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Direct probing of metal–oxygen chemistry at the solid/liquid interface is essential to unravel the reaction mechanism of metal–air batteries. Ambient pressure X-ray photoelectron spectroscopy (APXPS) is an effective tool to study metal–oxygen reactions but has been limited to solid-state environments. Here, for the first time, we demonstrate in situ probing of potassium oxygen reduction/evolution reaction (ORR/OER) via APXPS in ionic liquid-based air batteries. We reveal the formation and oxidation of K2O and K2O2 in K–O2 batteries, highlighting new reaction pathways in addition to the widely established one-electron process in K–O2 batteries. Importantly, we show that the formation and subsequent oxidation of K2O2 trigger irreversible cell chemistry, which could be responsible for capacity decay in K–O2 batteries. We further show that common impurities in air such as H2O and CO2 reduce chemical reversibility of ORR and OER. This study reveals root causes of irreversible cell chemistry in K–air batteries via direct probing of ionic liquid-based air batteries via APXPS, which can be widely applied to study the chemistry of solid/liquid interfaces of metal–air batteries.

Annealed Rh nanoclusters on an ordered thin film of Al2O3/NiAl(100) were shown to exhibit a promoted reactivity toward the decomposition of methanol-d4, under both ultrahigh vacuum and near-ambient-pressure conditions. The Rh clusters were grown with vapor deposition onto the Al2O3/NiAl(100) surface at 300 K and annealed to 700 K. The decomposition of methanol-d4 proceeded only through dehydrogenation, with CO and deuterium as products, on Rh clusters both as prepared and annealed. Nevertheless, the catalytic reactivity of the annealed clusters, measured with the production of either CO or deuterium per surface Rh site from the reaction, became at least 2–3 times that of the as-prepared ones. The promoted reactivity results from an altered support effect associated with an annealing-induced mass transport at the surface. Our results demonstrate a possibility to practically prepare reactive Rh clusters, regardless of the cluster size, that can tolerate an elevated reaction temperature, with no decreased reactivity.

Li1.5Al0.5Ge1.5(PO4)3 (LAGP) is a promising solid electrolyte for use in next-generation lithium batteries. Nevertheless, its lower bulk and grain-boundary ionic conductivities are major restrictions preventing its practical utilization. Mg was introduced into LAGP to form Li1.6Al0.4Mg0.1Ge1.5(PO4)3 (LAMGP) based on computational analysis. The doping of LAGP with Mg results in advantages such as increasing the Li+ concentration and expanding the material dimensions due to the larger ionic radius of Mg, leading to enhanced ionic conductivity. Mg had a two-birds-with-one-stone effect in the LAMGP electrolyte, not only generating super high bulk ionic conductivity of 7.435 mS cm−1, compared to 2.896 mS cm−1 in LAGP, but also generating low grain-boundary resistance due to improved densification. The lowering of the grain-boundary resistance and the increased densification are related to choosing the right precursor for the dopant. Using LAMGP as a hybrid solid electrolyte, a solid battery delivered great electrochemical performance in comparison to when LAGP was used. Interfacial analysis was also conducted, which revealed that the formation of an interface prevented the reduction of components in LAMGP by Li metal, therefore ensuring the long-term durability of LAMGP in liquid electrolyte. These results suggest that LAMGP is an auspicious solid electrolyte for achieving practical solid-state lithium batteries.

