Sodium-metal batteries present a more abundant alternative to lithium-based batteries, with high theoretical capacity and comparable reduction potential. Ether electrolytes perform well in sodium-metal batteries under continuous cycling and are presumed to have a stable solid-electrolyte interphase (SEI). However, the solubility of sodium SEI components is a cause for concern, and SEI evolution during calendar aging is not commonly studied for the ether sodium-metal system. In this work, SEI mass formation and dissolution are quantitatively measured for NaPF6 in diglyme. For varying potential hold levels, significant SEI dissolution is observed, from 55 to 76% of the originally formed SEI. Characterization shows that in addition to organic component dissolution, inorganic salts such as NaF and Na x PO y F z are unstable in SEI during open circuit rest. This instability results in continuous corrosion of sodium metal during calendar aging, highlighting an important understanding and concern of SEI stability in sodium-metal batteries.
Fast Na+ transport and durable interfacial stability remain challenging for wide-temperature Na- metal batteries. To address these issues, we developed a synergistic solvation-interphase regulation strategy by integrating methyl propanoate (MP) with a combined VC/NaDFOB additive pair. MP modifies the Na+ solvation sheath and facilitates Na+ desolvation, while VC and NaDFOB cooperatively generate a mechanically robust hybrid organicinorganic interphase. This coupled regulation enables enhanced ion transport and interfacial stability over a broad temperature range. The EC/EMC/MP + VC/NaDFOB electrolyte exhibits an ionic conductivity of 2.52 mS cm(-1) at -40 degrees C and an increased Na+ transference number. Na||Na3V2(PO4)(3) cells retain 96.5% of their initial capacity after 1000 cycles with an average Coulombic efficiency of 99.98% at room temperature. At -20 degrees C, the cells deliver 69.4 mAh g(-1) for over 900 cycles, corresponding to 82% of their room-temperature capacity. This work establishes a practical solvation-interphase regulation approach for wide-temperature Na- metal batteries.
Inverted organic photovoltaics (OPVs) feature operational stability; however, developing fully solution-processed devices remains challenging due to the poor wettability of PEDOT:PSS hole-transport layers (HTLs) on hydrophobic donor:acceptor bulk heterojunction active layers. Here, we demonstrate a surfactant-free, humidity-regulated spin-coating strategy for forming uniform PEDOT:PSS HTLs directly on PM6:Y6 active layers. By maintaining the relative humidity at 10% or lower during coating, continuous PEDOT:PSS films were obtained, enabling inverted OPVs with power conversion efficiency (PCE) above 14.5%. Furthermore, these devices retain over twice the PCE of molybdenum oxide-based devices after 100 h of light soaking under nitrogen. Bulk quantum efficiency analysis suggests that the acidic aqueous PEDOT:PSS dispersion may partially perturb the interface on the active layer, whereas it improves the overall device stability. This humidity-regulated coating approach provides a simple route toward solution-processable HTL integration in efficient and operationally stable inverted OPVs.
Increased energy density and safety relative to conventional lithium (Li)-ion batteries motivate the development of solid-state batteries (SSBs). However, maintaining interface stability at the metal anode-solid electrolyte (SE) interface remains a critical challenge to achieving practical areal capacities, especially during stripping/discharge. Here, a mesoscale model informed by atomistic simulations is employed to examine void formation at the Li metal-SE interface during discharge/stripping. The model reveals how void-formation-driven interfacial contact loss behavior depends on the microstructural properties of the polycrystalline Li anode. In agreement with prior studies, Li microstructures with small grain sizes promote self-diffusion-induced void healing and generally exhibit better interfacial contact. We further show the effect of operating conditions, such as applied pressure, stripping current density, and temperature, on the stripping performance for different Li microstructures. Through this study, we shed light on the importance of taking microstructural features into account in predicting interfacial contact evolution during stripping of Li metal SSBs.
Dip-coating is a simple yet versatile deposition method inherently compatible with complex, non-flat surfaces. Unlike conventional horizontal coatings, its vertical withdrawal configuration demands precise control over viscosity, surface tension, evaporation, and gravity to achieve uniform thin films. However, the performance of dip-coated perovskite solar cells (PSCs) has remained limited because commonly used volatile-solvent-dominated precursor inks provide inadequate morphological control. Also, conventional dip-coating strategies for rheological control are unsuitable for PSCs, as polymeric binders or high precursor concentrations can impair crystallization and charge transport. Here, by reversing the conventional DMF-dominant formulation, we identify an NMP-dominant DMF:NMP (= 7:93 (vol%/vol%)) solvent system that enables uniform, pinhole-free perovskite films via dip-coating. The resulting devices exhibit power conversion efficiencies exceeding 25%, representing the highest reported performance for dip-coated PSCs. Moreover, the ink enables conformal coating on textured, curved, and three-dimensionally complex surfaces. This work establishes an ink-design strategy for high-performance dip-coated PSCs, opening a practical pathway toward perovskite photovoltaics on nonplanar and structurally diverse substrates.
