Chemical and Biomolecular Engineering Research Works

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    Dynamic Modeling for the Design and Cyclic Operation of an Atomic Layer Deposition (ALD) Reactor
    (MDPI, 2013-08-19) Travis, Curtisha D.; Adomaitis, Raymond A.
    A laboratory-scale atomic layer deposition (ALD) reactor system model is derived for alumina deposition using trimethylaluminum and water as precursors. Model components describing the precursor thermophysical properties, reactor-scale gas-phase dynamics and surface reaction kinetics derived from absolute reaction rate theory are integrated to simulate the complete reactor system. Limit-cycle solutions defining continuous cyclic ALD reactor operation are computed with a fixed point algorithm based on collocation discretization in time, resulting in an unambiguous definition of film growth-per-cycle (𝑔𝑝𝑐). A key finding of this study is that unintended chemical vapor deposition conditions can mask regions of operation that would otherwise correspond to ideal saturating ALD operation. The use of the simulator for assisting in process design decisions is presented.
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    Shape-Changing Tubular Hydrogels
    (MDPI, 2018-02-22) Raghavan, Srinivasa R.; Fernandes, Neville J.; Cipriano, Bani H.
    We describe the creation of hollow tubular hydrogels in which different zones along the length of the tube are composed of different gels. Our method to create these gels is adapted from a technique developed previously in our lab for creating solid hybrid hydrogels. The zones of our tubular gel are covalently bonded at the interfaces; as a result, these interfaces are highly robust. Consequently, the tube can be picked up, manipulated and stretched without suffering any damage. The hollow nature of these gels allows them to respond 2–30-fold faster to external stimuli compared to a solid gel of identical composition. We study the case where one zone of the hybrid tube is responsive to pH (due to the incorporation of an ionic monomer) while the other zones are not. Initially, the entire tube has the same diameter, but when pH is changed, the diameter of the pH-responsive zone alone increases (i.e., this zone bulges outward) while the other zones maintain their original diameter. The net result is a drastic change in the shape of the gel, and this can be reversed by reverting the pH to its original value. Similar localized changes in gel shape are shown for two other stimuli: temperature and solvent composition. Our study points the way for researchers to design three-dimensional soft objects that can reversibly change their shape in response to stimuli.
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    Effect of a Cationic Surfactant on Microemulsion Globules and Drug Release from Hydrogel Contact Lenses
    (MDPI, 2019-06-06) Torres-Luna, Cesar; Hu, Naiping; Koolivand, Abdollah; Fan, Xin; Zhu, Yuli; Domszy, Roman; Yang, Jeff; Yang, Arthur; Wang, Nam Sun
    The present study evaluates the in vitro release of diclofenac sodium (DFNa) from contact lenses based on poly-2-hydroxyethyl methacrylate (pHEMA) hydrogels containing an embedded microemulsion to extend release duration. The oil (ethyl butyrate)-in-water microemulsion systems are prepared with two non-ionic surfactants, Brij 97 or Tween 80, together with a long-alkyl chain cationic surfactant, cetalkonium chloride (CKC). Without CKC, Brij 97 or Tween 80-based microemulsions showed average droplet sizes of 12 nm and 18 nm, respectively. The addition of CKC decreased the average droplet sizes to 2–5 nm for both non-ionic surfactants. Such significant reduction in the average droplet size corresponds to an increase in the DFNa release duration as revealed by the in vitro experiments. Contact lens characterization showed that important properties such as optical transparency and water content of Brij 97-based contact lenses with cationic microemulsions was excellent. However, the optical transparency of the corresponding Tween 80 based contact lenses was unsatisfactory. The results indicate that cationic microemulsion-laden contact lenses can benefit from combinatory effects of microemulsions and cationic surfactant at low CKC weight percentage, e.g., with the release of 70% of the drug in 45, 10, and 7 h for B97-CKC-0.45%, CKC-0.45%, and control lenses, respectively. However, the microemulsion effect on extending DFNa release became negligible at the highest CKC weight percentage (1.8%).