Lithium manganese oxide (LMO) is one of the most promising cathode materials for lithium-ion batteries. However, the dissolution of manganese and its deposition on the anode surface cause poor cycling stability. To alleviate these issues, a film composed of polyvinylidene difluoride (PVDF) and Li5.6Ga0.26La2.9Zr1.87Nb0.05O12 type garnet (PVDF@LGLZNO) is coated directly on the LMO electrode and it functions as a promising artificial cathode–electrolyte interphase (CEI). The film thickness is optimized taking into account the electrospinning–processing time. To realize a cell with good capacity retention, excellent rate capability and resilience under harsher conditions (e.g. elevated temperature or high rates), the coated LMO cathode is coupled with a new anode which consists of sulfurized carbon derived from polyacrylonitrile (S-C(PAN)). The electrode (LMO-30 min) coated with the PVDF@LGLZNO composite material shows outstanding cycling stability and rate capability, as well as capacity retention when compared to the bare electrode both at room temperature (25 °C) and elevated temperature (55 °C). The PVDF@LGLZNO fibrous film coating suppresses the dissolution of manganese both at high C-rates and 55 °C, as supported by XPS, whereas PVDF coated and bare LMO cathodes are not able to prevent further deterioration of themselves. The film significantly minimizes undesirable side reactions at the cathode–electrolyte interface and reduces charge transfer resistance. The new cell with PVDF@LGLZNO (LMO-30 min) modified cathode and S-C(PAN) anode delivers capacity retention of 77% after 1000 cycles at 1C, corresponding to an average capacity decay of 0.023% per cycle.

A hierarchically structured bimetallic nanocatalyst (NC) comprising a metallic Pd-nanocluster adjacent to local tetrahedral symmetric Ni-oxide and a thin layer of tetramethyl orthosilicate (TMOS) decoration (denoted as NiOTPd-T) is synthesized by sequential control of the metal ion adsorption followed by wet chemical reduction on a carbon nanotube support. By cross-referencing the results of the physical structure inspections, in situ ambient pressure X-ray photoelectron spectroscopy, and gas chromatography-mass spectrometer analysis, we demonstrate that the NiOTPd-T gains an optimum production yield of 1905.1 mmol g−1 of CH4 which is more than 10-fold improved as compared to that of TMOS decorated Pd nanocatalysts (Pd-T) at 573 K. Such an exceptional performance is attributed to the local synergetic collaboration between CO chemisorption on Pd atoms and H2 splitting on both the Pd and Ni atoms at the interface region. Once the collaboration is triggered, the subsequent NiOT reduction increases the number of metallic Ni sites. It further facilitates the H2 splitting, therefore optimizing the CH4 production yield of NiOTPd-T. Most importantly, to the best of our knowledge, with such a unique Pd-to-NiOT epitaxial structure, the NiOTPd-T catalysts exhibit the highest CH4 production yield among existing catalysts with the same loading and composition and of any geometric configuration.

Thin Sn films on Ag(111) grown at different Sn coverage and substrate temperature were characterized with low-energy electron diffraction and x-ray photoelectron spectra. The results show that surface alloying of Sn atoms on Ag(111) occurs at a temperature as low as 96 K, indicating a strong tendency to form a surface alloy between Sn and Ag. During the alloying, Sn atoms substitute Ag atoms in random locations, resulting in a disordered Sn/Ag(111) surface. The alloy surface becomes completely ordered with a (√3 × √3) R30° reconstruction (the √3 phase) only when it is annealed above 453 K, but annealing at 403 K converts all Sn atoms on Ag(111) into the alloy state; the surface coverage of Sn is no more than 1/3 monolayer with excess Sn diffusing into the Ag(111) substrate. These observations indicate that the √3 phase with the Sn-Ag surface alloy is the only ordered phase obtainable on Sn/Ag(111) once the Sn-Ag surface alloy is formed. It is consequently impracticable to grow non-alloy ordered phases, such as stanene, on Ag(111) epitaxially at a temperature above 96 K, showing evident discrepancies with the conclusions of the previous computational study.

Sulfurized polyacrylonitrile (S-cPAN) has been recognized as a particularly promising cathode material for lithium-sulfur (Li-S) batteries due to its ultra-stable cycling performance and high degree of sulfur utilization. Though the synthetic conditions and routes for modification of S-cPAN have been extensively studied, details of the molecular structure of S-cPAN remain yet unclear. Herein, a more reasonable molecular structure consisting of pyridinic/pyrrolic nitrogen (NPD/NPL) is proposed, based on the analysis of combined X-ray photoelectron spectroscopy, 13C/15N solid-state nuclear magnetic resonance, and density functional theory data. The coexistence of vicinal NPD/NPL entities plays a vital role in attracting S2 molecules and facilitating N-S bond formation apart from the generally accepted C-S bond in S-cPAN, which could explain the extraordinary electrochemical features of S-cPAN among various nitrogen-containing sulfurized polymers. This study provides new insights and a better understanding of structural details and relevant bond formation mechanisms in S-cPAN, providing a foundation for the design of new types of sulfurized cathode materials suitable for application in next-generation high-performance Li-S batteries.

