Sodium manganate positive electrode material with high sodium content as well as preparation method and application of sodium manganate positive electrode material

The invention belongs to the technical field of preparation of sodium ion battery positive electrode materials, and particularly relates to a sodium manganate positive electrode material with high sodium content and a preparation method and application thereof. The sodium manganate material with high sodium content is prepared by adopting a simple and feasible solid-phase method, the raw materials are firstly subjected to ball milling and pre-sintering treatment, so that the raw materials are more uniformly mixed, the sodium manganate precursor is obtained, and then the precursor is pressed into a wafer, so that particles are more tightly contacted, the area for reaction is larger, and the sodium manganate material with high sodium content is obtained. And then the surface phase and the interior of the precursor are uniformly heated in a microwave heating manner, so that the reaction is relatively consistently carried out at the same speed, and the generation of an impure phase is avoided. The preparation pro