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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]

Silicon (Si) with high theoretical capacity has attracted much attention as anode materials of lithium-ion batteries (LIBs). However, the tendency of Si particles to easily expand leads to the rapid attenuation of capacity, which greatly limits their practical applications. In this work, the nitrogen (N) and phosphorus (P) doped Si/CNTs carbon nanofibers (Si/CNTs/CNFs) composites has been fabricated and explored as electrode material for LIBs. N, P doped Si/CNTs/CNFs composites possess unique fiber network structure with suitable space, which can effective buffer volume expand during charge-discharge process. By evaluating lithium storage performances of N, P doped Si/CNTs/CNFs composites as Li-ion battery electrodes, excellent rate performance with a capacity of 529 mA h g−1 (at 5.0 A g−1) and remarkable cycling performance of 1142 m Ah g−1 after the 100 cycles (at 0.2 A g−1) are obtained. Such outstanding performances can be attributed to the unique fiber network structure and the doping of N and P, which provides a new avenue for the studies of high-performance Si based anode materials of LIBs. • Self-supporting N, P doped Si/CNTs/CNFs composites with fiber network. • This unique structure can effectively restrain the volume expansion and accelerate the transport of Li+. • Doping N and P elements also provide more electrochemical active sites. • N, P doped Si/CNTs carbon nanofibers deliver excellent lithium storage performances. [ABSTRACT FROM AUTHOR]