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Metal antimony (Sb) is a promising anode material of potassium-ion batteries (PIBs) for its high theoretical capacity but limited by its inferior cycle stability due to the serious volume expansion during cycling. Herein, we design and construct a kind of low-crystalline Sb nanoparticles coated with amorphous Sb2O3 and dispersed into three-dimensional porous carbon via a strategy involving NaCl template-assisted in-situ pyrolysis and subsequent low-temperature heat-treated in air. Significantly, the crystallinity and ratio of Sb/Sb2O3 have been precisely tuned and controlled, and the optimized sample of HTSb@Sb2O3@C-4 displays a high reversible specific capacity of 543.9 mAh g−1 at 0.1 A g−1, superior rate capability and excellent cycle stability (~273 mAh g−1 at 2 A g−1 after 2000 cycles) as an anode of PIBs. The outstanding potassium-ion storage performance can be ascribed to the appropriate crystallinity and the multiple-buffer-matrix structure comprising an interconnected porous conductive carbon to relieve the volume changes and suppress the aggregation of Sb, a Sb nanoparticle core to shorten the ion transport pathways and decrease the mechanical stress, and a low-crystalline Sb2O3 as the shell to consolidate the interface between Sb and carbon as well as facilitate the rapid electron transport. The dynamic analysis shows that the composite is mainly controlled by pseudocapacitance mechanism. This work provides a novel thought to design high-performance composite electrode in energy storage devices.

High entropy oxides (HEOs), as a new type of single-phase multielement solid solution materials, have shown many attractive features and promising application prospect in the energy storage field. Herein, six-element HEOs (CoNiZnFeMnLi)3O4 and (CoNiZnCrMnLi)3O4 with spinel structure are successfully prepared by conventional solid-phase method and present outstanding lithium storage performances due to the synergy effect of various electrochemically active elements and the entropy stabilization. By contrast, (CoNiZnFeMnLi)3O4 delivers higher initial discharge specific capacity of 1104.3 mAh·g−1, better cycle stability (84% capacity retention after 100 cycles at 100 mA·g−1) and rate performance (293 mAh·g−1 at 2000 mA·g−1) in the half-cell. Moreover, the full-cell assembled with (CoNiZnFeMnLi)3O4 and LiCoO2 provides a reversible specific capacity of 260.2 mAh·g−1 after 100 cycles at 500 mA·g−1. Ex situ X-ray diffraction reveals the electrochemical reaction mechanism of HEOs (CoNiZnFeMnLi)3O4, and the amorphous phase and the large amount of oxygen vacancies were obtained after the initial discharge process, which are responsible for the excellent cycle and rate performance. This research puts forward fresh insights for the development of advanced energy storage materials for high-performance batteries.

High-entropy oxides (HEOs) with numerous functional features such as high structure stability and superionic conductivity are considered as promising candidates of electrode materials for lithium-ion batteries (LIBs). In this study, a series of single-phase spinel-structured high-entropy oxides (FeCoNiCrMnXLi)3O4 (X = Cu, Mg, Zn) consisted of seven metal elements at equal molar ratio were synthesized by solid phase method. In-situ high-temperature XRD technique was used to investigate the structure evolution of (FeCoNiCrMnZnLi)3O4 and a single-phase HEO was acquired at 900 °C. As the anode of LIBs, all the HEOs (FeCoNiCrMnXLi)3O4 display excellent cyclic stability and rate capability owe to the expedite three-dimensional Li+ transport pathways of spinel structure, the entropy-dominated phase stabilization effect together with the abundant oxygen vacancies introduced by the incorporation of Li+. In comparison, the (FeCoNiCrMnZnLi)3O4 anode containing electrochemical active Zn with tetrahedral coordination structure shows better electrochemical lithium storage performances among the three samples. The ex-situ XRD of (FeCoNiCrMnZnLi)3O4 during the discharge/charge procedure shows an amorphous state structure after the first lithiation process and it retained for the de-lithiation process. This work provides a new strategy to design high-entropy energy-storage material and pave the way for understanding the storage mechanism of HEOs.

Carbonaceous materials are promising anode candidates for potassium-ion batteries, but currently the unsatisfactory cycling and rate performances due to the sluggish diffusion kinetic and serious structure damage during K+ insertion/extraction limit their practical application. Herein, a series of sulfur-doped porous carbons (SPCs) were prepared via a template-assisted freeze-drying followed by the carbonization and sulfuration processes at different temperatures. Among the three as-synthesized samples, SPC-600 exhibits the highest specific capacity (407 mAh·g−1 at 0.10 A·g−1), the best rate (242 mAh·g−1 at 2.00 A·g−1) and cycling performance (286 mAh·g−1 after 800 cycles at 0.50 A·g−1). All the SPCs display higher capacities than the undoped carbon materials. The excellent electrochemical performance of SPC can be ascribed to the abundant three-dimensional porous structure together with S-doping in the disordered carbon, which is favor of providing adequate reaction active sites as well as fast ion/electron transport paths. The density functional theory (DFT) calculations further demonstrate that the sulfur-doping can promote K-ion adsorption and storage. Meanwhile, the kinetic analyses reveal that surface-induced capacitive mechanism dominates the K-ion storage process in SPCs, which contributes to ultrafast charge storage. This work provides an effective strategy for fabricating high-performance potassium-ion storage electrode materials.

Niobium pentoxide (Nb2O5) material is a promising anode for lithium-ion batteries (LIBs) due to the outstanding cycle performance and rate capability. However, the relatively low capacity severely ...

