New Insight into the Role of Mn Doping on the Bulk Structure Stability and Interfacial Stability of Ni-Rich Layered Oxide

Nickel-rich layered oxides have developed into appealing cathode materials for lithium-ion batteries in recent years for the sake of high energy density and low cost, but they suffer from severe capacity deterioration during long-term cycling. Herein, Mn-doped nickel-rich Li(Ni_0.88Co_0.09Al_0.03)_1-δMn_δO₂ (δ=0, 0.01, 0.02) cathode materials with a nanoscale Ni_xMn_1−xO-type pillar layer are synthesized using a facile high-shear dry mixing and high-temperature calcination process in this study. The as-fabricated M0.01−NCA electrode with a Ni_xMn_1−xO-type layer about 20 nm exhibits excellent cycle performance compared with the pristine in coin-cells and in pouch cells (the long-term cycle number is four times that of the pristine). Detailed investigation of the fading mechanism is performed by HRTEM, ex-situ XRD, XPS et al. The enhanced performance is directly related to the synergetic effects of bulk inactive Mn⁴⁺ doping and the increased nanoscale Ni_xMn_1−xO-type pillar layer. The Mn dopants stabilize the lattice structure thus decreasing the microcracks, and the pillar layer protects the cathode from parasitic reactions with electrolytes during long-term cycling. This work gives a new insight into the role of Mn doping on the enhanced structure of nickel-rich layered oxides.