Search

Li–CO2/O2 batteries, a promising energy storage technology, not only provide ultrahigh discharge capacity but also capture CO2 and turn it into renewable energy. Their electrochemical reaction pathways' ambiguity, however, creates a hurdle for their practical application. This study used copper selenide (CuSe) nanosheets as the air cathode medium in an environmental transmission electron microscope to in situ study Li–CO2/O2 (mix CO2 as well as O2 at a volume ratio of 1:1) and Li–O2 batteries as well as Li–CO2 batteries. Primary discharge reactions take place successively in the Li–CO2/O2–CuSe nanobattery: (I) 4Li+ + O2 + 4e− → 2Li2O; (II) Li2O + CO2 → Li2CO3. The charge reaction proceeded via (III) 2Li2CO3 → 4Li+ + 2CO2 + O2 + 4e−. However, Li–O2 and Li–CO2 nanobatteries showed poor cycling stability, suggesting the difficulty in the direct decomposition of the discharge product. The fluctuations of the Li–CO2/O2 battery's electrochemistry were also shown to depend heavily on O2. The CuSe‐based Li–CO2/O2 battery showed exceptional electrochemical performance. The Li–CO2/O2 battery offered a discharge capacity apex of 15,492 mAh g−1 and stable cycling 60 times at 100 mA g−1. Our research offers crucial insight into the electrochemical behavior of Li–CO2/O2, Li–O2, and Li–CO2 nanobatteries, which may help the creation of high‐performance Li–CO2/O2 batteries for energy storage applications. [ABSTRACT FROM AUTHOR]

Layered transition metal dichalcogenides have great potential as anodes of sodium‐ion batteries (SIBs) due to their high theoretical specific capacity. However, the restacking severely limits their accessible sites, leading to undesirable specific capacity, cycle stability, and working temperature range. Herein, a hierarchical 2D VS2/Ti3C2Tx MXene hybrid is designed via a simple liquid‐mixing method, where VS2 is confined in the conductive Ti3C2Tx matrix with chemical connections built between them. The in situ transmission electron microscopy analyses reveal that the hybrid depends on a very fast and reversible intercalation/de‐intercalation process between VS2 and NaxVS2 (where x = 1) to store sodium. Theoretical calculations disclose that the Ti3C2Tx matrix remarkably enhances the charge transfer and alleviates the volume expansion of VS2 especially after Na+ is inserted. Consequently, such a rational design exhibits an intercalation pseudocapacitance‐dominant mechanism, with excellent specific capacity (522 mAh g−1 at 0.2 A g−1), rate capability (342 mAh g−1 at 10 A g−1), cycle life (116% after 3000 cycles), and also all‐climate workability (with high specific capacity and long‐term cycle stability even at 70 and −40 °C). This study may open up a new vision to design fast‐charging, long‐cycle, and all‐climate SIBs anodes based on the intercalation pseudocapacitance. [ABSTRACT FROM AUTHOR]

Cu-based nanocatalysts are the cornerstone of various industrial catalytic processes. Synergistically strengthening the catalytic stability and activity of Cu-based nanocatalysts is an ongoing challenge. Herein, the high-entropy principle is applied to modify the structure of Cu-based nanocatalysts, and a PVP templated method is invented for generally synthesizing six-eleven dissimilar elements as high-entropy two-dimensional (2D) materials. Taking 2D Cu2Zn1Al0.5Ce5Zr0.5Ox as an example, the high-entropy structure not only enhances the sintering resistance from 400 °C to 800 °C but also improves its CO2 hydrogenation activity to a pure CO production rate of 417.2 mmol g−1 h−1 at 500 °C, 4 times higher than that of reported advanced catalysts. When 2D Cu2Zn1Al0.5Ce5Zr0.5Ox are applied to the photothermal CO2 hydrogenation, it exhibits a record photochemical energy conversion efficiency of 36.2%, with a CO generation rate of 248.5 mmol g−1 h−1 and 571 L of CO yield under ambient sunlight irradiation. The high-entropy 2D materials provide a new route to simultaneously achieve catalytic stability and activity, greatly expanding the application boundaries of photothermal catalysis. Synergistically enhancing catalytic stability and activity of Cu-based nanocatalysts is an ongoing challenge. Here the authors report Cu-based high-entropy two-dimensional oxide as stable and active catalyst for photothermal CO2 hydrogenation under ambient sunlight irradiation. [ABSTRACT FROM AUTHOR]