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    Formation of Drug-Participating Catanionic Aggregates for Extended Delivery of Non-Steroidal Anti-Inflammatory Drugs from Contact Lenses
    (MDPI, 2019-10-10) Torres-Luna, Cesar; Koolivand, Abdollah; Fan, Xin; Agrawal, Niti R.; Hu, Naiping; Zhu, Yuli; Domszy, Roman; Briber, Robert M.; Wang, Nam Sun; Yang, Arthur
    This paper focuses on extending drug release duration from contact lenses by incorporating catanionic aggregates. The aggregates consist of a long-chain cationic surfactant, i.e., cetalkonium chloride (CKC), and an oppositely charged anti-inflammatory amphiphilic drug. We studied three non-steroidal anti-inflammatory (NSAID) drugs with different octanol–water partition coefficients; diclofenac sodium (DFNa), flurbiprofen sodium (FBNa), and naproxen sodium (NPNa). Confirmation of catanionic aggregate formation in solution was determined by steady and dynamic shear rheology measurements. We observed the increased viscosity, shear thinning, and viscoelastic behavior characteristic of wormlike micelles; the rheological data are reasonably well described using a Maxwellian fluid model with a single relaxation time. In vitro release experiments demonstrated that the extension in the drug release time is dependent on the ability of a drug to form viscoelastic catanionic aggregates. Such aggregates retard the diffusive transport of drug molecules from the contact lenses. Our study revealed that the release kinetics depends on the CKC concentration and the alkyl chain length of the cationic surfactant. We demonstrated that more hydrophobic drugs such as diclofenac sodium show a more extended release than less hydrophobic drugs such as naproxen sodium.
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    Two-Dimensional Zeolite Materials: Structural and Acidity Properties
    (MDPI, 2020-04-12) Schulman, Emily; Wu, Wei; Liu, Dongxia
    Zeolites are generally defined as three-dimensional (3D) crystalline microporous aluminosilicates in which silicon (Si4+) and aluminum (Al3+) are coordinated tetrahedrally with oxygen to form large negative lattices and consequent Brønsted acidity. Two-dimensional (2D) zeolite nanosheets with single-unit-cell or near single-unit-cell thickness (~2–3 nm) represent an emerging type of zeolite material. The extremely thin slices of crystals in 2D zeolites produce high external surface areas (up to 50% of total surface area compared to ~2% in micron-sized 3D zeolite) and expose most of their active sites on external surfaces, enabling beneficial effects for the adsorption and reaction performance for processing bulky molecules. This review summarizes the structural properties of 2D layered precursors and 2D zeolite derivatives, as well as the acidity properties of 2D zeolite derivative structures, especially in connection to their 3D conventional zeolite analogues’ structural and compositional properties. The timeline of the synthesis and recognition of 2D zeolites, as well as the structure and composition properties of each 2D zeolite, are discussed initially. The qualitative and quantitative measurements on the acid site type, strength, and accessibility of 2D zeolites are then presented. Future research and development directions to advance understanding of 2D zeolite materials are also discussed.
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    Motion of an Elastic Capsule in a Trapezoidal Microchannel under Stokes Flow Conditions
    (MDPI, 2020-05-17) Koolivand, Abdollah; Dimitrakopoulos, Panagiotis
    Even though the research interest in the last decades has been mainly focused on the capsule dynamics in cylindrical or rectangular ducts, channels with asymmetric cross-sections may also be desirable especially for capsule migration and sorting. Therefore, in the present study we investigate computationally the motion of an elastic spherical capsule in an isosceles trapezoidal microchannel at low and moderate flow rates under the Stokes regime. The steady-state capsule location is quite close to the location where the single-phase velocity of the surrounding fluid is maximized. Owing to the asymmetry of the trapezoidal channel, the capsule’s steady-state shape is asymmetric while its membrane slowly tank-treads. In addition, our investigation reveals that tall trapezoidal channels with low base ratios produce significant off-center migration for large capsules compared to that for smaller capsules for a given channel length. Thus, we propose a microdevice for the sorting of artificial and physiological capsules based on their size, by utilizing tall trapezoidal microchannels with low base ratios. The proposed sorting microdevice can be readily produced via glass fabrication or as a microfluidic device via micromilling, while the required flow conditions do not cause membrane rupture.
