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Cobalt‐glycolate (Co‐glycolate) is a kind of layered coordination polymer with abundant electrochemically active sites but low conductivity. The fabrication of heterostructures is a novel strategy to enhance the electrical conductivity. Herein, Co‐glycolate serves as a host substrate for the in situ growth of guest ZIF‐67 to build MOFs‐on‐CPs heterostructures (named Co‐glycolate /ZIF‐67) via a simple ligand‐exchange method as an anode for lithium‐ion batteries. A heterojunction interface with distorted lattice between the Co‐glycolate phase and the ZIF‐67 phase can be observed. Theoretical calculations and experimental results simultaneously prove that the formed heterojunction reduces the band gap and enhances the conductivity. Compared with both single components, optimized Co‐glycolate/ZIF‐67 shows a higher capacity and better cycling and rate performances due to the improved charge‐transfer rate of the heterostructure. Its specific capacity remains at 652 mAh g−1 after 800 cycles at 1 A g−1. These excellent electrochemical properties can be due to the smaller size, rough surface, and strong combination of a unique heterostructure as well as to the greatly reduced band gap of the individual components. A lithium‐storage mechanism for Co‐glycolate/ZIF‐67 was proposed. This work provides a new strategy for building MOFs‐on‐CPs heterostructures to improve the electrochemical performance of metal‐glycolate‐based electrode materials for energy‐storage and conversion systems. [ABSTRACT FROM AUTHOR]

Constructing heterogeneous components with a yolk−shell structure is highly desirable for improving the lithium-storage performance of metal oxides, owing to the unique synergies of nanostructures and composite materials. In this work, a novel heterogeneous hybrid of yolk−shell CuO@CuFe2O4 was synthesized through a simple two-step method. Starting with Cu2O, the yolk−shell precursor was prepared through an interfacial reaction. After subsequent heat treatment of the precursor in air, yolk−shell CuO@CuFe2O4 was obtained. A reasonable mechanism for the formation process of the yolk−shell CuO@CuFe2O4 has been presented. The relatively high electrical conductivity of CuFe2O4, unique yolk−shell structure, and firm shell of the CuO@CuFe2O4 account for the extremely enhanced electrochemical properties compared to bare CuO. In particular, discharge capacities of 505 and 36 mA h g−1 were delivered after 200 cycles at 500 mA g−1 by the yolk−shell CuO@CuFe2O4 and bare CuO, respectively. This work not only provides a promising alternative anode material for lithium-ion batteries, but also develops a new strategy to design the nanostructure and components of metal oxides for application in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

A dual-doping strategy was applied to fabricate the novel electrode materials. For the first time, the spinel hybrids of nanosized Ni x Co 1−x Fe 2 O 4 with N-doped graphene (N x -NG) were synthesized by a hydrothermal co-precipitation method. The size of Ni x Co 1−x Fe 2 O 4 (N x) nanoparticles on N-doped graphene can be tuned with the regulation of Ni/Co content. Among these nanocomposites, the Ni 0.4 Co 0.6 Fe 2 O 4 nanoparticles with the smallest average size of 10 nm are uniformly anchored on the N-doped graphene. The electrochemical characterizations display that the N 0.4 -NG exhibits the best electrochemical lithium storage performance compared to other five nanocomposites. It delivers a high capacity of 1367.0 mA h g−1 at the first discharge process，and the reversible capacity retention of 87% (2nd to 50th) at 0.1 A g−1. The excellent electrochemical performance of N 0.4 -NG can be owing to the small size of nanoparticles and its well-combination with N-doped graphene, which provide the large surface area and promote the ion/electron transfer rate. The synergistic effect resulted from the strong interaction between N 0.4 and N-doped graphene is contributed to the enhanced electrochemical performance of N 0.4 -NG. This study not only extends graphene-based electrode materials for lithium ion battery, but also promotes the development of energy resources. Unlabelled Image • A spinel hybrid of nanosized Ni x Co 1-x Fe 2 O 4 with N-doped graphene was fabricated. • Size of Ni x Co 1−x Fe 2 O 4 nanoparticles was tuned with the regulation of Ni/Co content. • A reversible capacity of 785.2 mA h g−1 of N 0.4 -NG after 50 cycles was obtained. [ABSTRACT FROM AUTHOR]

Abstract Despite many efforts devoted to explore novel electrode materials for lithium ion hybrid supercapacitors, the obtainable long-life cycling of existing anode materials are still inadequate for promising applications. This report demonstrates a new nanocomposite with TiNb 2 O 7 network nanostructure in situ anchored onto the holey graphene, which is designed as anode material for lithium ion hybrid supercapacitors. Impressively, electrochemical analyses show that the good rate performance (capacity retention of 73.5% from 0.05 to 5 A g−1) and long cycle life up to 1000 cycles at 1 A g−1 (a capacity retention of 91.5%) are attained. Furthermore, the lithium ion hybrid supercapacitor device consisting of this nanocomposite and activated carbon exhibits excellent cycling stability (90.2% of initial capacity after 3000 cycles), high energy density of 86.3 W h kg−1 (at 237.7 W kg−1) and high power density of 3.88 kW kg−1 (at 28.7 W h kg−1). This study ascribes the unprecedented performance to the high conductive holey graphene with abundant mesopores, the uniformly distributed TiNb 2 O 7 network nanostructure and the synergetic effect between them. Based on these findings, the presented nanocomposite has great potential in high performance lithium ion hybrid supercapacitors. Graphical abstract Image 1 Highlights • A novel composite of TiNb 2 O 7 network nanostructure and holey graphene was fabricated. • The long-term life with 91.5% capacity retention after 1000 cycles was obtained. • The Li-HSC device exhibits high energy density and excellent cycling stability. [ABSTRACT FROM AUTHOR]

