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A direct Z-scheme heterojunction via decorating Ag3PO4 quantum dots on SnS2 nanosheets results in highly selective and efficient solar-driven CO2-to-CO photoreduction.

Structural flexibility is a critical issue that limits the applications of MOF membranes for gas separation. Herein we propose a mixed-linker approach to suppress the structural flexibility of the CAU-10-based membranes. Specifically, pure CAU-10-PDC membrane is of high separation performance but at the same time highly unstable for the separation of CO2/CH4. A partial substitution (30 mol.%) of the linker PDC with BDC significantly improves its stability. Such an approach also allows for the aperture size of MOFs. The optimized CAU-10-PDC-H (70/30) membrane possesses a high separation performance for CO2/CH4 (separation factor of 76 and CO2 permeability of 1,111 Barrer under 2 bar of feed pressure at 35 ℃). A combination of in situ characterization with XRD and DRIFT spectroscopy, as well as DFT calculations, unveils the origin of the mixed-linker approach to enhancing the structural stability of the mixed-linker CAU-10-based membranes during the gas permeation tests.

Thermogravimetry (TG) combined with electrospray and atmospheric chemical ionization (ESI+APCI) mass spectrometry (MS) was developed to rapidly characterize thermal decomposition products of synthetic polymers and plastic products. The ESI-based TG-MS method is useful for characterizing thermally labile, nonvolatile, and polar compounds over an extensive mass range; and the APCI-based TG-MS counterpart is useful for characterizing volatile and nonpolar compounds. Both polar and nonpolar compounds can be simultaneously detected by ESI+APCI-based TG-MS.Analytes with different volatility were produced from TG operated at different temperatures, which were delivered through a heated stainless-steel tube to the ESI+APCI source where they reacted with the primary charged species generated from electrospray and atmospheric pressure chemical ionization (ESI+APCI) of solvent and nitrogen. The analyte ions were then detected by an ion trap mass spectrometer.A semi-volatile PEG 600 standard was used as the sample and protonated and sodiated molecular ions together with adduct ions including [(PEG)n + 15]The information obtained from the TG-ESI+APCI-MS analysis is useful in rapidly distinguishing different types of polymers and their products. In addition, the signals of the additives in the polymer products, including antioxidants and plasticizers, were also detected before the TG temperature reached T

Efficient O2 reduction reaction (ORR) for selective H2O generation enables advanced fuel cell technology. Non-precious metal (NPM) catalysts are viable and attractive alternatives to state-of-the-art Pt-based materials that are expensive. Cu complexes inspired by Cu-containing O2 reduction enzymes in nature have yet to reach their desired ORR catalytic performance. Here, the concept of mechanical interlocking is introduced to the ligand architecture to enforce dynamic spatial restriction on the Cu coordination site unachievable using other structural means. The utility of the kinetic effects from mechanical bond in transition metal catalysis is just about to emerge, and here the catenane ligands govern the O2 adduct binding mode, thereby steering the selectivity to generate H2O as the major product via the 4e– pathway, rivaling the selectivity of Pt. The kinetic effects from the interlocked catenane ligand also promotes product elimination and boosts the onset potential by 130 mV, the mass activity by 1.8 times, and the turnover frequency (TOF) by 1.5 folds as compared to the non-interlocked counterpart. Our Cu catenane complex represents one of the first examples to take advantage of mechanical interlocking to afford electrocatalysts with enhanced activity and selectivity. The mechanistic insights gained through this integrated experimental and theoretical study are envisioned to be of practical value not just to the area of ORR energy catalysis, but also with broad implications on interlocked metal complexes that are of critical importance to the general fields in redox reactions involving proton-coupled electron transfer (PCET) steps

Lithium metal anode material suffers from the formation of a dendritic structure and manufacturing difficulties in Li metal batteries. Although anode-free lithium metal batteries (AFLMBs) have rece...

