Factors affecting Capacity Retention in Hybrid Lithium-Sulfur Battery

A composite protective layer of LiPON and LATP is installed with Li metal electrode in lithium-sulfur battery cells on the goal to improve the cycleability. The Li-S cells with the protective layer as solid electrolyte and ether-based liquid electrolyte, named as hybrid cells, are compared to the standard cells. The investigations of galvanostatic cycling, electrochemical impedance spectroscopy (EIS), Scanning Electron Microscope (SEM), and X-ray Photo-electron Spectroscopy (XPS) were performed

7Li NMR Chemical Shift Imaging To Detect Microstructural Growth of Lithium in All-Solid-State Batteries.

All-solid-state batteries potentially offer safe, high-energy-density electrochemical energy storage, yet are plagued with issues surrounding Li microstructural growth and subsequent cell death. We use 7Li NMR chemical shift imaging and electron microscopy to track Li microstructural growth in the garnet-type solid electrolyte, Li6.5La3Zr1.5Ta0.5O12. Here, we follow the early stages of Li microstructural growth during galvanostatic cycling, from the formation of Li on the electrode surface to dendritic Li connecting both electrodes in symmetrical cells, and correlate these changes with alterations observed in the voltage profiles during cycling and impedance measurements. During these experiments, we observe transformations at both the stripping and plating interfaces, indicating heterogeneities in both Li removal and deposition. At low current densities, 7Li magnetic resonance imaging detects the formation of Li microstructures in cells before short-circuits are observed and allows changes in the electrochemical profiles to be rationalized

Combined operando and ex-situ monitoring of the Zn/electrolyte interface in Zn-ion battery systems

Operando optical microscopy enables imaging at the interface between the Zn electrode and the electrolyte of 1 M ZnSO4(aq) in the symmetrical Zn/Zn cells assembled as the pouch cells with the mechanical load of 0.8 MPa. The imaging was executed during cycling of Zn plating and stripping at the different current densities of 0.5, 1.0, 2.0, and 4.0 mA cm−2, and the areal capacity of 2 mAh·cm−2. When the current densities are below 4.0 mA cm−2, no intense Zn dendrites are observed. However, at 4.0 mA cm−2, the severe Zn dendrites can penetrate through the separator and cause short-circuiting. From the electrochemical perspective, the voltage profile of such system drops to almost zero volt. Both operando optical and ex-situ synchrotron X-ray imaging further prove the appearance of the Zn dendrites. By Raman spectroscopy and X-ray diffraction, the cycled Zn electrode surface contains passivation species of Zn4(OH)6SO4, ZnO, and Zn(OH)2 that could limit the active surface area for the Zn plating/stripping, accelerating the localized current density and favoring the growth of Zn dendrites. With the SiO2 additive of 0.5% w/v in 1 M ZnSO4(aq), the severe Zn dendrites disappear, as well as the cycled Zn/electrolyte interface becomes close to the pristine state; low degree of the Zn electrode roughness and the Zn surface passivation is noticed. The appearance of the claimed Zn surface morphology was also confirmed by Scanning Electron Microscopy (SEM). In turn, too low or too high SiO2 content in the electrolyte does not generate desirable effects. A high level of Zn dendrites and short circuiting are still recognized. Hence, both the operando and ex-situ characterizations can mutually validate the phenomena at the Zn/electrolyte interface

Sodium/Na β″ Alumina Interface:Effect of Pressure on Voids

Three-electrode studies coupled with tomographic imaging of the Na/Na-β″-alumina interface reveal that voids form in the Na metal at the interface on stripping and they accumulate on cycling, leading to increasing interfacial current density, dendrite formation on plating, short circuit, and cell failure. The process occurs above a critical current for stripping (CCS) for a given stack pressure, which sets the upper limit on current density that avoids cell failure, in line with results for the Li/solid-electrolyte interface. The pressure required to avoid cell failure varies linearly with current density, indicating that Na creep rather than diffusion per se dominates Na transport to the interface and that significant pressures are required to prevent cell death, &gt;9 MPa at 2.5</p

Modulating the Combinatorial Target Power of MgSnN via RF Magnetron Sputtering for Enhanced Optoelectronic Performance: Mechanistic Insights from DFT Studies

The unique structural features of many ternary nitride materials with strong chemical bonding and band gaps above 2.0 eV are limited and are experimentally unexplored. It is important to identify candidate materials for optoelectronic devices, particularly for light-emitting diodes (LEDs) and absorbers in tandem photovoltaics. Here, we fabricated MgSnN thin films, as promising II-IV-N semiconductors, on stainless-steel, glass, and silicon substrates via combinatorial radio-frequency magnetron sputtering. The structural defects of the MgSnN films were studied as a function of the Sn power density, while the Mg and Sn atomic ratios remained constant. Polycrystalline orthorhombic MgSnN was grown on the (120) orientation within a wide optical band gap range of ∼2.20-2.17 eV. The carrier densities of 2.18× 10 to 1.02 × 10 cm, mobilities between 3.75 and 2.24 cm/Vs, and a decrease in resistivity from 7.64 to 2.73 × 10 Ω cm were confirmed by Hall-effect measurements. These high carrier concentrations suggested that the optical band gap measurements were affected by a Burstein-Moss shift. Furthermore, the electrochemical capacitance properties of the optimal MgSnN film exhibited an areal capacitance of 152.5 mF/cm at 10 mV/s with high retention stability. The experimental and theoretical results showed that MgSnN films were effective semiconductor nitrides toward the progression of solar absorbers and LEDs

Visualizing plating-induced cracking in lithium-anode solid-electrolyte cells

Lithium dendrite (filament) propagation through ceramic electrolytes, leading to short circuits at high rates of charge, is one of the greatest barriers to realizing high-energy-density all-solid-state lithium-anode batteries. Utilizing in situ X-ray computed tomography coupled with spatially mapped X-ray diffraction, the propagation of cracks and the propagation of lithium dendrites through the solid electrolyte have been tracked in a Li/Li6PS5Cl/Li cell as a function of the charge passed. On plating, cracking initiates with spallation, conical ‘pothole’-like cracks that form in the ceramic electrolyte near the surface with the plated electrode. The spallations form predominantly at the lithium electrode edges where local fields are high. Transverse cracks then propagate from the spallations across the electrolyte from the plated to the stripped electrode. Lithium ingress drives the propagation of the spallation and transverse cracks by widening the crack from the rear; that is, the crack front propagates ahead of the Li. As a result, cracks traverse the entire electrolyte before the Li arrives at the other electrode, and therefore before a short circuit occurs