Seeding Atomic Silver into Internal Lattice Sites of Transition Metal Oxide for Advanced Electrocatalysis.

Transition metal oxides (TMOs) are widely studied for loading of various catalysts due to their low cost and high structure flexibility. However, the prevailing close-packed nature of most TMOs crystals has restricted the available loading sites to surface only, while their internal bulk lattice remains unactuated due to the inaccessible narrow space that blocks out most key reactants and/or particulate catalysts. Herein, using tunnel-structured MnO2, this study demonstrates how TMO's internal lattice space can be activated as extra loading sites for atomic Ag in addition to the conventional surface-only loading, via which a dual-form Ag catalyst within MnO2 skeleton is established. In this design, not only faceted Ag nanoparticles are confined onto MnO2 surface by coherent lattice-sharing, Ag atomic strings are also seeded deep into the sub-nanoscale MnO2 tunnel lattice, enriching the catalytically active sites. Tested for electrochemical CO2 reduction reaction (eCO2RR), such dual-form catalyst exhibits a high Faradaic efficiency (94%), yield (67.3 mol g-1 h-1) and durability (≈48 h) for CO production, exceeding commercial Ag nanoparticles and most Ag-based electrocatalysts. Theoretical calculations further reveal the concurrent effect of such dual-form catalyst featuring facet-dependent eCO2RR for Ag nanoparticles and lattice-confined eCO2RR for Ag atomic strings, inspiring the future design of catalyst-substrate configuration.

Bright, small sizes and hydro-dispersive NIR persistent luminescence nanoparticles modified with Si and amino groups for enhanced bioimaging.

Near-infrared (NIR) persistent luminescence nanoparticles (PLNPs) with high brightness, small sizes, good hydro-dispersivity, and intrinsic surface-functional groups are desirable in biological applications. In this work, Cr3+-doped zinc gallogermanates Zn1+xGa2-2xGexO4:Cr (ZGGC) PLNPs were hydrothermally synthesized via 3-aminopropyltriethoxysilane (APTES) as an additive, or APTES and cetyltrimethylammonium bromide (CTAB) as two co-additives. Addition of APTES not only dramatically enhances the 696 nm NIR luminescence intensity, but also obviously decreases the particle size and introduces amino groups. In particular, thex= 0.1 series ZGGC (ZGGC0.1) with the addition of n moles equivalent APTES (ZGGC0.1-nA) had smaller particle sizes than thex= 0.2 counterpart (ZGGC0.2-nA). The NIR afterglow intensities increased with the APTES introduction. The ZGGC0.2-2.5A sample (also named as ZGGC, Si, -NH2) exhibited maximum luminescence intensities both in solid and aqueous states. With APTES, Si atom is doped and -NH2groups are modified, the trap depth and density become larger, and the afterglow intensities and decay time are significantly enhanced. More notably, co-addition of CTAB (ZGGC0.2-2.5A-C) (also named as ZGGC, Si, -NH2') further enhances hydro-dispersivity and luminescence intensity, decreases particle sizes, and results in more prominent amino groups. The trap density is drastically higher than that without CTAB (i.e. ZGGC0.2-2.5A). Change of Cr3+microenvironment in the crystal and more defects introduction contribute to the enhanced brightness. As expected, the ZGGC,Si,-NH2' PLNPs possess excellent biocompatibility, deep tissue penetration and distinguished bioimaging properties, and rechargeability with orange LED light. The ZGGC,Si,-NH2' PLNPs should provide to be an excellent nanomaterial for various functionalization and bioimaging applications.

Effect of ZrS2 load single/dual-atom catalysts on the hydrogen evolution reaction: A first-principles study.

The hydrogen evolution effect of ZrS2 carrier loaded with transition metal single-atom (SA) was explored by first-principles method. ZrS2 was constructed with transition metal single-atom and dual-atom. The structure-activity relationship of supported single-atom catalysts was described by electronic properties and hydrogen evolution kinetics. The results show that the ZrS2 carrier-loaded atomic-level catalysts are more likely to occur in acidic environments, where the Mo SA load has a higher hydrogen precipitation capacity than the Pt SA. In the case of dual-atom adsorption, most of the hydrogen reduction processes are higher than that of single atom loading, which indicates that the outer orbital hybridization is more likely to lead to the interfacial charge recombination of the catalyst. Thereinto, Ni/Pt @ZrS2 has the lowest Gibbs free energy (0.08 eV), and the synergistic effect of transition metals induces the deviation of the center of the d-band from the Fermi level and improves the dissociation ability of H ions. The design provides a new catalytic model for the HER and provides some ideas for understanding the two-site catalysis.