Cu2ZnSnS4 (CZTS) has demonstrated excellent performance as an anode material for lithium-ion batteries. However, the repeated lithiation and delithiation create a cracking pattern and lead to island formation in the thin-film electrode, resulting in a capacity fading over cycling in lithium-ion batteries (LIB's). In order to control this crack behaviour, we introduce carbon into CZTS thin-films by a hydrothermal method to form CZTS@C composite. CZTS@C significantly reduced the crack pattern formation on the electrode surface as well as improved the conductivity of the CZTS@C electrode. At the early stages of lithiation and delithiation, the volume expansion and contraction of Li–CZTS@C create intra-granular cracking only at the surface level, and it offers a high capacity of about 785 mA h g−1 after 150 cycles at 1000 mA g−1 charging rate, excellent rate capability (942 mA h g−1, 678 mA h g−1 and 435 mA h g−1 at 500 mA g−1, 2000 mA g−1 and 5000 mA g−1), and superior cyclability (925 mA h g−1 even after 200 cycles at 500 mA g−1). The excellent electrochemical performance at high-current rates can be attributed to intra-granular cracking together with carbon coating that provides a short transportation length for both lithium ions and electrons. Moreover, the controlled cracking pattern formation in CZTS@C facilitates faster reaction kinetics, which open up a new solution for the development of high-power thin-film anodes for next-generation LIBs applications.

Revealing the active nature of oxide derived copper (OD-Cu) is of key importance to understand its remarkable catalytic performance during the cathodic CO2 reduction reaction (CO2RR) to produce valuable hydrocarbons. Using advanced spectroscopy, electron microscopy and electro active surface area characterization techniques, the electronic structure and the changes in the morphology/roughness of thermally oxidized copper thin films were revealed during CO2RR. For this purpose we developed an in situ cell for X-ray spectroscopy able to be operated accurately in the presence of gases or liquids to unite the role of the initial thermal oxide-phase and its active phase during the electrocatalytic reduction of CO2. It was found that the Cu(I) species formed during the thermal treatment are readily reduced to Cu0 during the CO2RR, whereas Cu(II) species are hardly reduced. In addition, Cu(II) oxide electrode dissolution was found to yield a porous/void structure, where the lack of electrical connection between isolated islands prohibits the CO2RR. Therefore, the active/stable phase for CO2RR is metallic copper, independent of its initial phase, with a significant change in its morphology upon its reduction yielding the formation of a rougher surface with higher number of under coordinated sites. Thus, the initial thermal oxidation of copper in air controls the reaction activity/selectivity due to the changes induced in electrode surface morphology/roughness and the presence of more under coordinated sites during the CO2RR.

Lithium metal anodes form a dendritic structure after cycling which causes an internal short circuit in flammable electrolytes and results in battery fires. Today's separators are insufficient for suppressing the formation of lithium dendrites. Herein, we report on the use of mesoporous silica thin films (MSTFs) with perpendicular nanochannels (pore size ∼5 nm) stacking on an anodic aluminum oxide (AAO) membrane as the MSTF⊥AAO separator for advancing Li metal batteries. The nanoporous MSTF⊥AAO separator with novel inorganic structures shows ultra-long term stability of Li plating/stripping in Li–Li cells at an ultra-high current density and capacity (10 mA cm−2 and 5 mA h cm−2). A significant improvement over the state-of-the-art separator is evaluated based on three performance indicators, e.g. cycle life, current density and capacity. In Li–Cu cells, the MSTF⊥AAO separator shows a coulombic efficiency of >99.9% at a current density of 10 mA cm−2 for more than 250 h of cycling. The separator gives improved rate capability in Li–LiFePO4 (LFP) batteries. The excellent performance of the MSTF⊥AAO separator is due to good wetting of electrolytes, straight nanopores with negative charges, uniform Li deposition and blocking the finest dendrite.

