Formation of Pillar-Ions in the Li Layer Decreasing the Li/Ni Disorder and Improving the Structural Stability of Cation-Doped Ni-Rich LiNi0.8Co0.1Mn0.1O2: A First-Principles Verification

A higher Ni content with less cobalt usage of lithium nickel cobalt manganese oxide cathode materials (LiNixCo0.1Mn0.1O2, 0.6 ⟨ x ⟩ 0.9) provides a higher power rating and higher energy density in lithium-ion batteries (LIBs). However, severe Li/Ni mixing is one of the main reasons for poor cycling stability in these materials. Cation doping effectively suppresses the mixing of Ni ions in the lithium layer of LiNixCo0.1Mn0.1O2. In this work, we investigate the effects of different cationic dopants (D) such as zirconium (Zr4+), zinc (Zn2+), calcium (Ca2+), magnesium (Mg2+), and aluminum (Al3+) in the Li layer, which act as a pillar for preventing degradation in the LiNi0.8–yCo0.1Mn0.1DyO2 (y = 0.033) cathode material for LIBs using density functional theory. In particular, a substituted dopant at the Ni3+-ion site suppresses the Ni3+-ion migration to the Li layer. During Li de-intercalation, the dopant migrates to the Li layer and acts as a pillar that enhances the structural stability. The pillared systems of both pristine and doped structures exhibit a more improved performance than non-pillared systems. An Al3+-doped pillared system displays a reduction in the height of the Li slab layer, resulting in a high Li diffusion energy barrier, which hinders easy Li diffusivity. However, the pillared systems doped with Zr4+- and Ca2+- in LiNi0.8–yCo0.1Mn0.1DyO2 act as better pillar-ions due to their high suppression energy of "neighbor Ni3+-ion migration", facile Li-ion diffusion, and enhanced electrochemical structural stability.