Access to high-performance Li-rich layered oxide cathodes via ammonium phosphate surface treatment.

Ammonium phosphate ((NH ₄ ) ₃ PO ₄ ) has been first used as a surface treatment reagent for Li-rich cathode materials. Compared to the conventional surface treatment, the samples treated with (NH ₄ ) ₃ PO ₄ exhibit an ultra-high initial Coulomb efficiency of 98.0% and excellent cycling stability. This is mainly attributed to the simultaneous construction of surface integrated structures, including oxygen vacancies, spinel phases, and Li ₃ PO ₄ coating. This study demonstrates the effectiveness of ammonium phosphate surface treatment and provides a new idea for designing other cathode materials.