Synthetic Pathway Determines the Non-equilibrium Crystallography of Li- and Mn-rich Layered Oxides

Li- and Mn-rich layered oxides show significant promise as electrode materials for future Li-ion batteries. However, accurate descriptions of its crystallography remain elusive, with both single-phase solid solution and multi-phase structures being proposed for high performing materials such as Li_1.2Mn_0.54Ni_0.13Co_0.13O₂. Herein, we report the synthesis of single- and multi-phase variants of this material through sol-gel and solid-state methods, respectively, and conclusively demonstrate that its crystallography is a direct consequence of the synthetic route and not an inherent property of the composition, as previously argued. This was accomplished via complementary techniques that probe the bulk and local structure followed by in situ methods to map the synthetic progression. As the electrochemical performance and anionic redox behaviour is often rationalised on the basis of the presumed crystal structure, clarifying the structural ambiguities is an important step towards harnessing its potential as an electrode material.