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    Effects of Protein Unfolding on Aggregation and Gelation in Lysozyme Solutions
    (MDPI, 2020-09-02) Nikfarjam, Shakiba; Jouravleva, Elena V.; Anisimov, Mikhail A.; Woehl, Taylor J.
    In this work, we investigate the role of folding/unfolding equilibrium in protein aggregation and formation of a gel network. Near the neutral pH and at a low buffer ionic strength, the formation of the gel network around unfolding conditions prevents investigations of protein aggregation. In this study, by deploying the fact that in lysozyme solutions the time of folding/unfolding is much shorter than the characteristic time of gelation, we have prevented gelation by rapidly heating the solution up to the unfolding temperature (~80 °C) for a short time (~30 min.) followed by fast cooling to the room temperature. Dynamic light scattering measurements show that if the gelation is prevented, nanosized irreversible aggregates (about 10–15 nm radius) form over a time scale of 10 days. These small aggregates persist and aggregate further into larger aggregates over several weeks. If gelation is not prevented, the nanosized aggregates become the building blocks for the gel network and define its mesh length scale. These results support our previously published conclusion on the nature of mesoscopic aggregates commonly observed in solutions of lysozyme, namely that aggregates do not form from lysozyme monomers in their native folded state. Only with the emergence of a small fraction of unfolded proteins molecules will the aggregates start to appear and grow.
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    Capsule Migration and Deformation in a Converging Micro-Capillary
    (MDPI, 2021-03-03) Wang, Yiyang; Dimitrakopoulos, Panagiotis
    The lateral migration of elastic capsules towards a microchannel centerline plays a major role in industrial and physiological processes. Via our computational investigation, we show that a constriction connecting two straight microchannels facilitates the lateral capsule migration considerably, which is relatively slow in straight channels. Our work reveals that the significant cross-streamline migration inside the constriction is dominated by the strong hydrodynamic forces due to the capsule size. However, in the downstream straight channel, the increased interfacial deformation at higher capillary numbers or a lower viscosity ratio and lower membrane hardness results in increased lateral cross-streamline migration. Thus, our work highlights the different migration mechanisms occurring over curved and straight streamlines.
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    Effect of Carbon Chain Length, Ionic Strength, and pH on the In Vitro Release Kinetics of Cationic Drugs from Fatty-Acid-Loaded Contact Lenses
    (MDPI, 2021-07-10) Torres-Luna, Cesar; Hu, Naiping; Domszy, Roman; Fan, Xin; Yang, Jeff; Briber, Robert M.; Wang, Nam Sun; Yang, Arthur
    This paper explores the use of fatty acids in silicone hydrogel contact lenses for extending the release duration of cationic drugs. Drug release kinetics was dependent on the carbon chain length of the fatty acid loaded in the lens, with 12-, 14- and 18-carbon chain length fatty acids increasing the uptake and the release duration of ketotifen fumarate (KTF) and tetracaine hydrochloride (THCL). Drug release kinetics from oleic acid-loaded lenses was evaluated in phosphate buffer saline (PBS) at different ionic strengths (I = 167, 500, 1665 mM); the release duration of KTF and THCL was decreased with increasing ionic strength of the release medium. Furthermore, the release of KTF and THCL in deionized water did not show a burst and was significantly slower compared to that in PBS. The release kinetics of KTF and THCL was significantly faster when the pH of the release medium was decreased from 7.4 towards 5.5 because of the decrease in the relative amounts of oleate anions in the lens mostly populated at the polymer–pore interfaces. The use of boundary charges at the polymer–pore interfaces of a contact lens to enhance drug partition and extend its release is further confirmed by loading cationic phytosphingosine in contact lenses to attract an anionic drug.
