Suppressing Li dendrite growth has gained research interest due to the high theoretical capacity of Li metal anodes. Traditional Celgard membranes which are currently used in Li metal batteries fall short in achieving uniform Li flux at the electrode/electrolyte interface due to their inherent irregular pore sizes. Here, the use of an ultrathin (≈1.2 nm) carbon nanomembrane (CNM) which contains sub‐nanometer sized pores as an interlayer to regulate the mass transport of Li‐ions is demonstrated. Symmetrical cell analysis reveals that the cell with CNM interlayer cycles over 2x longer than the control experiment without the formation of Li dendrites. Further investigation on the Li plating morphology on Cu foil reveals highly dense deposits of Li metal using a standard carbonate electrolyte. A smoothed‐particle hydrodynamics simulation of the mass transport at the anode–electrolyte interface elucidates the effect of the CNM in promoting the formation of highly dense Li deposits and inhibiting the formation of dendrites. A lithium metal battery fabricated using the LiFePO4 cathode exhibits a stable, flat voltage profile with low polarization for over 300 cycles indicating the effect of regulated mass transport.

Solid oxide electrolysis cells (SOECs) are devices that enable economically viable production of clean fuel such as hydrogen gas, which can be used in many industrial applications and serving as an energy carrier for renewable energy sources. Operation of SOEC at intermediate temperature (IT) range (400 to 600 °C) is highly attractive because many unexploited heat sources from industries can be utilized. Proton conducting SOECs based on barium− zirconium−cerate electrolytes show great potential for operating at this temperature range due to their high proton conductivity at reduced temperatures. In this study, a new tridoped BaCe 0.5 Zr 0.2 Y 0.1 Yb 0.1 Gd 0.1 O 3−δ (BCZYYbGd) electrolyte with very high chemical stability and proton conductivity is coupled with a PrNi 0.5 Co 0.5 O 3−δ steam electrode and a Ni-BCYYbGd hydrogen electrode for IT-SOEC operation. The dopants of the electrolyte were carefully designed to obtain the optimum stability and conductivity for IT-SOEC. The BCYYbGd electrolyte was stable over 200 h at 50 vol % steam in argon and at 600 °C, and a very high electrolysis current density of 2.405 A cm −2 was obtained at 600 °C and 1.6 V at 20 vol % of steam in argon. This system was also found to be highly reversible, exhibiting very high performance in SOFC mode and suggesting a potential candidate for next generation proton conducting electrolyte.

All-solid-state batteries using garnet-type solid-state electrolytes (SSEs) are promising candidates for safe, high energy density batteries due to their wide electrochemical stability window, high lithium-ion conductivity at room temperature, and the use of a lithium metal anode. However, garnet-type SSEs exhibit formidable challenges, including their instability in a moisture-containing atmosphere, high interfacial resistance, and the formation of lithium dendrites. Though several strategies have been deployed to alleviate the issues related to garnet-type SSEs against metallic lithium, most of the approaches fail to solve all the challenges. Herein, we demonstrate a surface modification strategy of the Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZT) garnet electrolyte by two-dimensional hexagonal boron nitride (h-BN) nanosheets to solve the interfacial issues. Detailed spectroscopic evidence elucidates that the h-BN interlayer effectively protects the LLZT from moisture-induced chemical degradation and suppresses the formation of adverse carbonate species for over 120 h in an open atmosphere. The h-BNcoated garnet SSE interface has shown a nearly 10-fold reduction in interfacial resistance value compared to the uncoated one and it exhibits stable lithium plating/stripping behavior for over 1400 cycles at 0.2 mA cm −2 . Advanced in situ Raman analysis reveals that the h-BN interlayers remain stable during cycling and inhibit the structural transformation of LLZT at the interface.