The widespread use of energy storage technologies has created a high demand for the development of novel anode materials in Li-ion batteries (LIBs) with high areal capacity and faster electron-transfer kinetics. In this work, carbon-coated Cu

Tuning the electronic band structure of black titania to improve photocatalytic performance through conventional band engineering methods has been challenging because of the defect-induced charge carrier and trapping sites. In this study, KSCN-modified hydrogenated nickel nanocluster-modified black TiO2 (SCN–H–Ni–TiO2) exhibits enhanced photocatalytic CO2 reduction due to the interfacial dipole effect. Upon combining the experimental and theoretical simulation approach, the presence of an electrostatic interfacial dipole associated with chemisorption of SCN has dramatic effects on the photocatalyst band structure in SCN–H–Ni–TiO2. An interfacial dipole possesses a more negative zeta potential shift of the isoelectric point from 5.20 to 3.20, which will accelerate the charge carrier separation and electron transfer process. Thiocyanate ion passivation on black TiO2 demonstrated an increased work function around 0.60 eV, which was induced by the interracial dipole effect. Overall, the SCN–H–Ni–TiO2 photocat...

Recently, rechargeable zinc-ion batteries (ZIBs) have gained a considerable amount of attention due to their high safety, low toxicity, abundance, and low cost. Traditionally, a composite manganese oxide (MnO2) and a conductive carbon having a polymeric binder are used as a positive electrode. In general, a binder is employed to bond all materials together and to prevent detachment and dissolution of the active materials. Herein, the synthesis of α-MnO2 nanowires on carbon cloth via a simple one-step hydrothermal process and its electrochemical performance, as a binder-free cathode in aqueous and nonaqueous-based ZIBs, is duly reported. Morphological and elemental analyses reveal a single crystal α-MnO2 having homogeneous nanowire morphology with preferential growth along {001}. It is significant that analysis of the electrochemical performance of the α-MnO2 nanowires demonstrates more stable capacity and superior cyclability in a dimethyl sulfoxide (DMSO) electrolyte ZIB than in an aqueous electrolyte system. This is because DMSO can prevent irreversible proton insertion as well as unfavorable dendritic zinc deposition. The application of the binder-free α-MnO2 nanowires cathode in DMSO can promote follow-up research on the high cyclability of ZIBs.

Understanding the role of the oxidation state of the Cu surface and surface-adsorbed intermediate species in electrochemical CO2 reduction is crucial for the development of selective CO2-to-fuel electrocatalysts. In this study, the electrochemical CO2 reduction mechanism over the Cu catalysts with various oxidation states was studied by using in situ surface-enhanced infrared absorption spectroscopy (SEIRAS), in situ soft X-ray absorption spectroscopy (Cu L-edge), and online gas chromatography measurements. The atop-adsorbed CO (COatop) intermediate is obtained on the electrodeposited Cu surface which primarily has the oxidation state of Cu(I). COatop is further reduced, followed by the formation of C1 product such as CH4. The residual bridge-adsorbed CO (CObridge) is formed on the as-prepared Cu surface with Cu(0) which inhibits hydrocarbon formation. In contrast, the CV-treated Cu electrode prepared by oxidizing the as-prepared Cu surface contains different amounts of Cu(I) and Cu(0) states. The major theme of this work is that in situ SEIRAS results show the coexistence of COatop and CObridge as the reaction intermediates during CO2 reduction and that the selectivity of CO2-to-ethylene conversion is further enhanced in the CV-treated Cu electrode. The Cu catalysts modulated by the electrochemical method exhibit different oxidation states and reaction intermediates as well as electrocatalytic properties.

Understanding the role of the oxidation state of the Cu surface and surface-adsorbed intermediate species in electrochemical CO

