Revisiting Cationic Doping Impacts in Ni-Rich Cathodes

Abstract

As a promising cathode material for high-energydensity Li-ion batteries, Ni-rich layered oxide cathode active materials deliver high specific capacity. However, their electrochemical performance degrades rapidly upon charge/discharge cycles probably due to electrochemical/thermochemical instabilities. While cationic doping in the transition-metal site has been regarded as an effective strategy to enhance the electrochemical performance, the true impact of cation doping is not well understood. To quantitatively assess the impact of cationic doping, in this work, the electrochemical performance and lattice oxygen stability of LiNi 0.82 Co 0.18 O 2 , isovalent Al 3+ -doped Li-Ni 0 . 8 2 Co 0 . 1 5 Al 0 . 0 3 O 2 , and high-valent Ti 4 + -doped Li-Ni 0.82 Co 0.15 Ti 0.03 O 2 were investigated. Despite significant improvements in electrochemical performance by Al 3+ and Ti 4+ doping, it was revealed that these cation dopings had no discernible effect on the lattice oxygen stability. Such information suggests that the electrochemical enhancement by Al 3+ /Ti 4+ doping is not attributed to the stabilization of lattice oxygen. This work highlights the importance of independent and quantitative experimental evaluations on kinetic electrochemical properties and thermodynamic stability of lattice oxygen to establish rational guidelines for doping strategy toward high-energy-density and reliable cathode-active materials.

Regulating Grind‐Induced Lattice Distortion for Nickel‐Rich Cathodes by Annealing

“…Among the samples, A-800 exhibits the lowest I 003 /I 104 ratio and the highest intensity of Li/Ni mixing, suggesting a poorly ordered layered structure. [28][29][30] This indicates that 800 °C annealing temperatures harm the electrochemical performance of the cathodes. Surface chemical analysis of the Ni 2p spectra through X-ray photoelectron spectroscopy (XPS) is performed on SC-NCM811, A-600, A-700, and A-800, as shown in Figure S9 (Supporting Information).…”

“…Among the samples, A‐800 exhibits the lowest I 003 /I 104 ratio and the highest intensity of Li/Ni mixing, suggesting a poorly ordered layered structure. [ 28–30 ] This indicates that 800 °C annealing temperatures harm the electrochemical performance of the cathodes.…”

Optimizing NCM811 nickel-rich cathode stability via suppressing asymmetric Li/Ni mixing by a “non-intrusive” strategy

“…13 The introduction of dopants effectively inhibits phase transitions and suppresses the release of lattice oxygen. 14 On the other hand, surface coating entails depositing a thin protective layer on the cathode material's surface to prevent direct contact with the electrolyte and mitigate unwanted side reactions. 15 Coating materials such as metal oxides, 16 phosphates, 17 and polymers 18 have been explored for their potential to improve the cycling performance and structural stability of cathode materials.…”