Modified Nickel-Rich Cathodes via Conformal Nanoparticle Coating of Precursors Using a Single Reactor Process

Abstract

Ni-rich LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathode materials, with a higher energy density compared to current commercial cathodes, are looked upon as the next improvement in lithium-ion batteries. However, modifications are needed to address issues of capacity fading due to a variety of degradation mechanisms, most of which initiate at the cathode/ electrolyte interface. In this work, this issue is addressed by modifying a typical coprecipitation method to develop a heterogeneous precursor composed of transition-metal hydroxides coated with nanoparticles of composition Mn 2.7 Co 0.3 O 4 . Reactor conditions and feedstock are altered to induce nanoparticle formation directly after NMC811 hydroxide secondary particle formation, with pH, feedstock solution, and reaction time being significant factors. The lithiated and sintered cathode maintains a high initial capacity of ∼215 mAh/g because of the Ni-rich base material and an improvement of capacity retention of over 40% at both 25 and 55 °C temperatures due to a conformal nanoscale coating of LiMn 1.8 Co 0.2 O 4 spinel material. Electrochemical analysis combined with transmission electron microscopy indicates that improvements are attributed to the suppression of impedance growth by reducing undesirable reactions between the Ni-rich cathode and electrolyte in the highly discharged state. This work demonstrates a practical method for synthesizing spinel-coated NMC during initial precursor synthesis as a step toward high-throughput commercialization of Ni-rich NMC cathodes.

Stability Enhancement and Microstructural Modification of Ni-Rich Cathodes via Halide Doping

“…NMC811 hydroxide precursors were synthesized via a coprecipitation route described in a previous study. 34 Summarily, a solution of transition-metal sulfates in the desired stoichiometric ratio is added dropwise to a glass-jacked reactor alongside the addition of an ammonia solution that functions as a chelating agent. The reactor pH is maintained at 11.0 ± 0.2 using a pH controller and NaOH buffer solution, which also functions as the precipitating agent.…”