Concerted Effect of Ion- and Electron-Conductive Additives on the Electrochemical and Thermal Performances of the LiNi0.8Co0.1Mn0.1O2 Cathode Material Synthesized by a Taylor-Flow Reactor for Lithium-Ion Batteries

To address the issue that a single coating agent cannot simultaneously enhance Li+-ion transport and electronic conductivity of Ni-rich cathode materials with surface modification, in the present study, we first successfully synthesized a LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material by a Taylor-flow reactor followed by surface coating with Li-BTJ and dispersion of vapor-grown carbon fibers treated with polydopamine (PDA-VGCF) filler in the composite slurry. The Li-BTJ hybrid oligomer coating can suppress side reactions and enhance ionic conductivity, and the PDA-VGCFs filler can increase electronic conductivity. As a result of the synergistic effect of the dual conducting agents, the cells based on the modified NCM811 electrodes deliver superior cycling stability and rate capability, as compared to the bare NCM811 electrode. The CR2032 coin-type cells with the NCM811@Li-BTJ + PDA-VGCF electrode retain a discharge specific capacity of ∼92.2% at 1C after 200 cycles between 2.8 and 4.3 V (vs Li/Li+), while bare NCM811 retains only 84.0%. Moreover, the NCM811@Li-BTJ + PDA-VGCF electrode-based cells reduced the total heat (Qt) by ca. 7.0% at 35 °C over the bare electrode. Remarkably, the Li-BTJ hybrid oligomer coating on the surface of the NCM811 active particles acts as an artificial cathode electrolyte interphase (ACEI) layer, mitigating irreversible surface phase transformation of the layered NCM811 cathode and facilitating Li+ ion transport. Meanwhile, the fiber-shaped PDA-VGCF filler significantly reduced microcrack propagation during cycling and promoted the electronic conductance of the NCM811-based electrode. Generally, enlightened with the current experimental findings, the concerted ion and electron conductive agents significantly enhanced the Ni-rich cathode-based cell performance, which is a promising strategy to apply to other Ni-rich cathode materials for lithium-ion batteries.

Mechanistic Study on Artificial Stabilization of Lithium Metal Anode via Thermal Pyrolysis of Ammonium Fluoride in Lithium Metal Batteries

The use of the "Holy Grail" lithium metal anode is pivotal to achieve superior energy density. However, the practice of a lithium metal anode faces practical challenges due to the thermodynamic instability of lithium metal and dendrite growth. Herein, an artificial stabilization of lithium metal was carried out via the thermal pyrolysis of the NH4F salt, which generates HF(g) and NH3(g). An exposure of lithium metal to the generated gas induces a spontaneous reaction that forms multiple solid electrolyte interface (SEI) components, such as LiF, Li3N, Li2NH, LiNH2, and LiH, from a single salt. The artificially multilayered protection on lithium metal (AF-Li) sustains stable lithium stripping/plating. It suppresses the Li dendrite under the Li||Li symmetric cell. The half-cell Li||Cu and Li||MCMB systems depicted the attributions of the protective layer. We demonstrate that the desirable protective layer in AF-Li exhibited remarkable capacity retention (CR) results. LiFePO4 (LFP) showed a CR of 90.6% at 0.5 mA cm-2 after 280 cycles, and LiNi0.5Mn0.3Co0.2O2 (NCM523) showed 58.7% at 3 mA cm-2 after 410 cycles. Formulating the multilayered protection, with the simultaneous formation of multiple SEI components in a facile and cost-effective approach from NH4F as a single salt, made the system competent.

Boosting the Interfacial Stability of the Li6PS5Cl Electrolyte with a Li Anode via In Situ Formation of a LiF-Rich SEI Layer and a Ductile Sulfide Composite Solid Electrolyte

