POMCPs with Novel Two Water-Assisted Proton Channels Accommodated by MXenes for Asymmetric Supercapacitors.

To develop high-performance supercapacitors, the negative electrode is at present viewed as one of the most challenging tasks for obtaining the next-generation of energy storage devices. Therefore, in this study, a polyoxometalate-based coordination polymer [Zn(itmb) 3 H 2 O][H 2 SiW 12 O 40 ]·5H 2 O (1) is designed and prepared by a simple hydrothermal method for constructing a high-capacity negative electrode. Polymer 1 has two water-assisted proton channels, which are conducive to enhancing the electrical conductivity and storage capacity. Then, MXene Ti 3 C 2 T x is chosen to accommodate coordination polymer 1 as the interlayer spacers to improve the conductivity and cycling stability of 1, while preventing the restacking of MXene. Expectedly, the produced composite electrode 1@Ti 3 C 2 T x shows an excellent specific capacitance (1480.1 F g -1 at 5 A g -1 ) and high rate performance (a capacity retention of 71.5% from 5 to 20 A g -1 ). Consequently, an asymmetric supercapacitor device is fabricated using 1@Ti 3 C 2 T x as the negative electrode and celtuce leaves-derived carbon paper as the positive electrode, which demonstrates ultrahigh energy density of 32.2 Wh kg -1 , and power density 2397.5 W kg -1 , respectively. In addition, the ability to illuminate a red light-emitting diode for several minutes validates its feasibility for practical application.