Effect of Mo doping on electrochemical Performance of Li(Ni 0.6 Mn 0.4 ) 1-x Mo x O 2 cathodes

Abstract

Cobalt-free, nickel-rich layered oxide cathode material LiNixMn1-xO2 (NM) has attracted much attention due to its 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 LiNixCOyMn1-x-yO2 (x ≥0.5, NCM) cathodes. To address these challenges, LiNi0.6Mn0.4O2 (NM64) and a series of Mo-doped Li(Ni0.6Mn0.4)(1-x)MoxO2 (x = 0, 0.01, 0.02, 0.03, 0.04, 0.05) cathode materials were designed and prepared by 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 more stable interface with significantly suppressed side reactions. Li(Ni0.6Mn0.4)0.98Mo0.02O2 cathode exhibited superior capacity retention of 86.83% after 100 cycles at 1.0 C (at 25℃ and 2.8-4.3 V), surpassing the NM matrix by 8.98% and demonstrating the remarkable cycling stability improvement. This work elucidates the structural and interfacial stabilization mechanisms induced by high-valent Mo doping, providing an effective approach to developing high-performance Co-free layered oxide cathodes.