Report Title:Introducing Specific Strategies for Designing Safer Li-ion and Na-ion Cells
Dr. Palani Balaya works as an Associate Professor at National University of Singapore. His research area includes developing safer lithium-ion battery and sodium-ion battery. He serves as Editorial Board Member of Journal of Power Sources (since 2025) and Ceramics International (since 2022). Elected as an Academician by the World Academy of Ceramics (WAC), Italy (2019) and Fellow of the American Ceramic Society (ACerS) in 2019. In 2025, he has been appointed as the Board of Directors to the ACerS and Advisory Board Member to the WAC. Delivered more than 160 talks (Plenary/Keynote/Invited) at international conferences/meetings and published 120 articles.
Abstract: Though Li-ion batteries are mostly used in a wide range of applications, their safety aspects are not fully addressed. Li-ion batteries are generally safe under standard operating conditions; however, they are known to undergo thermal runaway when subjected to a few operating abusive conditions such as mechanical (shock and vibrations), thermal (local heat generation at high rates) and electrical (exceeding cut-off voltage or lithium plating at high charge rates) etc., Similar observations are noted in the emerging direction of Na-ion batteries. Prolonged operation of the Li-ion or Na-ion cells at these abuse conditions results in poor energy efficiency which in turn is related to both the coulombic efficiency as well as voltage efficiency during charge/discharge cycles. These phenomena cause local heating in the cells which result in micro-shorting leading to thermal runaway. The voltage polarization responsible for the observed heat loss of the cells includes reversible loss due to entropy changes and irreversible loss due to internal resistance. Among several factors responsible for internal resistance of the cells, charge transfer resistance and Li or Na chemical diffusion at the positive electrodes are found to be the predominant contributors. We discuss here several design strategies to suppress thermal runaway by improving voltage efficiency of Li-ion and Na-ion cells. 1. Negligible voltage polarization is reported in LiFePO4 up to 20C due to enhanced 2-D Li chemical diffusion process caused by excess anti-site disorders. 2. Mg2+ substitution at Fe-site of the LiMnFePO4 substantially minimizes the voltage polarization due to enhanced Li chemical diffusion. 3. Use of glyme-based electrolytes in Na-ion cells favors non-flammability, higher thermal stability, and lower SEI resistance compared to carbonate-based electrolytes. 4. Zn substitution at V-site of Na3V2(PO4)3 reduces charge transfer resistance and increases Na chemical diffusion by an order of magnitude. 5. Use of solid electrolytes avoids solvation/de-solvation processes commonly known in liquid electrolytes, however poor ion transfer at the electrode/electrolyte boundaries introduces additional resistance causing inefficient charge transfer process compared to liquid electrolytes. This talk thus highlights several critical factors for designing Li-ion and Na-ion cells with enhanced safety features to suppress their thermal runaway.
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