In situ TEM Study of the Sodiation/Desodiation Mechanism of MnO 2 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 MnO 2 nanowire and different kinds of gel-electrolyte. It is found that after full sodiation, single crystalline MnO 2 nanowire is transformed to a mixed nanocrystalline phases of Na 2 O and MnO, and the following cycles are controlled by the reversible conversion reaction between NaMnO 2 and MnO. Both in situ electrochemical test and ex situ battery test show that the glyme-based gel-electrolyte is more suitable for the MnO 2 nanowires anode materials. It is also revealed that the MnO 2 nanowire expansion ratio strongly depends on the diameter of the nanowires. This work provides a new insight on the sodiation/desodiation mechanism in MnO 2 nanowire and gel-electrolyte, and may pave the path for the development of practical sodium-ion batteries with gel-electrolyte.