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Abstract Transition metal oxides have received considerable attention as promising electrode materials for the next generation high performance lithium-ion batteries and supercapacitors. However, transition metal oxides electrodes usually suffer from severe volume expansion and poor electrical conductivity, leading to fast capacity fading and low rate capability, which limit their commercialization in energy storage devices. Herein, we develop a bifunctional ZnO NiO microsphere electrode with yolk-shelled structure for lithium-ion batteries and supercapacitors by annealing tetracyanide-metallic-frameworks precursor of Zn[Ni(CN) 4 ]. Benefiting from its unique structure and composition, the yolk-shelled ZnO NiO microspheres as anode for lithium-ion batteries exhibits a high lithium storage capacity (978 mAh g−1 at 0.25 C) and superior rate performance (628 mAh g−1 at 2.5 C after 300 cycles). While for supercapacitors electrode, it delivers a high specific capacitance of 1350 F g−1 at a current density of 3.0 A g−1 and an excellent cycling stability with a capacity retention of 92.8% over 6000 cycles. The excellent electrochemical performance is ascribed to the synergistic effect between ZnO and NiO, and the yolk-shelled structure, which can provide rich active sites for electrochemical reaction, and effectively alleviate the volume expansion and structural pulverization of the electrode during charge-discharge cycling. Graphical abstract Image 1 Highlights • Yolk-shelled ZnO NiO bifunctional electrode was prepared by Zn[Ni(CN) 4 ] precursor. • It shows enhanced cycle performances with 628 mAh g−1 at 2.5 C after 300 cycles. • It exhibits high specific capacitance and an ultralong cycling lifetime for SCs. • The excellent performance is due to the unique structure and synergistic effect. [ABSTRACT FROM AUTHOR]

Hierarchical porous microflowers composed of porous Fe 2 O 3 /NiO nanoplates were synthesized via a facile cyanometallic framework-templated strategy. The synthesized Fe 2 O 3 /NiO microflowers were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and Brunauer Emmet Teller adsorption-desorption analysis. As anode materials for lithium ion batteries, the Fe 2 O 3 /NiO microflowers exhibit excellent electrochemical performance in terms of great lithium storage capacity (1652.6 mAh g −1 at 100 mA g −1 ) and good cycling stability (1210.4 mAh g −1 capacity retention at 50th cycle). This result can be attributed to the hierarchical porous structure of the Fe 2 O 3 /NiO microflowers, which could increase active sites for lithium ions storage, accommodate the volume expansion/contraction during charge-discharge cycles, and the synergistic effect between Fe 2 O 3 and NiO. [ABSTRACT FROM AUTHOR]

• Porous MoO 3 -Fe 2 O 3 hybrid micro-octahedrons were firstly synthesized. • MoO 3 -Fe 2 O 3 anode shows enhanced initial coulombic efficiency for lithium storage. • It gives an efficient strategy to fabricate MoO 3 -based anodes for advanced LIBs. A new porous MoO 3 -Fe 2 O 3 hybrid micro-octahedrons were successfully fabricated via a simple thermolysis of cyanide-metal framework precursor of Fe 2 [Mo(CN) 8 ]· x H 2 O. The uniform MoO 3 -Fe 2 O 3 micro-octahedrons (ca.1 µm) are assembled by numerous secondary nanoparticles, and the average size is about 60 nm. When used as anodes for lithium-ion batteries, the MoO 3 -Fe 2 O 3 micro-octahedrons exhibit superior electrochemical performances in terms of high initial coulombic efficiency of 81.9%, excellent cycle performance with capacity of 1218 mAh g−1 for 350 cycles at 0.2 A g−1 and rate capability. The outstanding electrochemical performance is attributed to the strong synergy between the two components and the unique porous microstructure, which not only provide high conductivity and rich Li+ diffusion pathway for electrochemical reaction, but also reduce agglomeration and fragmentation of the electrode during charge–discharge cycle. This work provides a new direction for the design and synthesis of Mo-based electrode materials with novel structures for high performance LIBs. [ABSTRACT FROM AUTHOR]

Co 3 O 4 , as a promising anode material for the next generation lithium ion batteries to replace graphite, displays high theoretical capacity (890 mAh g −1 ) and excellent electrochemical properties. However, the drawbacks of its poor cycle performance caused by large volume changes during charge-discharge process and low initial coulombic efficiency due to large irreversible reaction impede its practical application. Herein, we have developed a porous hollow Co 3 O 4 microfiber with 500 nm diameter and 60 nm wall thickness synthesized via a facile chemical precipitation method with subsequent thermal decomposition. As an advanced anode for lithium ion batteries, the porous hollow Co 3 O 4 microfibers deliver an obviously enhanced electrochemical property in terms of lithium storage capacity (1177.4 mA h g −1 at 100 mA g −1 ), initial coulombic efficiency (82.9%) and cycle performance (76.6% capacity retention at 200th cycle). This enhancement could be attributed to the well-designed microstructure of porous hollow Co 3 O 4 microfibers, which could increase the contact surface area between electrolyte and active materials and accommodate the volume variations via additional void space during cycling. [ABSTRACT FROM AUTHOR]

Heterointerface engineering has been proved to be an effective strategy to improve the electrochemical performances of electrode materials by overcoming inherent drawbacks of single phase electrode. However, the rational construction of heterogeneous composite with abundant heterogeneous interfaces for lithium-ion batteries (LIBs) remains a great challenge. Herein, graphene aerogel encapsulated FeSe 2 -Fe 2 O 3 heterojunction nanotubes (FeSe 2 -Fe 2 O 3 @GA) with inner-outer bi-interfacial structures were fabricated by freeze-drying method and partial selenization treatment. The built-in electric fields induced on the FeSe 2 -Fe 2 O 3 could greatly lower the activation energy for rapid charge transfer kinetics. And GA as outer surface not only could maintain the integrity of active material structure, but also enhance its electronic conductivity. Benefiting from these advantages, the FeSe 2 -Fe 2 O 3 @GA anode exhibits an improved electrochemical performance in term of lithium storage capacity (1515.6 mAh g−1 at 0.2 A g−1), cycle stability and high rate capability (492.7 mAh g−1 after 600 cycles at 1 A g−1). The kinetics analysis and theoretical calculation also interpret the significant role of heterointerface engineering construction in improving the reaction kinetics of lithium storage. [Display omitted] • FeSe 2 -Fe 2 O 3 heterojunction nanotubes encapsulated in graphene aerogel (FeSe 2 -Fe 2 O 3 @GA) were fabricated. • The 1D hollow porous nanotube could facilitate the electrolyte penetration for shortening Li+ diffusion path. • The GA could maintain the integrity of active material structure, and enhance its electronic conductivity. • The built-in electric fields could lower the activation energy for rapid charge transfer kinetics. • The FeSe 2 -Fe 2 O 3 @GA anode exhibits improved electrochemical performances. [ABSTRACT FROM AUTHOR]