The holes doping effect on the metal–insulator transition (MIT) behavior of VO2 film is investigated via the tetrafluorotetracyanoquinodimethane (F4TCNQ) molecules adsorption induced surface charge transfer. Comparing with the MIT process of pristine VO2 film, a critical temperature decrease of about 4 °C for the F4TCNQ covered VO2 sample is observed. The MIT depression mechanism is deeply investigated based on detailed experiments including synchrotron radiation photon electronic spectroscopy (SRPES), X-ray absorption near-edge structure (XANES) spectroscopy and variable temperature Raman spectroscopy. Results indicate that the electronic structures of F4TCNQ covered VO2 sample are changed clearly due to the effective holes doping. In addition, the doped holes also change the V 3d orbital occupancy and weaken the electron–electron correlation as well, lowering the crystalline stability energy. Both of the above effects are in favor of triggering the earlier occurrence of MIT, resulting in the decrease of critical temperature.

Tuning the Fermi level (EF) in Bi2Te3 topological-insulator (TI) films is demonstrated on controlling the temperature of growth with molecular-beam epitaxy (MBE). Angle-resolved photoemission spectra (ARPES) reveal that EF of Bi2Te3 thin films shifts systematically with the growth temperature (Tg). The key role that a Bi-on-Te(1) (BiTe1) antisite defect plays in the electronic structure is identified through extended X-ray-absorption fine-structure (EXAFS) spectra at the Bi L3-edge. Calculations of electronic structure support the results of fitting the EXAFS, indicating that the variation of EF is due to the formation and suppression of BiTe1 that is tunable with the growth temperature. Our findings provide not only insight into the correlation between the defect structure and electronic properties but also a simple route to control the intrinsic topological surface states, which could be useful for applications in TI-based advanced electronic and spintronic devices.

Highly ordered Ag films grown on cleaved mica with a two-step procedure were characterized in detail with several techniques for surface analysis, including low-energy electron diffraction, X-ray photoemission spectra, a scanning tunneling microscope and angle-resolved photoemission spectra. Silver films of a thickness ≥ 100 nm were deposited on mica substrates at 300 K and stored under ambient conditions. The Ag/mica films became atomically flat and free of contamination when they were transferred into ultra-high vacuum and prepared with sputtering and annealing. The experimental results indicate that the surfaces of the cleaned Ag/mica films have structural and electronic properties resembling those of a Ag(111) single crystal with ordered domains aligned over a macroscopic region, but the surfaces of the Ag/mica films became rough on annealing above 623 K. On the rough surfaces, the surface steps tended to bunch together, yielding flat terraces bound with steps of large heights. With the decreased thermal stability in mind, the Ag/mica film is adoptable as a cheap platform alternative to a Ag(111) single crystal for the growth of highly ordered overlayers.

The uncontrolled lithium dendrite growth during cycling causes safety issues that impede lithium metal batteries from practical applications. In anode-free lithium metal batteries (AFLMBs), the unregulated plating of lithium on bare copper enforces a more severe growth of lithium dendrite. Herein, we guide the direction of lithium (Li) depositions towards the backside of gold sputter perforated polyimide film (PI@Au), which serves as an anode current collector. Thus, Li can deposit on the surface of PI@Au, and subsequently, Li growth takes place in the direction away from the separator face (ASF). This backside deposition and growth tactic allow the battery to operate safely, even when lithium dendrite exists. Remarkably, the dendrite free separator facing (SF) of PI@Au anode demonstrates highly improve cycling stability. Hence, PI@Au//LFP cell is capable of maintaining capacity retention (CR) of 20% for 340 cycles with an average Coulombic efficiency (Av. CE) of 98.7% (0.5 mA/cm2). In contrast, the control cell (Cu//LFP) runs only for 165 cycles under the same value of CR. This work not only proposes an innovative approach in developing ultra-safe AFLMBs but also validates the feasibility of electrically nonconductive substrates as anode current collectors by modifying their lithiophilicity.

