Operando Neutron Powder Diffraction Using Cylindrical Cell Design: The Case of LiNi0.5Mn1.5O4 vs Graphite

In order to follow the structural changes correlated to the evolution of the lithium content in high voltage battery systems (based on a disordered LiNi0.5Mn1.5O4 (d-LNMO) and a graphite electrode), we developed a new cylindrical cell suitable for operando neutron diffraction measurements. The cell, containing two grams of electroactive materials, is able to cycle at a fast rate (1C) with reliable electrochemical performance. The operando neutron diffraction measurements revealed the evolution of the lattice parameters of both the d-LNMO and graphite phases, notably showing the transitions between graphite lithiation stages. Furthermore, as a result of Rietveld refinements, the lithium consumption could be attributed mainly to the formation of a solid electrolyte interphase (SEI) layer on the graphite surface. This approach provides important insights helping to optimize the loading of the electroactive materials in batteries, especially for high voltage systems in which side reactions and lithium consumption can occur during cycling.