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    Stretchable and Compliant Sensing of Strain, Pressure and Vibration of Soft Deformable Structures
    (MDPI, 2022-12-06) Yao, Darren Zi Hian; Cai, Catherine Jiayi; Chen, Po-Yen; Ren, Hongliang
    Soft robotic and medical devices will greatly benefit from stretchable and compliant pressure sensors that can detect deformation and contact forces for control and task safety. In addition to traditional 2D buckling via planar substrates, 3D buckling via curved substrates has emerged as an alternative approach to generate tunable and highly convoluted hierarchical wrinkle morphologies. Such wrinkles may provide advantages in pressure sensing, such as increased sensitivity, ultra-stretchability, and detecting changing curvatures. In this work, we fabricated stretchable sensors using wrinkled MXene electrodes obtained from 3D buckling. We then characterized the sensors’ performance in detecting strain, pressure, and vibrations. The fabricated wrinkled MXene electrode exhibited high stretchability of up to 250% and has a strain sensitivity of 0.1 between 0 and 80%. The fabricated bilayer MXene pressure sensor exhibited a pressure sensitivity of 0.935 kPa−1 and 0.188 kPa−1 at the lower (<0.25 kPa) and higher-pressure regimes (0.25 kPa–2.0 kPa), respectively. The recovery and response timing of the wrinkled MXene pressure sensor was found to be 250 ms and 400 ms, respectively. The sensor was also capable of detecting changing curvatures upon mounting onto an inflating balloon.
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    Examining the Electrochemical Properties of Hybrid Aqueous/Ionic Liquid Solid Polymer Electrolytes through the Lens of Composition-Function Relationships
    (Wiley, 2023-07-04) Ludwig, Kyle B.; Correll-Brown, Riordan; Freidlin, Max; Garaga, Mounesha N.; Bhattacharyya, Sahana; Gonzales, Patricia M.; Cresce, Arthur V.; Greenbaum, Steven; Wang, Chunsheng; Kofinas, Peter
    Solid polymer electrolytes (SPEs) have the potential to meet evolving Li-ion battery demands, but for these electrolytes to satisfy growing power and energy density requirements, both transport properties and electrochemical stability must be improved. Unfortunately, improvement in one of these properties often comes at the expense of the other. To this end, a “hybrid aqueous/ionic liquid” SPE (HAILSPE) which incorporates triethylsulfonium-TFSI (S2,2,2) or N-methyl-N-propylpyrrolidinium-TFSI (Pyr1,3) ionic liquid (IL) alongside H2O and LiTFSI salt to simultaneously improve transport and electrochemical stability is studied. This work focuses on the impact of HAILSPE composition on electrochemical performance. Analysis shows that an increase in LiTFSI content results in decreased ionic mobility, while increasing IL and water content can offset its impact. pfg-NMR results reveal that preferential lithium-ion transport is present in HAILSPE systems. Higher IL concentrations are correlated with an increased degree of passivation against H2O reduction. Compared to the Pyr1,3 systems, the S2,2,2 systems exhibit a stronger degree of passivation due to the formation of a multicomponent interphase layer, including LiF, Li2CO3, Li2S, and Li3N. The results herein demonstrate the superior electrochemical stability of the S2,2,2 systems compared to Pyr1,3 and provide a path toward further enhancement of HAILSPE performance via composition optimization.
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    Unclonable MXene Topographies as Robust Anti-Counterfeiting Tags via Fast Laser Scanning and Siamese Neural Networks
    (Wiley, 2023-05-19) Jing, Lin; Si, Huachun; Chen, Tianle; Hsiao, Li-Yin; Yang, Haochen; Little, Joshua M.; Li, Kerui; Li, Shuo; Xie, Qian; Chen, Po-Yen
    An ideal anti-counterfeiting technology is desired to be unclonable, nondestructive, mass-producible, and accompanied with fast and robust authentication under various external influences. Although multiple anti-counterfeiting technologies have been reported, few meet all of the above-mentioned features. Herein, a mechanically driven patterning process is reported to produce higher dimensional Ti3C2Tx MXene topographies in a scalable yet unclonable manner, which can be used as anti-counterfeiting tags. By using a high-speed confocal laser microscopy, the complex topographies can be extracted within one minute and then reconstructed into 3D physical unclonable function (PUF) keys. Meanwhile, a Siamese neural network model and a feature-tracking software are built to achieve a pick-and-check strategy, enabling highly accurate, robust, disturbance-insensitive tag authentication in practical exploitations. The 3D PUF key-based anti-counterfeiting technology features with several advances, including ultrahigh encoding capacities (≈10144 000-107 800 000), fast processing times (<1 min), and high authentication accuracy under various external disturbances, including tag rotations (≈0°‒360°), tag dislocation(s) in x(y) directions (≈0%‒100%), tag shifts in z-direction (≈0%‒28%), tag tilts (≈0°‒5°), differences in contrasts (20%‒60%) and laser power (6.0‒9.0 µW). The anti-counterfeiting technology promises information security, encoding capacity, and authentication efficiency for the manufacturer-distributor-customer distribution processes.
