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The artificial coatings are designed to prevent structural degradation, side reaction between cathode and electrolyte solution, and uncontrolled growth of passivating cathode-electrolyte interphase layer. In addition, improvement in the rate capability, capacity retention and thermal stability of Na-ion cathode with artificial coatings has been reported for Li-ion batteries. However, lack of insight into interactions between mechanical, chemical, and structural properties of cathodes and their interface in Na chemistry limits the design of novel cathode materials for rechargeable Na-ion batteries. Our study aims to elucidate the role of the surface modifications on the governing forces behind chemo-mechanical deformations in the cathodes during Na-ion intercalation. In this talk, I will first describe digital image correlation and multi-beam optical stress sensor measurement techniques to probe instability mechanisms in battery electrodes. The combination of these techniques previously provided information about the interfacial and structural deformations in alkali metal ion battery electrodes.¹I will discuss the chemo-mechanical instabilities in transition metal oxide cathodes for Na-ion batteries. Then, I will present the impact of the surface modification on the chemical and mechanical instabilities of the cathode materials for Na-ion batteries. The study utilized the atomic layer deposition technique to deposit artificial metal oxide layers on the surface of the NaCrO2 cathode. Also, the study investigated how the electrolyte additive (e.g. FEC) forms an artificial layer during battery cycling. In summary, the study bridges complicated chemo-mechanical deformations with surface modification in layer metal oxide cathodes for NIBs. ACKNOWLEDGMENTS This work is supported by National Science Foundation (award number 2321405). REFERENCESM. Wable et al., JOM, 76, 1099-1109, 2024. 

Na-ion batteries have taken more interest in recent years as an alternative battery chemistry to Li-ion batteries because of material abundance, cost, and sufficient volumetric energy density for large-scale energy storage applications. However, Na-ion batteries suffer from rapid capacity fade associated with chemo-mechanical instabilities such as the formation of resistive solid-electrolyte / cathode-electrolyte interphase (SEI/CEI) layers, irreversible phase formations, and particle fracture. The cathode materials are fragile, especially metal oxides, therefore Na-ion cathodes are more prone to mechanical deformations upon larger volumetric expansions/reductions during Na-ion intercalation. Electrolyte additives have been utilized to improve the electrochemical performance of Li-ion and Na-ion batteries by modifying the chemistry of the SEI layers. In situ stress measurements on Si anode in Li-ion batteries demonstrated the generation of less mechanical deformations in the electrode when cycled in the presence of FEC additives.¹However, there is not much known about the impact of electrolyte additives on the chemo-mechanical properties of CEI layers in Na-ion battery cathodes. Furthermore, the question still stands about how the electrolyte additives may impact the mechanical stability of the Na-ion cathodes. To address this gap, we systematically investigated the role of FEC additives on the electrochemical performance and associated chemo-mechanical instabilities in NaCrO2 cathodes. Experiments were performed in organic electrolytes with/without FEC additives. First, the talk will start with presenting the impact of FEC additives on the capacity retention and cyclic voltammeter profiles of NaCrO2 cathodes. Then, digital image correlation and multi-beam optical stress sensor techniques were employed to probe electrochemical strain and stress generation in the composite NaCrO2 cathodes during electrochemical cycling in organic electrolytes with/without FEC additives. Surface chemistry of the NaCrO2 cathodes after cycling was investigated with the FT-IR measurements. In summary, the talk will present contrast differences in the electrochemical and chemo-mechanical properties of NaCrO2 cathodes when cycled in the presence of the FEC additives. Acknowledgement: This work is supported by National Science Foundation (award number 2321405). Reference: 1) Tripathi et al 2023 J. Electrochem. Soc. 170 090544