Utilization of g-C3N4 as a single photocatalyst material without combination with other semiconductor remains challenging. Herein, we report a facile green method for synthesizing a metal free modified g-C3N4 photocatalyst. The modification process combines four different strategies in a one-pot thermal reaction: non-metal doping, porosity generation, functionalization with amino groups, and thermal oxidation etching. The as-prepared amino-functionalized ultrathin nanoporous boron-doped g-C3N4 exhibited a high specific surface area of 143.2 m2 g−1 which resulted in abundant adsorption sites for CO2 and water molecules. The surface amino groups act as Lewis basic sites to adsorb acidic CO2 molecules, which can also serve as active sites to facilitate hydrogen generation. Besides, the simultaneous use of ammonium chloride as a dynamic gas bubble template along with thermal oxidation etching efficiently boosts the delamination of the g-C3N4 layers to produce ultrathin sheets; this leads to stronger light–matter interactions and efficient charge generation. Consequently, the newly modified g-C3N4 achieved selective gas-phase CO2 reduction into CO with a production yield of 21.95 µmol g−1, in the absence of any cocatalyst. Moreover, a high hydrogen generation rate of 3800 µmol g-1h−1 and prominent apparent quantum yield of 10.6% were recorded. This work opens up a new avenue to explore different rational modifications of g-C3N4 nanosheets for the efficient production of clean energy.

Applications of lithium ion battery have been hampered by a lack of ideal anode materials in terms of capacity and stability. The emergence of metal chalcogenide as a candidate material has reinvigorated the search of a low cost and high capacity material system. However, debate about the underlying mechanisms and overall appraisal of its usage in lithium ion battery system remains. Here, a comprehensive study on the energy storage mechanism of copper zinc tin sulfide (CZTS) nanowalls possessing ultrahigh rate capability (500 mAh g−1 charged within 60 s) is reported. Structural evolutions along with the accompanying changes in the oxidation state upon charge/discharge were monitored by ex-situ X-ray diffraction and X-ray photoelectron spectroscopy. During lithiation, lithium ion reacted with CZTS to form lithium sulfides. At the same time, a sequential conversion reactions of copper, zinc and tin sulfides enabled the CZTS nanowalls to achieve excellent electrochemical performance (1400 mAh g−1 at a current density of 1000 mA g−1 over 400 cycles). Multi-element metal chalcogenides in conjunction with an adhesion-enhancing seed layer and a rational nanostructure design hold the key to such ultrahigh capacity and stable anode materials for next generation energy storage devices.

We evaluate hydrofluoroether (HFE) cosolvents with varying degrees of fluorination in the acetonitrile-based solvate electrolyte to determine the effect of the HFE structure on the electrochemical performance of the Li–S battery. Solvates or sparingly solvating electrolytes are an interesting electrolyte choice for the Li–S battery due to their low polysulfide solubility. The solvate electrolyte with a stoichiometric ratio of LiTFSI salt in acetonitrile, (MeCN)2–LiTFSI, exhibits limited polysulfide solubility due to the high concentration of LiTFSI. We demonstrate that the addition of highly fluorinated HFEs to the solvate yields better capacity retention compared to that of less fluorinated HFE cosolvents. Raman and NMR spectroscopy coupled with ab initio molecular dynamics simulations show that HFEs exhibiting a higher degree of fluorination coordinate to Li+ at the expense of MeCN coordination, resulting in higher free MeCN content in solution. However, the polysulfide solubility remains low, and no cr...

Dissolved polysulfides, formed during Li-S battery operation, freely migrate and react with both the Li anode and the sulfur cathode. These soluble polysulfides shuttle between the anode and cathode – the so-called shuttle effect – resulting in an infinite recharge process and poor Columbic efficiency. In this study, water present as an additive in the Li-S battery electrolyte is found to reduce the shuttle effect in Li-S batteries. Batteries where water content was below 50 ppm exhibited a substantial shuttle effect and low charge capacity. Alternatively, addition of 250 ppm water led to stable charge/discharge behavior with high Coulombic efficiency. XPS results show that H2O addition results in the formation of solid electrolyte interphase (SEI) film with more LiOH on Li anode which protects the Li anode from the polysulfides. Batteries cycled without water result in a SEI film with more Li2CO3 likely formed by direct contact between the Li metal and the solvent. Intermediate quantities of H2O in the electrolyte result in high cycle efficiency for the first few cycles which then rapidly decays. This suggests that H2O is consumed during battery cycling, likely by interaction with freshly exposed Li metal formed during Li deposition.

