Single-crystalline LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2 (denoted as SC-523) with micron size had been successfully synthesized through a facile method. Electrochemical impedance spectroscopy and differential scanning calorimetry were carried out to identify the improved electrochemical performance and desired thermal stability. Even after 100 cycles, SC-523 still delivered a discharge capacity of 151.1 mA h g.sup.-1 (capacity retention with 90.3%) at 1 C in voltage range from 3.0 to 4.5 V (vs. Li/Li.sup.+), while polycrystalline spherical LiNi.sub.0.5Co.sub.0.2Mn.sub.0.3O.sub.2 (denoted as PC-523) only exhibited 141.7 mA h g.sup.-1 (capacity retention with 78.4%). Besides, SC-523 shows a higher decomposition temperature of 332.13 °C, 14.61 °C higher than that of PC-523 during the thermal decomposition. Consequently, single-crystalline particles with robust morphological integrity ensure the enhanced cycling stability and thermal stability.