Solid-state lithium-ion batteries (SSBs) are a promising concept for future energy storage applications. Interestingly, the mechanical effects during operation of SSBs, and their correlation to the electrochemical performance, have rarely been investigated. In such systems, the rigid mechanical coupling between the active phases and the solid electrolyte will lead to more complex non-local strain effects than in the common liquid electrolyte-based lithium-ion batteries, where the chemical expansion or compression of the active phases is accommodated by the liquid electrolyte, and only local mechanical strain within the electrode particles exists. In this work we report on the pressure and height changes within typical solid-state batteries, which were measured in situ during galvanostatic cycling conditions. The continuous volume changes of both the anode and the cathode during lithiation/delithiation are responsible for a highly reproducible cycle of pressure changes during the operation of the solid-state battery cell. Bending and cracking of the solid-state battery cells are observed with X-ray tomography and provide evidence for the critical role of the macroscopic strain generated during cycling. Furthermore, these pressure and dilatometry measurements as well as X-ray tomography underline the importance of external confinement and pressure control for SSBs.

Sodium‐based batteries have attracted considerable attention and are recognized as ideal candidates for large‐scale and low‐cost energy storage. Sodium (Na) metal anodes are considered as one of the most promising anodes for next‐generation, high‐energy, Na‐based batteries owing to their high theoretical specific capacity (1166 mA h g⁻¹) and low standard electrode potential. Herein, an overview of the recent developments in Na metal anodes for high‐energy batteries is provided. The high reactivity and large volume expansion of Na metal anodes during charge and discharge make the electrode/electrolyte interphase unstable, leading to the formation of Na dendrites, short cycle life, and safety issues. Design strategies to enable the efficient use of Na metal anodes are elucidated, including liquid electrolyte engineering, electrode/electrolyte interface optimization, sophisticated electrode construction, and solid electrolyte engineering. Finally, the remaining challenges and future research directions are identified. It is hoped that this progress report will shape a consistent view of this field and provide inspiration for future research to improve Na metal anodes and enable the development of high‐energy sodium batteries.

All-solid-state batteries are intensively investigated, although their performance is not yet satisfactory for large-scale applications. In this context, the combination of Li₁₀GeP₂S₁₂ solid electrolyte and LiNi_1-x-yCo_xMn_yO₂ positive electrode active materials is considered promising despite the yet unsatisfactory battery performance induced by the thermodynamically unstable electrode|electrolyte interface. Here, we report electrochemical and spectrometric studies to monitor the interface evolution during cycling and understand the reactivity and degradation kinetics. We found that the Wagner-type model for diffusion-controlled reactions describes the degradation kinetics very well, suggesting that electronic transport limits the growth of the degradation layer formed at the electrode|electrolyte interface. Furthermore, we demonstrate that the rate of interfacial degradation increases with the state of charge and the presence of two oxidation mechanisms at medium (3.7 V vs. Li⁺/Li < E < 4.2 V vs. Li⁺/Li) and high (E ≥ 4.2 V vs. Li⁺/Li) potentials. A high state of charge (>80%) triggers the structural instability and oxygen release at the positive electrode and leads to more severe degradation.

A variety of batteries employing an alkaline zinc anode have been investigated and partially commercialized over the last decades. Of these, electrically rechargeable zinc–air batteries have been considered, since the mid 20th century, as a sustainable alternative for future green energy storage. Despite significant research efforts, it has so far not been possible to commercialize this battery on a large scale because of insufficient performance. The herein presented overview is not yet another review; on the basis of a total of 70 articles published during the last 20 years in lab-scale research, we assess the state-of-the-art performance of alkaline zinc anodes for application in zinc–air batteries. We define descriptors for the underlying analysis focusing on the practical relevance and reveal that the expectations for this battery type are unfortunately too high. Most importantly, the ultimate long-lasting alkaline zinc anode has yet to be identified; this is a challenging, but appealing task for interdisciplinary research.