Strategic pH-controlled synthesis of single-crystal LiNi0.6Co0.2Mn0.2O2 for maximized structural and electrochemical optimization in lithium-ion batteries

The development of single-crystalline LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) cathodes has garnered significant interest in lithium-ion batteries due to their superior cycle stability and capacity retention compared to polycrystalline counterparts. However, achieving high-performance single-crystalline NCM622 cathodes remains challenging due to uncontrolled particle growth and side reactions. This study highlights the importance of pH control in precursor synthesis, as it crucially influences nucleation and crystallinity, essential for single-crystal formation. Optimized conditions (pH = 11.2, denoted as HP-4/SC-4) promoted solid-state nucleation and controlled particle growth, enabling the formation of single crystals during sintering. The SC-4 cathode exhibited an initial discharge capacity of 172.56 mAh g −1 with 87.78 % Coulombic efficiency, retaining 80.10 % capacity after 200 cycles. Notably, Coulombic efficiency stabilized above 99 % after 200 cycles, indicating minimal side reactions. Structural characterization confirmed the stability of the single-crystal architecture, underscoring its potential for high-energy battery applications and long-term cycle performance.