The objective of this study was to develop an electrolyte composition for high-power Na-ion batteries for specific industrial applications. A particular focus was placed on investigating the impact of electrolyte composition on the battery performance at high and low temperatures, as well as the self-discharge. Electrolytes were tested at various solvent proportions, composed of selected carbonates (EC, PC, and EMC). Moreover, additives of different natures and various salt concentrations were investigated in an attempt to reach high power, especially at low temperatures. Experiments were divided into two groups. Firstly, electrolytes were examined by physicochemical methods. Viscosity and conductivity measurements were carried out to assess the dependency of the ionic transport on temperature for various electrolyte compositions. Secondly, the electrochemical characterization of selected formulations was carried out in two generations of cylindrical 18650 cells. Several tests verified the electrolyte contribution on battery performance, including galvanostatic cycling with potential limitations for measuring the SEI/CEI layers formation, self-discharge and recovery tests, stability and retention tests, and rate capability tests. Lastly, salt concentration impact on the battery performance was investigated in coin cells. The improved results achieved in this study shows that electrolyte formulation plays a vital role in Na-ion batteries for high power application.
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