Spinel LiNi0.5Mn1.5O4 (LNM) is a potential high-voltage cathode for commercial lithium-ion batteries (LIBs). Maintaining an appropriate amount of Mn3+ in LNM is necessary to improve the rate performance. However, Mn3+ dissolution in the interface of LNM and electrolyte leads to the fast capacity degradation. Therefore, designing a cathode to prevent Mn3+ loss during charge/discharge is important for high performance LIBs. Here we present an active core-shell design with coating another high-voltage cathode material LiCoPO4 (LCP) on the surface of LNM nanoparticles. The LCP layer can simultaneously induce Mn3+ ions at the interface between LCP and LNM, and act as a stable shell to prevent the loss of Mn3+. The optimized sample LNM@5%LCP possesses 128 mAh g−1 at 0.5 C and 115 mAh g−1 at 20 C rate, and maintains 96% of the initial capacity operated at 55 °C over 100 cycles.