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    Solvent-Free Electrolyte for High-Temperature Rechargeable Lithium Metal Batteries
    (Wiley, 2023-05-08) Phan, An L.; Jayawardana, Chamithri; Le, Phung ML; Zhang, Jiaxun; Nan, Bo; Zhang, Weiran; Lucht, Brett L.; Hou, Singyuk; Wang, Chunsheng
    The formation of lithiophobic inorganic solid electrolyte interphase (SEI) on Li anode and cathode electrolyte interphase (CEI) on the cathode is beneficial for high-voltage Li metal batteries. However, in most liquid electrolytes, the decomposition of organic solvents inevitably forms organic components in the SEI and CEI. In addition, organic solvents often pose substantial safety risks due to their high volatility and flammability. Herein, an organic-solvent-free eutectic electrolyte based on low-melting alkali perfluorinated-sulfonimide salts is reported. The exclusive anion reduction on Li anode surface results in an inorganic, LiF-rich SEI with high capability to suppress Li dendrite, as evidenced by the high Li plating/stripping CE of 99.4% at 0.5 mA cm−2 and 1.0 mAh cm−2, and 200-cycle lifespan of full LiNi0.8Co0.15Al0.05O2 (2.0 mAh cm−2) || Li (20 µm) cells at 80 °C. The proposed eutectic electrolyte is promising for ultrasafe and high-energy Li metal batteries.
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    Polymer nanomaterials for use as adjuvant surgical tools
    (Wiley, 2023-04-12) Erdi, Metecan; Sandler, Anthony; Kofinas, Peter
    Materials employed in the treatment of conditions encountered in surgical and clinical practice frequently face barriers in translation to application. Shortcomings can be generalized through their reduced mechanical stability, difficulty in handling, and inability to conform or adhere to complex tissue surfaces. To overcome an amalgam of challenges, research has sought the utilization of polymer-derived nanomaterials deposited in various fashions and formulations to improve the application and outcomes of surgical and clinical interventions. Clinically prevalent applications include topical wound dressings, tissue adhesives, surgical sealants, hemostats, and adhesion barriers, all of which have displayed the potential to act as superior alternatives to current materials used in surgical procedures. In this review, emphasis will be placed not only on applications, but also on various design strategies employed in fabrication. This review is designed to provide a broad and thought-provoking understanding of nanomaterials as adjuvant tools for the assisted treatment of pathologies prevalent in surgery.
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    Noble Metal Ion-Directed Assembly of 2D Materials for Heterostructured Catalysts and Metallic Micro-Texturing
    (Wiley, 2023-05-07) Little, Joshua M.; Sun, Jiayue; Kamali, Ali; Chen, Amy; Leff, Asher C.; Li, Yang; Borden, Leah K.; Dissanayake, Thilini U.; Essumang, Deborah; Oseleononmen, Benita O.; Liu, Dongxia; Woehl, Taylor J.; Chen, Po-Yen
    Assembling 2D-material (2DM) nanosheets into micro- and macro-architectures with augmented functionalities requires effective strategies to overcome nanosheet restacking. Conventional assembly approaches involve external binders and/or functionalization, which inevitably sacrifice 2DM's nanoscale properties. Noble metal ions (NMI) are promising ionic crosslinkers, which can simultaneously assemble 2DM nanosheets and induce synergistic properties. Herein, a collection of NMI–2DM complexes are screened and categorized into two sub-groups. Based on the zeta potentials, two assembly approaches are developed to obtain 1) NMI-crosslinked 2DM hydrogels/aerogels for heterostructured catalysts and 2) NMI–2DM inks for templated synthesis. First, tetraammineplatinum(II) nitrate (TPtN) serves as an efficient ionic crosslinker to agglomerate various 2DM dispersions. By utilizing micro-textured assembly platforms, various TPtN–2DM hydrogels are fabricated in a scalable fashion. Afterward, these hydrogels are lyophilized and thermally reduced to synthesize Pt-decorated 2DM aerogels (Pt@2DM). The Pt@2DM heterostructures demonstrate high, substrate-dependent catalytic activities and promote different reaction pathways in the hydrogenation of 3-nitrostyrene. Second, PtCl4 can be incorporated into 2DM dispersions at high NMI molarities to prepare a series of PtCl4–2DM inks with high colloidal stability. By adopting the PtCl4–graphene oxide ink, various Pt micro-structures with replicated topographies are synthesized with accurate control of grain sizes and porosities.