We observed the growth phase transition of n-alkanethiols (AT), CH3(CH2)n−1SH, n = 4–16, directly implanted on a bare Si(111) surface, forming an AT monolayer. These monolayers were characterized with static water-contact angle, high-resolution X-ray photoelectron spectroscopy, near-edge X-ray fine-structure spectroscopy, and grazing-angle reflection absorption Fourier-transform infrared spectroscopy. The integrated spectral results indicated that the implanted n-AT molecules formed a self-oriented and densely packed monolayer through formation of an S–Si bond. With the number of carbons in the alkyl chain at six or more, namely beginning at hexanethiol, the molecular monolayer began to develop an orientation-ordered structure, which is clearly shorter than that for AT monolayers on Au and Ag. This result implies that, with a stronger molecule–substrate interaction, an ordered molecular monolayer can form with a short chain.

Mesocrystals of high-magnesian calcites are commonly found in biogenic calcites. Under ambient conditions, it remains challenging to prepare mesocrystals of high-magnesian calcite in aqueous solution. We report that mesocrystals of calcite with magnesium content of ~20 mol % can be obtained from the phase transformation of magnesian amorphous calcium carbonate (Mg-ACC) in lipid solution or in air. The limited water content on the Mg-ACC surface would reduce the extent of the dissolution-reprecipitation process and bias the phase transformation pathway toward solid-state reaction. We infer from the selected area electron diffraction patterns and the dark field transmission electron microscopic images that the formation of Mg-calcite mesocrystals occurs via solid-state secondary nucleation, for which the phase transformation is initiated near the mineral surface and the crystalline phase propagates gradually toward the interior part of the microspheres of Mg-ACC.

Ultrathin bilayers (BLs) of bismuth have been predicated to be a two-dimensional (2D) topological insulator. Here we report on a new route to manufacture the high-quality Bi bilayers from a 3D topological insulator, a top-down approach to prepare large-area and well-ordered Bi(111) BL with deliberate hydrogen etching on epitaxial Bi2Se3 films. With scanning tunneling microscopy (STM) and X-ray photoelectron spectra (XPS) in situ, we confirm that the removal of Se from the top of a quintuple layer (QL) is the key factor, leading to a uniform formation of Bi(111) BL in the van der Waals gap between the first and second QL of Bi2Se3. The angle resolved photoemission spectroscopy (ARPES) in situ and complementary density functional theory (DFT) calculations show a giant Rashba splitting with a coupling constant of 4.5 eV A in the Bi(111) BL on Bi2Se3. Moreover, the thickness of Bi BLs can be tuned by the amount of hydrogen exposure. Our ARPES and DFT study indicated that the Bi hole-like bands increase with i...

The combined effect of concentrated electrolyte and cycling protocol on the cyclic performance of the anode-free battery (AFB) is evaluated systematically. In situ deposition of Li in the AFB configuration in the presence of a concentrated electrolyte containing fluorine-donating salt and resting the deposit enables the formation of stable and uniform SEI. The SEI intercepts the undesirable side reaction between the deposit and solvent in the electrolyte and reduces electrolyte and Li consumption during cycling. The synergy between the laboratory-prepared concentrated 3 M LiFSI in the ester-based electrolyte and our resting protocol significantly enhanced cyclic performances of AFBs in comparison to the commercial carbonate-based dilute electrolyte, 1 M LiPF6. Benefitting from the combined effect, Cu∥LiFePO4 cells delivered excellent cyclic performance at 0.5 mA/cm2 with an average CE of up to 98.78%, retaining a reasonable discharge capacity after 100 cycles. Furthermore, the AFB can also be cycled at a high rate up to 1.0 mA/cm2 with a high average CE and retaining the encouraging discharge capacity after 100 cycles. The fast cycling and stable performance of these cells are attributed to the formation of robust, flexible, and tough F-rich conductive SEI on the surface of the in situ-deposited Li by benefiting from the combined effect of the resting protocol and the concentrated electrolyte. A condescending understanding of the mechanism of SEI formation and material choice could facilitate the development of AFBs as future advanced energy storage devices.

