To achieve large-scale application of solvothermal method and settle structural collapse of polycrystalline ternary NCM cathode materials (LiNi_0.8Co_0.1Mn_0.1O₂, NCM811) during long charge and discharge cycling, single-crystalline NCM materials with high cycling stability were prepared by rapid ethanol−water solvothermal method. The morphology and electrochemical properties of NCM materials were characterized by X-ray diffractometry, cross-section scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical measurement. The results show that single-crystalline NCM synthesized with 60 min solvothermal time has the most excellent electrochemical performance. Its reversible capacity reaches 157.28 mA·h/g at 1C and retention rate achieves 55.06% after 200 cycles, which is much better than the polycrystalline NCM cathode material. Cross-section scanning electron microscopy results show that the single-crystalline NCM cathode material has no apparent cracks after 200 cycles.