Constructing “Li-rich Ni-rich” oxide cathodes for high-energy-density Li-ion batteries

Abstract

The current exploration of high-energy-density cathode materials for Li-ion batteries is mainly concentrated on either so-called “Li-rich” or “Ni-rich” oxides. However, both are suffering from formidable practical challenges. Here, we combine these two concepts to obtain “Li-rich Ni-rich” oxides in pursuit of more practical high-energy-density cathodes. As a proof of concept, we synthesized an array of Li_1+yNi_(3−5y)/3Mo_2y/3O₂ oxides, whose structures were identified to be the coexistence of LiNiO₂-rich and Li₄MoO₅-rich domains with the aid of XRD, TEM, and NMR techniques. Such an intergrowth structure of 5–20 nm size enables excellent mechanical and structural reversibility for the layered rock-salt LiNiO₂-rich domain upon cycling thanks to the robust cubic rock-salt Li₄MoO₅-rich domain enabling an “epitaxial stabilization” effect. As a result, we achieved high capacities (>220 mA h g⁻¹) with Ni contents as low as 80%; the Li_1.09Ni_0.85Mo_0.06O₂ member (y = 0.09) shows much improved cycling performances (91% capacity retention for 100 cycles at C/10) compared with pure LiNiO₂. This work validates the feasibility of constructing Li-rich Ni-rich compounds in the form of intergrowing domains and hence unlocks vast possibilities for future cathode design.