Strategies to Improve the Thermoelectric Figure of Merit in Thermoelectric Functional Materials.

In recent years, thermoelectric functional materials have been widely concerned in temperature difference power generation, electric refrigeration and integrated circui, and so on. In this paper, the design and research progress of thermoelectric materials around lifting ZT value in recent years are reviewed. Optimizing the carrier concentration to improve the Seebeck coefficient, the steady improvement of carrier mobility and the influence of energy band engineering on thermoelectric performance are discussed. In addition, the impact of lattice thermal conductivity on ZT value is also significant. We discuss the general law that the synergistic effect of different dimensions, scales, and crystal structures can reduce lattice thermal conductivity, and introduce the new application of electro-acoustic decoupling in thermoelectric materials. Finally, the research of thermoelectric materials is summarized and prospected in the hope of providing practical ideas for expanding the application and scale industrialization of thermoelectric devices.

An All-Solid-State Battery Based on Sulfide and PEO Composite Electrolyte.

Replacing liquid electrolytes with solid polymer electrolytes (SPEs) is considered as a vital approach to developing sulfur (S)-based cathodes. However, the polysulfides shuttle and the growth of lithium (Li) dendrites are still the major challenges in polyethylene oxide (PEO)-based electrolyte. Here, an all-solid-state Li metal battery with flexible PEO-Li10 Si0.3 PS6.7 Cl1.8 (LSPSCl)-C-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) composite cathode (FCC) and PEO-LSPSCl-LiTFSI composite electrolyte (S-CPE) is designed. The initial capacity of the Li|S-CPE|FCC battery is 414 mAh g-1 with 97.8% capacity retention after 100 cycles at 0.1 A g-1 . Moreover, the battery displays remarkable capacity retention of 80% after 500 cycles at 0.4 A g-1 . Cryo-transmission electron microscopy (Cryo-TEM) reveals rich large-sized Li2 CO3 particles at the Li/PEO interface blocking the Li+ transport, but the layer with rich Li2 O nanocrystals, amorphous LiF and Li2 S at the Li/S-CPE interface suppresses the growth of lithium dendrite and stabilizes the interface. In situ optical microscopy demonstrates that the excellent cyclic stability of FCC is ascribed to the reversible shuttle of P-S-P species, resulting from the movement of ether backbone in PEO. This study provides strategies to mitigate the polysulfide shuttle effect and Li dendrite formation in designing high energy density solid-state Li-S-based batteries.

Enabling Long Cycle Life and High Rate Iron Difluoride Based Lithium Batteries by In Situ Cathode Surface Modification.

Metals fluorides (MFs) are potential conversion cathodes to replace commercial intercalation cathodes. However, the application of MFs is impeded by their poor electronic/ionic conductivity and severe decomposition of electrolyte. Here, a composite cathode of FeF2 and polymer-derived carbon (FeF2 @PDC) with excellent cycling performance is reported. The composite cathode is composed of nanorod-shaped FeF2 embedded in PDC matrix with excellent mechanical strength and electronic/ionic conductivity. The FeF2 @PDC enables a reversible capacity of 500 mAh g-1 with a record long cycle lifetime of 1900 cycles. Remarkably, the FeF2 @PDC can be cycled at a record rate of 60 C with a reversible capacity of 107 mAh g-1 after 500 cycles. Advanced electron microscopy reveals that the in situ formation of stable Fe3 O4 layers on the surface of FeF2 prevents the electrolyte decomposition and leaching of iron (Fe), thus enhancing the cyclability. The results provide a new understanding to FeF2 electrochemistry, and a strategy to radically improve the electrochemical performance of FeF2 cathode for lithium-ion battery applications.

Application of MoS2-FeS functional carrier loaded Ni single-atom catalysts on HER: first principle.

