LiNi0.5Mn1.5O4-δ (LNMO) as Co-free cathode for lithium ion batteries via solution-gel synthesis: Particle size and morphology investigation

Abstract

LiNi 0.5 Mn 1.5 O 4-δ (LNMO) is a potential candidate for high voltage Co-free cathodes in lithium-ion batteries. In this study, pre-calcination temperature, time, and oven type are showcased as important parameters influencing the particle size and morphology of the LNMO powder synthesized from the aqueous citric acid-acetates-NH 3 based method. These parameters determine the amount of organic residues in the precursor powder. A superior initial discharge capacity and capacity retention are obtained by an optimum combination of the particle size and morphology for the Li|LNMO coin cells. Pre-calcination in a forced convection oven at 200 °C for 40 h results in a voluminous and foam-like LNMO precursor powder morphology with the lowest amount of organic residue, leading to a ~ 1-4 µm powder with well-defined facets. Applying 24 h pre-calcination at 170 °C in a natural convection oven results in large LNMO aggregates of ~ 70 µm. Ball-milling of the crystalline LNMO powder is effective to reduce the agglomeration and particle size but deteriorates the electrochemical performance. An initial discharge capacity of 121 mA h g-1 at 0.2 C and a capacity retention of 90% after 400 cycles at 2 C are obtained from the samples prepared by 40 h pre-calcination at 200 °C in a forced-convection oven.