Controlling the Microstructure of Cobalt-Free, High-Nickel Cathode Materials with Dopant Solubility for Lithium-Ion Batteries

Microstructural engineering is becoming notably importantin therealization of cobalt-free, high-nickel layered oxide cathodes forlithium-ion batteries since it is one of the most effective ways toimprove the overall performance by enhancing the mechanical and electrochemicalproperties of cathodes. In this regard, various dopants have beeninvestigated to improve the structural and interfacial stabilitiesof cathodes with doping. Yet, there is a lack of a systematic understandingof the effects of dopants on microstructural engineering and cellperformances. Herein, we show controlling the primary particle sizeby adopting dopants with different oxidation states and solubilitiesin the host structure as an effective way for tuning the cathode microstructureand performance. The reduction in the primary particle size of cobalt-freehigh-nickel layered oxide cathode materials, e.g., LiNi0.95Mn0.05O2 (NM955), with high-valent dopants,such as Mo6+ and W6+, gives a more homogeneousdistribution of Li during cycling with suppressed microcracking, cellresistance, and transition-metal dissolution compared to lower-valentdopants, such as Sn4+ and Zr4+. Accordingly,this approach offers promising electrochemical performance with cobalt-freehigh-nickel layered oxide cathodes.