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The interlayer spacing of V6O13 was adjusted by polyaniline intercalation for the first time to accelerate Mg2+ transport kinetics.

A novel I2-containing viologen-based COF was designed through introducing viologen units and I2, along with significantly improved capacity as well as electrode kinetics.

Rational electrode structure design is of great significance for realizing superior Na+ storage performance. Herein, a metal salt-induced polymer blowing-bubble approach followed by selenization procedure is developed to in-situ generate abundant sub-10 nm CoSe2 nanocrystals on 3D Se/N co-doped carbon networks (CoSe2@3DSNC). The phase transition from Co to CoSe2 and the incorporation of Se into the carbon layer are realized simultaneously to establish above configuration, in which the CoSe2 nanocrystals are anchored on interlayer expanded carbon networks. Such unique configuration endows electrode with lower Na+ diffusion energy barrier, higher Na+ storage capability and better structural durability. Reflected in SIBs, the optimized CoSe2@3DSNC delivers superior rate capability (310 mAh g−1 at 10 A g−1) and excellent long-term cycling stability (409 mAh g−1 after 1200 cycles at 5 A g−1). Moreover, this configuration can also be obtained in other metal selenides-carbon composite through a similar approach.

High-capacity Co2VO4 has become a potential anode material for lithium-ion batteries (LIBs), benefiting from its lower output voltage during cycling than other cobalt vanadates. However, the application of this new conversion-type electrode is still hampered by its inherent large volume variation and poor kinetics. Here, a 2D–2D heterostructure building strategy has been developed to enhance the electrode performance of Co2VO4 through construction of Co/Co2VO4 nanocomposites converted from the in situ phase separation of Co2V2O7·3.3H2O nanosheets. Co/Co2VO4 based on face-to-face contact exhibits the optimized stacking configuration, where Co nanocrystals give gaps of several nanometers between stacked Co2VO4 nanosheets, enabling full contact with the electrolyte, a shorter transport path of lithium ions and more reactive sites. With this design, Co/Co2VO4 anodes deliver outstanding reversible capacity (750 mA h g−1 at 1 A g−1) with ultrahigh capacity retention rate, and excellent cycle stability at high rate (520 mA h g−1 at 5 A g−1 retained after 400 cycles). An “active center's charge transfer—capacity compensation” model was proposed based on capacity analysis, XPS depth analysis and HRTEM observation to uncover the fundamental reason of the excellent cycle performance. This in situ 2D–2D heterostructure constructing strategy may open up the possibility for designing high-performance LIBs.

Lithium-ion batteries (LIBs) are widely regarded as a promising electrochemical energy storage device, due to their high energy density and good cycling stability. To date, the development of anode materials for LIBs is still confronted with many serious problems, and much effort is required for constructing more ideal anode materials. Herein, starting with metal–organic frameworks (MOFs), an amorphous VOx coated Fe3O4/C hierarchical nanospindle has been successfully synthesized. The obtained Fe3O4/C@VOx nanospindle has a uniform particle size of ∼100 nm in diameter and ∼400 nm in length and consists of ultrafine Fe3O4 nanoparticles (∼5 nm) embedded in a porous carbon matrix as the core and an amorphous VOx layer as the shell. Notably, as the anode material for LIBs, Fe3O4/C@VOx delivers a high coulombic efficiency (74.2%) and a large capacity of 845 mA h g−1 after 500 cycles at 1000 mA g−1. A prominent discharge reversible capacity of 340 mA h g−1 is also still retained at 5000 mA g−1. More importantly, the presented facile MOF-derived route could be easily extended to other functional materials for widespread applications.

