Investigation of Firing Conditions and Boron Fluxes for the Optimized Synthesis of LiNi_0.9Mn_0.05Co_0.05O₂ for High Energy Density Li‐Ion Batteries

Nickel‐rich layered oxide cathodes, such as LiNi 0.9 Mn 0.05 Co 0.05 O 2 (NMC 90‐5‐5) exhibit high energy densities but face challenges related to capacity fade and structural instability that arise during the material synthesis procedure. This study explores their synthesis shorter firing times and lower firing temperatures via large‐scale hydroxide precipitation and boron‐based fluxes during sintering. After optimisation, critical insight into the effect of the fluxes, on the structural and electrochemical properties of NMC 90‐5‐5 are investigated. Boric acid reduced bulk cation mixing and surface lithium residues, improving initial capacity (200 mAh g −1 ), rate capability, and charge transfer resistance. However, it led to significant capacity fade due to the irreversible phase transition at 4.1 V vs Li/Li+ (25% after 200 cycles). Conversely, borax yielded slightly lower initial capacity (185 mAh g −1 ), however, it exhibited superior cycle life performance, (75% capacity retention after 200 cycles). Boron and sodium were shown to doped further into the cathode particles, delaying the on‐set of the high voltage phase transition. This study highlights the role of boron‐based fluxes in tailoring the performance and cycle life of Ni‐rich NMC cathodes produced under lower energy synthesis conditions. This results in a significant reduction of energy and cost at scale.