The double-edged role of O2- in preparing superior electrochemical performance NCM layered cathode through molten salt synthesis process

The preparation of LiNi x Co y Mn z O 2 (NCM) cathode through molten salt (MSs) reaction has great advantage in electrochemical performance due to its uniform and well-controlled reaction environment. However, the critical role of O 2- which acts as the essential reactant has never been considered. Here, homogeneous NCM523 cathode particles with low Li/Ni intermixing were synthesized in LiCl-containing molten salts, benefiting from the excellent O 2- dissolving capability of LiCl. The critical role of LiCl shows that it can either promote the uniform crystallization or leads to the collapse of the layered structure. Furthermore, by considering both O 2- solubility and low melting point, the prepared NCM523 cathode shows high specific capacity (173 mAh g −1 at 0.1 C, 4.3–2.8 V) and excellent capacity retention (96 % after 150 cycles at 1 C cycling). The NCM cathode preparing process in molten LiCl containing MSs shows both advance in thermodynamics and kinetics. This approach can also be successfully extended to other NCM cathode materials.