Atomic layer deposition (ALD), as a thin film deposition technique, has been explored as a viable path to improve the performance of lithium-ion batteries. However, a trade-off between the species transport (capacity) and protection (lifetime), resulting from the insulating properties of ALD films, is the key challenge in ALD technology. Here we report a breakthrough to overcome this trade-off by coating an ultrathin conformal cerium dioxide (CeO2) film on the surfaces of LiMn2O4 particles. The optimized CeO2 film (≈3 nm) coated particles exhibit a significant improvement in capacity and cycling performance compared to uncoated (UC), Al2O3 coated, and ZrO2 coated samples at room temperature and 55 °C for long cycling numbers. The initial capacity of the 3 nm CeO2-coated sample shows 24% increment compared to the capacity of the uncoated one, and 96% and 95% of the initial capacity is retained after 1000 cycles with 1C rate at room temperature and 55 °C, respectively. The detailed electrochemical data reveal that the suppression of the impedance rise and the facile transport of the species are the main contributors to the success. CeO2 films are conformally coated on LiMn2O4 particles by atomic layer deposition (ALD). The optimized CeO2 film (≈3 nm) coated particles exhibit significantly higher initial capacity and much better stability than the uncoated samples, and ZrO2 and Al2O3 ALD coated samples. The detailed electrochemical data reveal that the suppression of the impedance rise and the facile transport of the species are the main contributors to the success.