&alpha, &omega, diperfluorohexylquaterthiophene (DFH-4T) has been an attractive n-type material employed in the development of high-mobility organic field-effect transistors. This paper presents a systematic study of the relationship between DFH-4T transistor performance and film structure properties as controlled by deposited thickness. When the DFH-4T thickness increases from 8 nm to 80 nm, the room-temperature field-effect mobility increases monotonically from 0.01 to 1 cm2&middot, V&minus, 1&middot, s&minus, 1, while the threshold voltage shows a different trend of first decrease then increase. The morphology of thin films revealed by atomic force microscopy shows a dramatic change from multilayered terrace to stacked rod like structures as the film thickness is increased. Yet the crystallite structure and the orientation of molecular constituent, as determined by X-ray diffraction and near-edge X-ray absorption fine structure respectively, do not differ much with respect to film thickness increase. Further analyses of low-temperature transport measurements with mobility-edge model demonstrate that the electronic states of DFH-4T transistors are mainly determined by the film continuity and crystallinity of the bottom multilayered terrace. Moreover, the capacitance-voltage measurements of DFH-4T metal-insulator-semiconductor diodes demonstrate a morphological dependence of charge injection from top contacts, which well explains the variation of threshold voltage with thickness. The overall study provides a deeper understanding of microstructural and molecular growth of DFH-4T film and clarify the structural effects on charge transport and injection for implementation of high-mobility top-contact transistors.

In-depth mechanistic understanding of CO2 reduction reaction (CRR) and CO2 evolution reaction (CER) is the prerequisite to develop stable and efficient Li–CO2 batteries. In this study, we investigate the redox reaction of CO2 on the porous carbon surface in ionic liquid electrolyte via synchrotron-based in situ ambient pressure X-ray photoelectron spectroscopy (APXPS) technique. We used ionic liquid to facilitate CO2 capture and stabilize CRR intermediate anions owing to its strong solvation for Li+. We demonstrate that pure CO2 reduction is not electrochemically active at room temperature on porous carbon electrode and its kinetics can be remarkably improved by H2O, which could be responsible for the discrepancy on CRR kinetics in the literature. However, in the presence of H2O, the formed LiOH gradually converted to Li2CO3 leading to severe electrolyte degradation in charging reaction. With the assistance of O2 in the ionic liquid-based electrolyte, we show, for the first time, CRR yields a low-valence amorphous carbon and Li2O2/Li2O in the Li–CO2 batteries. The formed amorphous carbon, Li2O2 and Li2O exhibit higher rechargeability and faster kinetics compared with Li2CO3-oxidation. These new findings provide direct evidence of CRR mechanism and insights in resolving the discrepancy on CRR kinetics in Li–CO2 batteries.

We report the synthesis and characterization of alloyed Sn–Pb methylammonium mixed-halide perovskites (CH3NH3SnyPb1–yI3–xClx) to extend light harvesting toward the near-infrared region for carbon-based mesoscopic solar cells free of organic hole-transport layers. The proportions of Sn in perovskites are well-controlled by mixing tin chloride (SnCl2) and lead iodide (PbI2) in varied stoichiometric ratios (y = 0–1). SnCl2 plays a key role in modifying the lattice structure of the perovskite, showing anomalous optical and optoelectronic properties; upon increasing the concentration of SnCl2, the variation of the band gap and band energy differed from those of the SnI2 precursor. The CH3NH3SnyPb1–yI3–xClx devices showed enhanced photovoltaic performance upon increasing the proportion of SnCl2 until y = 0.75, consistent with the corresponding potential energy levels. The photovoltaic performance was further improved upon adding 30 mol % tin fluoride (SnF2) with device configuration FTO/TiO2/Al2O3/NiO/C, produc...

