Transition metal hydroxides have attracted a lot of attention as the electrode materials for supercapacitors owing to their relatively high theoretical capacity, low cost, and facile preparation methods. However, their low intrinsic conductivity deteriorates their high-rate performance and cycling stability. Here, self-supported sheets-on-wire CuO@Ni(OH)2/Zn(OH)2 (CuO@NiZn) composite nanowire arrays were successfully grown on copper foam. The CuO nanowire backbone provided enhanced structural stability and a highly efficient electron-conducting pathway from the active hydroxide nanosheets to the current collector. The resulting CuO@NiZn as the battery-type electrode for supercapacitor application delivered a high capacity of 306.2 mAh g−1 at a current density of 0.8 A g−1 and a very stable capacity of 195.1 mAh g−1 at 4 A g−1 for 10,000 charge–discharge cycles. Furthermore, a quasi-solid-state hybrid supercapacitor (qss HSC) was assembled with active carbon, exhibiting 125.3 mAh g−1 at 0.8 A g−1 and a capacity of 41.6 mAh g−1 at 4 A g−1 for 5000 charge–discharge cycles. Furthermore, the qss HSC was able to deliver a high energy density of about 116.0 Wh kg−1. Even at the highest power density of 7.8 kW kg−1, an energy density of 20.5 Wh kg−1 could still be obtained. Finally, 14 red light-emitting diodes were lit up by a single qss HSC at different bending states, showing good potential for flexible energy storage applications.

Novel hierarchical microspheres of aggregated silicon nanoparticles (p-Si microsphere) with nanometre gaps have been synthesized through reverse microemulsion in combination with a modified magnesiothermic reduction approach using silica (~200 nm) as the precursor. The hierarchical porous structure of p-Si microspheres is composed of abundant intergranular gaps (100-200 nm) in the interconnected nanosized Si particles, along with ultrafine Si nanosized grains (5 nm) and intragranular voids formed in interconnected nanosized Si particles. The hierarchical microspheres of aggregated Si nanoparticles possess a high specific surface area of 136 m 2 g À 1 and can achieve a high tap density of 0.3 g cm À 3 .Such a novel microstructure with a large surface area and void gaps between interconnected Si nanoparticles can accommodate the volume change of Si during the lithium ion (Li + ) alloying/dealloying process. Meanwhile, the mesoporous structure facilitates Li + penetration into the nano-Si grain interface, significantly shortening the Li + diffusion pathway as well as enhancing the heterogeneous reaction sites. Such hierarchical microspherical Si anodes demonstrated excellent cycling stability, delivering reversible capacity of 845 mAh g À 1 after 200 cycles at 0.2 A g À 1 and rate performance with a high reversible capacity of 681 mAh g À 1 at 1 A g À 1 with 97 % of initial capacity retention.[a] Dr.

Na3V2(PO4)3 (NVP) is an attractive cathode material for sodium storage because of its NASICON structure with high ionic conductivity and stability. However, its poor electronic conductivity and large volume change have limited its intensive application. Here, we use 1‐butanol as a co‐solvent to synthesize NVP (bNVP) microparticles with a uniform carbon coating layer. We discovered that butanol can effectively improve the graphitization level of the carbon, giving rise to a much higher electronic conductivity compared to the sample synthesized without butanol (pristine NVP, pNVP). As expected, bNVP demonstrates high reversible capacities of 110.3 mAh g−1 at 1 C, superior high‐rate performance of 98 mAh g−1 at 10 C, and enhanced cycling stability of 94 % capacity retention after 3500 cycles at 30 C, which are far better than pNVP, exhibiting great potential for high‐power sodium‐ion batteries.