The stability of functional carriers single-atom catalysts can be effectively guaranteed by using stable mineral materials to support low dimensional catalytic materials. In this paper, the theoretical calculation of electrochemical hydrogen evolution reaction (HER) of the composite functional single-atom catalysts supported by single-atom Ni was carried out using first-principles method. And the original structure of MoS2,amorphous structure and S-vacancy structure are studied. Through the analysis and discussion of electronic properties, adsorption energy and active sites, it is found that Ni@Amorphous MoS2-FeS has excellent effect of hydrogen evolution in acidic environment, ΔGHis 0.312 eV, and the other two structures supporting Ni single-atom also have excellent HER properties in a wide range of pH. This design broadens the research idea of single-atom catalysts carriers and provides a new direction for the research and development of electrocatalytic materials.

Size-Dependent Chemomechanical Failure of Sulfide Solid Electrolyte Particles during Electrochemical Reaction with Lithium.

The very high ionic conductivity of Li10GeP2S12 (LGPS) solid electrolyte (SE) makes it a promising candidate SE for solid-state batteries in electrical vehicles. However, chemomechanical failure, whose mechanism remains unclear, has plagued its widespread applications. Here, we report in situ imaging lithiation-induced failure of LGPS SE. We revealed a strong size effect in the chemomechanical failure of LGPS particles: namely, when the particle size is greater than 3 µm, fracture/pulverization occurred; when the particle size is between 1 and 3 µm, microcracks emerged; when the particle size is less than 1 µm, no chemomechanical failure was observed. This strong size effect is interpreted by the interplay between elastic energy storage and dissipation. Our finding has important implications for the design of high-performance LGPS SE, for example, by reducing the particle size to less than 1 µm the chemomechanical failure of LGPS SE can be mitigated.

In Situ Visualization of Lithium Penetration through Solid Electrolyte and Dead Lithium Dynamics in Solid-State Lithium Metal Batteries.

The two biggest promises of solid-state lithium (Li) metal batteries (SSLMBs) are the suppression of Li dendrites by solid-state electrolyte (SSE) and the realization of a high-energy-density Li anode. However, LMBs have not met their expectations due to Li dendrite growth causing short-circuiting. In fact, Li dendrites grow even more easily in SSE than in liquid electrolyte, but the reason for this remains unclear. Here we report in situ transmission electron microscopy observations of Li dendrite penetration through SSE and "dead" Li formation dynamics in SSLMBs. We show direct evidence that large electrochemomechanical stress generates cracks in the SSE and drives Li through the SSE directly. We revealed that fresh Li nucleation sites emerged in every discharge cycle, creating new "dead" Li in the following charging cycle and becoming the dominant Coulombic efficiency decay mechanism in SSLMBs. These results indicate that engineering flaw size and reducing electronic conductivity in SSEs are essential to improve the performance of SSLMBs.

Lithium Deposition-Induced Fracture of Carbon Nanotubes and Its Implication to Solid-State Batteries.

The increasing demand for safe and dense energy storage has shifted research focus from liquid electrolyte-based Li-ion batteries toward solid-state batteries (SSBs). However, the application of SSBs is impeded by uncontrollable Li dendrite growth and short circuiting, the mechanism of which remains elusive. Herein, we conceptualize a scheme to visualize Li deposition in the confined space inside carbon nanotubes (CNTs) to mimic Li deposition dynamics inside solid electrolyte (SE) cracks, where the high-strength CNT walls mimic the mechanically strong SEs. We observed that the deposited Li propagates as a creeping solid in the CNTs, presenting an effective pathway for stress relaxation. When the stress-relaxation pathway is blocked, the Li deposition-induced stress reaches the gigapascal level and causes CNT fracture. Mechanics analysis suggests that interfacial lithiophilicity critically governs Li deposition dynamics and stress relaxation. Our study offers critical strategies for suppressing Li dendritic growth and constructing high-energy-density, electrochemically and mechanically robust SSBs.

In Situ TEM Studies of Sodium Polysulfides Electrochemistry in High Temperature Na-S Nanobatteries.

