A new facile approach to the surface modification of LiNi0.5Mn1.5O4 by lithium polyacrylate coating is demonstrated. This strategy is based on mild polymer electrolyte coating from aqueous lithium polyacrylate solution. The LiNi0.5Mn1.5O4 (LNM) and 1% PAALi coated LNM (LNM@1%PAALi) are characterized by XRD, SEM, TEM, ICP-OES, galvanostatic charge-discharge tests and electrochemical impedance spectra (EIS). XRD and SEM results indicate that there are no clear difference between LNM and LNM@1%PAALi. HRTEM results indicate PAALi is uniformly coated on LiNi0.5Mn1.5O4. ICP-OES results indicate that PAALi coating can effectively prevent the Ni ions and roughly prevent Mn ions dissolving from LiNi0.5Mn1.5O4 cathode materials. Galvanostatic charge-discharge tests show that the discharge capacity of LNM@1%PAALi reaches up to 131.5 mAh g−1 at 0.2C and the value is still as high as 101.5 mAh g−1 at 12C. In addition, LNM@1%PAALi shows high coulombic efficiency and retains 90.0% of its initial discharge capacity after 200 cycles. EIS proves that LNM@1%PAALi cells has distinct lower ohmic resistance of the electrolyte. SEM of the cycled electrodes implies that PAALi can promote the formation of valid SEI film, being favor of the compatibility between LNM and electrolyte.