In the archetypal lithium-rich cathode compound Li1.2Ni0.13Co0.13Mn0.54O2, a major part of the capacity is contributed from the anionic (O2−/−) reversible redox couple and is accompanied by the transition metal ions migration with a detrimental voltage fade. A better understanding of these mutual interactions demands for a new model that helps to unfold the occurrences of voltage fade in lithium-rich system. Here we present an alternative approach, a cationic reaction dominated lithium-rich material Li1.083Ni0.333Co0.083Mn0.5O2, with reduced lithium content to modify the initial band structure, hence ~80% and ~20% of capacity are contributed by cationic and anionic redox couples, individually. A 400 cycle test with 85% capacity retention depicts the capacity loss mainly arises from the metal ions dissolution. The voltage fade usually from Mn4+/Mn3+ and/or On−/O2− reduction at around 2.5/3.0 V seen in the typical lithium-rich materials is completely eliminated in the cationic dominated cathode material.

Tuning the electronic band structure of black titania to improve photocatalytic performance through conventional band engineering methods has been challenging because of the defect-induced charge carrier and trapping sites. In this study, KSCN-modified hydrogenated nickel nanocluster-modified black TiO

Tin-based composites are promising anode materials for high-performance lithium-ion batteries (LIBs); however, insufficient conductivity, as well as fatal volume expansion during cycling lead to poor electrochemical reversibility and cycling stability. In this work, we demonstrate the lithium-ion storage behaviors of SnS2 anode material deposited on different electrode supports. The SnS2 grown on 3D hierarchical carbon nanotube-carbon cloth composites (SnS2-CNT-CC) shows superior capacity retention and cycle stability, compared to that on planar Mo sheets and carbon cloth. The specific capacity of SnS2 on Mo, CC, and CNT-CC is around 240, 840, and 1250 g−1, respectively. The SnS2-CNT-CC electrode outperforms in the cyclic performance and rate capability compared to other electrode configurations due to the multi-electron pathway and high surface area derived from 3D hierarchical CNT-CC electrode support. Furthermore, a significant decrease in the charge transfer resistance is observed by utilizing 3D hierarchical CNT-CC electrode support. The use of 3D hierarchical structures as electrode support could be the best alternative to enhance the electrochemical performances for the next generation LIBs.

The phase transition behaviors of a supported bilayer of dipalmitoylphosphatidyl-choline (DPPC) have been systematically evaluated by in situ sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). By using an asymmetric bilayer composed of per-deuterated and perprotonated monolayers, i.e., DPPC-d(75)/DPPC and a symmetric bilayer of DPPC/DPPC, we were able to probe the molecular structural changes during the phase transition process of the lipid bilayer by SFG spectroscopy. It was found that the DPPC bilayer is sequentially melted from the top (adjacent to the solution) to bottom leaflet (adjacent to the substrate) over a wide temperature range. The conformational ordering of the supported bilayer does not decrease (even slightly increases) during the phase transition process. The conformational defects in the bilayer can be removed after the complete melting process. The phase transition enthalpy for the bottom leaflet was found to be approximately three times greater than that for the top leaflet, indicating a strong interaction of the lipids with the substrate. The present SFG and AFM observations revealed similar temperature dependent profiles. Based on these results, the temperature-induced structural changes in the supported lipid bilayer during its phase transition process are discussed in comparison with previous studies.

Direct copolymerization of CO2 and 1,4-butanediol to yield poly(butylene carbonate) oligomers has been recently realized using CeO2 as a catalyst and 2-cyanopyridine as a dehydrating agent. In this study, CeO2 nanorod and nanocube were synthesized, characterized, and compared their catalytic activities with commercial CeO2 nanoparticle and submicronparticle. Reaction testing reveals that CeO2 nanorod exhibits a much higher yield of polycarbonate oligomer than other CeO2 catalysts. Surface characterizations indicate that CeO2 nanorod displays a significantly higher CO2 uptake and stronger interactions with CO2, properties that could be beneficial to activate stable CO2 molecule. In-situ infrared spectroscopy suggests that bidentate carbonate, i.e., CO2 adsorbs over the CeO2 surface with an oxygen atom and an oxygen vacancy coordinated with a cerium atom, is the key intermediate associated with the observed catalytic activities. These results manifest the importance of surface oxygen vacancy of CeO2 for activating CO2 to proceed non-reductive conversion.

