Is Aluminium Useful in NiMn Cathode Systems?: A Study of the Effectiveness of Al in Co-Free, Ni-Rich Positive Electrode Materials for Li-Ion Batteries

Aluminium has become a dopant of interest in many positive electrode materials, particularly the widely used LiNi1-x-yMnxCoyO2 (NMC). Despite the shift of the positive electrode active material space towards Co-free alternatives, the benefits of Al-doping in Co-free LiNixMn1-xO2 (NM) systems have yet to be extensively studied. In this work a series of polycrystalline NM and NMA pairs are compared head-to-head to better understand the effect of Al in Ni-rich, Co-free systems in terms of electrochemical, mechanical, surficial, and thermal stability. The materials tested vary in Ni-content, Al-doping amount as well as secondary particle size, as these parameters influence the effect of Al-presence on certain aspects of material performance. Although Al can bring certain advantages to NM materials, Al-substitution does not universally lead to improved performance in these systems.