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Abstract For the advancement of high‐energy asymmetric supercapacitors, the breakthrough point is matching charge storage capacity and balanced electrode kinetics between the positive and negative electrodes. Herein, Mn 3 O 4 nanosheets composed of nanoparticles are anchored on activated carbon cloth (ACC) as the positive electrode by electrodeposition. FeOOH nanoparticles derived from NaFe 3 (SO 4 ) 2 (OH) 6 truncated cubes serve as the negative electrode. Due to the unique sheet‐like network structure, ultrahigh mass‐loading (73.3 mg cm −2 ), and enhanced kinetics, the Mn 3 O 4 @ACC electrode exhibits an ultrahigh specific capacitance of 12.77 F cm −2 . Besides, the FeOOH@ACC electrode with a low‐crystalline structure also exhibits a maximum specific capacitance of 17.84 F cm −2 . The Na + diffusion process, the charge storage mechanism, and the electrochemical reaction kinetics of the Mn 3 O 4 @ACC are investigated by ex situ characterization. Theoretical calculations show that Mn 3 O 4 has metallic electronic conductivity and reveal the adsorption and diffusion mechanism of Na ions during the electrode process. The assembled aqueous Mn 3 O 4 //FeOOH asymmetric supercapacitor device successfully extends the operating voltage to 2.2 V and exhibits a high energy density of 3.75 mWh cm −2 and ultra‐long cycle life (81.6% capacity retention after 26,000 cycles). Therefore, this study provides a feasible pathway for the further development of asymmetric supercapacitors with high energy density.
Xu et al. (Wed,) studied this question.