High-temperature sodium-sulfur battery (HT Na-S) technology has attracted substantial interest in the stationary energy storage sector due to its low cost and high energy density. However, the currently used solid electrolyte (ß-alumina) is expensive and can only be operated at high temperatures, which compromises safety. On the other hand, liquid electrolytes in room temperature sodium-sulfur batteries (RT Na-S) are susceptible to dendrite formation and polysulfide shuttle. Consequently, an electrolyte with both solid (shuttle blocking) and liquid (ionic conductivity) properties to overcome the above-mentioned issues is highly desired. Herein, a high-performance quasi-solid state crosslinked gel polymer electrolyte (GPE) prepared in situ using pentaerythritol triacrylate (PETA) exhibiting high ionic conductivity of 2.33 mS cm −1 at 25 °C is presented. The GPE-based electrolyte shows high stability resulting in a high discharge capacity of >600 mAh g s −1 after 2500 cycles with an average Coulombic efficiency of 99.91%. Density functional theory calculations reveal a weak interaction between the Na + ions and the oxygen molecules of the PETA moiety, which leads to a facile cation movement. The crosslinked polymer network is tightly connected to the cathode and can confine sulfides, thereby facilitating the conversion process.

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.

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With the increasing demand for safer, more stable, and energy dense batteries, investigations into single crystal layered oxide cathodes have gained momentum. However, translating considerations from polycrystalline to single‐crystalline particles and their ensembles is not one‐to‐one. Lithium diffusion path length, surface, dopants and coatings, as well as the synthetic methods used take on different dimensions for single‐crystalline particles. In this concept article, we review key considerations that must be made when developing well‐performing single crystal layered oxide cathodes. We discuss how diffusion limitations can affect material stability in addition to how improvements to diffusivity can act as a method to simultaneously improve rate capability and surface stability. In addition, we briefly discuss how the unique feature of faceting and the synthetic design space for single‐crystalline particles should be conceptualized.

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.