Sulfide-based all-solid-state lithium-ion batteries (ASSLIBs) are promising candidates in the next generation of energy storage technology; the voltage mismatch and the resulting side reactions at the interface between the cathode and the solid electrolyte, however, dramatically deteriorate their cycling performance. Herein, for the first time, we report that the chemical interaction between LiCoO₂ (LCO) and TiO₂ can be regulated by two additives, carbon and Li₂CO₃, which in situ form a continuous ultrathin pure-phase Li₂CoTi₃O₈ (LCTO) layer with a stable 3D network of spinel structures, relatively low electronic conductivity (2.5 × 10⁻⁸ S cm⁻¹) and high lithium diffusion coefficient (D_Li⁺ = 8.22 × 10⁻⁷ cm² s⁻¹) on the surface of LCO. When assembled in ASSLIBs, such an LCTO layer functions as an interlayer between the LCO and the Li₁₀GeP₂S₁₂ solid electrolyte (LGPS). As a consequence, the original interface LCO/LGPS is substituted by two new interfaces LCO/LCTO and LCTO/LGPS. DFT calculations indicate that, compared with the LCO/LGPS, the new interfaces are not only thermodynamically and electrochemically more compatible, but also have higher interfacial affinity. Therefore, the relevant ASSLIB exhibits evidently reduced interfacial impedance, and it also displays a high initial capacity of 140 mA h g⁻¹ and a reversible discharge specific capacity of 116 mA h g⁻¹ after 200 cycles at room temperature (0.1C). In comparison, the ASSLIB assembled without the LCTO interlayer delivers an initial capacity of 98 mA h g⁻¹ and only retains 22.4% capacity after 100 cycles (0.1C). Even at a high cutoff voltage (4.5 V vs. Li/Li⁺), the ASSLIB with the LCTO interlayer could also exhibit a high initial capacity of 180 mA h g⁻¹ and a remarkable retention of 132 mA h g⁻¹ after 100 cycles.

Mitigating interfacial reactions in composite cathode materials remains a key challenge for high-performance all-solid-state batteries (ASSBs), particularly those employing argyrodite-based electrolytes coupled with high-voltage cathodes. Here we study the interfacial chemical reactivity of a Li_1−xNi_0.5Mn_0.3Co_0.2O₂ (NMC532) and Li₆PS₅Cl (LPSC) composite using galvanostatic electrochemical impedance spectroscopy, complemented by surface and bulk-sensitive X-ray techniques. By decoupling the time-dependent interfacial degradation from the overall degradation, we show that the redox reaction between NMC532 (oxidant) and LPSC (reductant) is the main origin of degradation. The chemical reaction products share chemical similarities with the ones after the electrochemical reaction. The analysis shows the oxidation activity of transition metals in the cathode composite is Ni^4+/3+ > Mn⁴⁺/Co³⁺ > Ni^2+/3+. Molecular-dynamics simulations reveal that the reaction is driven by the Li⁺ diffusion from LPSC to the delithiated-NMC532, leading to the LPSC's structural decomposition and collapse.

A thermodynamic model was developed and validated to analyze a high-performance solid oxide fuel cell and gas turbine (SOFC-GT) hybrid power system for electric aviation. This study used a process simulation software package (ProMax) to study the role of SOFC design and operation on the feasibility and performance of the hybrid system. Standard modules, including compressor, turbine, heat exchanger, reforming reactor, and combustor were used from the ProMax tool suite while a custom module was created to simulate the SOFC stack. The model used an SOFC test data set as an input. Additional SOFC stack performance effects, such as pressure, temperature, and utilization of air and fuel, were added from open source data. System performance predictors were SOFC specific power, fuel-to-electricity conversion efficiency, and hybrid system efficiency. Using these input data and predictors, a static thermodynamic performance model was created that can be modified for different system configurations and operating conditions. Prior to creating the final aircraft performance model, initial demonstration models were developed to validate output results. We used the NASA SOFC model as a benchmark, which was created with their Numerical Propulsion System Simulator (NPSS) software framework. Our output results matched within 1% of both the NASA model and open source SOFC performance data. With confidence gained in the accuracy of this model, a 1-MW SOFC-GT hybrid power system was constructed for an aircraft propulsion concept. Overall hybrid system efficiencies of > 75% FTE were observed during standard 36,000 feet cruise flight conditions.

Central to commercializing metal–air batteries is the development of highly efficient and stable catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this study, a composite catalyst with a unique interpenetrating network (denoted as NiCo₂O₄@MnO₂-CNTs-3) was synthesized and exhibited better bifunctional activity (ΔE = 0.87 V) and durability than both Pt/C and Ir/C catalysts. The improved performance arises from three factors: (i) MnO₂ promotes the ORR while NiCo₂O₄ facilitates the OER; (ii) carbon nanotubes improve the electronic conductivity; and (iii) the highly porous structure enables the adsorption–desorption of O₂ and enhances the structural stability. As a result, the primary and rechargeable Zn–air battery affords a high power density and specific capacity (722 mA h g⁻¹), an outstanding discharge stability (255 mW cm⁻² after 1000 cycles) and a high cycling stability (over 2280 cycles). Electron microscopy and electrochemical analysis revealed that the degradation of the rechargeable Zn–air battery performance resulted from the damage of the air electrode and the hydrogen evolution reaction on the zinc electrode. A flexible Zn–air battery employing a solid-state electrolyte showed an exciting stability (540 cycles) and high power density (85.9 mW cm⁻²), suggesting that the anion exchange membrane effectively prevents the migration of Zn²⁺ ions and the deposition of carbonates.