Spinel LiNi_0.5Mn_1.5O₄ (LNMO) cathode draws significant attention in the field of energy storage due to its unique voltage plateau. To further enhance the long-term electrochemical stability of LNMO, the LNMO cathode covered with an ultrathin ZrO₂ layer was prepared through atomic layer deposition (ALD). It is found that the LNMO cathode deposited with 20 layers of ZrO₂ (LNMOZ20) exhibits the best electrochemical performance, achieving a high discharge capacity of 117.1 mA·h/g, with a capacity retention of 87.4% after 600 cycles at a current density of 1C. Furthermore, even at higher current densities of 5C and 10C, the LNMOZ20 electrode still demonstrates excellent stability with discharge capacities reaching 111.7 and 103.6 mA·h/g, and capacity retentions maintaining at 81.0% and 101.4% after 2000 cycles, respectively. This study highlights that the incorporation of an ultrathin ZrO₂ layer by ALD is an effective strategy for enhancing the long-term cycling stability of LNMO cathodes.