Understanding polysulfide electrochemistry in high temperature sodium-sulfur (HT-Na-S) batteries is crucial for their practical applications. Currently the discharge capacity of commercial HT-Na-S battery achieves only one third of its theoretical capacity due to polysulfides formation, understanding of which is limited due to technical difficulty in direct imaging polysulfides. Herein, in situ transmission electron microscopy implemented with a microelectromechanical systems (MEMS) heating device is used to investigate the electrochemical reactions of HT-Na-S batteries. The formation and evolution of transient polysulfides during cycling are revealed in real-time. Upon discharge, sulfur transforms to long-chain polysulfides, short-chain polysulfides, and finally Na2 S or its mixture with polysulfides, and the process is reversible during charge at high temperatures. Surprisingly, by introducing nanovoids into the sulfur cathode to buffer the large volume change thus preserving the integrity of the electronic/ionic pathways and reducing the diffusion distance of Na+ ions, the sulfur cathode is fully discharged to Na2 S rather than the conventionally observed Na2 S2 at 300 °C. Moreover, the electrochemical reaction is swift and highly reversible. The in situ studies provide not only new understanding to the polysulfide electrochemistry, but also critical strategies to boost the capacity and cyclability of HT-Na-S batteries for large-scale energy storage applications.

Lithium whisker growth and stress generation in an in situ atomic force microscope-environmental transmission electron microscope set-up.

Lithium metal is considered the ultimate anode material for future rechargeable batteries1,2, but the development of Li metal-based rechargeable batteries has achieved only limited success due to uncontrollable Li dendrite growth3-7. In a broad class of all-solid-state Li batteries, one approach to suppress Li dendrite growth has been the use of mechanically stiff solid electrolytes8,9. However, Li dendrites still grow through them10,11. Resolving this issue requires a fundamental understanding of the growth and associated electro-chemo-mechanical behaviour of Li dendrites. Here, we report in situ growth observation and stress measurement of individual Li whiskers, the primary Li dendrite morphologies12. We combine an atomic force microscope with an environmental transmission electron microscope in a novel experimental set-up. At room temperature, a submicrometre whisker grows under an applied voltage (overpotential) against the atomic force microscope tip, generating a growth stress up to 130 MPa; this value is substantially higher than the stresses previously reported for bulk13 and micrometre-sized Li14. The measured yield strength of Li whiskers under pure mechanical loading reaches as high as 244 MPa. Our results provide quantitative benchmarks for the design of Li dendrite growth suppression strategies in all-solid-state batteries.

Air-Stable Lithium Spheres Produced by Electrochemical Plating.

Lithium metal is an ideal anode for next-generation lithium batteries owing to its very high theoretical specific capacity of 3860 mAh g-1 but very reactive upon exposure to ambient air, rendering it difficult to handle and transport. Air-stable lithium spheres (ASLSs) were produced by electrochemical plating under CO2 atmosphere inside an advanced aberration-corrected environmental transmission electron microscope. The ASLSs exhibit a core-shell structure with a Li core and a Li2 CO3 shell. In ambient air, the ASLSs do not react with moisture and maintain their core-shell structures. Furthermore, the ASLSs can be used as anodes in lithium-ion batteries, and they exhibit similar electrochemical behavior to metallic Li, indicating that the surface Li2 CO3 layer is a good Li+ ion conductor. The air stability of the ASLSs is attributed to the surface Li2 CO3 layer, which is barely soluble in water and does not react with oxygen and nitrogen in air at room temperature, thus passivating the Li core.

Efficacy investigation of transpostceliac single-port 3-channel laparoscope in the treatment of complex renal cyst.

This study aims to investigate the surgical method and long-term efficacy of transpostceliac single-port 3-channel laparoscope in the treatment of complex renal cyst. A retrospective analysis was performed towards the 37 patients who underwent renal cyst unroofing decompression with single-port laparoscope from Jun. 2012 to Jul. 2013. The surgery was performed through the postceliac approach, a 2.5 cm incision was made 4-5 cm away from the iliac spine of midaxillary line, the Olympus single-port TriPort was then implanted, with the laparoscopic channel and the other two operation channels all as 5 mm. The operation was completed with the forceps and scissors which had flexible fronts. The cysts of the 37 patients were performed the appropriate surgical treatments according to their subtype grouping, on case was transferred to the open surgery, and there was no blood transfusion case. The operation time was 11-42 min, with the mean time as 23 min; the bleeding volume was 10-50 ml, with the mean volume as 26 ml; the postoperative follow-up was 1-6 months, and the ultrasound review did not find the recurrence of cyst; the postoperative lumbar scar was approximately 2.5 cm, and the patients could leave the bed and perform some acts on the exact day of the surgery; the hospitalization time was 1-2 d, with the average time as 1.2 d. The efficacy of the transpostceliac single-port 3-channel laparoscope in the treatment of complex renal cyst was positive, with low recurrence rate, and worthy of further promotion.