 mAh g−1 after 2000 cycles at 1 A g−1. Furthermore, we demonstrate a highly flexible NIC system employing the TiO2/CFC anode and carbon fibers (CFs) as the cathode material. The flexible TiO2/CFC//CFs NIC device achieved a high energy density of 73.8 Wh kg−1 and high power density of 13,750 W kg−1, as well as long-term cycling stability over 4000 cycles with a capacity retention of ∼90%.

The bismuth nanosheets grown on carbon fiber cloth were designed. For sodium-ion batteries, the Bi/CFC electrode exhibited a high reversible capacity of 350 and 240mAhg−1 after 300cycles at 50 and 200mAg−1, as well as a good rate capability. Besides, the electrode displayed two flat potential profiles during the charge/discharge process. The results suggest that the Bi/CFC electrode has excellent potential as an anode for sodium-ion batteries. Keywords: Sodium-ion battery, Binder-free anode, Bismuth

We report the synthesis of novel chrysanthemum-like Bi 2 S 3 nanostructures as a high-performance anode material for lithium and sodium storage. For lithium ion batteries application, the chrysanthemum-like Bi 2 S 3 nanostructures demonstrate high discharge capacity, excellent rate performance and long-term cycling stability. Amazingly, it exhibits superior cycling stability of ∼2% capacity loss after 300 cycles with high capacity of 480 mA g −1 remained. The performance is highly improved when compared to the previous reported results of Bi 2 S 3 -based materials. Most importantly, the chrysanthemum-like Bi 2 S 3 demonstrates good electrochemical properties for sodium ion batteries application. It displays good cycling stability with a stable capacity of 437 mA h g −1 over 250 cycles at 0.5 A g −1 and excellent high-rate capability. This work will attract more attention to this material, with further improving its performance to speed up its practical use as anode for future Na-ion batteries.

Transition metal chalcogenides have attracted increasing attentions as electrode materials for energy storage devices. Their electrochemical properties are largely determined by morphologies and structures. In this paper, we reported the fabrication of CoSe2/C dodecahedra with tunable interior structures, such as solid, yolk-shell, and double-shell structured interiors. Dodecahedron-shaped cobalt-organic frameworks are used as the sacrificial template, in which the cobalt species react with selenium to in situ form CoSe2 nanoparticles. Moreover, the organic framework is converted into nitrogen-doped carbon framework. The controllable preparation of CoSe2/C composite with diversified interior structures can be realized by a temperature determined annealing process in argon atmosphere. In particular, the unusual double-shell structured composites with non-spherical shells and heterogeneous intervals are formed. The possible formation mechanism of the structure is proposed. As electrode materials for supercapacitors, the double-shelled CoSe2/C composites exhibit high capacitance, good rate capability and long-term cycling stability.

Vanadium oxides with a layered structure are promising candidates for both lithium-ion batteries and sodium-ion batteries (SIBs). The self-template approach, which involves a transformation from metal-organic frameworks (MOFs) into porous metal oxides, is a novel and effective way to achieve desirable electrochemical performance. In this study, porous shuttle-like vanadium oxides (i.e., V2O5, V2O3/C) were successfully prepared by using MIL-88B (V) as precursors with a specific calcination process. As a proof-of-concept application, the asprepared porous shuttle-like V2O3/C was used as an anode material for SIBs. The porous shuttle-like V2O3/C, which had an inherent layered structure with metallic behavior, exhibited excellent electrochemical properties. Remarkable rate capacities of 417, 247, 202, 176, 164, and 149 mAh·g−1 were achieved at current densities of 50, 100, 200, 500, 1,000, and 2,000 mA·g−1, respectively. Under cycling at 2 A·g−1, the specific discharge capacity reached 181 mAh·g−1, with a low capacity fading rate of 0.032% per cycle after 1,000 cycles. Density functional theory calculation results indicated that Na ions preferred to occupy the interlamination rather than the inside of each layer in the V2O3. Interestingly, the special layered structure with a skeleton of dumbbell-like V–V bonds and metallic behavior was maintained after the insertion of Na ions, which was beneficial for the cycle performance. We consider that the MOF precursor of MIL-88B (V) can be used to synthesize other porous V-based materials for various applications.

Coupling electrode materials with carbon substrates to construct flexible aqueous Zn-ion batteries (ZIBs) with excellent electrochemical performance is an attractive research focus. However, further improving the Zn2+/electron diffusion kinetics in such systems is still desirable. Herein, we present a novel hydrophilic carbon substrate that employs acid-treated natural halloysite and carbon nanotubes for the first time as structural and interfacial modifiers for loading V3S4 as a composite cathode (denoted as HCC-V3S4) for flexible ZIBs. The devices exhibit a high specific capacity of 148 mA h·g-1 under a current density of 0.5 A·g-1 (95% retention after 200 cycles), excellent rate performance, and a high energy density of 155.7 W h·kg-1, together with a high-power density of 5000 W·kg-1. The promising electrochemical property can be associated with the formation of the hydrophilic surface/interface and with the good conductivity of the composite electrode, which increases the Zn2+/electron transmission rate. Owing to the cost-effective design of the flexible substrate and the ZIB's impressive electrochemical performance, the fabricated device shows good potential applications in portable and wearable electronics.