<p>Mn-site doping in spinel LiMn₂O₄ (LMO) mitigates Mn³⁺-induced Jahn-Teller distortion. However, this strategy faces inherent trade-offs. Specifically, low-valent doping weakens oxygen bonding, while high-valent doping increases Mn³⁺ content. To overcome these limitations, this work proposes dual-lanthanide (La³⁺/Ce³⁺) co-doping. Through sol-gel synthesis, LiLa_0.1Ce_0.1Mn_1.8O₄ (LLCMO) achieves synergistic performance enhancements. Particularly, La reduces Mn³⁺ content to 43.13%, suppressing lattice distortion and widening Li+ diffusion pathways via its large ionic radius. Concurrently, Ce (in a mixed Ce³⁺/Ce⁴⁺ state) enhances charge delocalization, lowering electron transfer barriers and boosting conductivity. Critically, La-Ce cooperation mitigates Mn dissolution while stabilizing the spinel framework. Consequently, LLCMO exhibits a 3.2-fold higher Li+ diffusion coefficient than pristine LMO. Furthermore, it delivers 111.2 mAh g⁻¹ at 0.5 C with 90.9% retention after 100 cycles, and remarkably retains 76.0 mAh g⁻¹ after 1000 cycles even at 10 C. Thus, this dual-doping strategy establishes a generalizable design principle for enhancing stability/kinetics in diverse cathodes via a synergistic division-of-labor mechanism.</p><p></p>