LiNi0.8Co0.15Al0.05O2 (NCA)@Cr2O5 composite electrode combines the high rate-capability characteristics of NCA with the stability of Cr2O5, playing a synergistic role in improving the cyclic stability, initial dis-charge capacity and the security of low cut-off voltage (2.0 V). When the mass ratio of Cr2O5 in NCA is 45％(mass), the capacity retention rate increases from 58.5％without Cr2O5 to 69.3％in the range of 2.0–4.3 V. The initial discharge capacity of NCA@Cr2O5 composite material is 211.4 mA?h?g?1, its first coulombic effi-ciency is 94.2％, and the charging capacity remains approximately constant when mixed with 15％(mass) Cr2O5. The reason for the improvement of the initial charge–discharge efficiency (ICDE) was explained. Impedance and cyclic voltammetry analysis reveal more detailed reasons of the observed improvements. Compared with NCA cathode material, the NCA@Cr2O5 composite material can provide not only addi-tional stable sites and channels for Li+ insertion/extraction to make up for the loss of active Li+ sites and prevent the accumulation of Li+in the circulation process, but also protect the NCA electrode from the corrosion of the electrolyte decomposition by the Cr2O5 nanoparticles adhering to NCA interface.