No abstract

Aqueous rechargeable batteries are becoming increasingly important to the development of renewable energy sources, because they promise to meet cost‐efficiency, energy and power demands for stationary applications. Over the past decade, efforts have been devoted to the improvement of electrode materials and their use in combination with highly concentrated aqueous electrolytes. Here the latest ground‐breaking advances in using such electrolytes to construct aqueous battery systems efficiently storing electrical energy, i.e., offering improved energy density, cyclability and safety, are highlighted. This Review aims to timely provide a summary of the strategies proposed so far to overcome the still existing hurdles limiting the present aqueous batteries technologies employing concentrated electrolytes. Emphasis is placed on aqueous batteries for lithium and post‐lithium chemistries, with potentially improved energy density, resulting from the unique advantages of concentrated electrolytes.

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Sodium‐ion technology has the potential to become the next generation of low cost and environmentally friendly electrochemical energy storage system for grid‐level applications. The low cost and abundant raw materials employed in sodium cells have driven the recent increasing interest in sodium‐ion batteries (SIBs), which appear especially appealing, since manufacturers can use the already existing production technology of lithium‐ion batteries. However, SIBs are still an early stage technology, which requires several issues affecting cell performance to be addressed. Despite the accelerated development of cathode materials, anode materials still require further investigation and optimization to reach high energy density performance. In the pursuit of high capacity anode materials, several alloying‐, conversion‐, and combined conversion–alloying‐based electrodes have been investigated. This review offers a comprehensive overview on the recent progresses toward the realization of “beyond‐insertion” anode materials. The role of nanostructuration with the associated advantages and disadvantages is presented for each class of compounds, combined with the main strategies adopted to improve the electrochemical behavior. Finally, an overview of the challenges and perspectives associated with the development of the next generation of anode materials is presented with a particular focus on the role of the electrolyte solutions and solid/electrolyte interphase.