Aiming at the problem of uneven mixing during the preparation of LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) by high-temperature solid-state method, a nanoscale porous NiO material was synthesized as nickel source in this paper to prepare NCM622 cathode materials with high performance by traditional high-temperature solid-state method. X-ray diffraction and a scanning electron microscope were used to characterize the obtained materials. An electrochemical workstation and battery tester were also used to characterize the electrochemical performance of the prepared samples. The results showed that the obtained nickel source (nanoscale NiO) had a porous nanoscale structure, which could be mixed evenly with other raw materials by ball milling operation without the aid of liquid phase, so as to solve the shortcoming (uneven mixing) of the solid-phase method. The obtained NCM622 material (calcination at 900 °C for 10 h) not only had good layered structure, but also showed low cation mixing degree. The sample also had a discharge specific capacity of 196.4 mAh·g⁻¹ at 0.1 C during the normal charge-discharge voltage range (2.8–4.3 V), showing excellent high capacity performance. Moreover, its 95.0% discharge capacity retention rate after 100 cycles at 0.5 C (under half-cell condition) was also impressive, indicating good cycle stability.