No abstract

Lithium‐ion batteries are the most commercially successful electrochemical devices, extensively used in intelligent electronics, electric vehicles, grid energy storages, etc. However, there still needs to be further improvement of their performance such as in energy density, cyclability, rate capability, and safety. To do so, it is necessary to understand the detailed structural evolution progress inside the battery. Many advanced imaging techniques have been developed to directly monitor the status and get some key information inside the battery. For advanced imaging techniques, superhigh resolution, fully informative function, nondestruction of the sample, and in situ observation are required. This review introduces and discusses some recent important progress on a variety of advanced imaging techniques for battery research. These imaging techniques have enabled the visualization of sub‐micrometer level chemical valence distribution, evolution of solid‐electrolyte interface, Li dendrite growth, and trace amount of gassing, etc., which greatly promote the development of rechargeable batteries. Of particular note, a new ultrasonic imaging technique has been recently developed to monitor gas generation, the electrolyte wetting process, and the state of charge in the battery. Finally, a perspective is given on some future developments in the imaging techniques for Li‐ion batteries and other rechargeable batteries.

We introduce a stirred self-stratified battery (SSB) that has an extremely simple architecture formed by a gravity-driven process. The oxidizing catholyte is separated from the reducing Zn anode by a liquid aqueous electrolyte layer. The Coulombic efficiency is always higher than 99%, even when stirring is applied to promote the charge-discharge rate. Moreover, the proposed SSB is intrinsically exempt from common failure mechanisms of other batteries; thus, its cycling stability is excellent, which is crucial for energy storage applications.

Chemical/electrochemical stability at the interfaces greatly affects the performance of solid-state batteries (SSBs). However, the interfacial behavior in SSBs remains elusive due to the subsurface nature of interfaces and the lack of proper characterization methods. Herein, ultrasonic imaging technology is employed to non-destructively investigate the interfacial stability in solid-state pouch cells. Bene ting from the high sensitivity of ultrasound to the gas/vacuum, in-situ ultrasonic imaging can effectively probe the inner gas release and interfacial degradation in pouch cells during long-term cycling. The safety issue of SSBs is highlighted by the ammable gas release detected in ultrasonic images. And the increased interfacial resistance either from contact loss or passivation layer growth is well distinguished.The gradual oxidation and gassing at the cathode interface are tracked by ultrasonic imaging, which leads to the capacity fading of SSBs. The ultrasonic imaging technology is demonstrated to be a powerful tool to evaluate the interfacial stability in SSBs, which can guide the rational design of interfaces and enhance the performance of SSBs.