Defects-type three-dimensional Co3O4 nanomaterials for energy conversion and low temperature energy storage

Abstract The COVID-19 outbreak begin in winter in 2020, and there is a shortage of cryogenic batteries for thermometers. Herein, an effective strategy is designed to improve the electrochemical performance of Co3O4 nanoflowers, so as to solve the dilemma that the energy storage device cannot work normally due to too low temperature. Note that the incorporation of point defects (oxygen vacancies) into the primitive lattice of Co3O4 nanoflowers provide additional electrochemical active sites and greatly shorten the ion diffusion distance. The defect-type Co3O4 (D-Co3O4) nanoflowers exhibit enhance specific capacitance of 1630 mF cm−2 at 1 mA cm−2 and conspicuous cycle stability of 91% up to 5000 cycles, as well as outstanding low temperature performance. The assemble symmetrical supercapacitor (SSC, D-Co3O4||D-Co3O4) device offer a wider voltage window of 1.4 V and obtain the maximum volume energy density of 0.94 mW h cm−3 and the power density of 3.5 mW cm−3. Meanwhile, the D-Co3O4 nanoflowers has good electrocatalytic activity in basic solution for oxygen evolution reaction (OER), and display the lowest initial potential and small overpotential. Therefore, this work highlights the role of the design defects of materials for building di-functional electrode materials for energy storage and conversion.