Rate Performance Investigation of an Iron-Doped Mn-Based Tunnel Type Cathode Containing Sodium, Lithium and Titanium for Low-Cost Li-Ion Batteries

While Cobalt-free layered cathode materials such as NMA (LiNi_1-x-yMn_xAl_yO₂) have garnered increased attention for applications in high energy density Li-ion batteries, the raw material cost of nickel is not immune to market fluctuations; thus, it would be advantageous to safeguard against it in the future. In this sense, Li+/Na+ exchange ion has been extensively explored as an effective method to prepare high-performance Mn-based layered cathodes for Li-ion batteries. In this work, tunnel type Na_xLi_yFe _0.16Mn_0.65Ti_0.19O₂ with 0<x<0.44 and 0<y<0.65 has been prepared by solid-state synthesis followed by Li+/Na+ ion exchange and cycled to a high (4.8 V vs. Li/Li+) cut-off voltage to achieve high energy density. However, long-term cycling at a higher upper cut-off voltage exacerbates harmful surface and bulk degradation mechanisms that compromise the overall lifetime and thermal stability of the cell. Herein, in situ operando X-ray diffraction, SEM-EDX, solid-state NMR and electrochemical tests are combined to get more insight into the structural changes affecting the rate performance of the new cathode material.