Manganese oxides have attracted great interest in electrochemical energy storage due to high theoretical specific capacitance and abundant valence states. The multiple valence states in the redox reactions are beneficial for enhancing the electrochemical properties. Herein, three manganese microspheres were prepared by a one-pot hydrothermal method and subsequent calcination at different temperatures using carbon spheres as templates. The trivalent manganese of Mn 2 O 3 exhibited multiple redox transitions of Mn 3 + /Mn 2 + and Mn 4 + /Mn 3 + during the intercalation/deintercalation of electrolyte ions. The possible redox reactions of Mn 2 O 3 were proposed based on the cyclic voltammetry and differential pulse voltammogram results. Mn 2 O 3 microsphere integrated the advantages of multiple redox couples and unique structure, demonstrating a high specific capacitance and long cycling stability. The symmetric Mn 2 O 3 //Mn 2 O 3 device yielded a maximum energy density of 29.3 Wh kg À 1 at 250 W kg À 1 .

A NiCo layered double hydroxide (LDH) has been regarded as a promising electrode material for supercapacitors. However, the low electronic conductivity, limited electroactive sites, and self-agglomeration hinder its large-scale application. Herein, MXene-coated nickel ion-exchanged ZIF skeleton-cavity LDHs (ZSC-LDH@MXene) were fabricated to enhance the electrochemical performance of NiCo LDHs. The ZSC-LDH@MXene integrated the advantages of various materials, providing abundant metal active sites and fast redox reaction kinetics and enhancing the specific capacity of the electrode. The MXene nanosheets can construct abundant conductive networks, enhancing the electronic conductivity of the NiCo LDH. The nanosheetassembled ZIF skeleton-cavity structure can facilitate electron/ion transport, enlarge the electrolyte accessibility, and expose abundant electroactive sites. Furthermore, the hollow cavity can relieve the volume expansion during the charging/discharging cycles. Ultimately, the as-obtained ZSC-LDH@MXene electrode manifested a large specific capacity of 1029.6 C g −1 at 1 A g −1 , a superior rate capability of 62.6% at 30 A g −1 , as well as outstanding cycling performance with a 92.0% capacity retention at 10 A g −1 over 10,000 cycles. The assembled ZSC-LDH@MXene//AC hybrid supercapacitor exhibited a superb energy density of 43.7 W h kg −1 at 789 W kg −1 .