Performance and ageing behavior of water-processed LiNi0.5Mn0.3Co0.2O2/Graphite lithium-ion cells

In this study, water-processed LiNi0.5Mn0.3Co0.2O2 cathodes (NMC532) are investigated. Notably, corrosion of aluminum current collector occurring in aqueous processing owing to alkalinity of NMC slurry is avoided through addition of phosphoric acid which buffers the slurry pH, or by using a carbon-coated collector. The impact of small amounts of phosphoric acid on the electrochemical performance is evaluated in half-cells, and the best formulations are selected to perform further ageing tests in pouch cells. In particular, post mortem analyses such as electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy are conducted on the cathodes after long-term cycling in Li-ion cells to fully understand the enhanced cycling stability observed with H3PO4-containing water-based cathode. These analyses allow to conclude on the influence of the binder, the current collector, and the aqueous immersion of the NMC532 powder.