Due to its good mechanical properties and high ionic conductivity, the sulfide-type solid electrolyte (SE) can potentially realize all-solid-state batteries (ASSBs). Nevertheless, challenges, including limited electrochemical stability, insufficient solid-solid contact with the electrode, and reactivity with lithium, must be addressed. These challenges contribute to dendrite growth and electrolyte reduction. Herein, a straightforward and solvent-free method was devised to generate a robust artificial interphase between lithium metal and a SE. It is achieved through the incorporation of a composite electrolyte composed of Li6PS5Cl (LPSC), polyethylene glycol (PEG), and lithium bis(fluorosulfonyl)imide (LiFSI), resulting in the in situ creation of a LiF-rich interfacial layer. This interphase effectively mitigates electrolyte reduction and promotes lithium-ion diffusion. Interestingly, including PEG as an additive increases mechanical strength by enhancing adhesion between sulfide particles and improves the physical contact between the LPSC SE and the lithium anode by enhancing the ductility of the LPSC SE. Moreover, it acts as a protective barrier, preventing direct contact between the SE and the Li anode, thereby inhibiting electrolyte decomposition and reducing the electronic conductivity of the composite SE, thus mitigating the dendrite growth. The Li|Li symmetric cells demonstrated remarkable cycling stability, maintaining consistent performance for over 3000 h at a current density of 0.1 mA cm-2, and the critical current density of the composite solid electrolyte (CSE) reaches 4.75 mA cm-2. Moreover, the all-solid-state lithium metal battery (ASSLMB) cell with the CSEs exhibits remarkable cycling stability and rate performance. This study highlights the synergistic combination of the in-situ-generated artificial SE interphase layer and CSEs, enabling high-performance ASSLMBs.

Heteroatom-Coordinated Palladium Molecular Catalysts for Sustainable Electrochemical Production of Hydrogen Peroxide

Currently, hydrogen peroxide (H2O2) manufacturing involves an energy-intensive anthraquinone technique that demands expensive solvent extraction and a multistep process with substantial energy consumption. In this work, we synthesized Pd-N4-CO, Pd-S4-NCO, and Pd-N2O2-C single-atom catalysts via an in situ synthesis approach involving heteroatom-rich ligands and activated carbon under mild reaction conditions. It reveals that palladium atoms interact strongly with heteroatom-rich ligands, which provide well-defined and uniform active sites for oxygen (O2) electrochemically reduced to hydrogen peroxide. Interestingly, the Pd-N4-CO electrocatalyst shows excellent performance for the electrocatalytic reduction of O2 to H2O2 via a two-electron transfer process in a base electrolyte, exhibiting a negligible amount of onset overpotential and >95% selectivity within a wide range of applied potentials. The electrocatalysts based on the activity and selectivity toward 2e- ORR follow the order Pd-N4-CO > Pd-N2O2-C > Pd-S4-NCO in agreement with the pull-push mechanism, which is the Pd center strongly coordinated with high electronegativity donor atoms (N and O atoms) and weakly coordinated with the intermediate *OOH to excellent selectivity and sustainable production of H2O2. According to density functional theory, Pd-N4 is the active site for selectivity toward H2O2 generation. This work provides an emerging technique for designing high-performance H2O2 electrosynthesis catalysts and the rational integration of several active sites for green and sustainable chemical synthesis via electrochemical processes.

Generating Multi-Carbon Products by Electrochemical CO2 Reduction via Catalytically Harmonious Ni/Cu Dual Active Sites

Despite the unique advantages of single-atom catalysts, molecular dual-active sites facilitate the C-C coupling reaction for C2 products toward the CO2 reduction reaction (CO2 RR). The Ni/Cu proximal dual-active site catalyst (Ni/Cu-PASC) is developed, which is a harmonic catalyst with dual-active sites, by simply mixing commercial Ni-phthalocyanine (Ni-Pc) and Cu-phthalocyanine (Cu-Pc) molecules physically. According to scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) energy dispersive spectroscopy (EDS) data, Ni and Cu atoms are separated, creating dual-active sites for the CO2 RR. The Ni/Cu-PASC generates ethanol with an FE of 55%. Conversely, Ni-Pc and Cu-Pc have only detected single-carbon products like CO and HCOO- . In situ X-ray absorption spectroscopy (XAS) indicates that CO generation is caused by the stable Ni active site's balanced electronic state. The CO production from Ni-Pc consistently increased the CO concentration over Cu sites attributed to subsequent reduction reaction through a C-C coupling on nearby Cu. The CO bound (HCOO- ) peak, which can be found on Cu-Pc, vanishes on Ni/Cu-PASC, as shown by in situ fourier transformation infrared (FTIR). The characteristic intermediate of *CHO instead of HCOO- proves to be the prerequisite for multi-carbon products by electrochemical CO2 RR. The work demonstrates that the harmonic dual-active sites in Ni/Cu-PASC can be readily available by the cascading proximal active Ni- and Cu-Pc sites.

