Excellent Performance of Sodium Ion Battery Cathode Materials Benefiting from the Inorganic Acid Regulating Strategy

The cathode material NaNi1/3Fe1/3Mn1/3O2 (NFM111) is known as an O3-type layered oxide for sodium ion batteries. It has the advantages of high energy density and easy synthesis. However, the residual alkali leads to capacity decay and air stability decline. And its storage and application are limited. The residual alkali content on the surface of NFM111 is reduced through phosphoric acid treatment. The initial discharge capacity of the modified material is 162 mA h g–1 at 0.1 C. Meanwhile, the material still has a capacity of 140.7 mA h g–1 at 0.1 C after exposure to air. This treatment strategy increases the specific discharge capacity of the material at 25 and −20 °C and improves the cycle stability and air stability. It provides an effective and reliable method for the production and application of sodium ion battery cathode materials.