Elucidation of synergistic effect of Mg-co-doping on electrochemical performance of Mn-doped LiNiO2

Abstract

• The Li + /Ni 2+ cation mixing can be reduced by Mg co-doping. • The Mg co-doping may suppress the alteration of the lattice volume. • The Mg co-doping has a negligible effect on the interfacial property. • The superior performance of material is further gained via Mg co-doping. • The Mg-Mn co-doping has synergistic effects on stabilizing the LiNiO 2 material. Element doping is one of the most efficient strategies to boost the stability and performance of LiNiO 2 -based materials, to obtain a thorough understanding of the role of element doping. Particularly, the synergistic effect of the co-doped elements will be crucial for the design of the materials. Herein, we synthesize a series of Mg incorporated LiNiO 2 with a fixed Mn-doping content to better understand the synergistic effect of Mg co-doping. It is demonstrated that the incorporation of the Mg 2+ ions in the Li slabs leads to suppression of the Li + /Ni 2+ mixing and decreases the crystal lattice volume change during lithiation/delithiation processes. Therefore, the electrochemical stability of the material can be further enhanced, in addition to the stabilization effect of Mn-doping. The capacity retention of LiNiO 2 doped with 4 mol% Mn and 0.3 mol% Mg (LiNi 0.957 Mn 0.04 Mg 0.003 O 2 ) is 88.26 % after 200 cycles at 0.5C. This is also highlighted by the improved capacity retention at 4.6 V upper cutoff voltage. Moreover, due to the “pillar effect” of the co-doped Mg 2+ ions in the Li slabs, the material exhibits superior rate capability. The findings may be beneficial for the development of Co-free nickel-rich materials for the lithium-ion batteries.