A better understanding of how interfacial structure affects charge carrier recombination would benefit the development of highly efficient organic photovoltaic (OPV) devices. In this paper, transient photovoltage (TPV) and charge extraction (CE) measurements are used in combination with synchrotron radiation photoemission spectroscopy (SRPES) to gain insight into the correlation between interfacial properties and device performance. OPV devices based on PCDTBT/PC71BM with a Ca interlayer were studied as a reference system to investigate the interfacial effects on device performance. Devices with a Ca interlayer exhibit a lower recombination than devices with only an Al cathode at a given charge carrier density (n). In addition, the interfacial band structures indicate that the strong dipole moment produced by the Ca interlayer can facilitate the extraction of electrons and drive holes away from the cathode/polymer interface, resulting in beneficial reduction in interfacial recombination losses. These results help explain the higher efficiencies of devices made with Ca interlayers compared to that without the Ca interlayer.

Ru–Pd nanoparticles (NPs) with Pt atomic cluster modification were synthesized using polyol reactions with a sequence design. Such modification resulted in the formation of Ru in the inner core and Pd on the outer shell structure (Rucore–Pdshell) via transmetalation between the Pt ion and Pd atom followed by thermal reduction. The Pt modified Rucore–Pdshell NPs improve the on-set potential by 0.041 volt and reduce Pt loading to less than ∼2%, as compared with that of carbon supported Pt NPs. For the optimum case, the MA (current degradation) of Ru–Pd NPs is improved (suppressed) by ∼345% (18.1%) in the accelerated degradation test (ADT) at 0.85 volt (vs. RHE) for 5000 cycles by intercalating Pt clusters (2 to 9 at%) in the NP surface. These improvements are attributed to the electron localization and reinforcement by surface Pt clusters, which facilitated the oxygen reduction activity and chemical durability of NPs.

A study of Fe-ion intercalation in Bi2Te3 probed by the x-ray diffraction, magnetization, Hall measurement, and spectra of synchrotron x-ray photoemission spectroscopy is reported, in which a large positive magnetoresistance (MR) and a high carrier mobility for applications have been achieved and probed in the quenched FexBi2Te3 single crystals with x = 0.01 and 0.15. Large positive MR of ∼470% with a Hall mobility of ∼44000 cm2/Vs at 5 K and 6 T has been observed on a quenched Fe0.01Bi2Te3 sample with a quenching temperature Tq of 400 °C, where the electrical parameters can be tuned by Tq. Larger c-axis lattice constants and electron-dominant carriers in the quenched samples lead to the inference that the doped Fe atoms are mostly located at the intercalated van der Waals gap positions and exist as a metallic state of Fe0, which is confirmed by the synchrotron x-ray photoemission spectroscopy (XPS) spectra. Combining the x-ray diffraction, magnetization, and Hall-coefficient studies, here we pave a simple way for probing into the location of Fe dopants in Bi2Te3. In addition, novel magnetotransports of Fe-doped Bi2Te3 associated with the absence of ferromagnetism have been presented, and satisfy the scenario that the topological surface state persists without the loss of topological insulating characteristics of the linear band dispersion, and the large MR may originate from the surface magnetism, even in the presence of Fe impurities. This study also discusses the huge enhancement of Hall mobility arising from the surface Dirac electrons that are accompanied with a modified band structure in quenched Fe0.01Bi2Te3.

For typical organic transistors with a lateral source/drain contact geometry, self-assembled monolayer (SAM) has been extensively applied to modify the organic/dielectric interface state and to improve the in-plane charge transport. Here, we demonstrate that SAM modification can also be applied to improve the out-of-plane charge transport in vertical organic field-effect transistors (VOFETs), leading to a simultaneous increase in the on-current and ON/OFF ratio. We investigate a series of phosphonic acid (PA) SAMs with different alkyl chain length for modification of p-type dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) VOFETs and their corresponding lateral transistors for comparison. The perforated source electrode of VOFETs is fabricated using surfactant-assisted colloidal lithography, which provides excellent control of the perforations fill factor and allows the introduction of an insulating cap layer to eliminate the off-current. Overall, the VOFET modified with dodecyl-PA SAM shows the optimal performance, with a 6 times enhanced mobility (and on-current) and a larger ON/OFF ratio compared to the unmodified device. Similar performance enhancement is also observed in the lateral transistors with SAM modifications. From detailed analyses of DNTT film morphology, crystallinity, and molecular orientation, we demonstrate that SAM modification exerts a strong impact on film morphology not only near the interface but also in the bulk, which plays a major factor for enhancing the mobilities in two types of transistors. The highest mobility obtained in the dodecyl-PA SAM modified VOFET is primarily attributed to the formation of largest grains with a resultant decrease of boundary defect density, despite that the crystallinity and molecular packing are not much improved than the other devices.

