Solid-state fast ionic conductors are of great interest due to their application potential enabling the development of safer high-performance energy and conversion systems ranging from batteries through supercapacitors to fuel cells, electrolyzers, and novel neuromorphic devices. However, identifying fast ion conductors has remained a slow trial-and-error search process. High-throughput computational screening methods such as our bond valence site energy method can significantly accelerate this materials design, but their implementation not only needs to be computationally efficient and dependable but also simple to be used by experimentalists in order to find widespread usage for guiding experimental efforts to promising classes of candidate materials. To bridge the current gap between computational method developers and application-oriented users, we combine the computationally low-cost bond valence site energy calculations in our softBV software tool using a new automated pathway analysis toolthe bond valence pathway analyzer (BVPA). The integration of BVPA gives rapid comprehensive access to and simplifies the visualization of the desired information on the characteristics of ion transport properties in candidate materials. Examples for the main application of identifying suitable structure types for fast ion transport as solid electrolytes or mixed conducting electrode materials with high-rate capability are given. A new dopant predictor further simplifies defect engineering of the candidate systems by automatically suggesting suitable substitutional dopants for each site in the structure based on a new machine-learned approach.

The redox targeting reaction of Li-storage materials with redox mediators is the key process in redox flow lithium batteries, a promising technology for next-generation large-scale energy storage. The kinetics of the Li-coupled heterogeneous charge transfer between the energy storage material and redox mediator dictates the performance of the device, while as a new type of charge transfer process it has been rarely studied. Here, scanning electrochemical microscopy (SECM) was employed for the first time to determine the interfacial charge transfer kinetics of LiFePO/FePO upon delithiation and lithiation by a pair of redox shuttle molecules FcBr and Fc. The effective rate constant k was determined to be around 3.70-6.57 × 10 cm/s for the two-way pseudo-first-order reactions, which feature a linear dependence on the composition of LiFePO, validating the kinetic process of interfacial charge transfer rather than bulk solid diffusion. In addition, in conjunction with chronoamperometry measurement, the SECM study disproves the conventional "shrinking-core" model for the delithiation of LiFePO and presents an intriguing way of probing the phase boundary propagations induced by interfacial redox reactions. This study demonstrates a reliable method for the kinetics of redox targeting reactions, and the results provide useful guidance for the optimization of redox targeting systems for large-scale energy storage.

Fast-ion conducting Na11Sn2PS12 prepared by ball-milling allowed us to realize the first all-solid-state Na–Se battery, which can reach 500 charge–discharge cycles at room temperature.

Among the solid electrolytes studied for all-solid-state sodium batteries (ASSBs), Na3SbS4 (NAS) appears particularly promising due to its unique combination of high ionic conductivity and compatibility with humid air, which lowers the cost of processing and facilitates large-scale industrial applications. Considering that partial substitution of sulfur with halide ions increases the number of mobile sodium vacancies, we developed a low-cost structural modification to NAS by integrating the doping step with the aqueous synthesis. Here, we focus on the effect of bromide doping of NAS on its ionic conductivity and kinetic electrochemical stability. The extent and location of Br doping are clarified by X-ray diffraction analysis. The impact of doping on the ion transport properties is studied by static energy landscape analyses and molecular dynamics simulations. Our Br-doped NAS exhibits greatly reduced activation energy down to 0.12 eV. Therefore, the total ionic conductivity is more than doubled from 0.13 to 0.31 mS cm–1, allowing for solid-state batteries with lower overpotentials. Stable cycling profiles of the doped NAS versus both sodium metal anodes and sodium–tin alloy anodes evidenced a major enhancement of the electrochemical stability and thus a path toward longer cycle life ASSBs.

NASICON-type Li 1+ x Al x Ge 2– x (PO 4 ) 3 (LAGP) is a promising electrolyte with high ionic conductivity (>10 –4 S cm –1 ), excellent oxidation stability, and moderate sintering temperature. However, preparing dense LAGP pellets with high ionic conductivity is still challenging because of the hazards of dopant loss and partial decomposition on conventional sintering. Here, spark plasma sintering (SPS) of LAGP membranes is explored as a promising ultrarapid manufacturing technique, yielding dense electrolyte membranes. Optimizing the SPS temperature is important to achieve desirable density and hence ionic conductance. Our results show that LAGP samples spark plasma-sintered at 750 °C exhibit the highest total ionic conductivity of 3.9 × 10 –4 S cm –1 with a compactness of 97% and nearly single-crystalline particles. Our solid-state NMR results, X-ray diffraction studies, and scanning electron microscopy micrographs confirm that the achievable ionic conductivity is controlled by the retention of the Al dopant within the LAGP phase, necking between particles, and the minimization of grain boundaries between crystallites within a particle. To benchmark the performance of our spark plasma-sintered solid electrolyte membranes over conventionally prepared LAGP, we demonstrate their favorable performance in hybrid Li–air batteries. The highest energy efficiency is achieved for the fastest ion-conducting membrane sintered at 750 °C.