In situ TEM study of the sodiation/desodiation mechanism of MnO2 nanowire with gel-electrolytes

Abstract

In this work, in situ transmission electron microscopy study of the electrochemical sodiation and desodiation processes was performed in a nanobattery which consisted of a single MnO2 nanowire and different kinds of gel-electrolyte. It is found that after full sodiation, single crystalline MnO2 nanowire is transformed to a mixed nanocrystalline phases of Na2O and MnO, and the following cycles are controlled by the reversible conversion reaction between NaMnO2 and MnO. Both in situ electrochemical test and ex situ battery test show that the glyme-based gel-electrolyte is more suitable for the MnO2 nanowires anode materials. It is also revealed that the MnO2 nanowire expansion ratio strongly depends on the diameter of the nanowires. This work provides a new insight on the sodiation/desodiation mechanism in MnO2 nanowire and gel-electrolyte, and may pave the path for the development of practical sodium-ion batteries with gel-electrolyte.