Major challenges in the development of solid-state batteries using garnet-type solid-state electrolytes (SSEs) include suppressing dendrite growth, improving moisture stability, and reducing interfacial resistance. Prior attempts to remove surface impurities of SSEs through dry polishing caused high interfacial resistance that proves this method to be unviable. Further, several efforts on depositing thin-film protective layers on SSEs without understanding surface chemistry failed to demonstrate improved electrochemical performance. Here, we report the simultaneous removal of the surface impurities and protection of the SSE against air and moisture by regulating its surface chemistry. In situ X-ray photoelectron spectroscopy (XPS) studies revealed that primary surface contaminants such as lithium carbonate (Li 2 CO 3 ) and lithium hydroxide on the SSE, Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZT), could be removed by either argon-ion sputtering at 227 °C or annealing at 777 °C in ultrahigh vacuum conditions. To protect the cleaned LLZT surface from further ambient contamination, in situ atomic layer deposition was used to deposit ∼3 nm-thick h-BN using tris(dimethylamino)borane and ammonia precursors at 450 °C. Intermittent XPS analysis confirmed the absence of Li 2 CO 3 formation and the stability of h-BN-coated LLZT pellets for over 2 months of exposure to atmospheric air and moisture. Electrochemical impedance spectroscopy studies revealed that an ultrathin layer of ∼3 nm h-BN drastically reduced the interfacial resistance from 1145 to 18 Ω cm 2 (∼65× reduction). Li plating/stripping studies revealed a constant polarization of 27 mV at a 0.5 mA cm −2 current density over prolonged cycling and a high critical current density of 0.9 mA cm −2 . An all-solid-state battery using a LiFePO 4 cathode exhibited a stable capacity of 130 mAh g −1 for over 100 cycles and a negligible capacity fade-off of 0.11 mAh g −1 per cycle at an average Coulombic efficiency of 98.4%.

Although various fluorescent‐based nanoparticles are treated as cellular imaging probes, approaching the construction of a biocompatible subcellular imaging probe is challenging. At the same time, the recognition of wasted pharmaceutical drugs by some fluorescent nanoprobes is important and urgently required. We report a “structural memory” concept for simple one‐pot synthesis of bright green fluorescent (quantum yield of up to 61%) carbon dots (C‐dots) from triphenylphosphonium (TPP) as a carbon precursor that will simultaneously act as an effective vehicle for mitochondria labeling in cancer cells and as a selective tetracycline sensor. The ubiquitous TPP residues upon the C‐dots’ surface easily recognize the cellular mitochondria. Tetracycline has been selectively and instantaneously detected through rapid fluorescence on‐off response from C‐dots where other drugs remained silent in nature, even after longer incubation. This quenching response is ascribed to the static quenching effect and position of functional groups of the targeted drug which can play a dominating role. The reason for strong fluorescence exhibition from C‐dots has been well explained by considering different factors. Such types of C‐dots have been shown to be universal mitochondria‐targeting nanoprobes, non‐cytotoxic, and effective as a tetracycline detector. This finding should open a new avenue for in‐vivo therapeutic application and sensing of pharmaceutical drugs in real clinical applications.

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Measurement levels of As 3+ and Fe 3+ ions have attracted considerable research attention for environmental and living being's health safety issues. Herein, we report a green synthetic approach to prepare bright yellow fluorescent carbon dots (C-dots) from a ophenylenediamine and pyrazole mixture. A large Stokes shift of up to 145 nm was observed under an excitation wavelength of 415 nm. The metal ion sensing study affirmed that the C-dots' aqueous dispersion underwent a strong fluorescence quenching for selective As 3+ and Fe 3+ ion sensing with detection limits of 24.4 and 63.4 nM, respectively. In addition, a red shift of the C-dots' emission was noticed in the case of Fe 3+ ion incubation. Furthermore, the C-dots were coated on a simple paper strip and embedded in a solid silica aerogel porous matrix in which detection was carried out through the visible and fluorescence color changes. The quenching of the C-dots' fluorescence was ascribed to the static quenching effect, which was proved by UV−vis absorbance and time-resolved fluorescence spectroscopy techniques. In addition, this method was successfully used to detect these ions in real water samples in the presence of other contaminants. Moreover, intracellular detection of the ions has been successfully performed in living cells at a lower concentration. The methodology reported here opens a new window in real and on-site applications.

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