Key Words:Sodium alloys;Anodes - Binary alloys - Cathodes - Dendrites (metallography) - Doping (additives) - Electric batteries - Electrolytes - Liquids - Metal ions - Metal nanoparticles - Metals - Phase interfaces - Porous materials - Potassium alloys - Reaction kinetics - TiO2 nanoparticles - Titanium dioxide
Abstract:The significant issues with alkali metal batteries arise from their poor electrochemical properties and safety problems, limiting their applications. Herein, TiO<inf>2</inf> nanoparticles embedded into N-doped porous carbon truncated ocatahedra (TiO<inf>2</inf>⊂NPCTO) are engineered as a cathode material with different metal anodes, including solid Na or K and liquid Na–K alloy. Electrochemical performance and kinetics are systematically analyzed, with the aim to determine detailed electrochemistry. By using a galvanostatic intermittent titration technique, TiO<inf>2</inf>⊂NPCTO/NaK shows faster diffusion of metal ions in insertion and extraction processes than that of Na-ions and K-ions in solid Na and K. The lower reaction resistance of liquid Na–K alloy electrode is also examined. The higher b-value of TiO<inf>2</inf>⊂NPCTO/NaK confirms that the reaction kinetics are promoted by the surface-induced capacitive behavior, favorable for high rate performance. This superiority highly pertains to the distinct liquid−liquid junction between the electrolyte and electrode, and the prohibition of metal dendrite growth, substantiated by symmetric cell testing, which provides a robust and homogeneous interface more stable than the traditional solid−liquid one. Hence, the liquid Na–K alloy-based battery exhibits to better cyclablity with higher capacity, rate capability, and initial coulombic efficiency than solid Na and K batteries.<br/> © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Volume:15
Issue:12
Translation or Not:no