Lithium-ion batteries (LIBs) function as power sources in various environments and the effect of temperature is one of the major factors which limits the performance and proper operations in in cold climates or high altitude areas and in space applications. Hence, the poor charge/discharge rate and short lifetime of LIBs in low-temperature areas have restricted its application for electric vehicle (EV) or a hybrid EV. In this work, copper zinc tin sulfide (CZTS) thin-film anode materials with different mixtures of electrolytes has been prepared to study the electrochemical performance at low-temperature environments. The CZTS anode, prepared from EC/DEC/DMC electrolyte has demonstrated higher efficiency and reversible capacity at -10 oC as compared to the binary electrolyte obtained from EC/DEC electrolyte. The performance of the electrolyte at different temperature ranges and the corresponding electrochemical performance of CZTS electrode is systematically analyzed. The Kinetics and surface morphology of the as-prepared CZTS anode has been analyzed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and Scanning electron microscope (SEM) respectively. As compared to the room temperature capacity, the CZTS has demonstrated outstanding capacity retention around 55.3 % at -10 oC in the ternary solvent electrolyte mixtures after 100 cycles at 500 mA/g current density. However, in the binary EC-DEC based electrode, a rapid capacity degradation with a capacity retention of only around 27.2 % of the room temperature capacity has been observed at the same experimental conditions. This method could be an alternative approach to study the effect of electrolyte and the performance of the anode materials in the design of thin-film micro-batteries for next-generation sub-zero temperature applications. The detail characterization and experimental results with the future perspective of this study will be discussed here.

Recently, rechargeable zinc-ion batteries (ZIBs) have gained a considerable amount of attention due to their high safety, low toxicity, abundance, and low cost. Traditionally, a composite manganese oxide (MnO2) and a conductive carbon having a polymeric binder are used as a positive electrode. In general, a binder is employed to bond all materials together and to prevent detachment and dissolution of the active materials. Herein, the synthesis of &alpha, MnO2 nanowires on carbon cloth via a simple one-step hydrothermal process and its electrochemical performance, as a binder-free cathode in aqueous and nonaqueous-based ZIBs, is duly reported. Morphological and elemental analyses reveal a single crystal &alpha, MnO2 having homogeneous nanowire morphology with preferential growth along {001}. It is significant that analysis of the electrochemical performance of the &alpha, MnO2 nanowires demonstrates more stable capacity and superior cyclability in a dimethyl sulfoxide (DMSO) electrolyte ZIB than in an aqueous electrolyte system. This is because DMSO can prevent irreversible proton insertion as well as unfavorable dendritic zinc deposition. The application of the binder-free &alpha, MnO2 nanowires cathode in DMSO can promote follow-up research on the high cyclability of ZIBs.

In situ EQCM experiments were used to investigate the stability and roughness changes occurring in a sulfur-carbon cathode utilized for a Li-S battery during the charge-discharge process. Results show that the sulfur-carbon cathode gains mass during the first discharge plateau (∼2.4 V) due to the formation of the long chain polysulfides during the discharge (lithiation) process. However, further discharge to below 2.4 V yields an increase in the crystal resistance (Rc) suggesting the sulfur-carbon cathode becomes rougher. During the charge (delithiation) process, the roughness of the sulfur-carbon cathode decreases. Time dependent measurements show that the electrode surface becomes rougher with the deeper discharge, with the change occurring following a step to 1.5 V. The sulfur-carbon cathode exhibits stable Rc and frequency behavior initially, but then becomes rougher in subsequent following cycles.

