subsequently increasing demand for lightweight and highly flexible power modules is essentially one of the critical challenges for the progress of miniaturized portable and wearable electronics. [1] 1D fiber supercapacitor, as a promising candidate among various electrode materials, has been intensively investigated. The fiber supercapacitors (FSCs) can be easily integrated into extremely small devices with tiny sizes and various kinds of shapes due to their small volume and high flexibility. [2] Consequently, the construction of solidstate flexible energy storage systems is of great significance for the new generation of electronic devices.Graphene-based fiber supercapacitor has been widely applied in engineering field because of its superior electrical conductivity and large specific surface area for the past few years. [3] However, the 2D structure makes graphene sheets tending to aggregate during the preparation process. [4] Therefore, one way to solve this problem is to use carbon fibers as substrates. Apart from the high flexibility, the carbon fiber substrate possesses high surface area and desirable electrochemical stability. The doping of heteroatom could significantly improve electrochemical performance of graphene-based fiber supercapacitors. Specifically, the heteroatoms such as nitrogen (N), boron (B), sulfur (S), phosphorus (P) substituting some atoms in carbon nanomaterials is an effective way to tailor their electron-donor properties, [5] then to further improve their conductivity and electrochemical performances. In general, P-doped nanofibers were successfully prepared by impregnating H 3 PO 4 , (NH 4 ) 3 PO 4 , and triphenylphosphine (TPP) into the carbon materials, respectively, followed by carbonization. [6] In order to achieve a better application in an industrial production, an easy-handling fabrication process, with a lower reaction temperature and using attractive source of phosphorus, has become a key challenge for graphene-based fiber supercapacitors.Carbon materials, known as the most common class of electric double-layer materials, can deliver long cycling life, but their specific capacitance is limited, especially used as negative electrode in alkaline electrolyte. The pseudocapacitor materials such as conductive polymers and metal oxides can show high Fiber supercapacitors (FSCs) are promising energy storage devices in portable and wearable smart electronics. Currently, a major challenge for FSCs is simultaneously achieving high volumetric energy and power densities. Herein, the microscale fiber electrode is designed by using carbon fibers as substrates and capillary channels as microreactors to space-confined hydrothermal assembling. As P-doped graphene oxide/carbon fiber (PGO/CF) and NiCo 2 O 4based graphene oxide/carbon fiber (NCGO/CF) electrodes are successfully prepared, their unique hybrid structures exhibit a satisfactory electrochemical performance. An all-solid-state PGO/CF//NCGO/CF flexible asymmetric fiber supercapacitor (AFSC) based on the PGO/CF as the negative e...