Lewis Acid Probe for Basicity of Sulfide Electrolytes Investigated by 11B Solid-State NMR

Sulfide-based solid-state lithium-ion batteries (SSLIB) have attracted a lot of interest globally in the past few years for their high safety and high energy density over the traditional lithium-ion batteries. However, sulfide electrolytes (SEs) are moisture-sensitive which pose significant challenges in the material preparation and cell manufacturing. To the best of our knowledge, there is no tool available to probe the types and the strength of the basic sites in sulfide electrolytes, which is crucial for understanding the moisture stability of sulfide electrolytes. Herein, we propose a new spectral probe with the Lewis base indicator BBr3 to probe the strength of Lewis basic sites on various sulfide electrolytes by 11B solid-state NMR spectroscopy (11B-NMR). The active sulfur sites and the corresponding strength of the sulfide electrolytes are successfully evaluated by the proposed Lewis base probe. The probed strength of the active sulfur sites of a sulfide electrolyte is consistent with the results of DFT (density functional theory) calculation and correlated with the H2S generation rate when the electrolyte was exposed in moisture atmosphere. This work paves a new way to investigate the basicity and moisture stability of the sulfide electrolytes.

The Entanglement of Li Capping and Deposition: An Operando Optical Microscopy Study

Dendrite growth and low Coulombic efficiency impede the practical application of Li-metal batteries. As such, monitoring Li deposition and stripping in real-time is crucial to understanding the fundamental lithium growth kinetics. This work presents an operando optical microscopic technique that enables precise current density control and quantification of Li layer properties (i.e., thickness and porosity) to study Li growth in various electrolytes. We discover the robustness and porosity of the remaining capping layer after the Li stripping process as the critical features governing the subsequent dendrite propagation behavior, resulting in distinct capping and stacking phenomena that affect Li growth upon cycling. While dendrite propagation quickly occurs through the fracture of the fragile Li capping layer, uniform Li plating/stripping can be facilitated by the compact and robust capping layer even at high current densities. This technique can be extended to evaluate dendrite suppression treatments in various metal batteries, providing in-depth information on metal growth mechanisms.

Synergistic dual electrolyte additives for fluoride rich solid-electrolyte interface on Li metal anode surface: Mechanistic understanding of electrolyte decomposition

Improving the quality of the solid-electrolyte interphase (SEI) layer is highly imperative to stabilize the Li-metal anodes for the practical application of high-energy-density batteries. However, controllably managing the formation of robust SEI layers on the anode is challenging in state-of-the-art electrolytes. Herein, we discuss the role of dual additives fluoroethylene carbonate (FEC) and lithium difluorophosphate (LiPO₂F₂, LiPF) within the commercial electrolyte mixture (LiPF₆/EC/DEC) considering their reactivity with Li metal anodes using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. Synergistic effects of dual additives on SEI formation mechanisms are explored systematically by invoking different electrolyte mixtures including pure electrolyte (LP47), mono-additive (LP47/FEC and LP47/LiPF), and dual additives (LP47/FEC/LiPF). The present work suggests that the addition of dual additives accelerates the reduction of salt and additives while increasing the formation of a LiF-rich SEI layer. In addition, calculated atomic charges are applied to predict the representative F_1s X-ray photoelectron (XPS) signal, and our results agree well with the experimentally identified SEI components. The nature of carbon and oxygen-containing groups resulting from the electrolyte decompositions at the anode surface is also analyzed. We find that the presence of dual additives inhibits undesirable solvent degradation in the respective mixtures, which effectively restricts the hazardous side products at the electrolyte-anode interface and improves SEI layer quality.

In-Depth Insight into a Passive Film through Hydrogen-Bonding Network in an Aqueous Zinc Battery

Electrochemical stability and interfacial reactions are crucial for rechargeable aqueous zinc batteries. Electrolyte engineering with low-cost aqueous electrolytes is highly required to stabilize their interfacial reactions. Herein, we propose a design strategy using glutamic additive and its derivatives with modification of hydrogen-bonding network to enable Zn aqueous battery at a low concentration (2 m ZnSO₄ + 1 m Li₂SO₄). Computational, in situ/ex situ spectroscopic, and electrochemical studies suggest that additives with moderate interactions, such as 0.1 mol % glutamic additive (G1), preferentially absorb on the Zn surface to homogenize Zn²⁺ plating and favorably interact with Zn²⁺ in bulk to weaken the interaction between H₂O and Zn²⁺. As a result, uniform deposition and stable electrochemical performance are realized. The Zn||Cu half-cell lasts for more than 200 cycles with an average Coulombic efficiency (CE) of >99.32% and the Zn||Zn symmetrical cells for 1400 h with a low and stable overpotential under a current density of 0.5 mA cm^-2, which is better than the reported results. Moreover, adding 0.1 mol % G1 to the Zn||LFP full cell improves its electrochemical performance with stable cycling and achieves a remarkable capacity of 147.25 mAh g^-1 with a CE of 99.79% after 200 cycles.

