Post‐lithium‐ion battery technology is considered a key element of future energy storage and management. Apart from high gravimetric and volumetric energy densities, economic, ecologic and safety issues become increasingly important. In that regards, both the anode and cathode materials must be easily available, recyclable, non‐toxic and safe, which renders magnesium‐sulfur (Mg−S) batteries a promising choice. Herein, we present Mg−S cells based on a sulfurated poly(acrylonitrile) composite cathode (SPAN), together with a halogen‐free electrolyte containing both Mg[BH4]2 and Li[BH4] in diglyme and a high‐specific surface area magnesium anode based on Rieke magnesium powder. These cells deliver discharge capacities of 1400 and 800 mAh/gsulfur with >99 % Coulombic efficiency at 0.1 C and 0.5 C, respectively, and are stable over at least 300 cycles. Energy densities are 470 and 400 Wh/kgsulfur at 0.1 C and 0.5 C, respectively. Rate tests carried out between 0.1 C and 2 C demonstrate good rate capability of the cells. Detailed mechanistic studies based on X‐ray photoelectron spectroscopy and electric impedance spectroscopy are presented.

We report on a room temperature (RT) sodium‐sulfur (Na−S) battery based on a sodium anode, a sulfurated poly(acrylonitrile) (SPAN) cathode and an electrolyte containing sodium tetrakis(hexafluoroisopropyloxy) borate (Na[B(hfip)4]; hfip=hexafluoroisopropoxide) in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and fluoroethylene carbonate (FEC). The hfip anion as a weakly coordinating anion (WCA) provides high anodic stability, high ionic conductivity, and superior electrochemical performance in carbonate‐based solvents. The Na‐SPAN cell exhibits an initial discharge capacity of 1360 normalmnormalAnormalh4ptnormalgnormals-1 and a remarkable reversible capacity of 1072 normalmnormalAnormalh4ptnormalgnormals-1 after 1000 cycles at 3 C (C=C‐rate, 5.025 normalA4ptnormalgnormals-1 ) with an insignificant average capacity decay of less than 0.021 % per cycle. A careful choice of the discharge cut‐off potential (DCP) reveals that a DCP of 0.2 V allows for stable cycling for more than 500 cycles while a DCP of 0.5 V results in a constant capacity decay. The excellent cycle stability at a DCP of 0.2 V is likely to be caused by the high conversion of the SPAN‐bound sulfur into Na2S.

Due to its ultra-high capacity and moderately low potential, silicon (Si) shows potential in replacing graphite-based anodes. Unfortunately, Si suffers from severe intrinsic volume expansions that restrict its practical use. Herein, we present a tailored copolymer, poly­(acrylamide)-co-poly­(hydroxymethylacrylate), p­(AM-co-HMA), as a multifunctional binder for Si anodes, which forms a 3D network structure via a thermally induced self-cross-linking reaction. The formed cross-linked binder structure provides both covalent and hydrogen bonds and thereby improves both the adhesion between the individual electrode components and the current collector as well as the adhesion between the individual Si particles. Overall, the p­(AM-co-HMA)-based binder offers superior electrochemical performance for high-loading Si anodes compared to traditionally applied binder systems.