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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]

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]

• 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]