Sodium-ion batteries are increasingly becoming important in the energy storage field owing to their low cost and high natural abundance of sodium. Cobalt-based sulfide materials have been extensively studied as anode materials owing to their remarkable Na storage capability. Nevertheless, the application of cobalt-based sulfides is hampered by their serious capacity degradation and unsatisfactory cycling stability due to severe structural changes during cycling. Therefore, it is important to comprehensively summarize advances in the understanding and modification of cobalt-based sulfides from various perspectives. In the present review, recent advances on various cobalt-based sulfides, such as CoS, CoS2, Co3S4, Co9S8, NiCo2S4, CuCo2S4, and SnCoS4, are outlined with particular attention paid to strategies that improve their sodium storage performance. First, the mechanisms of charge storage are introduced. Subsequently, the key barriers to their extensive application and corresponding strategies for designing high-performance cobalt-based sulfide anode materials are discussed. Finally, key developments are summarized and future research directions are proposed based on recent advancements, aiming to offer possible fascinating strategies for the future promotion of cobalt-based sulfides as anode materials applied in sodium-ion batteries.

Cobalt sulfides have attracted much attention as multifunctional electrocatalysts to trigger important reactions, for example, hydrogen evolution, oxygen evolution, and oxygen reduction reactions, and as electrodes for lithium or sodium ion storage. Nevertheless, the delivery of cobalt sulfide structures with high performance with long-term stability is still a challenge. In the current work reported here, via employing a metal–organic framework (MOF) as the starting material, a simple oxygen-assisted etching strategy to synthesize Co9S8 nanoparticles coated with N-doped few-layer graphene (CS@NFLG) was developed. Microstructure studies show that the graphene layer is doped with the nitrogen element and forms a continuous three-dimensional (3D) conductive network, which protects the inner Co9S8 nanoparticles in the harsh reaction environment and modulates the electronic interactions with the Co9S8 particle surface. Because of the advantages of the unique microstructure, CS@NFLG possesses excellent HER activity in an acidic medium (0.5 M H2SO4) at a low onset overpotential of 50 mV with a small Tafel slope of 73 mV dec−1. Meanwhile, the sample presents remarkable sodium storage properties in terms of a high reversible capacity, good rate capabilities, and good stability. In particular, the CS@NFLG electrode delivers a specific capacity of 505 mA h g−1 after 100 cycles at 0.5 A g−1. Moreover, the CS@NFLG electrode still maintains a high specific capacity of 442.3 mA h g−1 after 400 cycles at a high current density of 1.2 A g−1. This work shows that nanoscale “top-down” etching from the bottom is a promising route for the fine modulation of the structure and composition at the electronic and atomic scales, thus showing great prospects for use in energy storage and conversion applications.

In recent years, Nb-based oxides, especially Nb2O5, due to their unique structural advantages, have stimulated scholars’ extensive research enthusiasm in the field of energy storage systems including lithium ion batteries (LIBs) and sodium ion batteries (SIBs), excellent chemical stability and outstanding rate capability dominated by pseudocapacitive nature. In addition, Nb-based oxides usually have a higher operating voltage (> 1.0 V vs Li+/Li), which can effectively prevent the decomposition of organic electrolytes and the formation of solid electrolyte interface films in batteries. This review systematically summarizes the different crystal structures of Nb2O5 and the lithium storage mechanism based on theoretical calculations, as well as the comparison of various synthesis strategies. In addition, the advanced research progress of niobium-based oxides as anode materials in LIBs and SIBs is summarized from the perspective of nanostructure control engineering that affects electrochemical performance. It also puts forward reasonable cognition and challenges for future research, which is conducive to the design of energy storage equipment that meets the needs of sustainable development. The design and optimization of various synthesis methods facilitate the formation of a variety of heterogeneous nanostructures, leading to reversible storage of Li and Na ions.

The rational exploitation of non-precious metal catalyst with high activity, strong durability and low cost for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of vital importance for metal–air batteries. Herein, a composite of Co3O4 nanoparticles confined in three-dimensional (3D) N-doped porous carbon (Co-NpCs) was prepared by a simple freeze-drying and in situ pyrolysis method. The effect of different dosages of Co(NO3)2 on the catalytic performance was discussed. The Co-NpC-12% exhibits the best catalytic performance (E1/2 = 0.78 V, better stability than 20% Pt/C) in ORR and in OER among all the as-synthesized samples. Furthermore, it also exhibits the best bifunctional activity (ΔE = 0.849 V). The excellent properties of Co-NpCs are mainly due to the synergy between Co3O4 and carbon. Firstly, a high Co3O4 loading amount can boost the defect level of the N-doped hierarchical porous carbon and expose more active sites. Secondly, the unique in situ pyrolysis guarantees a large-area contact between Co3O4 and carbon as well as a strong C–O–Co bonding, which promotes charge transfer, avoids the peeling of Co3O4 nanoparticles and effectively improves the stability of the material. This work is expected to offer a feasible strategy to produce metal oxide/carbon nanocomposite and push forward the development of bifunctional electrocatalyst with high activity and stability.

Design and synthesis of advanced electrode materials with fast and stable ion storage are of importance for energy storage applications. Herein, we propose that introducing the heterogeneous interf...

Transition metal oxides nanostructures are drawing much attention as promising electrodes for advanced rechargeable batteries. However, due to the intrinsic low electronic conductivity and substant...

The preparation of nanostructured MnO2 from low-grade pyrolusite using a H2SO4 roasting-water leaching process without any reducing agent is studied in this paper. In the second step of our study, we synthesize different morphologies of MnO2 created by hydrothermal reactions by controlling the ferric ion concentration in the reaction system; this process does not require any surfactant, template or additional materials. X-ray diffraction (XRD), scanning electron microscopy (SEM) and chemical composition analysis are used to investigate the components and morphological structure of the roasting clinker by adjusting the roasting temperature. We discuss the effect of the ferric ion concentration in the filtrate on the phase structure, microstructure, specific surface area and electrochemical performance of the MnO2. The results indicate that the ferric ion concentration has a significant influence on the morphology and internal structure of the MnO2 products, which subsequently changes the specific surface area and electrochemical properties of the material. In the different nanostructured MnO2 products, hollow γ-MnO2 microspheres composed of small nanorods obtained from the MnSO4 solution of 500 °C exhibit the highest specific surface area (63.9 m2 g−1). The studied sample presents excellent electrochemical behavior for supercapacitor applications. The proposed approach is simple, economical and reasonable, and therefore provides new ideas for the sustainable development of low-grade pyrolusite.