Description of Photodegradation Mechanisms and Structural Characteristics in Carbon@Titania Yolk-Shell Nanostructures by XAS

Carbon@titania yolk-shell nanostructures are successfully synthesized at different calcination conditions. These unique structure nanomaterials can be used as a photocatalyst to degrade the emerging water pollutant, acetaminophen (paracetamol). The photodegradation analysis studies have shown that the samples with residual carbon nanospheres have improved the photocatalytic efficiency. The local electronic and atomic structure of the nanostructures are analyzed by X-ray absorption spectroscopy (XAS) measurements. The spectra confirm that the hollow shell has an anatase phase structure, slight lattice distortion, and variation in Ti 3d orbital orientation. In situ XAS measurements reveal that the existence of amorphous carbon nanospheres inside the nano spherical shell inhibit the recombination of electron-hole pairs; more mobile holes are formed in the p-d hybridized bands near the Fermi surface and enables the acceleration of the carries that significantly enhance the photodegradation of paracetamol under UV-visible irradiation. The observed charge transfer process from TiO₂  hybridized orbital to the carbon nanospheres reduces the recombination rate of electrons and holes, thus increasing the photocatalytic efficiency.

Efficient H2 Evolution Coupled with Anodic Oxidation of Iodide over Defective Carbon-Supported Single-Atom Mo-N4 Electrocatalyst

We successfully prepared nitrogen-doped defective carbon spheres (Mo-N₄/d-C) with a high loading of 0.996 wt % via a designed vapor-deposition process for IOR-based hydrogen generation. The synthesized Mo-N₄/d-C catalyst provides a record current density of 10 mA cm^-2 at 0.77 V. Further, the Mo-N₄/d-C catalyst shows a Tafel slope of 25.58 mV dec^-1, exceptional stability over time in acidic media, a higher hydrogen generation rate of 0.1063 mL g_cat^-1 min^-1, a high Faradaic efficiency of 99.8%, and a reduction of the energy consumption up to ∼50% for hydrogen evolution by anodic oxidation reaction of iodide (IOR) compared with the conventional OER-based electrolysis. Computational calculations demonstrate that the Mo-N₄/d-C structure plays a vital effect on the activity of iodide oxidation, which is competitive with the Pt catalyst.

Highly Concentrated Salt Electrolyte for a Highly Stable Aqueous Dual-Ion Zinc Battery

A zinc metal anode for zinc-ion batteries is a promising alternative to solve safety and cost issues in lithium-ion batteries. The Zn metal is characterized by its high theoretical capacity (820 mAh g^-1), low redox potential (0.762 V vs SHE), low toxicity, high abundance on Earth, and high stability in water. Taking advantage of the stability of Zn in water, an aqueous Zn ion battery with low cost, high safety, and easy-to-handle features can be developed. To minimize water-related parasitic reactions, this work utilizes a highly concentrated salt electrolyte (HCE) with dual salts─1 m Zn(OTf)₂ + 20 m LiTFSI. MD simulations prove that Zn²⁺ is preferentially coordinated with O in the TFSI^- anion from HCE instead of O in H₂O. HCE has a broadened electrochemical stability window due to suppressed H₂ and O₂ evolution. Some advanced ex situ and in situ/in operando analysis techniques have been applied to evaluate the morphological structure and the composition of the in situ formed passivation layer. A dual-ion full Zn||LiMn₂O₄ cell employing HCE has an excellent capacity retention of 92% after 300 cycles with an average Coulombic efficiency of 99.62%. Meanwhile, the low concentration electrolyte (LCE) cell degrades rapidly and is short-circuited after 66 cycles with an average Coulombic efficiency of 96.91%. The battery's excellent cycling performance with HCE is attributed to the formation of a stable anion-derived solid-electrolyte interphase (SEI) layer. On the contrary, the high free water activity in LCE leads to a water-derived interfacial layer with unavoidable dendrite growth during cycling.

