Guidelines for All-Solid-State Battery Design and Electrode Buffer Layers Based on Chemical Potential Profile Calculation.

Protective coatings on cathode active materials have become paramount for the implementation of solid-state batteries; however, the development of coatings lacks the understanding of the necessary coating properties. In this study, guidelines for the design of solid electrolytes and electrode coatings in all-solid-state batteries are proposed from the viewpoint of the steady-state Li chemical potential profile across the battery cell. The model calculation of the (electro)chemical potential profile in all-solid-state batteries is established by considering the steady-state mixed ionic and electronic conduction in the solid electrolyte under the assumption of local equilibrium. For quantitative discussion, the potential profiles within oxygen ion conductors are calculated instead of Li/Na ion conductors as their partial electronic conductivities have not been reported so far in sufficient detail. Based on the calculated chemical potential profile, two main conclusions are obtained: (1) the decisive factor for the formation of the chemical potential profile of the neutral mobile component (e.g., oxygen or lithium) in the solid electrolyte is its electronic conductivity (and the activity dependence), and (2) a particularly large potential drop is formed in a region where the electronic conductivity becomes small. While these conclusions are valid and general for any solid electrolyte device, they are particularly important for the design of protective coatings and the understanding of the functionality of self-assembled solid electrolyte interphases in all-solid-state batteries. To protect the solid electrolyte from decomposition by reduction/oxidation at the anode/cathode interfaces, a sufficient chemical potential drop is necessary within the coating layer or directly at the interphase layer. To achieve this situation, the coating/interphase materials need to have a lower electronic conductivity than the solid electrolyte.

Stereoselective cathodic synthesis of 8-substituted (1R,3R,4S)-menthylamines.

The electrochemical generation of menthylamines from the corresponding menthone oximes equipped with an additional substituent in position 8 is described. Due to 1,3-diaxial interactions a pronounced diastereoselectivity for the menthylamines is found.

Simple cathode design for Li­S batteries: cell performance and mechanistic insights by in operando X-ray diffraction.

Rechargeable batteries have been receiving increasing attention over the past several years, particularly with regard to the accelerated development of electric vehicles, but also for their potential in grid storage applications. Among the broad range of cathode active materials, elemental sulfur has the highest theoretical specific capacity, thereby making it one of the most promising positive electrode materials these days. In the present work, we show that already a simple cathode design (cathodes with a non-optimized composite microstructure) provides good electrochemical performance both in coin and pouch cells with sulfur loadings of 2 mg cm−2. Our research data demonstrate that (1) specific capacities of 1000 mA h g−1 can be achieved over 60 cycles at room temperature while the cyclability at elevated temperatures (here, θ > 40 °C) is poor, (2) the discharge is the kinetically rate-limiting process, (3) the major fraction of active sulfur in the electrode is lost during the formation cycle at C/50 and (4) the Li­S cells suffer from drying-out due to continuous electrolyte decomposition on the lithium metal anode. In addition, in operando X-ray diffraction shows Li2S formation (grain size of <10 nm) on discharge and the appearance of single phase ß-sulfur in the sub-100 nm size range ­ rather than the thermodynamically stable orthorhombic polymorph (α-sulfur) ­ by the end of the charge cycle.