Two-dimensional (2D) transition-metal dichalcogenide materials show potential for use in alkali metal ion batteries owing to their remarkable physical and chemical properties. Nevertheless, the electrochemical energy storage performance is still impaired by the tendency of aggregation, volume, and morphological change during the conversion reaction and poor intrinsic conductivity. Until now, ultrathin molybdenum disulfide nanosheets with a metallic-phase structure on the inner surface of mesoporous hollow carbon spheres (M-MoS2@HCS) have rarely been investigated as an anode for sodium-ion batteries. In this work, a novel M-MoS2@HCS anode was designed and synthesized by employing a template-assisted solvothermal reaction. Structural and chemical analyses indicate that the M-MoS2 nanosheets with a larger interlayer spacing compared to their semiconductor counterpart grow on the inner surface of HCS via covalent interactions. When used as the anode materials for Na+ storage, the M-MoS2@HCS anode presents durable and rapid sodium storage properties. The developed electrode shows a reversible capacity of 291.2 mAh g-1 at a high current density of 5 A g-1. After 100 cycles at 0.1 A g-1, the reversible capacity is 401.3 mAh g-1 with a capacity retention rate of 79%. After 2500 cycles at 1.0 A g-1, the electrode still delivers a reversible capacity of 320.1 mAh g-1 with a capacity retention rate of 75%. The excellent sodium storage capability of the MoS2@HCS electrode is explained by the special structural design, which reveals great potential to accelerate the practical applications of transition-metal dichalcogenide electrodes for sodium storage.

The development of a reliable non-enzymatic multi-analyte biosensor is remained a great challenge for biomedical and industrial applications. In this prospective, rationally designed electrode materials having voltage switchable electrocatalytic properties are highly promising. Here, we report vanadium doped ZnO engineered nanostructures (Zn1-xVxO where 0 ≤ x ≤ 0.1) which exhibit voltage switchable electrocatalytic properties for accurate measurements of glucose and hydrogen peroxide. Microstructures and chemical analysis show that the oxygen vacancies in the material can be tuned by controlling the stoichiometric ratios which play key role for voltage dependent measurements of different analytes. The developed Zn1-xVxO nanostructures exhibit outstanding sensing ability for binary analytes with a high selectivity, low detection limit, thermal stability and long-term stability. The Zn0.9V0.1O/glassy carbon (GC) electrode shows 3-fold increase in reproducible sensitivity for both glucose (655.24μA mM-1cm-2) and H2O2(13309.37μA mM-1cm-2) as compared to the pristine ZnO/GC electrode. Moreover, the electrode also shows good response for human blood serum and commercially available samples. The results demonstrate that defect engineering is a promising route for the development of cost-effective non-enzymatic multi-analyte sensors for practical applications.

Tin-based materials have attracted intensive attention as promising high-capacity anodes for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). However, they suffer from serious capacity fading owing to the inherent huge volume changes and sluggish kinetics. Herein, we propose a facile and scalable self-assembly NaCl template-assisted in situ catalytic strategy for preparing monodisperse multicore–shell SnSb@SnOx/SbOx@C nanoparticles (10–30 nm) space-confined in three-dimensional (3D) graphene-like porous carbon networks. In the unique nanostructure, the synergistic effect of Sn and Sb and abundant free space provided by porous carbon network effectively relieves the volume change, the amorphous SnOx/SbOx shell enhances the interface interaction between SnSb and carbon as well as facilitates ion diffusion, the graphitic carbon shells and the 3D graphene-like carbon network with high mechanical flexibility not only inhibits the aggregation and pulverization of SnSb, but also improves the integrity and conductivity of electrode. Thus, the nanocomposite electrode deliver a high specific capacity, superior rate capability (337.3 mAh g−1 and 244.3 mAh g−1 at 5 A g−1 for LIBs and SIBs, respectively), and excellent cycling stability (capacity retention of 93% after 200 cycles at 1 A g−1 for LIBs; capacity retention of 80% after 500 cycles at 2 A g−1for SIBs). This work provides new strategy for the design and fabrication of nanocomposite with robust interface interaction for electrochemical energy conversion and storage application.

Cobalt (II, III) oxide (Co3O4) nanostructures have attracted much attention as a candidate for anode materials in lithium-ion batteries (LIBs) due to its unique physical/chemical properties and high specific capacity. However, critical issues, such as low electronic conductivity, inefficient ionic diffusion, and large volume change during battery operation, have to be addressed before practical applications. In this work, we report a facile chemical reduction approach to modify Co3O4 nanocubes by NaBH4 solution treatment. The microstructure and chemical composition analysis indicate that the modified Co3O4 nanocubes are oxygen deficient and other secondary phases are not formed during the processing. The degree of oxygen deficiency can be well controlled by altering the concentration of NaBH4 solution. When evaluated as the anodes for LIBs, the optimized sample shows a reversible capacity of 873.5 mAhg−1 after 50 cycles at a current density of 0.1 Ag−1, and a charge-discharge capacity of 569.1 mAhg−1 at a higher current density of 5 Ag−1. The balanced oxygen deficiency and crystallinity in the chemically reduced nanostructured electrodes are supposed to be responsible for the improved lithium storage properties. We believe that the facile solution-based chemical reduction strategy provides an alternative way to control the defects in different functional nanostructures for broader applications.