Lithium Oxalate as a Lifespan Extender for Anode-Free Lithium Metal Batteries

Anode-free lithium metal batteries (AFLMBs) have been extensively studied due to their intrinsic high energy and safety without a metallic Li anode in cell design. Yet, the dendrite and dead-Li buildup continuously consumes the active Li upon cycling, leading to the poor lifespan of AFLMBs. Here, we introduce lithium oxalate into the cathode as an electrode additive providing a Li reservoir to extend the lifespan of AFLMBs. The AFLMB using 20% lithium oxalate and a LiNi0.3Co0.3Mn0.3O2 composite cathode exhibits >80 and 40% capacity retention after 50 and 100 cycles, respectively, outperforming the poor cycle life of fewer than 20 cycles obtained from the cell using a pure LiNi0.3Co0.3Mn0.3O2 cathode. Surprisingly, the average Coulombic efficiency of AFLMBs is found to improve as the amount of lithium oxalate increases in the composite cathode. This abnormal phenomenon could be attributed to the as-formed carbon dioxide after the first activation cycle forming a Li2CO3-rich solid-electrolyte interphase and improving the Li deposition and stripping efficiency. The findings in this work provide a new strategy to delay the capacity roll-over of AFLMBs from an electrode engineering perspective, which can be coupled with other approaches such as functional electrolytes synergistically to further improve the cycle life of AFLMBs for practical application.

Intercalation of Zinc Monochloride Cations by Deep Eutectic Solvents for High-Performance Rechargeable Non-aqueous Zinc Ion Batteries

Zinc ion batteries have been extensively studied with an aqueous electrolyte system. However, the batteries suffer from a limited potential window, gas evolution, cathode dissolution, and dendrite formation on the anode. Considering these limitations, we developed an alternative electrolyte system based on deep eutectic solvents (DESs) because of their low cost, high stability, biodegradability, and non-flammability, making them optimal candidates for sustainable batteries. The DES electrolyte enables reversible Zn plating/stripping and effectively suppresses zinc dendrite formation. Furthermore, in-depth characterizations reveal that the energy storage mechanism can be attributed to [ZnCl]⁺ ion intercalation and the intermediate complex ion plays a pivotal role in electrochemical reactions, which deliver a high reversible capacity of 310 mAh g^-1 at 0.1 A g^-1and long-term stability (167 mAh g^-1 at a current density of 0.3 A g^-1 after 300 cycles, Coulombic efficiency: ∼98%). Overall, this work represents our new finding in rechargeable batteries with the DES electrolyte.

A Powerful Protocol Based on Anode-Free Cells Combined with Various Analytical Techniques

Lithium (Li) metal is the ultimate negative electrode due to its high theoretical specific capacity and low negative electrochemical potential. However, the handling of lithium metal imposes safety concerns in transportation and production due to its reactive nature. Recently, anode-free lithium metal batteries (AFLMBs) have drawn much attention because of several of their advantages, including higher energy density, lower cost, and fewer safety concerns during cell production compared to LMBs. Pushing the reversible Coulombic efficiency (CE) of AFLMBs up to 99.98% is key to achieving their 80% capacity retention over more than 1000 cycles. However, interfacial irreversible phenomena such as electrolyte decomposition reactions on both electrodes, dead Li formation, and Li dendrite formation result in poor capacity retention and short circuits in LMBs and AFLMBs. Therefore, it is of great importance and scientific interest to explore those interfacial irreversible phenomena to improve the cell's cycle life. Although significant contributions toward mitigating electrolyte decomposition, dead lithium, and dendritic lithium formation have been reported at the lithium anode, real irreversible phenomena are usually hidden or difficult to discover due to excess lithium employed in LMBs and simultaneous events taking place in both electrodes or at the interfaces.An integrated protocol is suggested to include Li||Cu, cathode||Li, and cathode||Cu configurations to provide overall quantification and determination of various sources of irreversible Coulombic efficiency (irr-CE) in AFLMBs and LMBs. Combining Li||Cu, cathode||Li, and cathode||Cu configurations is essential for separating the root sources of the capacity loss and irr-CE in LMBs and AFLMBs. Remarkably, integrating an anode-free cell with various analytical techniques can serve as a powerful protocol to decouple and quantify those interfacial irreversible phenomena according to our recent reports.In this Account, we focus on the protocol based on an anode-free cell combined with various analytical methods to investigate interfacial irreversible phenomena. Complementary advanced tools such as transmission X-ray microscopy (visualizing Li plating/stripping mechanism), nuclear magnetic resonance spectroscopy (quantifying dead lithium), and gas chromatography-mass spectroscopy (decoupling interfacial reactions) were employed to extract the intrinsic reasons and sources of individual irreversible reactions in LMBs and AFLMBs. Quantitative evaluation of nucleation and growth of Li metal deposition are addressed, along with solid electrolyte interphase (SEI) fracture, visualization of lithium dendrite growth, decoupling of oxidative and reductive electrolyte decomposition mechanisms, and irreversible efficiency (i.e., dead Li and SEI formation) to reveal the intrinsic causes of individual irr-CE in AFLMBs. Meanwhile, an anode-free protocol can also be utilized as a powerful and multifunctional tool to develop electrolyte formulations or artificial layers for LMBs and AFLMBs. Therefore, we also suggest that the anode-free configurations with significant irreversible phenomena can effectively screen and develop new electrolytes. Finally, the concepts of the protocol with an anode-free cell combined with various advanced analytical tools can be extended to provide an in-depth understanding of other metal batteries and solid-state anode-free metal batteries.

