Joern Kulisch

A comprehensive approach is reported to construct stable and high volumetric energy density lithium–sulfur batteries, by coupling a multifunctional and hierarchically structured sulfur composite with an in‐situ cross‐linked binder. Through a combination of first‐principles calculations and experimental studies, it is demonstrated that a hybrid sulfur host composed by alternately stacking graphene and layered graphitic carbon nitride embraces high electronic conductivity as well as high polysulfide adsorptivity. It is further shown that the cross‐linked elastomeric binder empowers the hierarchical sulfur composites—multi‐microns in size—with the ability to form crack‐free and compact high‐loading electrodes using traditional slurry processing. Using this approach, electrodes with up to 14.9 mg cm −2 sulfur loading and an extremely low electrolyte/sulfur ratio as low as 3.5: 1 µL mg −1 are obtained. This study sheds light on the essential role of multifaceted cathode design and further on the challenges facing lithium metal anodes in building high volumetric energy density lithium–sulfur batteries.

for more than 600 cycles, whereas symmetric Li|Li cells demonstrate stable performance for more than 1000 cycles even at higher areal capacity and current density. We attribute the excellent performance of both Li|NCM and Li|Li cells to the formation of a stable and efficient solid electrolyte interphase (SEI) on the surface of the Li metal electrodes cycled in FEC-based electrolyte solutions. The composition of the SEI on the Li and the NCM electrodes is analyzed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. A drastic capacity fading of Li|NCM cells is observed, followed by spontaneous capacity recovery during prolonged cycling. This phenomenon depends on the current density and the amount of the electrolyte solution and relates to kinetic limitations because of SEI formation on the Li anodes in the FEC-based electrolyte solution.

Abstract As potential next‐generation energy storage devices, solid‐state lithium batteries require highly functional solid state electrolytes. Recent research is primarily focused on crystalline materials, while amorphous materials offer advantages by eliminating problematic grain boundaries that can limit ion transport and trigger dendritic growth at the Li anode. However, simultaneously achieving high conductivity and stability in glasses is a challenge. New quaternary superionic lithium oxythioborate glasses are reported that exhibit high ion conductivity up to 2 mS cm −1 despite relatively high oxygen: sulfur ratios of more than 1:2, that exhibit greatly reduced H 2 S evolution upon exposure to air compared to Li 7 P 3 S 11 . These monolithic glasses are prepared from vitreous melts without ball‐milling and exhibit no discernable XRD pattern. Solid‐state NMR studies elucidate the structural entities that comprise the local glass structure which dictates fast ion conduction. Stripping/plating onto lithium metal results in very low polarization at a current density of 0.1 mA cm −2 over repeated cycling. Evaluation of the optimal glass composition as an electrolyte in an all‐solid‐state battery shows it exhibits excellent cycling stability and maintains near theoretical capacity for over 130 cycles at room temperature with Coulombic efficiency close to 99.9%, opening up new avenues of exploration for these quaternary compositions.

We report on a family of lithium fast ion conductors, Li3+x[SixP1–x]S4, that exhibit an entropically stabilized structure type in a solid solution regime (0.15 < x < 0.33) with superionic conductivity above 1 mS·cm–1. Exploration of the influence of aliovalent substitution in the thermodynamically unstable β-Li3PS4 lattice using a combination of single crystal X-ray and powder neutron diffraction, the maximum entropy method, and impedance spectroscopy reveals that substitution induces structural splitting of the localized Li sites, effectively stabilizing bulk β-Li3PS4 at room temperature and delocalizing lithium ion density. The optimal material, Li3.25[Si0.25P0.75]S4, exhibits inherent entropic site disorder and a frustrated energy landscape, resulting in a high conductivity of 1.22 mS·cm–1 that represents an increase of three orders of magnitude compared to bulk β-Li3PS4 and one order of magnitude higher than the nanoporous form. The enhanced ion conduction and lowered activation barrier with increasing site disorder as a result of aliovalent “tuning” reveals an important strategy toward the design of fast ion conductors that are vital as solid state electrolytes.

Abstract Copper sulfide (CuS) is an attractive electrode material for batteries, thanks to its intrinsic mixed conductivity, ductility and high theoretical specific capacity of 560 mAh g −1 . Here, CuS is studied as cathode material in lithium solid‐state batteries with an areal loading of 8.9 mg cm −2 that theoretically corresponds to 4.9 mAh cm −2 . The configuration of the cell is LiLi 3 PS 4 [CuS (70 wt%) + Li 3 PS 4 (30 wt%)]. No conductive additive is used. CuS undergoes a displacement reaction with lithium, leading to macroscopic phase separation between the discharge products Cu and Li 2 S. In particular, Cu forms a network of micrometer‐sized, well‐crystallized particles that seems to percolate through the electrode. The formed copper is visible to the naked eye. The initial specific discharge capacity at 0.1 C is 498 mAh g(CuS) −1 , i.e., 84% of its theoretical value. The initial Coulomb efficiency (ICE) reaches 95%, which is higher compared to standard carbonate‐based liquid electrolytes for the same cell chemistry (≈70%). After 100 cycles, the specific capacity reaches 310 mAh g(CuS) −1 . With the current composition, the cell provides 58.2 Wh kg −1 at a power density of 7 W kg −1 , which is superior compared to other transition metal sulfide cathodes.