A typical electrochemical battery undergoes spontaneous ignition and subsequent blast from overheating, which may arise due to various reasons such as short-circuit, overcharge, over-discharge, poor handling, etc. Thus, safety is a prerequisite for energy storage systems along with performance and cost, especially when targeting grid-scale applications. Sodium-ion batteries (SIB) are promising candidates for the next-generation energy storage systems for large-scale, especially grid storage systems, due to its resource abundance and low cost. However, the sluggish reaction kinetics associated with the large radius of the sodium ions result in serious polarizations and unwanted side reactions, which in turn triggers rapid degradation of the electrode material by manifesting as an exothermic reaction. In addition, SIB has a highly soluble solid electrolyte interphase (SEI) layer. Continuous exothermic decomposition and restoration of the unstable SEI layer lead to inadequate SEI coverage on the electrode surface and undesired side reactions, which in turn accelerates the cell heat generation and initiates thermally catastrophic events.The formation and properties of the SEI layer are governed by the choice of electrolytes in the batteries. Thus, the investigation of the thermal energy generated during the chemical/electrochemical reactions in the presence of different electrolyte solutions is of utmost importance from the context of safe battery operation. In this study, 1 M of NaPF6 or NaClO4 salts were used either in a single solvent or mixed carbonate solvents (EC, PC, DEC).&nbsp; As electrolyte additives have a role in stabilizing the SEI layer and the onset of thermal runaway is closely related to the stability of the SEI layer, FEC additive was chosen in combinations with carbonate solvents for comparison. Thermal stability studies were conducted for tin (Sn) electrodes (micro and nano) in different electrolytes using differential scanning calorimetry (DSC) and accelerating rate calorimetry (ARC) tests. Further, a comprehensive thermo-electrochemical analytics approach is adopted to simulate and identify the kinetic parameters (e.g., the heat of reaction, activation energy, and frequency factor, etc.) from calorimetric experiments. The physics-based model captures the multiple deleterious side reactions to accurately predict the response of alloy-based electrodes in SIBs under thermal abuse conditions. To have a better understanding of the thermal behavior of SIBs, this study focuses on the thermal instability signatures of electrode-electrolyte interaction. The discussion presented here about the thermal failure issues of SIBs using alloy-based Sn material as an exemplar system will serve as a design guideline to select the electrolytes to build a safer SIB.

Analysis of Thermal Stability of Sodium-Ion Batteries

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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