Nickel-rich LiNi_0.8Co_0.1Mn_0.1O₂ (LNCM811) is a promising lithium-ion battery cathode material, whereas the surface-sensitive issues (i.e., side reaction and oxygen loss) occurring on LNCM811 particles significantly degrade their electrochemical capacity retentions. A uniform Li₂ZrO₃ coating layer can effectively mitigate the problem by preventing these issues. Instead of the normally used weak hydrogen-bonding interaction, we present a covalent interfacial engineering for the uniform Li₂ZrO₃ coating on LiNi_0.8Co_0.1Mn_0.1O₂ materials. Results indicate that the strong covalent interactions between citric acid and Ni_0.8Co_0.1Mn_0.1(OH)₂ precursor effectively promote the adsorption of ZrO₂ coating species on Ni_0.8Co_0.1Mn_0.1(OH)₂ precursor, which is eventually converted to uniform Li₂ZrO₃ coating layers of about 7 nm after thermal annealing. The uniform Li₂ZrO₃ coating endows LNCM811 cathode materials with an exceptionally high capacity retention of 98.7% after 300 cycles at 1 C. This work shows the great potential of covalent interfacial engineering for improving the electrochemical cycling capability of Ni-rich lithium-ion battery cathode materials.