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    Pearl-Like Sheen in Soft Capsules: An Unusual Optical Effect that is Reversibly Induced by Temperature
    (Wiley, 2023-05-26) Rath, Medha; Fear, Allison; Woehl, Taylor J.; Raghavan, Srinivasa R.
    A pearl-like sheen (i.e., pearlescence) is seen in many natural materials like nacre and in some commercial paints and cosmetics. This phenomenon is attributed to the interaction of light with plate-like particles in the material. Here, for the first time, pearlescence is demonstrated in soft millimeter-scale capsules that contain no plate-like particles. The capsules have a thin (~500 µm) outer shell of N-isopropylacrylamide (NIPA) hydrogel, which has a lower critical solution temperature (LCST) of 32 °C. When a transparent NIPA-shelled capsule is heated above this LCST, it turns pearlescent. The effect is reversible, with the transparent state being recovered upon cooling. This is the first example of reversible pearlescence in any solid. Specular reflectance measurements show that the pearlescence of the capsules is comparable to that of natural pearls. Pearlescence is not observed in NIPA hydrogels; it arises only in NIPA-shelled capsules, and that too only when the shell is thin. Above its LCST, the NIPA shell shrinks and gets stretched, and nanoscale NIPA-rich domains arise within this shell, which induce the pearlescence. This study sheds fresh insight into the nature of pearlescence, on how it can be tuned, and on how this property can be introduced into various soft materials.
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    High-Performance Lithium Metal Batteries Enabled by a Fluorinated Cyclic Ether with a Low Reduction Potential
    (Wiley, 2023-01-02) Wu, Min; Wang, Zeyi; Zhang, Weiran; Jayawardana, Chamithri; Li, Yue; Chen, Fu; Nan, Bo; Lucht, Brett L.; Wang, Chunsheng
    Electrolyte engineering is crucial for developing high-performance lithium metal batteries (LMB). Here, we synthesized two cosolvents methyl bis(fluorosulfonyl)imide (MFSI) and 3,3,4,4-tetrafluorotetrahydrofuran (TFF) with significantly different reduction potentials and add them into LiFSI-DME electrolytes. The LiFSI/TFF-DME electrolyte gave an average Li Coulombic efficiency (CE) of 99.41 % over 200 cycles, while the average Li CEs for MFSI-based electrolyte is only 98.62 %. Additionally, the TFF-based electrolytes exhibited a more reversible performance than the state-of-the-art fluorinated 1,4-dimethoxylbutane electrolyte in both Li||Cu half-cell and anode-free Cu||LiNi0.8Mn0.1Co0.1O2 full cell. More importantly, the decomposition product from bis(fluorosulfonyl)imide anion could react with ether solvent, which destroyed the SEI, thus decreasing cell performance. These key discoveries provide new insights into the rational design of electrolyte solvents and cosolvents for LMB.
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    Cell-Like Capsules with “Smart” Compartments
    (Wiley, 2023-03-09) Ahn, So Hyun; Borden, Leah K.; Bentley, William E.; Raghavan, Srinivasa R.
