Understanding the growth mechanism of lithium-rich layered oxides in molten salts route for high performance lithium-ion batteries

Lithium-rich layered oxides (LLOs) with "single-crystal" structures can effectively reduce stress caused by volume distortion and improve stability. However, current work has primarily focused on the growth behavior of LLOs in single molten salt systems, with limited investigation into the impact of molten salt quantity on growth. This study explores the growth behavior of precursors and LLOs in different molten salt systems (NaCl, KCl, CsCl) and varying salt concentrations, while also examining the effect of cations on LLOs performance. By adjusting the molar ratio of molten salt to precursor, two distinct growth pathways are achieved: a lower molar ratio promotes a chemical topological transformation, while a higher ratio favors a dissolution-recrystallization mechanism. Additionally, the growth behavior of crystals is influenced by molten salt viscosity; higher viscosity inhibits product growth. When KCl is employed as the molten salt with a ratio of 4, the resulting flake structure demonstrates excellent cycling stability (86.2 % capacity retention after 150 cycles at 1C), attributed to a reduced percentage of spinel-like structure. This work not only provides insights into the crystal growth modes of layered oxides in molten salt systems but also facilitates the exploration of the relationship between crystal morphology and battery performance.