Tuning Dynamically Formed Active Phases and Catalytic Mechanisms of In Situ Electrochemically Activated Layered Double Hydroxide for Oxygen Evolution Reaction

The active phase and catalytic mechanisms of Ni-based layered double hydroxide (LDH) materials for oxygen evolution reaction (OER) have no common consensus and remain controversial. Moreover, engineering the site activity and the number of active sites of LDHs is an efficient approach to advance the OER activity, as the thickness and stacking structure of the LDHs layer limit the catalytic activity. This work presents an interesting in situ approach of tuning the site activity and number of active sites of NiMn-LDHs, which exhibit the superior OER performance (onset overpotential of 0.17 V and overpotential of 0.24 V at 10 mA cm^-2). The fundamental mechanistic insights and active phases during the OER process are characterized by in operando techniques along with the computational density functional theory calculations, revealing that the Ni site constitutes the OER activity and the dynamically generated NiOOH moiety is the active phase. We also prove that Ni sites undergo a reversible oxidation state under the working conditions to create active NiOOH species which catalyze the water to generate oxygen. These findings suggest that the Ni(III) phase in NiMn-LDHs is the OER active site and Mn promotes the electronic properties of Ni sites. Utilizing in situ/in operando techniques and theoretical calculation, we find that the in situ intercalation of guest anions allows the expansion of the LDH layers and keeps the active NiOOH species under the oxidation state of +3 via electron coupling, which ultimately tunes the site populations and site activity toward the superior OER activity, respectively. This work thus targets to provide insight into strategies to design the next generation of highly active catalysts for water electrolysis and fuel cell technologies.

Probing Single-Atom Catalysts and Catalytic Reaction Processes by Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy

Developing advanced characterization techniques for single-atom catalysts (SACs) is of great significance to identify their structural and catalytic properties. Raman spectroscopy can provide molecular structure information, and thus, the technique is a promising tool for catalysis. However, its application in SACs remains a great challenge because of its low sensitivity. We develop a highly sensitive strategy that achieves the characterization of the structure of SACs and in situ monitoring of the catalytic reaction processes on them by shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) for the first time. Using the strategy, Pd SACs on different supports were identified by Raman spectroscopy and the nucleation process of Pd species from single atoms to nanoparticles was revealed. Moreover, the catalytic reaction processes of the hydrogenation of nitro compounds on Pd SACs were monitored in situ, and molecular insights were obtained to uncover the unique catalytic properties of SACs. This work provides a new spectroscopic tool for the in situ study of SACs, especially at solid-liquid interfaces.

New Insights into the N-S Bond Formation of a Sulfurized-Polyacrylonitrile Cathode Material for Lithium-Sulfur Batteries

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 (N_PD/N_PL) 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 N_PD/N_PL 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.

Decoupling the origins of irreversible coulombic efficiency in anode-free lithium metal batteries

Anode-free lithium metal batteries are the most promising candidate to outperform lithium metal batteries due to higher energy density and reduced safety hazards with the absence of metallic lithium anode during initial cell fabrication. In general, researchers report capacity retention, reversible capacity, or rate capability of the cells to study the electrochemical performance of anode-free lithium metal batteries. However, evaluating the behavior of batteries from limited aspects may easily overlook other information hidden deep inside the meretricious results or even lead to misguided data interpretation. In this work, we present an integrated protocol combining different types of cell configuration to determine various sources of irreversible coulombic efficiency in anode-free lithium metal cells. The decrypted information from the protocol provides an insightful understanding of the behaviors of LMBs and AFLMBs, which promotes their development for practical applications.