Transition metal oxides show unique physical and chemical properties, and thus have a wide range of applications, including the electrodes for batteries, supercapacitors, and catalysts. However, poor electrical conductivity of the metal oxides hinder the above applications. In this work, we report a facile method to generate oxygen vacancies in cubic Co3O4 particles by thermal annealing in Ar atmosphere. By carefully controlling annealing condition, the oxygen vacancies can be well modulated while the formation of any other phases is avoided. The microstructure and chemical composition of the Co3O4 particles are studied by different methods. Lithium storage measurements show that the Co3O4 anodes with optimized oxygen vacancies (Co3O4-250) show a specific capacity of 904.2 mAhg−1 at a current density of 0.1 Ag−1, and charge/discharge rate capability of 530.5 mAhg−1 at 5.0 Ag−1. Well controlled oxygen vacancies together with sub-micrometer scale morphology in the annealed Co3O4 electrodes are responsible for the enhanced lithium storage properties. The current oxygen vacancy modulation strategy can also be used for other energy related applications, such as sodium ion batteries and electrocatalysts, with improved performance.

Rational design of electrode architecture and utilization of distinct components are effective strategies to further enhance the performance of supercapacitors. In this work, a novel hybrid heterostructure consisting of NiCo2O4 nanorods with diameter between 10 nm and 20 nm grown on three-dimensional porous carbon (3D-OPC) is successfully fabricated via a simple direct nucleation on 3D-OPC matrix under hydrothermal conditions. The merits of highly conductive porous carbon and short ion transport channels in NiCo2O4 nanorods together with the synergistic effect between NiCo2O4 and 3D-OPC result in a higher specific capacitance of 1297 F g−1 at 0.5 A g−1 and enhanced rate capability (1253.6 Fg−1 at 5 A g−1) compared with urchin-like NiCo2O4. Moreover, an asymmetric supercapacitor device using hybrid NiCo2O4/3D-OPC and porous carbon as electrodes delivers a high energy density of 29.23 Wh kg−1 at 1.55 kW kg−1, outstanding power density (7.75 kW kg−1 at 27.38 Wh kg−1), and good cycling stability (capacitance retention of 87.6% after 3000 cycles at 1 A g−1), making it as one of the most promising candidates for electrochemical energy storage.

Design and preparation of capable anode materials is key to the development potassium-ion battery. In this study, N-doped biomorphic carbon is prepared from walnut septum by pyrolysis and then used as potassium-ion battery anode materials. The target carbon exhibits hierarchical porous structures with a specific surface area of 99.6 m2 g−1 and an interlayer spacing of 0.376 nm. When used as anode for potassium-ion battery, the N-doped hierarchical porous carbon exhibits high initial reversible capacity of 263.6 mAh g−1 at 0.1 A g−1 with an initial coulombic efficiency of 55.1%. At a high current density of 1 A g−1, it still shows ultralong cycling stability with a discharge capacity of 119.9 mAh g−1 after 1000 cycles. The excellent performance is attributed to the improved ions diffusion kinetics and electrons conductivity derived from hierarchical porous structures, large interlayer spacing, and nitrogen doping. Further calculation by cyclic voltammetry indicates that the mixed mechanisms of capacitance and ion-diffusion explain potassium-ion storage. At a low scan rate ion-diffusion behaviors provide an almost identical capacity with capacitance, and capacitive behaviors become dominant mechanisms with an increase in scan rate. The results would offer a new way to develop hard carbon anodes for potassium-ion battery.

Porous carbon nanostructures with hetero-atom doping are regarded as a promising anode candidate for rechargeable alkalis ion batteries. Herein, a novel boron-doped 3D hierarchical porous carbon network (B-CN) was prepared via a unique in situ double-template (NaCl and HBO3) method. The as-obtained B-CN with high specific surface area (480 m2 g−1), high-defect B-doping (2.74 at. %) and high volume of hierarchical pores (1.28 cm3/g) exhibits a reversible capacity as high as 200 mAh g−1 at 0.1 A g−1 after 100 cycles and superior rate capability of 189 mAh g−1 at 5 A g−1 for Na-ion batteries. It also exhibits excellent cycling performance (496 mAh g−1 after 100 cycles at 0.1 A g−1) and rate capacity (285 mAh g−1 at 5 A g−1) in Li-ion batteries. The outstanding electrochemical performance of B-CN can be attributed to the large surface area with more active sites produce by B-doping, short ions diffusion length and continuous electrons transport pathway provided by 3D hierarchical porous carbon architecture. Moreover, the surface-dominated redox reaction rendered by our tailored B-doped carbon nanostructures is a promising strategy for developing electrode materials with high rate capability. The convenient synthesis process offers a new tactic in fabricating high performance energy storage device.

The development of a highly sensitive and selective non-enzymatic electrode catalyst for the detection of a target molecule was remained a great challenge. In this regard, bimetallic nanowires (BMNWs) are considered as promising electrode material for their fascinating physical/chemical properties superior to a single system. In this article, nickel cobalt (Ni x –Co) BMNWs with tunable stoichiometry were prepared by a template assisted electrodeposition method and their catalytic performance was investigated for the detection of hydrogen peroxide (H2O2). It has been found that Ni–Co (0.5:1) BMNWs/PC electrode exhibits superior non-enzymatic sensing ability toward H2O2 detection with a high selectivity. The electrode shows fast response within ∼3 s and an excellent reproducible sensitivity of 2211.4 μAmM−1 cm−2, which is the best compared to the individual Ni, Co, Ni–Co (0.3:1) BMNWs and previously reported electrodes. In addition, the electrode shows a linear response in the wide concentration range from 0.005 mM to 9 mM, low detection limit of 0.5 μM (S/N = 3.2) and a relatively long-term storage (50 d). Moreover, the sensor reveals excellent results for H2O2 detection in the real samples. The enhanced sensitivity of the Ni–Co (0.5:1) BMNWs based electrode may be due to the stable structure and synergy of Ni and Co. The results demonstrate that the catalytic activity of the electrode binary catalyst towards H2O2 detection can be improved by adjusting the Ni/Co ratio in BMNWs. The excellent performance of the electrode suggests that Ni–Co BMNWs are promising candidate for the construction of cost-effective electrochemical sensors for medical and industrial applications.

