The effect of Mo doping on the electrochemical performance of Li(Ni0.6Mn0.4)1−xMoxO2 cathodes

Abstract

Cobalt-free, nickel-rich layered oxide cathode materials LiNi_xMn_1−xO₂ (NM) have attracted much attention due to their high specific capacity and low cost. However, cobalt-free cathode materials have more serious problems such as Li/Ni disorder and structural degradation compared to ternary LiNi_xCO_yMn_1−x−yO₂ (x ≥ 0.5, NCM) cathodes. To address these challenges, LiNi_0.6Mn_0.4O₂ (NM64) and a series of Mo-doped Li(Ni_0.6Mn_0.4)_(1−x)Mo_xO₂ (x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05) cathode materials were designed and prepared by a high-temperature solid-phase method, and the effect of Mo doping on the structure and electrochemical performance of NM64 cathodes was systematically investigated. Mo doping not only suppresses Li/Ni mixing and enlarges interlayer spacing but also effectively inhibits primary particle overgrowth, resulting in refined particle morphology that enhances structural stability and Li+ transport kinetics. Consequently, the Mo-doped NMM cathodes exhibit a more stable interface with significantly suppressed side reactions. The Li(Ni_0.6Mn_0.4)_0.98Mo_0.02O₂ cathode exhibited a superior capacity retention of 86.83% after 100 cycles at 1.0C (at 25 °C and 2.8–4.3 V), surpassing the NM matrix by 8.98% and demonstrating a remarkable cycling stability improvement. This work elucidates the structural and interfacial stabilization mechanisms induced by high-valent Mo doping, providing an effective approach for developing high-performance Co-free layered oxide cathodes.