    Eukaryotic cells have inner compartments (organelles), each with distinct properties and functions. One mimic of this architecture, based on biopolymers, is the multicompartment capsule (MCC). Here, MCCs in which the inner compartments are chemically unique and “smart,” i.e., responsive to distinct stimuli in an orthogonal manner are created. Specifically, one compartment alone is induced to degrade when the MCC is contacted with an enzyme while other compartments remain unaffected. Similarly, just one compartment gets degraded upon contact with reactive oxygen species generated from hydrogen peroxide (H2O2). And thirdly, one compartment alone is degraded by an external, physical stimulus, namely, by irradiating the MCC with ultraviolet (UV) light. All these specific responses are achieved without resorting to complicated chemistry to create the compartments: the multivalent cation used to crosslink the biopolymer alginate (Alg) is simply altered. Compartments of Alg crosslinked by Ca2+ are shown to be sensitive to enzymes (alginate lyases) but not to H2O2 or UV, whereas the reverse is the case with Alg/Fe3+ compartments. These results imply the ability to selectively burst open a compartment in an MCC “on-demand” (i.e., as and when needed) and using biologically relevant stimuli. The results are then extended to a sequential degradation, where compartments in an MCC are degraded one after another, leaving behind an empty MCC lumen. Collectively, this work advances the MCC as a platform that not only emulates key features of cellular architecture, but can also begin to capture rudimentary cell-like behaviors.
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    Thermal Percolation of Antiperovskite Superionic Conductor into Porous MXene Scaffold for High-Capacity and Stable Lithium Metal Battery
    (Wiley, 2022-10-09) Li, Yang; Kong, Long; Yang, Haochen; Li, Shuai; Deng, Zhi; Li, Shuo; Wang, Liping; Lee, Jim Yang; Zhao, Yusheng; Chen, Po-Yen
    Lithium metal battery is considered an emerging energy storage technology due to its high theoretical capacity and low electrochemical potential. However, the practical exploitations of lithium metal batteries are not realized because of uncontrollable lithium deposition and severe dendrite formation. Herein, a thermal percolation strategy is developed to fabricate a dual-conductive framework using electronically conductive Ti3C2Tx MXene aerogels (MXAs) and Li2OHCl antiperovskite superionic conductor. By melting Li2OHCl at a low temperature, the molten antiperovskite phase can penetrate the MXA scaffold, resulting in percolative electron/ion pathways. Through density functional theory calculations and electrochemical characterizations, the hybridized lithiophilic (MXA)−lithiophobic (antiperovskite) interfaces can spatially guide the deposition of lithium metals and suppress the growth of lithium dendrites. The symmetric cell with MXA–antiperovskite electrodes exhibits superior cycling stability at high areal capacities of 4 mAh cm−2 over 1000 h. Moreover, the full cell with MXA−antiperovskite anode and high-loading LiFePO4 cathode demonstrates high energy and power densities (415.7 Wh kgcell−1 and 231.0 W kgcell−1) with ultralong lifespans. The thermal percolation of lithium superionic conductor into electronically conductive scaffolds promises an efficient strategy to fabricate dual-conductive electrodes, which benefits the development of dendrite-free lithium metal anodes with high energy/power densities.
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    Salt-in-Salt Reinforced Carbonate Electrolyte for Li Metal Batteries
    (Wiley, 2022-08-30) Liu, Sufu; Zhang, Weiran; Wan, Hongli; Zhang, Jiaxun; Xu, Jijian; Rao, Jiancun; Deng, Tao; Hou, Singyuk; Nan, Bo; Wang, Chunsheng
    The instability of carbonate electrolyte with metallic Li greatly limits its application in high-voltage Li metal batteries. Here, a “salt-in-salt” strategy is applied to boost the LiNO3 solubility in the carbonate electrolyte with Mg(TFSI)2 carrier, which enables the inorganic-rich solid electrolyte interphase (SEI) for excellent Li metal anode performance and also maintains the cathode stability. In the designed electrolyte, both NO3− and PF6− anions participate in the Li+-solvent complexes, thus promoting the formation of inorganic-rich SEI. Our designed electrolyte has achieved a superior Li CE of 99.7 %, enabling the high-loading NCM811||Li (4.5 mAh cm−2) full cell with N/P ratio of 1.92 to achieve 84.6 % capacity retention after 200 cycles. The enhancement of LiNO3 solubility by divalent salts is universal, which will also inspire the electrolyte design for other metal batteries.