Carbonaceous materials are used as the anode for rechargeable lithium-ion batteries (LIBs), however, lithium dendrites are easily formed during cycling due to the low lithium insertion potential (~0.1 V versus Li+/Li). As alternative anodes, transition metal oxides based on conversion mechanism have attached much attention. But the high lithiation potential (>1.0 V vs. Li+/Li) usually leads to a low output voltage and energy density when used in a full cell configuration. Herein, Zn-substituted Co3O4 submicron spheres are successfully synthesized by a facile solvothermal reaction and subsequent calcination method. When used as the anode for LIB, the optimized sample shows a specific capacity of 686 mAh g−1 at 0.8 A g−1 after 500 cycles, and a specific capacity of 692.9 mAh g−1 at a higher current density of 3.2 A g−1 in a half-cell. Thanks to the controlled Zn substitution, the discharge voltage plateau is 0.16 V lower than that of the pure Co3O4 anode at a current density of 0.4 A g−1. Further investigation of the 0.5Zn-Co3O4//LiCoO2 full cells also displays a high capacity (400.7 mAh g−1 after 200 cycles at 0.4 A g−1) and an excellent rate capability (658.1 mAh g−1 at 1.6 A g−1) compared with the Co3O4//LiCoO2 full cells. This work confirms that substituting suitable metal elements into sub-micron conversion based anodes can reduce the voltage plateau, which is of great significance for the practical applications in high performance energy storage devices.

Transition metal oxides have attracted considerable attention as possible electrode materials for lithium-ion batteries. However, poor electrical conductivity and volume change during cycling result in low rate capacity and rapid capacity fading, which hinder the practical applications of those electrodes. In this work, we report a facile approach to modify Co3O4 nanoparticles (NPs) by laser irradiation treatment. The structural and composition of the samples were studied by different techniques. The results show that the surface of the as-prepared particles transforms to a thin CoO layer, and oxygen vacancies are generated after the laser treatment. Compared to the as-prepared Co3O4 NPs, the laser treated sample shows a higher reversible capacity of 833.4 mAhg−1 after 100 cycles at a current density of 0.1 Ag-1. A capacity of 348.4 mAhg−1 can be obtained at a rate of 5 Ag-1. The unique microstructure that induced by laser irradiation in the Co3O4 NPs is responsible for the improved lithium storage properties.

A layered potassium vanadate K0.23V2O5 has been successfully prepared by the hydrothermal method and evaluated as an anode material for lithium-ion and potassium-ion batteries. High structural stability is demonstrated by the ex situ X-ray diffraction (XRD) and ex situ scanning electron microscopy (SEM). When used as an anode material for lithium-ion batteries, the K0.23V2O5 exhibits a reversible capacity of 480.4 mAh g−1 at 20 mA g−1 after 100 cycles and 439.7 mAh g−1 at 200 mA g−1 after 300 cycles as well as good cycling stability. Even at a high current density of 800 mA g−1, a high reversible capacity of 202.5 mAh g−1 can be retained, indicating excellent rate performance. Whereas in potassium-ion batteries, it retains a capacity of 121.6 mAh g−1 after 150 cycles at 20 mA g−1 and 97.6 mAh g−1 at 100 mA g−1 after 100 cycles. Such superior electrochemical performance of K0.23V2O5 can be ascribed to the special flower-like morphology and structure. Overall, the results highlight the great potential of K0.23V2O5 as an anode material for both lithium-ion and potassium-ion batteries.

Hollow urchin-like NiCo2O4 microspheres (∼3 μm) with a large specific surface area (158.57 m2 g−1) have been synthesized by a facile template-free hydrothermal method and a morphology evolution mechanism of “bundles-solid spheres-hollow urchin-like microspheres” was proposed. The hollow urchin-like structure appears when the hydrothermal time is increased to 8 h, which can be accelerated by the addition of excess urea. Benefiting from the unique three-dimensional (3D) hollow structure and the desired composition, the NiCo2O4 microspheres exhibit an excellent reversible specific capacity for lithium ion batteries (991 mA h g−1 after 50 cycles) and sodium ion batteries (322.3 mA h g−1 after 50 cycles). The unique 3D hollow structure offers enough space to alleviate volume expansion caused by the Li+/Na+ insertion/extraction, and the perfect electrical conductivity of spinel binary metal oxides facilitates the transport of ions and electrons. A high capacitance contribution of 90% was achieved for LIBs at 0.3 mV s−1, while the capacitance contributions for SIBs were only 36% at 0.3 mV s−1 and 73% even at 5 mV s−1, which indicates that a capacitive-controlled charge storage mechanism plays a dominant role in the Li+ storage of NiCo2O4 microspheres. This work has guiding significance in the preparation of electrode materials with high electrochemical performance.

