Mitigating water-induced surface degradation in water-based Ni-rich Li-ion battery electrodes
S. Radloff, Rares‐George Scurtu, Gilberto Carbonari, Markus Hölzle, Thomas Diemant, Maral Bozorgchenani, Florian Klein, Margret Wohlfahrt‐Mehrens
Abstract
Replacement of the toxic solvent used during manufacturing of cathode electrodes for Li-ion batteries with water is an essential step on the road towards eco-friendly battery production. This study aims to improve the performance of pilot-scale water-based LiNi0.83Co0.12Mn0.05O2 cathodes. The importance of proper electrode treatment before cell assembly to achieve maximum cell performance is demonstrated. Temperatures ranging from room temperature to 170 °C were applied to the electrodes to investigate the impact of residual moisture in pouch cells. Electrochemical cycling showed that despite a much higher amount of residual moisture a low drying temperature was beneficial. X-ray photoelectron spectroscopy indicated that with increasing temperature a phase reconstruction in the near-surface region of the cathode material particles is the cause for the difference in performance. This was further supported by impedance spectroscopy showing growing charge-transfer resistance arcs with higher temperature, which split into two contributions with ongoing cycling. Already temperatures above 100 °C resulted in more pronounced surface reconstruction and stronger impedance increase lowering the long-term cycling stability, while the residual moisture seemed to have only a minor impact. By optimizing the drying temperature, the long-term cycling stability could be improved from 1000 to 1700 cycles before reaching 80% capacity retention.