Despite its high theoretical capacity, silicon anode has limited intrinsic conductivity and experiences significant volume changes during charge-discharge. To overcome these issues, facile metal-assisted chemical etching and in-situ polymerization of aniline are employed to produce a dense 1D polyaniline/silicon nanowire forest without noticeable agglomeration as a free-standing anode for lithium-ion batteries. This hybrid electrode possesses high cycling performance, delivering a stable capacity capped at 2 mAh cm À 2 for 346 cycles of charge-discharge. Maximum capacity of 2 mAh cm À 2 is also achievable at high-rate cell testing of 2 mA cm À 2 , which cannot be obtained by the anode with plain silicon wafer and silicon nanowire only. The introduction of polyaniline on the silicon nanowire is shown to reduce the solid electrolyte interface (SEI) resistance, stabilize the SEI layer, further alleviate the effect of volume changes, and boost the conductivity of the hybrid anode, resulting in the high electrochemical performance of the anode.

Flexible supercapacitors are attracting interest in wearable technologies as they can withstand mechanical deformations while delivering their energy storage function. Among frequently investigated electrode materials for flexible supercapacitors, polyaniline/graphene composites are favorable due to their synergistic properties that assure excellent specific capacitance, cycling stability, and high rate capability. This review highlights recent strategies to advance structural designs and synthesis methods of polyaniline/ graphene electrodes for flexible supercapacitors. Firstly, the general mechanism and feature of the flexible supercapacitor will be discussed, followed by current challenges that focus on two key aspects, structural design and synthesis of the electrode. Next, by sorting the composites based on their morphological dimensionalities (i. e., one-, two-, and threedimensional), and focusing the discussion on the two key aspects, we evaluate recent and effective strategies to develop flexible supercapacitors with polyaniline/graphene composite electrode. Finally, future perspectives are given for broader applications of the flexible supercapacitors.

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Silicon has attracted considerable attention for use as high-capacity anodes of lithium-ion microbatteries. However, its extreme volume change upon (de-)lithiation still poses a challenge for adoption as it leads to severe active lithium loss that shortens the cycle life. Here, we fabricate three-dimensional monocrystalline vertical silicon nanowires on a silicon wafer using low-cost metal-assisted chemical etching, then cover them with lithium using thermal evaporation prior to the battery operation as the pre-lithiation step, to investigate its impact on electrochemical performance. To reveal the underlying physical and electrochemical mechanisms, we also process a comparative planar monocrystalline silicon. We find that pre-lithiation results in improved (de-)lithiation behavior, especially in planar silicon-based cells, while silicon nanowire-based cells exhibit low capacity in early cycles. This study sheds light on the surface design and structural modification of monocrystalline silicon nanowires with respect to pre-lithiation by lithium thermal evaporation.