• Energy Research

Emerging energy storage systems based on abundant and cost-effective materials are key to overcome the global energy and climate crisis of the 21st century.

AbstractSodium‐ion batteries are an emerging technology that is still at an early stage of development. The electrode processing for anode and cathode is expected to be similar to lithium‐ion batteries (drop‐in technology), yet a detailed comparison is not published. There are ongoing questions about the influence of the active materials on processing parameters such as slurry viscosity, coating thicknesses, drying times, and behavior during fast drying. Herein, the expected drying time for the same areal capacity of anodes (graphite vs. hard carbon) and cathodes (lithium iron phosphate vs. Prussian blue analogs) are compared based on respective specific capacities reported in the literature. Estimates are made for the materials’ impact on production speed or dryer length. Within the experimental part, water‐based slurries of the same composition are mixed using different active materials according to identical procedure and the viscosity is compared. When drying at a constant drying rate (0.75 g m−2 s−1), lithium iron phosphate electrodes with different areal capacities (1–3 mAh cm−2) are shown to have the highest adhesion. For high drying rates (3 g m−2 s−1) at constant areal capacity, especially the investigated electrodes based on hard carbon show that no binder migration occurs.

The high capacity of sulfur makes lithium–sulfur (Li–S) batteries the most promising next‐generation battery systems. With a significantly higher theoretical specific energy than conventional lithium‐ion batteries, this technology is intensely investigated. However, currently used cathodes have some critical drawbacks which affect the performance of Li–S batteries. Atomic layer deposition (ALD) demonstrates its power for solving some emerging issues in energy‐storage systems. The application of alumina (Al2O3) to the cathode surface improves the morphology and/or chemistry, providing a solution for some of the most common issues of Li–S batteries. Herein, the cathode of Li–S batteries is coated with alumina by ALD. In addition, the optimal parameters for ALD application to sulfur‐based electrodes are reported. It is demonstrated that alumina deposition results in an improved capacity of the system. The process temperature plays an important role, in particular for few‐cycle ALD processes, aiding better cell performance. Higher numbers of ALD cycles, especially at elevated process temperatures, result in considerable sulfur loss, which significantly lowers the cell performance. Cathodes coated with alumina at low process temperatures and with low numbers of ALD cycles are promising alternatives for conventional Li–S cathodes as they increase the capacity of the system considerably.

Summary New applications and emerging markets in electromobility and large-scale stationary energy storage require the development of new electrochemical systems with higher energy density than current batteries. Rechargeable metal–air batteries, mainly lithium–air and zinc–air systems, are considered one of the most promising candidates. In contrast to lithium, zinc is abundant, inexpensive and its electrodeposition in aqueous electrolytes is relatively easy. Unfortunately, achieving a rechargeable zinc–air battery is still hindered by various technical problems related to the reversibility and lifetime of the electrodes. The most widely used electrolyte in zinc–air batteries has been the classical aqueous alkaline. In this context and with the main objective of providing a complete overview, we studied a wide number of articles starting from the beginning of the development of secondary zinc–air batteries (1970–1980s) to more recent works, with the aim of compiling all available information. It is essential to revise older papers to find relevant information that may get otherwise forgotten and not taken into account to develop new solutions. This information could also be applied in other storage systems based on zinc as nickel–zinc, zinc hybrid or zinc-ion. Copyright © 2016 John Wiley & Sons, Ltd.