Dual-Doped Cubic Garnet Solid Electrolytes with Superior Air Stability

Li₇La₃Zr₂O₁₂ (LLZO) garnet is one kind of solid electrolyte drawing extensive attention due to its good ionic conductivity, safety, and stability toward lithium metal anodes. However, the stability problem during synthesis and storage results in high interfacial resistance and prevents it from practical applications. We synthesized air-stable dual-doped Li_6.05La₃Ga_0.3Zr_1.95Nb_0.05O₁₂ ((Ga, Nb)-LLZO) cubic-phase garnets with ionic conductivity of 9.28 × 10^-3 S cm^-1. The impurity-phase species formation on the garnet pellets after air exposure was investigated. LiOH and Li₂CO₃ can be observed on the garnet pellets by Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) once the garnets are exposed to humid air or come in contact with water. The (Ga, Nb)-LLZO garnet is found to form less LiOH and Li₂CO₃, which can be further reduced or removed after drying treatment. To confirm the stability of the garnet, an electrochemical test of the Li//Li symmetric cell was also performed in comparison with previously reported garnets (Li₇La_2.75Ca_0.25Zr_1.75Nb_0.25O₁₂, (Ca, Nb)-LLZO). The dual-doped (Ga, Nb)-LLZO showed less polarized and stable plating/stripping behavior than (Ca, Nb)-LLZO. Through Rietveld refinement of XRD patterns of prepared materials, dopant Ga was found to preferably occupy the Li site and Nb takes the Zr site, while dopant Ca mainly substituted La in the reference sample. The inherited properties of the dopants in (Ga, Nb)-LLZO and their structural synergy explain the greatly improved air stability and reduced interfacial resistance. This may open a new direction to realize garnet-based solid electrolytes with lower interfacial resistance and superior air stability.

Synergistic Mn-Co catalyst outperforms Pt on high-rate oxygen reduction for alkaline polymer electrolyte fuel cells

Alkaline polymer electrolyte fuel cells are a class of fuel cells that enable the use of non-precious metal catalysts, particularly for the oxygen reduction reaction at the cathode. While there have been alternative materials exhibiting Pt-comparable activity in alkaline solutions, to the best of our knowledge none have outperformed Pt in fuel-cell tests. Here we report a Mn-Co spinel cathode that can deliver greater power, at high current densities, than a Pt cathode. The power density of the cell employing the Mn-Co cathode reaches 1.1 W cm-2 at 2.5 A cm-2 at 60 oC. Moreover, this catalyst outperforms Pt at low humidity. In-depth characterization reveals that the remarkable performance originates from synergistic effects where the Mn sites bind O2 and the Co sites activate H2O, so as to facilitate the proton-coupled electron transfer processes. Such an electrocatalytic synergy is pivotal to the high-rate oxygen reduction, particularly under water depletion/low humidity conditions.

Ultrafast x-ray absorption near edge spectroscopy of Fe3O4 using a laboratory based femtosecond x-ray source

Ultrafast time-resolved x-ray absorption near edge spectroscopy (XANES) experiment was performed on a magnetite (Fe₃O₄) film using a femtosecond laser plasma x-ray source delivering Bremsstrahlung radiation. Ultrafast temporal evolution of the XANES of Fe₃O₄ following an excitation by an infra-red (IR) laser pulse was observed in a pump-probe scheme. The Fe K x-ray absorption edge shifts towards low energy upon IR excitation as much as 12 eV, which is mainly attributed to the charge transfer between the Fe ions. The shift in the absorption edge occurred within about 150 fs, typical time of non-thermal electronic redistribution. The charge transfer also causes an ultrafast increase in the IR transmission in the similar time scale.

Designed Synergetic Effect of Electrolyte Additives to Improve Interfacial Chemistry of MCMB Electrode in Propylene Carbonate-Based Electrolyte for Enhanced Low and Room Temperature Performance

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.

In situ analytical techniques for battery interface analysis

Interface is a key to high performance and safe lithium-ion batteries or lithium batteries.

Biosensors Incorporating Bimetallic Nanoparticles

This article presents a review of electrochemical bio-sensing for target analytes based on the use of electrocatalytic bimetallic nanoparticles (NPs), which can improve both the sensitivity and selectivity of biosensors. The review moves quickly from an introduction to the field of bio-sensing, to the importance of biosensors in today's society, the nature of the electrochemical methods employed and the attendant problems encountered. The role of electrocatalysts is introduced with reference to the three generations of biosensors. The contributions made by previous workers using bimetallic constructs, grouped by target analyte, are then examined in detail; following which, the synthesis and characterization of the catalytic particles is examined prior to a summary of the current state of endeavor. Finally, some perspectives for the future of bimetallic NPs in biosensors are given.