Tin-based metal oxides usually suffer from severe capacity fading resulting from aggregation and considerable volume variation during the charge/discharge process in lithium ion batteries. In this work, a novel nanocomposite (MTO/N-RGO) of hollow amorphous MnSnO 3 (MTO) nanoparticles and nitrogen-doped reduced graphene oxide (N-RGO) has been designed and synthesized by a two-step method. Firstly, the nitrogen-doped graphene nanocomposite (MTO/N-RGO-P) with MnSn(OH) 6 crystal nanoparticles was synthesized by a facile solvothermal method. Subsequently, the MTO/N-RGO nanocomposite was obtained through the post heat treatment of MTO/N-RGO-P. The designed heterostructure and well-combination of the hollow amorphous MTO and N-RGO matrix can accelerate the ionic and electronic transport, and simultaneously accommodate the aggregation and volume variation of MTO nanoparticles during the lithiation–delithiation cycles. The as-prepared hybrid of MTO and N-RGO (MTO/N-RGO) exhibits a high reversible capacity of 707 mAh g −1 after 110 cycles at 200 mA g −1 , superior rate capability, and long-term cyclic life with high capacity of 610 mAh g −1 over 1000 cycles at 400 mA g −1 . Superior capacity retention of 97.3% over 1000 cycles was obtained. This work opens new opportunities to fabricate the high-performance electrode materials with heterostructure for lithium storage systems, especially for novel multi-metal oxide based nanocomposites with high cycling stability. [ABSTRACT FROM AUTHOR]

SnO 2 /NiFe 2 O 4 /Graphene (SNG) nanocomposites have been fabricated by a one-step hydrothermal synthesis method for Lithium ion batteries. Due to the synergetic effect between graphene, NiFe 2 O 4 and SnO 2 nanoparticle, the nanocomposites show good electrochemical performance. It is found that the electrochemical performance was enhanced with increasing content of SnO 2. Typically, the nanocomposite with 50 wt% SnO 2 exhibits a high reversible capacity of 731.5 mA h/g at a current density of 200 mA/g after 50 cycles, which can remain 80.9% of the first cycle. The material also exhibits a relatively high discharge capacity of 613 mA h/g at 800 mA/g after 100 cycles. These improved electrochemical performances are attributed to the capacity of NiFe 2 O 4 /SnO 2 and the SnO 2 buffer layers impede the pulverization of electrode material during lithium insertion/extraction. Furthermore, graphene sheet can enhance electrical conductivity and accommodate the volume change in some extent, which can keep the structure integrate, and then improving the cycling stability and rate capability. SnO 2 /NiFe 2 O 4 /Graphene (SNG) nanocomposites are fabricated by one-step hydrothermal method and the materials are utilized as anode material for high-performance Lithium ion batteries. Image 1 • One step hydrothermal synthesis of SnO 2 /NiFe 2 O 4 /Graphene for Lithium ion batteries. • NiFe 2 O 4 /SnO 2 contributes to the high capacity of SnO 2 /NiFe 2 O 4 /Graphene. • SnO 2 has cushioning effect on the insertion and release of lithium ions. • Graphene provides high surface to slow down the volume change. [ABSTRACT FROM AUTHOR]

• Hierarchical layered Fe 3 O 4 QDs@C/rGO array derived from MIL-100(Fe)/GO. • Graphene and mesoporous carbon act as conductive support for anchoring Fe 3 O 4 QDs. • Multi-porous channels increase interface contacts and facilitate ion transportation. • Synergetic effect in Fe 3 O 4 QDs@C/rGO array results in the enhanced LIB performance. Herein, a double-buffering strategy is presented to boost the lithium storage potential of Fe 3 O 4. Firstly, the skeleton of MIL-100 (Fe) MOF is grown on graphene oxide, as a self-assembled template via in-situ solvothermal approach, which transform into ultrafine, well-dispersed and mesoporous carbon coated Fe 3 O 4 QDs (4 nm) imbedded on reduced graphene oxide (Fe 3 O 4 QDs@C/rGO), by pyrolysis. Each component in such a well-designed porous hierarchical structure significantly contributes to the remarkable enhancement of lithium ion storage performance, leading to high reversible capability with excellent prolonged cyclic stability after 2000 cycles (505 mAh g−1 at 2.0 A g−1). Both, Graphene sheets and mesoporous carbon act as conductive support for anchoring uniform Fe 3 O 4 QDs with confined double buffering for cyclic volume flux. Multi-channels with uniform mesopores in the self-assembled array and 4 nm QDs of Fe 3 O 4 confined in conductive carbon shells were favorable to enhance the interfacial electron/ion transfer, leading to the excellent rate and cycling performance with released volume changes upon Li+ insertion/extraction. The present research work provides a promising outset design and synthesis strategies for metal oxide QDs based nanocomposites, which may also be extended to the other electrode material system. [ABSTRACT FROM AUTHOR]