As the demand for high-energy batteries to power electric vehicles continues to grow, Ni-rich cathode materials have emerged as promising candidates due to their high capacity. However, these materials are prone to rapid degradation under increased voltages, posing significant challenges for their long-term stability and safety. In this study, we investigate the effects of tantalum (Ta) doping on the performance and stability of LiNi0.80Mn0.1Co0.1O2 (NMC811) cathode materials. Using a combined theoretical and experimental approach, we employ density functional theory (DFT) and cluster expansion models to analyze the electronic structure and oxygen vacancy formation enthalpy in Ta-doped NMC811. Experimental validation is conducted using cycling and gas measurements via on-line electrochemical mass spectrometry (OEMS) on in-house synthesized cathode active materials. Both theoretical and experimental approaches show an improvement in oxygen binding due to tantalum doping, with the DFT results highlighting the impact of Ni4+ concentration on the proximity of the vacancy. Our results suggest that Ta doping inhibits the formation of oxygen vacancy-induced side phases, reducing cracking and enhancing the longevity and safety of Ni-rich cathodes.