The emergence of flexible and portable real-time healthcare electronics has stimulated the fast production of compact, lightweight, and high electrochemical performance flexible energy storage systems. [1][2][3][4] Flexible supercapacitors (FSCs) are favored among various energy storage devices because they offer much greater capacitance, excellent cycling stability, rapid charge/discharge rate, and high-power density. [5][6][7][8] Typically, 2D materials, such transitional metal dichalcogenides (TMDs) and metal carbides (MXenes) are promising nanomaterials that enhance the performance of FSCs due to their metallicity. However, semiconductor 2D materials like black phosphorus show low capacitive behaviors but can provide large surface area to prepare hybrid nanocomposites in combination with conductive polymers.Polyaniline (PANI) is extensively utilized in the development of FSCs due to its outstanding electrochemical activity and inherent flexibility as mentioned earlier. [9][10][11] Nevertheless, the majority of reported FSCs based on PANI electrodes exhibit thick and distorted structures. This not only prevents electrolyte ion migration and absorption, but also causes structural distortion of PANI upon charge-discharge cycles, leading to lower capacitance and longevity of the cycle. [12][13][14] In order to resolve the above obstacles, 2D nanomaterials (e.g., black phosphorous (BP), MXene) are combined with PANI during polymerization to improve the surface area, establish internal space, and improve structural stability upon ambient condition. [15] Correspondingly, different materials, such as carbon nanotubes (CNT) and reduced graphene oxides (rGO), have been chosen to strengthen PANI-based electrodes and impede the creation of a thick and distorted structure. [10,16] Recent studies focused on electronic proprieties of layered BP and potential applications in optoelectronics [17][18][19] as well as electrochemical energy storage devices. [20][21][22] The wider spacing between nearby puckered layers facilitates easy intercalation and rapid ion diffusion, thus improving the overall performance of energy storage devices. [23,24] To obtain high electrochemical performance, various kinds of conductive materials have been hybridized with BP electrodes, [25] including CNT@BP, [26,27] polypyrrole@BP, [28,29] Ti 3 C 2 T x @BP quantum dot, [30] rGO@BP, [31][32][33] poly(3,4-ethylenedioxythiophene)@BP, [34] PANI@BP, [35,36] and Flexible energy storage devices are becoming significantly important to power wearable and portable devices that monitor physiological parameters for many biomedical applications. Many hybrid nanomaterials based on 2D materials are used in order to improve the performance of flexible energy storage devices. Here, a hybrid nanocomposite is synthesized through in situ polymerization of aniline in the presence of black phosphorus (BP) nanoflakes. This nanocomposite, polyaniline (PANI)@BP, is employed to fabricate flexible supercapacitor (FSC) electrodes. PANI@BP FSCs can provide a power source for b...