By using the intrinsic polymorphism nature of Nb2O5 material, we employ three typical Nb2O5 phases (orthorhombic (T), tetragonal (M) and monoclinic (H) phases) in a single material, and optimize the phase composition to form nanodomains, which are achieved by carefully adjusting the calcination parameters. The resulting sponge-like Nb2O5 nanoplate anodes exhibit attractive rate performance and cycle stability. Specifically, the optimized electrode shows a reversible capacity of 321 mAh g−1 at 1 C (1 C = 200 mA g−1) after 200 cycles. At a high current density of 10 C, the electrode delivers a reversible capacity of 152 mAh g−1. Long term durability tests show that the electrode performs an excellent cycling performance at a current density of 5 C over 1000 cycles with a capacity loss of 0.06 mAh g−1 per cycle. The excellent lithium storage properties are due to the unique multiple phases and nanoscale interface inside the electrode, which facilitate the storing of more ions and the rapid ion transportation during the charging/discharging process. The proposed electrode design strategy provides an alternative route to develop advanced electrodes for energy storage.

Hierarchical Fe 3 O 4 architectures assembled with porous nanoplates ( p -Fe 3 O 4 ) were synthesized. Due to the strong shape anisotropy of the nanoplates, the p -Fe 3 O 4 exhibits increased microwave resonance towards high frequency range. The improved microwave absorption properties of the p -Fe 3 O 4 , including dielectric loss and magnetic loss, are attributed to the enhanced electric polarization and interfacial polarization induced by oxygen vacancies and high surface area.

Highly mesoporous cobalt oxide nanosheets are grown on nickel foam (M-Co3O4/NF) by a hydrothermal method. Ag nanoparticles with 10–50 nm diameters are uniformly distributed on the surface of the mesoporous Co3O4 nanosheets (Ag/M-Co3O4/NF) after chemical bath reaction. Moreover, we discovered that the homogeneous distribution of Ag nanoparticles on free-standing, highly mesoporous Co3O4 nanosheets showed the synergistic effect of the high electrocatalyst reactions toward the ORR from Ag and OER from M-Co3O4. Highly mesoporous Co3O4 nanosheets with a thickness of 10 nm as free-standing cathode for Li-O2 battery are beneficial to accommodating insoluble discharge products and facilitating oxygen diffusion and electrolyte impregnation. Ag nanoparticles can improve the electrical conductivity of the O2 electrode and provide a catalytic activity for ORR at the same time. The Ag/M-Co3O4/NF exhibited a robust catalytic activity as cathode for Li-O2 batteries with a high reversible capacity of 2471.1 mA h g−1, a low discharge/charge overpotential, and a cycle life of 124 cycles (under the curtaining capacity of 500 mA h g−1). The preliminary results indicate that Ag/M-Co3O4/NF is an efficient and stable bifunctional cathode for Li-O2 batteries.

Exploring high-activity and durable 3d transition metal electrocatalyst for oxygen evolution reaction (OER) is one of the key issues in the water splitting reaction. Herein, a series of copper-based alloy (CuM, M = Fe, Co, Ni; FeCo, FeNi, CoNi; FeCoNi) nanoparticles have been synthesized by a rapid microwave-assisted solution phase method. Electrochemical measurements show that the catalysts possess outstanding OER activity as well as excellent long-term durability in alkaline electrolyte. The optimized samples of FeCoCu and FeCoNiCu exhibit superior activity with low overpotentials (265 and 269 mV at 10 mA cm-2), small Tafel slopes (49 and 48.9 mV dec-1), and low loss of activity after a 24 h stability test, which are much better than that of commercial RuO2. The significant OER activity and stability are mainly attributed to the synergistic effect of multiple metal elements. The alloying strategy promotes the combination of the highly active iron, cobalt and nickel elements with the excellent conductive copper element, which not only changes the electronic structure of the material surface, but also accelerates the electron transfer and provides more active sites, thereby improving the electrocatalytic performance of the material. This work demonstrates an efficient and rapid method to prepare low cost electrocatalysts, which is important for the applications in energy conversion devices.

Excessive carbon dioxide (CO2) emissions cause serious harm to nature and humans, and electrochemical CO2 reduction reaction (ECO2RR) is a potential method to solve the current crisis. Due to the high selectivity for multicarbon (C2+) oxygenate and hydrocarbons, copper-based catalysts have attracted extensive attention and research. In this review, we summarize in detail the design strategies of copper-based catalysts to improve the performance of ECO2RR, including structure, defect, compounds-derived catalysts, bimetallic construction, and heterogeneous engineering. The correlation between the formation mechanism of the C–C bond and the structural characteristics of the catalyst is discussed in detail. Finally, the main challenges of reducing CO2 to C2+ products such as low selectivity, low activity, and low stability are discussed. According to current literature, this review also provides distinctive insights and some potential strategies for the design and performance optimization of copper-based catalysts.

Olivine structure LiMnPO 4 /C cathode is synthesized by a hydrothermal method with high specific surface area Li 3 PO 4 precursor in PEG400-H 2 O mixed solution system. The synthetic conditions are systematically optimized and statistical analysis using orthogonal experiments. The physical and electrochemical properties of Li 3 PO 4 and LiMnPO 4 /C samples prepared under the optimized conditions are investigated in detail. The XRD and SEM results show that Li 3 PO 4 powders are pure phase with uniformly hollow spherical morphology. The Nitrogen adsorption-desorption isotherm exhibits the specific surface area of Li 3 PO 4 powders are 79.19 m 2 /g. LiMnPO 4 reveals a well ordered olivine structure and possess small and unagglomerated particles, which generates from the Li 3 PO 4 precursor structure. The electrochemical measurements show that pure LiMnPO 4 /C sample prepared under the optimal conditions delivers a maximum discharge capacity of 121.3 mAh/g at a 0.1 C rate. After 100 cycles, the discharge capacity decreases to 115.1 mAh/g with the capacity retention of 94.89%.

