As one of the most promising cathode materials for lithium-ion batteries, nickel-rich layered oxide LiNi0.83Co0.11Mn0.06O2 (NCM83) has an inherent issue with rapid capacity decay caused by phase change and interface side reactions during the charge/discharge cycling. Herein, an effectively synergistic strategy for improving the structural stability and electrochemical performance of NCM83 cathodes has been proposed, combining surface polymeric coating with bulk doping by the high-temperature solid-phase method. The comprehensive results demonstrate that the niobium (Nb) element can be successfully bulk-doped into the crystal lattice, which could increase the layer spacing, thus stabilizing the crystal structure and minimizing the Li+/Ni2+ mixing in the as-prepared NCM83 cathode. Meanwhile, a small amount of Nb in the form of oxide and a layer of polyaniline (PANI) was coated on the NCM83 cathode’s surface. This not only can prevent electrolyte erosion and inhibit side reactions but also can effectively improve the transport coefficient of Li+ during the charge and discharge process. The optimized NCM83 cathode exhibited outstanding discharge-specific capacity (236.79 mAh g–1 at 0.2 C rate and 215.67 mAh g–1 at 2 C rate), stable cycling performance (capacity retention of 84.4% after 100 cycles at 2 C), and excellent rate performance (150.58 mAh g–1 at 10 C) by taking advantage of the synergistic effects. The synergistic strategy using Nb doping in combination with a surface polymeric coating can enhance the fundamental understanding of the high-nickel layered oxide cathodes for lithium-ion batteries.