We evaluate hydrofluoroether (HFE) cosolvents with varying degrees of fluorination in the acetonitrile-based solvate electrolyte to determine the effect of the HFE structure on the electrochemical performance of the Li-S battery. Solvates or sparingly solvating electrolytes are an interesting electrolyte choice for the Li-S battery due to their low polysulfide solubility. The solvate electrolyte with a stoichiometric ratio of LiTFSI salt in acetonitrile, (MeCN)

In this manuscript, we analyze the electrochemical behavior of a self-assembled monolayer (SAM) of a Cu-based O2 reduction catalyst. We construct a hybrid bilayer membrane (HBM) by appending a lipid monolayer on top of the SAM and control proton flux to the catalyst by incorporating an alkyl phosphate proton carrier in the lipid layer of the HBM. The HBM platform is interrogated using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) experiments performed as a function of solution pH indicate that the Cu(I)/Cu(II) couple of the catalyst without lipid involves the transfer of one proton per electron. With lipid, however, the number of protons transferred per electron for the Cu(I)/Cu(II) decreases and varies with pH depending upon the structural integrity of the lipid layer. Upon adding the proton carrier to the lipid, both the number of protons transferred during the Cu(I)/Cu(II) redox event and the integrity of the lipid layer increase. Furthermore, we report the pH dependence of the O2 reduction reaction (ORR) as mediated by the Cu catalyst inside the HBM with proton carrier. Taken together, these results provide mechanistic insight into an electrochemical platform that is broadly useful in studying proton-coupled electron transfer (PCET) reactions.

Lithium (Li) metal is considered as the ultimate anode material for the development of next-generation batteries.1 However, Li metal electrode forms dendritic structure after cycling which causes an internal short circuit.2, 3 In this work, we grew mesoporous silica thin film (MSTF) with perpendicular nanochannels and ultra-small pore diameter (~5 nm diameter) onto the anodic aluminum oxide (AAO) membrane as the MSTF⊥AAO separator. The nanoporous MSTF⊥AAO separator with novel inorganic structures shows stable Li deposition for more than 1600 h of operation in Li-Li cells under a very high current density and capacity of 10 mA cm–2 and 5 mAh cm–2. The separator gives improved rate capability in Li-NMC batteries. The excellent performance of the MSTF⊥AAO nanoporous separator is due to good wetting of electrolytes, straight nanopores, uniform deposition of Li and blocking the finest dendrite. Our designed separators provide a groundbreaking model to regulate Li plating/stripping behavior. References Cheng, X.-B.; Zhang, R.; Zhao, C.-Z.; Zhang, Q., Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review. Chem. Rev. 2017, 117 (15), 10403-10473. Xu, W.; Wang, J.; Ding, F.; Chen, X.; Nasybulin, E.; Zhang, Y.; Zhang, J.-G., Lithium metal anodes for rechargeable batteries. Energy Environ. Sci. 2014, 7 (2), 513-537. Zhang, S. S., A review on the separators of liquid electrolyte Li-ion batteries. Power Sources 2007, 164 (1), 351-364.

Lithium metal anode has been regarded as the "Holy Grail" of next-generation battery technologies. In order to stabilize the electrodeposited Li metal for safe and high energy batteries, highly concentrated electrolytes (solvate electrolytes) have been proposed to suppress the formation of Li dendritic structure and polysulfide dissolution in lithium-sulfur (Li-S) batteries. (1-5) In this talk, we use in situ transmission X-ray microscopy (TXM) to study the effect of solvate electrolyte on Li plating/stripping process. In situ TXM images show that electrodeposited Li particles with uniform density are formed in solvate electrolyte during initial plating process. The effect of solvate electrolyte on the mechanism of Li growth is studied in detail. Additionally, in situ spectroscopy including Raman and X-ray spectroscopy (X-ray diffraction and X-ray absorption spectroscopy) are used to investigate sulfur reaction mechanism and the interaction between polysulfide and solvate electrolyte. We found that the sulfur species formed in the solvate electrolyte are different from the sulfur species formed in conventional DOL/DME electrolyte. These results suggest that solvate electrolyte changes both polysulfide solubility and sulfur reaction mechanism. We next propose different solvate electrolytes with low polysulfide solubility and high stability toward Li metal to enhance the capacity retention of Li-S batteries. References: [1] L. Suo et al., Nat. Commun. 2013, 4, 1481. [2] K. Dokko et al., J. Electrochem. Soc. 2013, 160, A1304. [3] M. Cuisinier et al., Energy Environ. Sci., 2014, 7, 2697. [4] Y. Yamada et al., J. Electrochem. Soc. 2015, 162 (14), A2406. [5] L. Cheng et al., ACS Energy Lett. 2016, 1, 503.