LiMn 23/24 Mg 1/24 PO 4 ·LiAlO 2 /C is synthesized by a co-hydrothermal method in water/PEG system using Li 2 CO 3 , AAO and Mn 1-x Mg x PO 4 as raw material. The electronic structure and micromorphology of multi-component compound LiMn 1-x Mg x PO 4 /C (x = 0, 1/24, 1/12, 1/6) and nano-hybrid LiMn 23/24 Mg 1/24 PO 4 ·LiAlO 2 /C cathode materials are studied by first-principles calculation and experimental research including XRD, SEM, TEM. The calculated band gap of LiMn 23/24 Mg 1/24 PO 4 /C is 2.296 eV, which is lower than other percentages Mg 2+ doping samples. Electrochemical tests exhibit LiMn 23/24 Mg 1/24 PO 4 /C has better cycling performance and rate capability than other contents Mg 2+ doping samples with the discharge capacity of 143.5 mAh/g, 141.5 mAh/g, 139.2 mAh/g and 136.3 mAh/g at 0.05C, 0.1C, 0.5C and 1C in order. After compositing and preparation of LiMn 23/24 Mg 1/24 PO 4 ·LiAlO 2 /C composite material by co-hydrothermal route, the initial discharge capacity reaches up to 151.8 mAh/g, which suggests that co-modified with Mg 2+ doping and LiAlO 2 compositing material can improve the electronic conductivity of LiMnPO 4 /C by facilitating the lithium ion diffusion rate in the interior of the materials.

Polyaniline (PANI) coated Fe3O4 hollow nanospheres (h-Fe3O4@PANI) have been successfully synthesized and investigated as anode materials for lithium ion batteries (LIBs). The structure and composition analyses have been performed by employing X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results show a good combination between h-Fe3O4 and PANI with a conductive state. When evaluated as anode materials for LIBs, the h-Fe3O4@PANI nanocomposites exhibit excellent LIB performance with enhanced reversible capacity, good cycling performance and rate capability as compared to h-Fe3O4 and solid Fe3O4 (s-Fe3O4) nanospheres. The improved electrochemical performance of the nanocomposite is considered due to the hollow nature of the products and the coated PANI layers.

The structural damage induced by huge volume change during lithiation/delithiation results in poor cycle stability of tin-based anode materials, which becomes the major obstacle to their practical application. In this work, we fabricated three-dimensional (3D) porous bowl-shaped carbon cages interspersed with carbon coated Ni–Sn alloy nanoparticles (Ni3Sn2 and Ni3Sn4; 10–30 nm) by a freeze-drying method with self-assembled NaCl as a template followed by annealing. Both Ni3Sn2/C and Ni3Sn4/C exhibit excellent electrochemical performance as anode materials for lithium-ion batteries. In particular, the Ni3Sn4/C nanocomposites exhibit superior rate capability (735, 661, 622, 577, 496, and 377 mA h g−1 at 0.1, 0.2, 0.5, 1, 2, and 5 A g−1, respectively) and excellent cycling stability (568 mA h g−1 at 0.5 A g−1 for the second cycle and gradually increased to 732 mA h g−1 after 200 cycles). The superior electrochemical performance is attributed to the synergetic effect of Ni–Sn alloy nanoparticles and 3D porous bowl-shaped carbon networks. The uniformly embedded Ni–Sn alloy nanoparticles can effectively alleviate the absolute stress/strain and shorten the Li+ diffusion path, and Ni in the Ni–Sn alloy acts as a buffer to suppress the volume expansion. Moreover, the 3D bowl-shaped carbon networks with high conductivity can provide abundant space for volume expansion, suppress the agglomeration of Ni–Sn nanoparticles, ensure the structural integrity, and facilitate lithium-ion diffusion as well as electron transportation.

•The compressive mechanical properties are improved by carbon micro-alloying.•Microstructure of the alloy is modified by carbon addition.•Solidification behavior is changed by carbon addition.

Co3O4 materials have been widely studied as lithium-ion batteries (LIBs) anode due to the high theoretical specific capacity. However, the poor inherent conductivity and large volume change are the main limitations. To address these issues, we propose a mild liquid-phase reduction strategy by using hydrazine hydrate to modify the Co3O4 porous nanosheet electrodes. Through controlling the hydrazine hydrate volume, the generation of oxygen vacancies in the Co3O4 electrodes can be adjusted. When tested as the anodes for LIB, the optimized electrode delivers a reversible capacity of 1036.7 mAh g−1 after 55 cycles at a current density of 0.5 A g−1, and a specific capacity of 434.6 mAh g−1 at a higher current density of 2 A g−1. The improved electrochemical performance is attributed to the porous structure of the nanosheet and the presence of oxygen vacancies.

Transition metal oxide (TMO) anodes show promising applications in energy storage due to the unique physical and chemical properties and high theoretical capacity to storage ions. Their practical usages are restricted by low intrinsic electronic conductivity, sluggish ionic diffusion, and large volume change during continuous cycling. In this work, we propose a strategy of selective solution-phase reduction on specific crystalline planes to generate the defect chemistry and thus improve the intrinsic electronic conductivity. Taking Co3O4 electrode as a typical example, we prepared the structures with different exposed planes, which were then subjected to solution-phase reduction at room temperature. When used as the electrodes for lithium ion batteries, the optimized material possesses a high reversible capacity of 873.5 mAh g−1 at a current of 0.1 A g−1, even at a large current density of 5 A g−1, a remarkable discharge capacity of 569.1 mA h g−1 can still be achieved. The improved performance is attributed to the synergistic effects of the optimized amount of Co2+ species and oxygen vacancies. The current strategy can be extended to other TMO electrodes, paving an alternative way to optimize the electrochemical performance for different applications.

Hollow Fe3O4 microspheres assembled with nanoparticles were successfully synthesized without the addition of any templates or subsequent treatments. When used as the anode materials for lithium-ion battery (LIB), the products showed good lithium storage properties, demonstrating their promising applications for advanced LIB.

