Poor thermal stability and severe structural degradation of Ni-rich LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode during the (de)lithiation process hinder its further application. As a typical thermal barrier material and ion conductor, La2Zr2O7 (LZO) was herein served as the multifunctional modification layer due to its excellent thermal stability, robust chemical stability, and prominent Li+ conductivity. Through optimizing the contents of LZO, 2 wt.% LZO-coated NCM622 (2LZO-NCM) displayed the much improved cycling stability (66.0% capacity retention at 0.2 °C after 300 cycles at 55 °C) and rate capability (73.0 mAh g−1 at 5 °C) as compared with the pristine NCM622 (59.3%, 22.4 mAh g−1). An aging test, differential scanning calorimetry research, and kinetics analysis were conducted to unveil the improvement mechanism of electrochemical performances for 2LZO-NCM, mainly owing to the relieved structure degradation, boosted thermal stability, and enhanced electrochemical kinetics after LZO modification, synergistically contributing to the improved electrochemical performances. This work provides a universal avenue to enhance the thermal stability and electrochemical performances of the NCM622 cathode via employing the thermal barrier material as a coating layer, even in other cathodes beyond NCM622.