“…Notably, our device delivers a maximum energy density of 0.0487 and 10.19 mWh cm −3 , while the power densities are 0.553 and 129.1 mW cm −3 , respectively. As shown in Figure h, our asymmetric yarn SCs show a higher electrochemical performance than the recently reported fiber‐based SCs, such as Ni‐Co DHs//pen ink fiber SCs (0.00957 mWh cm −2 ), PPy@MnO 2 @rGO yarn SCs (1.1 mWh cm −3 ), PEDOT@MnO 2 //C@Fe 3 O 4 yarn SCs (0.0335 mWh cm −2 ), PPy@CNTs@UY yarn SCs (0.00613 mWh cm −2 ), hair/Ni/rGO/MnO 2 //hair/Ni/rGO fiber SCs (1.81 mW h cm −3 ), MnO 2 @TiN//N‐MoO 3− x fiber SCs (2.29 mWh cm −3 ), A‐CFT fiber SCs (0.35 mWh cm −3 ), CW/PNC/PEDOT//CW/CMK‐3 (0.01 mWh cm −2 ) . The enhanced eletrochemical performance can be attributed to the following factors: 1) the functionalized SS yarn has large surface area which is good for growth of active material and the electrolyte ion diffusion for fast and reversible capacitive reaction, leading to the achievement of high‐energy density supercapacitors; 2) the functionalized yarn with a rough surface can provide a strong adhesive force between the grown active material and the yarn, which benefits the long‐time cycling stability; and 3) there is enough space between active material particles, and thus volume expansion brought by the fast and long‐term capacitive reaction can be effectively buffered.…”