Search for: All records

Transition metal oxides (TMO) are a promising group of cathode structures due to their tunable chemistry and great versatility of structures for Na-ion batteries. These features offer room for improvements in capacity and nominal voltage of the cathode. The composition of TMO cathodes can be expressed as NaxMeO2 where Me denotes transition metal (e.g. Mn, Fe, Cr, and Ni.). During cycling, the repeated insertion and removal of Na ions into the structure of the TMOs results in complex phase transformations and associated continuous volumetric expansions/reductions. The TMO cathodes can experience a mechanical failure (e.g., particle fracture) due to their brittleness. Furthermore, the interaction between transition metals in TMO structure with electrolyte as well as reduction of electrolyte species, could lead to the formation of cathode-electrolyte (CEI) interphase layers. These chemo-mechanical instabilities play a vital role in the electrochemical performance of the TMO cathodes. However, there is not much known about how mechanics, electrochemistry, and structural evolution couple in TMO cathodes for Na-ion batteries. In this presentation, 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. [1] Then, I will discuss the chemo-mechanical deformations in transition metal oxide cathodes (e.g. NaCrO2, NaFeO2 and NaNiO2) at higher state-of-charge. Then, I will present instability mechanisms in transition metal oxide cathodes when charged at higher voltages. In summary, the study bridges complicated structural deformations with in-situ analysis of mechanical degradations in layer metal oxide cathodes for Na-ion batteries. ACKNOWLEDGMENTS Ö. Ö. Ç. is thankful for the financial support from the National Science Foundation Faculty Early Career Development (CAREER) Program (Award number 2402216). We are grateful to Dr. Christopher Johnson, Dr. Eungje Lee, Dr. Jehee Park and Dr. Jihyeonat Gim at Argonne National Laboratory for synthesizing NaFeO₂and NaNiO₂cathodes. REFERENCESM. Wable et al., JOM, 76, 1099-1109, 2024 

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. 

Abstract Rechargeable Na-based batteries have received tremendous attention as a post-lithium energy storage device due to their lower cost and competitive energy density for grid-storage and transportation applications. However, the practical performance of Na-based batteries suffers from severe chemo-mechanical instabilities in electrode materials associated with structural and interfacial deformations during cycling. Mitigating these instabilities is crucial for achieving higher performance in Na-based batteries for widespread commercialization and industrial utility. This perspective focuses on the state-of-the-art in Na metal and Na-ion batteries, with an emphasis on chemo-mechanical phenomena in electrode materials. The perspective points out the current challenges in hard carbon, alloy, and Na metal anodes as well as transition metal oxides, Prussian blue analogs, and polyanion-type cathodes together with issues related to cathode–anode electrolyte interphase. Advanced characterization techniques are briefly discussed to shed light on the complex instability mechanisms in Na-based electrodes. We also delve into several material-based strategies to design next-generation Na electrodes for improved performance. 

Na-ion batteries (NIBs) have emerged as a promising alternative due to their similar energy storage mechanisms to lithium-ion batteries (LIBs) while utilizing earth-abundant, sustainable, and cost-effective materials, making them ideal candidates for large-scale grid energy storage applications. Layered transition metal oxide cathodes, which have proven successful in LIBs, are also attractive for NIBs due to their high specific capacity, tunable structure, variety of redox-active elements, and the ease of synthesis and scalability. Despite these advantages, NIB cathodes face challenges such as structural instability at higher state-of-charge, poor rate capability, and limited cycle life. Overcoming these limitations requires a thorough understanding of the fundamental structural changes occurring within electrodes during cycling.¹ This study provides a comprehensive investigation into the stress and strain evolution of NaCrO₂cathodes during electrochemical cycling. Operando strain and stress measurements were performed on NaCrO₂composite electrodes within a custom cell assembly, employing digital image correlation and curvature measurement techniques, respectively.²The cells were cycled using a 1 M NaClO₄in PC electrolyte. During low-voltage cycling (2.3 V to 3.6 V vs Na⁰), significant irreversible strain was observed during the initial cycle, which diminished upon subsequent cycles. Negative strain occurred during desodiation at lower states of charge, transitioning to positive strain at higher states of charge. Conversely, during sodiation, negative strain appeared at lower states of discharge and positive strain at higher states of discharge. During higher-voltage cycling (2.3 V to 4.2 V vs Na⁰), substantial irreversible strain was detected, primarily resulting from structural collapse when more than 80% of Na-ions was removed from the structure. Phase transitions were identified through ex-situ XRD analysis, while changes in charge-transfer resistance were monitored throughout the cycling process using in-situ impedance measurements. This study offers valuable insights into the structural evolution of NaCrO₂cathodes, providing a foundation for developing more stable and efficient materials for sodium-ion batteries. Acknowledgement:This work is supported by National Science Foundation's (NSF) Faculty Early Career Development (CAREER) Program, 2142726. References:Chan-Yeop Yu, et. al.Energy Environ. Sci., 2015,8, 2019-2026.Minal Wable, et. al.Energy Adv., 2024, 3, 601-608 

