Developing nonflammable electrolytes with stable lithium-metal interfaces and reversible Li plating/stripping remains a critical challenge for lithium metal batteries. Herein, a sulfolane-based nonflammable electrolyte containing lithium trifluoromethanesulfonate (LiOTf), lithium nitrate (LiNO 3 ) and fluoroethylene carbonate (FEC) is developed by regulating Li + solvation and interfacial chemistry. NMR spectroscopy and ab initio molecular dynamics simulations reveal that partial substitution of LiOTf with LiNO 3 redistributes the first Li + solvation shell, reducing sulfolane coordination while increasing anion participation. Raman and FT-IR analyses further indicate that FEC modifies the local interaction network among electrolyte components. The optimized Li[OTf/NO 3 ]-FEC electrolyte exhibits a low viscosity of 34.4 cP, an ionic conductivity of 0.63 mS cm −1 and favorable self-extinguishing behavior. FEC also promotes an inorganic-rich SEI containing LiF, Li 3 N, LiN x O y , Li 2 O, Li 2 SO 4 and Li 2 SO 3 , resulting in lower interfacial resistance and more uniform Li deposition. Consequently, Li//Li cells exhibit an overpotential of ∼0.12 V and stable cycling for ∼270 h at 0.5 mA cm −2 and 0.5 mAh cm −2 , while Li//Cu cells maintain 97–98% Coulombic efficiency for over 100 cycles with an average efficiency of 96.48% by the modified Aurbach method. Li//LiMn 2 O 4 cells retain 85.7% capacity after 587 cycles at 100 mA g −1 and 67.2% after 1600 cycles at 500 mA g −1 . These results demonstrate that combining Li + solvation regulation with FEC-assisted interphase engineering is an effective strategy for stable, nonflammable lithium metal batteries.
This study investigates a chloride-assisted electrochemical conversion process for transforming compact, passivated Fe-Cr-Ni alloy scrap into recoverable oxide powders with enhanced acid leachability. The scrap contained 69.94 wt% Fe, 17.16 wt% Cr, and 6.90 wt% Ni. Electrochemical analyses showed that hydroxide electrolytes promoted the formation of compact oxide/hydroxide passive films, whereas chloride electrolytes induced passive film destabilization and sustained anodic dissolution. In KCl electrolyte, anodically released metal species subsequently precipitated and were recovered as oxide powders containing Fe2O3, Cr2O3, and NiO. Increasing the KCl concentration from 1 to 4 mol/L increased ionic conductivity and lowered the anode potential required to maintain the imposed current density. Among the examined conditions, 4 mol/L KCl provided the lowest and most stable anode-potential response while maintaining a powder yield comparable to those obtained at 2–3 mol/L. The electrochemically formed oxide powders exhibited an average particle size of 144.2 nm at 4 mol/L KCl. Under identical leaching conditions of 4 mol/L H2SO4 at 50 °C for 30 min, dissolution efficiencies increased from 10.46%, 8.13%, and 9.23% for Fe, Cr, and Ni in untreated bulk scrap to 93.47%, 92.41%, and 96.64%, respectively, for the electrochemically formed oxide powders. This comparison indicates that the improved leaching response resulted from coupled electrochemical phase conversion and powder formation, rather than from an isolated particle-size reduction effect. These results demonstrate that chloride-assisted electrochemical conversion serves as an upstream activation step for downstream hydrometallurgical processing of passivated Fe-Cr-Ni alloy scrap.
Reversible solid oxide cells (RSOCs) offer a highly efficient pathway for clean energy conversion and storage by switching between power generation and fuel synthesis modes. However, their widespread commercialization is fundamentally hindered by sluggish electrochemical reaction kinetics, performance degradation, and insufficient long-term durability under harsh operating conditions. Conventional ex-situ characterization fails to capture the dynamic structural and chemical evolution of critical materials during operation, obscuring the underlying mechanisms of performance decay. This review summarizes fundamental principles of advanced in-situ / operando methodologies and their applications in unravelling dynamic changes of RSOC materials, covering morphology evolution, crystal-phase transformation, metal valence variation, local coordination environment modulation, as well as identification of active sites and reaction mechanisms. The integration between experimental observations and theoretical calculations for uncovering atomic-scale mechanisms is highlighted. Current technical bottlenecks are analyzed, and targeted perspectives are proposed, aiming to provide strategic guidance for constructing advanced characterization workflows and developing high-performance, robust RSOC materials.
Reversible solid oxide cells (RSOCs) offer a highly efficient pathway for clean energy conversion and storage by switching between power generation and fuel synthesis modes. However, their widespread commercialization is fundamentally hindered by sluggish electrochemical reaction kinetics, performance degradation, and insufficient long-term durability under harsh operating conditions. Conventional ex-situ characterization fails to capture the dynamic structural and chemical evolution of critical materials during operation, obscuring the underlying mechanisms of performance decay. This review summarizes fundamental principles of advanced in-situ/operando methodologies and their applications in unravelling dynamic changes of RSOC materials, covering morphology evolution, crystal-phase transformation, metal valence variation, local coordination environment modulation, as well as identification of active sites and reaction mechanisms. The integration between experimental observations and theoretical calculations for uncovering atomic-scale mechanisms is highlighted. Current technical bottlenecks are analyzed, and targeted perspectives are proposed, aiming to provide strategic guidance for constructing advanced characterization workflows and developing high-performance, robust RSOC materials.
High-speed in situ observation of transient product evolution during high-temperature molten-salt electrolysis is essential for understanding and controlling electrochemical materials processing. However, the observation with sufficient temporal resolution remains limited by thermal radiation, optical distortion, and corrosive environments. In this research, we developed a high-speed laser shadowgraph system enabling short-exposure imaging of both electrode regions during electrolysis in molten LiCl–KCl at 723 K. Imaging with a temporal resolution of 0.0005 s simultaneously resolved anodic bubble evolution and a metal-fog region near the cathode. The anodic bubbles underwent recurrent growth, coalescence, collective detachment, transient clearing of the visible electrode surface, and regeneration. Quantification of the projected bubble area fraction revealed gradual accumulation followed by abrupt decreases associated with collective detachment, demonstrating pulsatile gas release under steady current. Moreover, detached large bubbles deformed the metal-fog boundary, indicating hydrodynamic coupling between products at opposing electrodes. The high-speed in situ observation system reveals transient product-formation and transport dynamics inaccessible to time-averaged measurements.
