AnEutectic SaltBoosts Lithiation Kinetics of Co-FreeLayered Cathode Crystallization Achieving Superior ElectrochemicalPerformances

The transition to sustainable lithium-ion batteries is accelerating the quest for cobalt-free (Co-free) cathodes, offering a promising avenue to reduce production costs without compromising energy density. However, the synthesis of Co-free cathodes is impeded by challenges, such as cation disordering, particle defects, and surface residues, which significantly degrade battery performance. Although existing solutions have made strides in addressing these issues individually, a simple and scalable method to address them comprehensively is urgently needed. We introduce an efficient strategy that leverages the kinetic advantages of a LiOH-LiNO₃ eutectic salt mixture to enhance lithiation kinetics during the calcination of LiNi_0.8Mn_0.2O₂ cathodes, thereby overcoming crystallization-related hurdles. Our comparative study demonstrates that the eutectic salt accelerates mass transport at lower temperatures and enhances Ni-ion oxidation at higher temperatures, broadening the effective lithiation temperature window and accelerating topotactic phase transformations. This leads to cathodes with reduced cation disorder, diminished particle voids, and decreased surface residue, culminating in substantial improvements in the initial Coulombic efficiency, cycling stability, and rate capability. Our method presents a comprehensive solution to the intrinsic crystallization challenges of Co-free materials, streamlining the synthesis process and significantly enhancing the cathode performance, paving the way for large-scale industrial production.