<p>This study demonstrates a synergistic dual-doping strategy employing Ca²⁺ and Br⁻ to optimize the electrochemical performance of LiNi_0.8Co_0.1Mn_0.1O₂ (NCM) cathodes. Experimental and theoretical analyses reveal that Ca²⁺ doping stabilizes the lattice structure via a "pillar effect" in the Li layer and strengthens Ca-O bonding energy, achieving an exceptional capacity retention of 90.06% of Ca-NCM after 100 cycles at 1 C. In contrast, Br⁻ doping facilitates Li⁺ extraction/insertion through weakened Li-Br bonds, delivering a high discharge capacity of 244.8 mAh·g⁻¹ of Br-NCM at 0.1 C, yet suffers from poor cyclability (67.12% retention) due to insufficient relative electron number near the Fermi level (1.4998). Remarkably, the Ca²⁺-Br⁻ dual-doped NCM integrates these advantages, synergistically enhancing electronic and ionic conductivity. Density functional theory (DFT) calculations confirm a narrowed bandgap (2.2614 → 1.7792&#xa0;eV) and doubled relative electron number (0.6188 → 2.0443) near the Fermi level, significantly improving electronic conductivity. This mitigates polarization (0.187 → 0.103&#xa0;V) and reduces interfacial resistance, enabling a capacity retention of 87.79% of Ca-Br-NCM at 1 C. Simultaneously, Li⁺ migration barriers decrease by 32% (0.967 → 0.658&#xa0;eV) due to expanded Li layer spacing, boosting rate capability (166.3 mAh·g⁻¹ at 5 C). The dual doping thus balances high capacity (234.1 mAh·g⁻¹), cyclability (87.79%), and rate performance (41.2% improvement at 5 C vs. pristine NCM), outperforming single-doped counterparts. These findings provide atomic-scale insights into the coupling mechanism of anion-cation dual doping, advancing the design of high-performance layered oxide cathodes for next-generation lithium-ion batteries.</p>