Ultrafine-grained (UFG) pure Al with uniform and stable microstructure produced by friction stir processing (FSP) significantly increased the high-cycle fatigue (HCF) strength compared with coarse-grained and other UFG materials prepared by severe plastic deformation (SPD). There was no obvious surface damage for FSP-UFG pure Al and the improved fatigue damage resistance can be attributed to the uniform microstructure and high microstructural stability. The ring-island stress distribution of FSP-UFG impeded the formation of large-scale shear bands, and enhanced the coordinated deformation during cyclic deformation. In addition to the enhanced tensile strength, increasing the fatigue strength exponent, which is decided by the microstructural stability, is also an effective method of improving the fatigue strength.

We report a facile method to synthesise and modify porous Co3O4 nanosheets. The nanosheets are prepared by hydrothermal reaction and calcination, then reduced with an H2/Ar mixed gas at 250 °C within 1 min. The modification treatment generates oxygen vacancies and Co3O4/CoO interface structure. Electrochemical measurements show that the nanosheets (Co3O4-30) reduced for 30 s have excellent electrochemical performance. After the Co3O4-30 electrode was cycled 200 times under 0.5 Ag-1, the reversible capacity was 892 mAh g−1. A reversible capacity of 250 mAh g−1 can be achieved even at a higher current density of 5.0 Ag-1. The good lithium storage performance is attributed to oxygen vacancies and appropriate Co3O4/CoO interface structure. This study provides a facile strategy to construct improved transition metal oxide electrodes for energy storage and conversion.

NiO porous nanosheets were synthesized by a facile hydrothermal reaction and subsequent calcination in air. Oxygen vacancies were generated by reducing treatment under H2/Ar atmosphere at an elevated temperature. The phase composition, morphology, microstructure and chemical composition of the samples were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). When used as the anode materials for lithium ion batteries, the optimized NiO electrode possessed a reversible capacity of 678.8 mAh g−1 after 30 cycles at a current density of 0.1 A g−1, while the reversible capacity of the untreated electrode was only 82.5 mAh g−1. At a higher current density of 1.0 A g−1, the reversible capacity was 152.2 mAh g−1, which is 15 times larger than that of the pristine NiO electrode. The synergistic effects of optimized oxygen vacancies and porous sheet-like morphology are responsible for the enhanced lithium storage properties.

A hybrid composed of sulfur self-doped 3D hierarchical porous carbon (S-3DHPC) with a high defect density area and a high specific surface is prepared through direct carbonization of coal and activators without any additional template. The synthesized S-3DHPC is directly used as an electrode for supercapacitors and potassium ion batteries. The large surface area of the three-dimensional carbon network allowed full contact of the electrolyte with the electrode interface, and the transport path of the electrolyte ions and K+ is shorter. In addition, S-type doping in hierarchical porous carbon improves the electronic conductivity and provides superior electrochemical performance. The S-3DHPC electrode with 431.7 F g−1 at 1 A g−1 in a 3 M KOH electrolyte demonstrates an adequate rate performance and cycle stability. In particular, the assembled S-3DHPC-based flexible symmetric supercapacitor exhibits a high energy density of 17.8 Wh kg−1 at a power density of 652 W kg−1. Furthermore, S-3DHPC as the anode for K-ion batteries exhibits a high reversible capacity of 212.9 mAh g−1 at 50 mA g−1, an excellent rate capability, and outstanding cycling performance. Therefore, S-3DHPC has broad application prospects as a high-performance energy storage electrode material.

Traditionary oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) electrocatalysts are mainly precious metal materials, but their expensive cost and low amount of storing limit their applications in Li–O2 batteries. Here is a simple way to report that we synthesis cobalt nanoparticle in-situ encapsulated into N-doped carbon polyhedral (Co@NC) by pyrolyzing ZIF-67 and we find that 900 °C is the optimal temperature for pyrolysis. The Co@NC and Co@NC-900/acetylene black (AB) is used as a bifunctional electrocatalysts and an oxygen electrode in Li–O2 batteries respectively. The Co@NC-900/AB can be the promising non-noble-metal-based oxygen electrode in Li–O2 batteries.

In this study, biomorphic hard carbon is prepared from corn husk using the one-step carbonization method and used as a potassium-ion battery anode material. The biocarbon anode with extremely small specific surface area (3.4 m2 g−1) demonstrates better electrochemical performance than those with large specific surface areas. Particularly, at a current density of 0.1 A g−1, the carbon electrode delivers first discharge and charge capacities of 396.2 and 231.0 mAh g−1, respectively. After 100 cycles, the reversible capacity retention rate is 89.1%. Moreover, at a high current density of 1 A g−1, the reversible capacity reaches approximately 135.3 mAh g−1 after 500 cycles. This excellent performance is attributed to the enhancement of ion diffusion kinetics because of the hierarchically porous structures, effect of nitrogen and oxygen heteroatoms and rational interlayer spacing of biocarbon materials. In comparison, activated biocarbon exhibits lower reversible capacity, ascribed to the formation of more solid electrolyte interphase and destruction of hierarchical structures via KOH activation. Cyclic voltammetry calculation indicates that both capacitance and diffusion are responsible for the excellent K ion storage.

A novel nanocomposite of ultrafine SnO2 nanoparticles encapsulated in 3D porous carbon is prepared by freeze-drying followed with sintering and dealloying strategy. The SnO2 nanoparticles are obtained by selective etching of Cu from Cu6Sn5 nanoparticles. The ultrafine oxide nanoparticles together with 3D porous carbon network are highly effective in accommodating the huge volume change of SnO2 during potassiation and depotassiation processes. As a result, the obtained sample presents excellent potassium-ion storage performance including high reversible capacity (270.3 mAh g−1 at 100 mA g−1 after 200 cycles and capacity retention close to 80%), ultralong cycle lifespan and excellent rate performance (144.6 mAh g−1 at 2 A g−1).