The development and understanding of transition metal (TM) based oxides for applications in electrochemical energy storage, viz., essentially for the next generation alkali metal-ion battery systems, has incentivized the research on materials development. Less Co-containing or Co-free, Ni-containing ‘cation ordered’/layered Li-TM-oxides, as a cathode material for Li-ion batteries, suffer from structural instability due to ‘TM-migration’ from the TM-layer to the Li-layer upon Li-removal (i.e., "cation disordering"), especially at deep states of delithiation at the high cell voltages (typically beyond ~4.2 V vs. Li/Li⁺). Such structural instability causes mechanical instability, significant impedance build-up and fade in Li-storage capacity; thus, limiting the cell voltages to ≤ 4.2 V for stable operation. The deleterious ‘TM(Ni)-migration’ pathway involves the vacant tetrahedral site (t-site) of the Li-layer as the intermediate crystallographic site. Therefore, we explored here the possibility of suppressing the ‘Ni-migration’ by ‘blocking’ the t-site with a cationic dopant that is stable at that location; viz., possibly a d¹⁰/d⁰ TM-ion. In this regard, our simulations based on density functional theory revealed that the concerned t-site is an energetically favoured and stable site for d¹⁰ Zn²⁺. The same was supported by a detailed analysis of the crystallographic data (including bond valence sum) obtained with the as-prepared Zn-doped Li-NMC, with Zn-ions substituting for Li-ions (i.e., Li_0.9Zn_0.05Ni_0.33Mn_0.33Co_0.33O₂ composition). The simulations also predicted that, as hypothesized, Zn-doping is likely to prevent ‘Ni-migration’ upon Li-removal. In agreement with the above, upon being subjected to long-term galvanostatic cycling using a high upper cut-off voltage of 4.7 (vs. Li/Li⁺), the Zn-doped Li-NMC exhibited significantly improved cyclic stability, near-complete suppression of ‘cation mixing, and negligible build-up of impedance (as well as potential hysteresis), as compared to the un-doped counterpart. From a broader perspective, such subtle tuning of the composition-structure can potentially be extended to other TM-oxide-based materials, including the very high Ni-containing Li-TM-oxide cathodes; rendering them structurally stable at very high cell voltages and, thus, leading to the successful development of high capacity and high voltage cathodes, possessing good long-term cyclic stability, for the next-generation Li-ion batteries.