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Homogeneous SnO2 hollow spheres have been synthesized through a hydrothermal method without a template, followed by in situ polymerization of PANI. The resulting SnO2 hollow spheres were uniformly deposited onto the surface or embedded into the PANI nanofibers to form a SnO2–PANI network structure. As electrode materials, the SnO2–PANI composites exhibit greatly enhanced specific capacitance (477 F g−1 at a current density of 1 A g−1) and superior cycling performance (no capacitance loss after 3000 galvanostatic charge–discharge cycles). These intriguing features are attributed to the interaction between the SnO2 hollow spheres and PANI network. On the one hand, the SnO2 spheres not only provide larger area for electrochemical reaction but also release volume expansion during the charge–discharge process. On the other hand, the conducting PANI improves electrical conductivity and maintains mechanical integrity of the composites as well. [ABSTRACT FROM AUTHOR]

The development of high-performance electrode materials and the rational design of asymmetric structures are the two main keys to fabricating micro-supercapacitors (MSCs) with high energy density. Transition metal compounds, especially nickel–cobalt phosphides and hydroxides, are promising electrode materials with excellent pseudo-capacitance. However, they are rarely used in fabricating asymmetric MSCs (AMSCs) due to the limitations of the preparation method. In this work, we constructed hierarchical Ni–Co–P@LDH nanocomposites with outstanding mass specific capacitance (1980 F g−1 at 1 A g−1) via a multi-step electrodeposition method, which is employed with FeOOH to fabricate an interdigital AMSC device (Ni–Co–P@LDHs//PVA–KOH//FeOOH). The as-prepared device exhibits a high working voltage (1.4 V), a large specific capacitance (24.0 mF cm−2 at 0.14 mA cm−2), a high energy density (6.54 μW h cm−2 at a power density of 100 μW cm−2) and good cycling stability (86.5% of capacitance retention after 5000 cycles). This work may provide novel methods for the synthesis of high-performance nickel–cobalt composite materials and their potential applications in interdigital AMSC devices. [ABSTRACT FROM AUTHOR]