Reversible Ca metal deposition remains one of the major challenges in the development of rechargeable Ca metal batteries. Among proposed electrolyte design strategies, alkali-metal incorporation has emerged as a promising approach for improving Ca plating/stripping. In this work, Na[B(hfip)4] (hfip = hexafluoroisopropoxy) was introduced as an additive into a Ca[B(hfip)4]2/DME electrolyte, and its influence on Ca plating/stripping was evaluated using electrochemical measurements and SEM-EDX characterization of the deposits. Additive-level Na incorporation resulted in reduced polarization, increased Coulombic efficiency, and improved cycling stability, with the Ca:Na = 95:5 electrolyte exhibiting the best performance and a maximum Coulombic efficiency of 83%. Comparison of two commercially available carbon-coated Al current collectors revealed that substrate properties influence the electrochemical response, with graphitic domains supporting additional reversible redox processes attributed to intercalation of solvated cations. Galvanostatic measurements at different deposited capacities and current densities showed that both parameters strongly influence electrochemical performance and deposit morphology. Lower deposited capacities and higher current densities promoted smaller, more uniformly distributed deposits and improved cycling stability, whereas higher deposited capacity resulted in deposit agglomeration and accelerated performance degradation. XPS analysis further demonstrated that Na incorporation alters the interphase chemistry, decreasing Ca–F and carbonate contributions while increasing the Ca–O contribution and introducing Na-containing species. Overall, the results demonstrate that additive-level Na improves the reversibility of Ca plating/stripping while maintaining Ca-based deposition.
The optimization of electrocatalyst infiltrate was carried out to enhance the performance of solid oxide fuel cells (SOFCs) with mixed ionic-electronic conductor (MIEC) Gd0.1Ce0.9O2-δ (GDC) electrolytes. While infiltrated nano-catalysts based on Pr–Sr–Co (PSC) and cobalt-free Pr–Sr–Ni (PSN) and Pr–Sr–Fe (PSF) oxides exhibit high intrinsic catalytic activity, their morphological evolution with repeated infiltration cycles drastically alters full-cell electrochemistry. Inadequate loading limits phase connectivity, while excessive loading causes agglomeration and reduces the triple phase boundary. This study systematically investigates the impact of volumetric infiltrate loading on the microstructural connectivity, effective exchange current density (i0), and area-specific resistance (ASR) of full cells utilizing a Pr and Sm-doped GDC scaffold. We demonstrate that in MIEC systems, the open-circuit voltage (OCV) and peak power density (PPD) are highly sensitive to catalyst loading. Comparison between before and after optimization revealed significant performance improvements. PSC and PSN exhibit impressive PPDs of 1.9 W/cm2 and 1.7 W/cm2, respectively, at 650 °C, with remarkably low electrode polarization of 0.01 Ωcm2. Additionally, PSN demonstrated excellent long-term stability in full-cell tests, highlighting its potential as a robust cobalt-free electrode. This work demonstrates that optimized infiltration and catalyst selection are critical for maximizing cell performance.
