Peculiarities of charge-discharge processes in Prussian white electrodes with different level of dehydration

Abstract

Prussian White (PW) is a promising cathode material for sodium-ion batteries. PW exhibits advantages such as high specific capacity, ease of synthesis, and low cost. However, the presence of interstitial and coordinated water in PW materials significantly influences their electrochemical properties. In this work, a dehydration of the commercial PW powder and an impact of the preheating of the PW electrodes on their structural and electrochemical behavior have been examined using in situ/operando neutron and X-ray diffraction, along with complex TG-IR and FTIR techniques. The dehydration of the PW powder under the vacuum annealing conditions occurs mainly between 100 and 150 °C. At temperatures above 180 °C, a decomposition of the PW powder is detected. Preheating the electrode at 180 °C promotes the formation of a larger fraction of dehydrated rhombohedral phase, resulting in higher capacity compared to electrodes without preheating and preheated at 140 °C. Carbon content has been shown to be an important factor for stable electrode cycling. Capacity values of ∼100 mAh g–1 and 83 mAh g–1 at 5 C and 10 C cycling rates, respectively, are achieved when using 15 wt% content of carbon additive for the electrode preparation. Structural aspects of the degradation of PW electrodes during cycling are discussed.