Enhancing electrochemical performance of lithium-rich manganese-based cathode materials through lithium sulfate coating

The surface modification of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode material is carried out by heat treatment of the mixtures of Mn_0.75Ni_0.25C₂O₄ and (NH₄)₂SO₄ absorbed on the surface of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ material. The structural analysis by XRD, XPS, FTIR, and Raman spectroscopy demonstrates that Li₂SO₄ and metal oxides exist in the coating layer. The loading of coating layer and the calcination temperature play a crucial role in the initial Coulomb efficiency and cyclic stability of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode material. Compared with the pristine and metal oxide-coated sample, modified Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ with Li₂SO₄ coating exhibits higher first discharge specific capacity (233 mAh g⁻¹ at 0.1 A g⁻¹) and longer cyclic stability (retention of 94.7% at 1 A g⁻¹). The enhancement of the electrochemical performance can be attributed to the increased reversibility Mn³⁺/Mn⁴⁺ redox reaction and the reduced irreversible migration of transition metal ion.