Probing the Formation Mechanism and Chemical States of Carbon-Supported Pt−Ru Nanoparticles by in Situ X-ray Absorption Spectroscopy

The understanding of the formation mechanism of nanoparticles is essential for the successful particle design and scaling-up process. This paper reports findings of an X-ray absorption spectroscopy (XAS) investigation, comprised of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) regions, to understand the mechanism of the carbon-supported Pt-Ru nanoparticles (NPs) formation process. We have utilized Watanabe's colloidal reduction method to synthesize Pt-Ru/C NPs. We slightly modified the Watanabe method by introducing a mixing and heat treatment step of Pt and Ru oxidic species at 100 degrees C for 8 h with a view to enhance the mixing efficiency of the precursor species, thereby one can achieve improved homogeneity and atomic distribution in the resultant Pt-Ru/C NPs. During the reduction process, in situ XAS measurements allowed us to follow the evolution of Pt and Ru environments and their chemical states. The Pt LIII-edge XAS indicates that when H2PtCl6 is treated with NaHSO3, the platinum compound is found to be reduced to a Pt(II) form corresponding to the anionic complex [Pt(SO3)4]6-. Further oxidation of this anionic complex with hydrogen peroxide forms dispersed [Pt(OH)6]2- species. Analysis of Ru K-edge XAS results confirms the reduction of RuIIICl3 to [RuII(OH)4]2- species upon addition of NaHSO3. Addition of hydrogen peroxide to [RuII(OH)4]2- causes dehydrogenation and forms RuOx species. Mixing of [Pt(OH)6]2- and RuOx species and heat treatment at 100 degrees C for 8 h produced a colloidal sol containing both Pt and Ru metallic as well as ionic contributions. The reduction of this colloidal mixture at 300 degrees C in hydrogen atmosphere for 2 h forms Pt-Ru nanoparticles as indicated by the presence of Pt and Ru atoms in the first coordination shell. Determination of the alloying extent or atomic distribution of Pt and Ru atoms in the resulting Pt-Ru/C NPs reveals that the alloying extent of Ru (JRu) is greater than that of the alloying extent of Pt (JPt). The XAS results support the Pt-rich core and Ru-rich shell structure with a considerable amount of segregation in the Pt region and with less segregation in the Ru region for the obtained Pt-Ru/C NPs.

In situ EXAFS investigation of carbon-supported Pt clusters under potential control

The transformation of carbon supported Pt clusters under potential control in 1M HClO4 solution was investigated by in-situ X-ray absorption spectroscopy measurements. Both XANES and EXAFS data are used to show the structure evolution of the Pt clusters at various potentials. It showed that the white line area and the edge energy increase with the applied potential in the range 0.1-1.5V. The coordination number of oxygen and platinum on the Pt/C electrode increases and decreases, respectively, with the applied potential. It is found that the size of Pt cluster does not grow during the electrode fabrication. However, the crystallization of Pt cluster occurs during the potential cycling.

Mice lacking specific nicotinic acetylcholine receptor subunits exhibit dramatically altered spontaneous activity patterns and reveal a limited role for retinal waves in forming ON and OFF circuits in the inner retina

Before phototransduction, spontaneous activity in the developing mammalian retina is required for the appropriate patterning of retinothalamic connections, and there is growing evidence that this activity influences the development of circuits within the retina itself. We demonstrate here that the neural substrate that generates waves in the mouse retina develops through three distinct stages. First, between embryonic day 16 and birth [postnatal day 0 (P0)], we observed both large, propagating waves inhibited by nicotinic acetylcholine receptor (nAChR) antagonists and small clusters of cells displaying nonpropagating, correlated calcium increases that were independent of nAChR activation. Second, between P0 and P11, we observed only larger propagating waves that were abolished by toxins specific to alpha3 and beta2 subunit-containing nAChRs. Third, between P11 and P14 (eye opening) we observed propagating activity that was abolished by ionotropic glutamate receptor antagonists. The time course of this developmental shift was dramatically altered in retinas from mice lacking the beta2 nAChR subunit or the beta2 and beta4 subunits. These retinas exhibited a novel circuit at P0, no spontaneous correlated activity between P1 and P8, and the premature induction at P8 of an ionotropic glutamate receptor-based circuit. Retinas from postnatal mice lacking the alpha3 nAChR subunit exhibited spontaneous, correlated activity patterns that were similar to those observed in embryonic wild-type mice. In alpha3-/- and beta2-/- mice, the development and distribution of cholinergic neurons and processes and the density of retinal ganglion cells (RGCs) and the gross segregation of their dendrites into ON and OFF sublaminae were normal. However, the refinement of individual RGC dendrites is delayed. These results indicate that retinal waves mediated by nAChRs are involved in, but not required for, the development of neural circuits that define the ON and OFF sublamina of the inner plexiform layer.