Atomic force microscopy (AFM) is employed to reveal the morphological changes of the supported phospholipid bilayers hydrolyzed by a phospholipase A2 (PLA2) enzyme in a buffer solution at room temperature. Based on the high catalytic selectivity of PLA2 toward l -enantiomer phospholipids, five kinds of supported bilayers made of l - and d -dipalmitoylphosphatidylcholines (DPPC), including l -DPPC (upper leaflet adjacent to solution)/ l -DPPC (bottom leaflet) (or l / l in short), l / d , d / l , d / d , and racemic ld / ld , were prepared on a mica surface in gel-phase, to explicate the kinetics and mechanism of the enzyme-induced hydrolysis reaction in detail. AFM observations for the l / l bilayer show that the hydrolysis rate for l -DPPC is significantly increased by PLA2 and most of the hydrolysis products desorb from substrate surface in 40 min. As d -enantiomers are included in the bilayer, the hydrolysis rate is largely decreased in comparison with the l / l bilayer. The time used to hydrolyze the as-prepared bilayers by PLA2 increases in the sequence of l / l , l / d , ld / ld , and d / l ( d / d is inert to the enzyme action). d -enantiomers in the enantiomer hybrid bilayers remain on the mica surface at the end of the hydrolysis reaction. It was confirmed that the hydrolysis reaction catalyzed by PLA2 preferentially occurs at the edges of pits or defects on the bilayer surface. The bilayer structures are preserved during the hydrolysis process. Based on these observations, a novel kinetics model is proposed to quantitatively account for the PLA2-catalyzed hydrolysis of the supported phospholipid bilayers. The model simulation demonstrates that PLA2 mainly binds with lipids at the perimeter of defects in the upper leaflet and leads to a hydrolysis reaction, yielding species soluble to the solution phase. The lipid molecules underneath subsequently flip up to the upper leaflet to maintain the hydrophilicity of the bilayer structure. Our analysis shows that d -enantiomers in the hybrid bilayers considerably reduce the hydrolysis rate by its ineffective binding with PLA2.

Li–S batteries are a promising next-generation battery technology. Due to the formation of soluble polysulfides during cell operation, the electrolyte composition of the cell plays an active role in directing the formation and speciation of the soluble lithium polysulfides. Recently, new classes of electrolytes termed “solvates” that contain stoichiometric quantities of salt and solvent and form a liquid at room temperature have been explored due to their sparingly solvating properties with respect to polysulfides. The viscosity of the solvate electrolytes is understandably high limiting their viability; however, hydrofluoroether cosolvents, thought to be inert to the solvate structure itself, can be introduced to reduce viscosity and enhance diffusion. Nazar and co-workers previously reported that addition of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) to the LiTFSI in acetonitrile solvate, (MeCN)_2–LiTFSI, results in enhanced capacity retention compared to the neat solvate. Here, we evaluate the effect of TTE addition on both the electrochemical behavior of the Li–S cell and the solvation structure of the (MeCN)_2–LiTFSI electrolyte. Contrary to previous suggestions, Raman and NMR spectroscopy coupled with ab initio molecular dynamics simulations show that TTE coordinates to Li^+ at the expense of MeCN coordination, thereby producing a higher content of free MeCN, a good polysulfide solvent, in the electrolyte. The electrolytes containing a higher free MeCN content facilitate faster polysulfide formation kinetics during the electrochemical reduction of S in a Li–S cell likely as a result of the solvation power of the free MeCN.