Cr-doped composite positive electrode material and preparation method and application thereof

The invention discloses a Cr-doped composite positive electrode material and a preparation method and application thereof, and belongs to the technical field of sodium ion batteries, the material is Cr-doped sodium ferric fluorophosphate coated with a carbon layer structure, due to introduction of Cr, the sodium ferric fluorophosphate structure is more stable, the electrode material is not prone to falling off in the circulation process, and the service life of the electrode material is prolonged. According to the preparation method, a sodium source, an iron source, a chromium source, a phosphorus source, a fluorine source and an organic carbon source are subjected to solid-phase ball milling and high-temperature heat treatment to prepare the carbon-coated Cr-doped sodium ferric fluorophosphate composite positive electrode material; a performance test is carried out on the sodium ion battery assembled by taking the Cr-doped sodium ferric fluorophosphate/carbon as the positive electrode material, and the resul