Tuning Cation Disorder in LiNi 0 . 5 Mn 1 . 5 O 4 via Room Temperature Continuous‐Flow Co‐Precipitation and Controlled Heat Treatment

Abstract

A room temperature, continuous coprecipitation process with in‐line dynamic mixing (ACTIM) was used to synthesize a precursor (up to 0.42 kg h −1 ) to the high‐voltage cathode LiNi 0 . 5 Mn 1 . 5 O 4 (LNMO), consuming ~39% less energy at the coprecipitation step than a more conventional batch synthesis route. The coprecipitate was lithiated in air via a two‐step heat treatment (500 °C/5 h and then 850 °C/12 h), followed by a third treatment at 650, 700 or 750 °C to tune cation disorder. X‐ray Photoelectron Spectroscopy (XPS) gave surface Mn 3+ fractions of ca. 38, 46 and 53% for the 650, 700 and 750 °C samples, respectively, with (Mn K‐edge) X‐ray Absorption Spectroscopy (XAS) indicating the same trend in the bulk. The 750 °C sample under electrochemical testing, delivered a specific capacity of 124, 116 and 81 mAh g −1 at 0.1, 1 and 5 C, respectively. Furthermore, adding 2.5 wt % multi‐walled carbon nanotubes (MWCNTs) to the electrode raised the rate capability to 98 mAh g −1 at 5 C and 91 mAh g −1 at 10 C, with 98.4% capacity retention after 100 cycles at a 1 C current rate. The primary contribution of this work lies in demonstrating that a scalable, ambient temperature, energy‐efficient continuous‐flow coprecipitation process can produce LNMO cathodes with tunable disorder‐related characteristics.