Co3O4 is a promising anode candidate for Li-ion and Na-ion batteries (LIBs and SIBs) owing to its intrinsic merits. Nevertheless, drastic volume expansion upon charge/discharge causes fast capacity decay, which hugely hinders its commercial application. Introducing carbon materials as a coating layer is considered to be an effective strategy to improve the structural stability. However, the coating layer may be fractured upon repeated insertion/extraction due to the lack of void space. Therefore, constructing void space is crucial for achieving prolonged cycling stability. Herein, we design a successive coating-eching strategy to fabricate Cu-doped Co3O4@N-doped Carbon with interior void space (Cu-Co3O4@Void@NC). The void space allows the inner active material to expand freely without breaking the outer protective layer. Simultaneously, the unbroken NC layer is conductive to the formation of a stable SEI film. In addition, Cu-doping can enhance the inherent electrical conductivity of Co3O4, which is proved by the density functional theory (DFT) calculations. When evaluated as LIBs and SIBs anode, Cu-Co3O4@Void@NC delivers superior electrochemical performance (562 mAh g−1 after 1000 cycles at 5 A g−1 in LIBs and 312 mAh g−1 after 300 cycles at 2 A g−1 in SIBs).

High-capacity Co

Constructing heterojunctions holds huge potential for tuning material properties owing to the built-in charge transfer driving force, which is beneficial for the migration behavior of Li-ions. While both the electrochemistry and heterojunctions of alloying-type anodes have been studied, the role of heterojunctions in improving the Li-ion storage performance of conversion-type anodes is unclear. In this work, porous Co3O4/TiO2 nanosheets (P-Co3O4/TiO2 NSs) were fabricated to successfully construct a p–n junction by coating n-type TiO2 on p-type Co3O4 NSs. The formation of the built-in electric field in the p–n junction significantly facilitates the charge transfer kinetics and the amorphous TiO2 layer accommodates the volume change of the Co3O4 NSs, manifesting the superiority of applying the p–n junction in a conversion-type anode for the first time. When evaluated as lithium-ion battery (LIB) anodes, the P-Co3O4/TiO2 NSs deliver high specific capacity, long-term cycling stability and remarkable rate capability (801 mA h g−1 after 1600 cycles at a current density of 2 A g−1).

Lithium-ion batteries (LIBs) are widely regarded as a promising electrochemical energy storage device, due to their high energy density and good cycling stability. To date, the development of anode materials for LIBs is still confronted with many serious problems, and much effort is required for constructing more ideal anode materials. Herein, starting with metal-organic frameworks (MOFs), an amorphous VO

Cobalt selenide (CoSe2), a promising anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), still encounters the undesirable rate capability and cycling stability. Interface engineering offers a useful strategy to boost the electrochemical performance of electrode materials. Herein, an interface engineered material based on CoSe2/ZnSe nanoparticles confined in the hierarchical branched architecture constructed by N-doped carbon-nanotube-grafted nanorods (CoSe2/ZnSe@NC-NT/NRs) is developed, which delivers extraordinary Li+/Na+ storage capability as reflected in LIBs and SIBs. Large energy band gap difference between CoSe2 and ZnSe builds a strong built-in electric field at as-engineered interfaces. The emergence of built-in electric field can reduce the migration barriers of Li+/Na+ at the interfaces to facilitate the charge transfer behavior and improve the reaction kinetics in bulk phase. Additionally, carbon framework with hierarchical branched architecture can furnish numerous pathways for ions transport and alleviate the structural collapse. The present work could guide the future designing of electrode materials by rational interface engineering for high-performance anode of alkali-ion batteries.

To achieve high-efficiency lithium ion batteries (LIBs), an effective active electrode material is vital. For the first time, mesoporous single crystals cobalt-doped Fe2O3 (MSCs Co-Fe2O3) is synthesized using formamide as a pore forming agent, through a solvothermal process followed by calcination. Compared with mesoporous single crystals Fe2O3 (MSCs Fe2O3) and cobalt-doped Fe2O3 (Co-Fe2O3), MSCs Co-Fe2O3 exhibits a significantly improved electrochemical performance with high reversible capacity, excellent rate capability, and cycling life as anode materials for LIBs. The superior performance of MSCs Co-Fe2O3 can be ascribed to the combined structure characteristics, including Co-doping and mesoporous single-crystals structure, which endow Fe2O3 with rapid Li+ diffusion rate and tolerance for volume change.

To achieve high-efficiency lithium ion batteries (LIBs), an effective active electrode material is vital. For the first time, mesoporous single crystals cobalt-doped Fe