The unregulated growth of lithium dendrite upon cycling is hampering the applications of lithium metal batteries. The inherent artificial solid electrolyte interphase (SEI) formed during the first few cycles cannot provide the desired stability of lithium deposition. In the anode free battery (AFB) configuration, uncontrolled lithium plating on bare copper imposes a more serious lithium dendrite growth. Herein, we modify the copper current collector with a binder-free ultra-thin spin-coated graphene oxide (GO). The synchronize smooth and conductive GO-coated artificial SEI with lithium fluoride derived from fluoroethylene carbonate (FEC) electrolyte additive greatly control the lithium deposition. Accordingly, the synergistic effect enables smooth, uniform, and dendrite-free lithium plating. Moreover, the AFB with GO film and 5% FEC in the carbonate-based electrolyte is capable of achieving high coulombic efficiency of an average 98% and attains ~44% of its initial capacity after 50 cycles. In contrast, the full cell with bare Cu//LiNi1/3Mn1/3Co1/3O2 (NMC) has a coulombic efficiency of 89% and retains 26.9% after 20 cycles. Our results demonstrate that the synergy of GO-coated artificial SEI with FEC additive can be a promising approach to impede lithium dendrites growth and result in enhanced electrochemical performance in an AFB.

The performance of lithium ion batteries rapidly falls at lower temperatures due to decreasing conductivity of electrolytes and solid electrolyte interphase (SEI) on graphite anode. Hence, it limits the practical use of lithium ion batteries at subzero temperatures and also affects the development of lithium ion batteries for widespread applications. The SEI formed on the graphite surface is very influential in determining the performance of the battery. Herein, a new electrolyte additive, 4-chloromethyl-1,3,2-dioxathiolane-2-oxide (CMDO), is prepared to improve the properties of commonly used electrolyte constituents-ethylene carbonate (EC), and fluoroethylene carbonate. The formation of an efficient passivation layer in propylene carbonate-based electrolyte for MCMB electrode was investigated. The addition of CMDO resulted in a much less irreversible capacity loss and induces thin SEI formation. However, the combination of the three additives played a key role to enhance reversible capacity of MCMB electrode at lower or ambient temperature. The electrochemical measurement analysis showed that the SEI formed from a mixture of the three additives gave better intercalation-deintercalation of lithium ions.

Interfaces between metal electrodes and π-conjugated polymers play an important role in the organic optoelectronic devices. In this paper, the molecular orientation of the pristine poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (APFO3) films, chemical reactions and the electronic structure during the interface formation of Ca/APFO3 have been investigated in detail using synchrotron radiation photoemission spectroscopy (SRPES), X-ray photoemission spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. It is shown that the APFO3 film has a high degree of orientational ordering with its aromatic ring tilted at an angle of 43° from the substrate, and the 9,9-dioctyl fluorene unit (F8) is almost in the same plane as the benzothiazole unit (BT). Upon vapor-deposition of Ca onto APFO3 at room temperature, Ca dopes electrons into APFO3 and induces the downward band bending of APFO3. Moreover, Ca can diffuse into the APFO3 subsurface and react with N, S and C atoms of APFO3. Finally, the barrier of electron injection at the Ca/APFO3 interface is derived by the energy level alignment diagram. These results enable us to gain comprehensive insights into APFO3 and will facilitate the reasonable design of high performance devices based on APFO3.

A proper design of the injection barrier between a source electrode and an active layer is essential to achieve high-performance vertical organic field-effect transistors (VOFETs). Here, we show that a modification of metallic source electrodes with thiol-based self-assembled monolayers (SAMs) is effective in controlling the electrode work function and injection barrier into the active layer, leading to a significantly reduced off-current and undegraded on-current in an optimized VOFET. For the studied C60 VOFETs with Ag electrodes, the on/off ratio improves from