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 

Hard carbon is a promising anode material for Na-ion batteries due to its lower operation voltage and satisfactory capacity. It can be synthesized from waste material resources with a pyrolysis process.¹Hard carbon is an amorphous material containing randomly oriented graphene layers with numerous structural defects and nanovoids. Hard carbon has larger interlayer spacing than crystalline graphite and this feature allows Na ions to be intercalated into Hard carbon reversibly.²However, the practical performance of hard carbons suffers from poor rate capability and low initial Coulombic efficiency. Unfortunately, not much is known about the driving forces behind the interfacial and structural deformations in Hard carbon during battery cycling. Also, the storage mechanism of Na- ions in hard carbon is still under debate.³ To address this gap, in this study, we utilized operando mechanical measurements to probe electrochemical stress and strain generation in the Hard Carbon during battery cycling. The composite electrode was prepared by mixing Hard Carbon, CMC, and Super P Carbon in the ratio of 8.5:1.0:0.5 in mass, respectively. Digital image correlation and multi-beam optical stress sensor were utilized to monitor strain and stress generation in the electrode, respectively while cycling at a constant current between 0.01 to 2.0 V vs Na^0/+. In this talk, we will present potential-dependent mechanical deformation in Hard carbon and discuss the charge storage mechanism under the guidance of operando mechanical measurements. Acknowledgement:This work is supported by the National Science Foundation (award number 2344722). We are grateful to Dr. Montse Casas-Cabanas and Dr. Damien Saurel from CIC energiGUNE for providing the Hard Carbon samples. References:1) N. Nieto et al.ChemSusChem2023, 16, e202301053; 2) N. Tapia-Ruizet al2021J. Phys. Energy3031503; 3) H. Alptekin et al., ACS Appl. Energy Mater. 2020, 3, 10, 9918–9927 

Sodium chromium oxide, NaCrO2, exhibits promising features as a cathode electrode in Na-ion batteries, yet it encounters challenges with its capacity fading and poor cycle life. NaCrO2 undergoes multiple phase transitions during Na ion intercalation, eventually leading to chemical instabilities and mechanical deformations. Here, we employed the digital image correlation (DIC) technique to probe electrochemical strain generation in the cathode during cycling via cyclic voltammetry and galvanostatic cycling. The electrode undergoes significant irreversible mechanical deformations in the initial cycle, and irreversibility decreases in the subsequent cycles. During desodiation and sodiation, the electrode initially undergoes volume contraction at lower state-of-(dis)charge followed by expansions at a higher state-of-(dis)charge. The similar progression between strain and capacitive derivatives points out the phase-transition-induced deformations in the electrode. The evolution of cumulative irreversible strains with cycling time indicates the irreversibility rising from the formation of cathode-electrolyte interphase layers. The study demonstrates valuable insights into mechanical deformations in NaCrO2 electrodes during battery cycling, which is critical to engineer mechanically robust cathodes for Na-ion batteries. 

The battery chemistry must be diversified to achieve a sustainable energy landscape by effectively utilizing renewable energy sources. Alkali metal-ion, all-solid-state, metal-air batteries, and multivalent batteries offer unique cost, safety, raw material abundance, energy, and power density solutions. However, realizing these “Beyond Li-ion batteries” must uncover their working principles and performance & property relationship. In this aspect, mitigating chemo-mechanical instabilities in the structure and surface of the electrodes plays a crucial role in their performance. Unfortunately, the coupling between electrochemical and mechanical interactions is often poorly understood due to a lack of operando characterization. This review article explains the working principles of curvature measurement and digital image correlation for measuring stress and strain generations in battery materials. We provided specific examples of how these operando mechanical measurements shed light on instabilities in alkali-metal ion electrodes, solid electrolytes, Li-O2 batteries, and aqueous Zn-ion batteries. Operando mechanical measurements offer an effective way to map changes in the physical fingerprint of the battery materials, therefore providing crucial information to elucidate instabilities in battery materials. 

Layer-structured Na intercalation compounds such as NaxMO2 (M=Co, Mn, Cr) have attracted much attention as cathode materials for sodium-ion batteries due to their high volumetric and gravimetric energy densities. Among them, NaCrO2 with layered rock salt structure is one of the promising cathodes since NaCrO2 has a desirable flat and smooth charge/discharge voltage plateau.1 In addition, NaCrO2 has the highest thermal stability at charged state which makes it a potentially safer cathode material.2 The NaCrO2 exhibits a reversible capacity of 110 mAh g-1 with good cycling performance.3 However, the transition metal oxide (TMO) cathode materials in NIBs undergo severe chemo-mechanical deformations which leads to capacity fade and poor cycling and is the limiting factor of NIBs. The electrochemical characterization and examination of the electrode structure were the primary focus of several investigations. To improve the lifespan and performance of electrode materials for Na-ion batteries, it is vital to comprehend how Na ions impact the chemo-mechanical stability of the electrodes. In this talk, we will discuss the driving forces behind the structural and interfacial deformations on NaCrO2 cathodes. Digital image correlation measurements were conducted to probe strain evolution in the electrode during cycling. The free-standing composite NaCrO2 electrode was used for stain measurements in custom-cell assembly. The battery was cycled against Na metal in 1 M NaClO4 in PC. The first part of the study involves structural and interfacial deformations in the lower voltage range of 2.3 V to 3.5 V where x<0.5 in NaxCrO2. And the second part focuses on the structural and interfacial deformations in the voltage range of 2.3 V to 4.7 V where x>0.5 in NaxCrO2. In the preliminary studies, we observed that the initial insertion of Na ions leads to negative strain evolution (contraction) in the electrode, followed by expansions in the electrode at a higher state of discharge. Similar phenomena are also observed during charge cycles, where extraction of Na results in an initial contraction in the electrode, followed by expansion at a higher state of charge. Understanding the mechanisms behind chemo-mechanical deformations will allow to tune structure & material property for better electrochemical performance.