Multiscale tomographic analysis of the thermal failure of Na-Ion batteries

Abstract

In recent years, the ability to examine the processes that cause the catastrophic failure of batteries as a result of thermal runaway has improved substantially. In this work, the effect of thermal runaway on the microstructure of the electrodes of a Na-ion battery is examined using X-ray computed tomography for the first time. The thermal failure induced via accelerating rate calorimetry enabled the examination of failed electrodes, which were subsequently compared with fresh samples. Microstructural analysis shows changes in both electrodes as a result of the thermal runaway process at the micrometre length-scale. It is seen that the cathode shows the largest changes in structure, with the anode remaining morphologically similar post-failure at the sub-micron length-scale. The formation of a highly X-ray attenuating layer, which is proposed to be a metallic product of the thermal 2 runaway reaction, is observed, indicating that the thermal runaway mechanisms which occur in Na-ion batteries may be similar to those reported for Li-ion systems.

Elucidating the Sodiation Mechanism in Hard Carbon by Operando Raman Spectroscopy

“…7 Furthermore, the rate of self-heating is lower than for Li-ion technologies. 8,9 These considerations contribute to the promise of higher safety in Na-ion systems compared with their Li-ion counterparts. However, the solid electrolyte interphase (SEI), which is a layer that forms on the surface of the carbon during the initial sodiation, resulting from the decomposition of the electrolyte at the pristine carbon surface, is reported to be primarily inorganic for Na-ion systems and less stable and more soluble compared with the Li-ion SEI, which is primarily organic.…”

“…Sodium-ion (Na-ion) batteries are receiving increasing attention, particularly for stationary applications, such as load leveling, and have a number of significant benefits over lithium-ion (Li-ion) batteries. − Whereas lithium is only present in limited amounts in the earth’s crust and is found in local deposits, sodium is more plentiful, is ubiquitously found, and has a substantially lower cost. , Additionally, an expensive copper current collector is required for the anode in Li-ion systems because lithium alloys with aluminum. This is not the case with sodium; therefore, aluminum can be used as the current collector for both electrodes, saving on cost.…”

“…Moreover, because copper is not present, Na-ion cells can be discharged fully to 0 V for safer storage and transportation since aluminum does not dissolve into the electrolyte at these voltages . Furthermore, the rate of self-heating is lower than for Li-ion technologies. , These considerations contribute to the promise of higher safety in Na-ion systems compared with their Li-ion counterparts. However, the solid electrolyte interphase (SEI), which is a layer that forms on the surface of the carbon during the initial sodiation, resulting from the decomposition of the electrolyte at the pristine carbon surface, is reported to be primarily inorganic for Na-ion systems and less stable and more soluble compared with the Li-ion SEI, which is primarily organic. − Although the SEI in Li-ion systems is relatively well understood, further work is required to understand and improve the stability of the SEI in Na-ion systems to benefit both cycle life and safety, as it protects against further electrolyte decomposition on the carbon surface. , …”

Emerging X-ray imaging technologies for energy materials

“…[11,[27][28][29][30] The application of digital volume correlation tools has been demonstrated as an effective means to quantify the local change in these 'time-lapse' images, which can identify strain within heterogeneous electrodes [28,31,32]. Besides Li-ion batteries, X-ray imaging has been widely applied to study other emerging battery chemistries including Na-ion, Li-sulfur, and Zinc [33][34][35]. Figure 1.…”

Electrochemical formation protocols for maximising the life-time of a sodium ion battery

“…In LIB various chemical and electrochemical (side) reactions occur at the electrode/electrolyte interfaces to form the interface layer, this is also observed for NIBs which contain similar chemistries. 5,6 The process is time consuming, and can often take several weeks, depending upon the cell type. 7 These interfaces are best known as the SEI formed at the negative electrode (anode) and cathode electrolyte interface (CEI) formed at the positive electrode (cathode).…”