Lithium-oxygen (Li-O2) batteries have been considered as an ideal solution to solving the global energy crisis. Silver (Ag) or Ag-based catalyst have been extensively studied due to their high catalytic activities in Li-O2 batteries. However, it remains a challenge to track the catalytic mechanism during the charge/discharge process. Here, a nanoscale processing method was used to assemble a Li-O2 nanobattery in an aberration-corrected environmental transmission electron microscope (ETEM), where a single Ag nanowire (NW) was used as catalyst for O2 electrode. A visualization of the lithium ion insertion process during the electrochemical reactions were achieved in this nanobattery. Numerous Ag nanoparticles (NPs) were observed on the surface of the Ag NW, which were covered by the discharge product Li2O2. By simultaneously studying the evolution of the interface and the phase transformation, it can be concluded that those Ag NPs wrapped around Ag NW acted as catalyst during the subsequent charge/discharge reaction. Based on those studies, Ag NPs decorated on porous carbon were synthesized, and it can simultaneously improve the cycling stability (100 cycles) and the maximum specific capacity (17,371 mAh·g−1 at a current density of 100 mA·g−1) in a coin cell Li-O2 battery. This study suggests that nanoscale Ag may be a promising catalyst for Li-O2 battery. [ABSTRACT FROM AUTHOR]

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 Fe3O4 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. [ABSTRACT FROM AUTHOR]

As a typical hard but brittle material, Si tends to fracture abruptly at a stress well below its theoretical strength, even if the tested volume goes down to submicron scale, at which materials are usually nearly free of flaws or extended defects. Here, via the thermal–oxidation–mediated healing of the surface that is the preferred site for cracks or dislocations initiation, the premature fracture can be effectively inhibited and the over 50% homogeneous plastic strain with the near‐theoretical strength (twice the value of the unhealed counterpart) are united in submicron‐sized Si particles. In situ transmission electron microscope observations and atomistic simulations elucidate the confinement effect from the passivated and smoothened thermal oxide, which retards the dislocation nucleation and transforms the dominant deformation mechanism from partial dislocation to the more mobile full dislocation. This work demonstrates an effective and feasible surface engineering pathway to optimize the mechanical properties of Si at small scales. [ABSTRACT FROM AUTHOR]

All‐solid‐state battery (ASSB) is a potential future energy storage technology to power the future world. However, the solid–solid contacts among the various components in ASSB often require a high stack pressure which is unrealistic in practical applications. Here it is shown that by carbon‐coating Sb2Se3 (Sb2Se3@C) nanorods, a record low stack pressure is attained, and the Sb2Se3@C electrode exhibits outstanding performance of 862 mAh g−1 over 50 cycles at 0.1 A g−1 when it is operated at 5 MPa stack pressure in an ASSB using LiIn anode and Li10Si0.3PS6.7Cl1.8 solid‐state electrolytes. Furthermore, a record high active material loading (the mass fraction of Sb2Se3@C being 0.7 in composite cathode) is achieved, and the Sb2Se3@C based ASSB delivers a reversible capacity of 2.6 mAh cm−2 at 0.1 A g−1 after 100 cycles. This work provides a strategy to significantly increase the cathode active material loading and dramatically reduce the stack pressure of ASSBs, which brings it one step closer toward the practical implementation of ASSBs for energy storage applications. [ABSTRACT FROM AUTHOR]

Transition metal sulfides (TMSs) are considered as promising anode materials for sodium-ion batteries (SIBs) due to their high theoretical capacities. However, the relatively low electrical conductivity, large volume variation, and easy aggregation/pulverization of active materials seriously hinder their practical application. Herein, okra-like NiS 2 /FeS 2 particles encapsulated in multichannel N-doped carbon nanofibers (NiS 2 /FeS 2 @MCNFs) are fabricated by a coprecipitation, electrospinning, and carbonization/sulfurization strategy. The combined advantages arising from the hollow multichannel structure in carbon skeleton and heterogeneous NiS 2 /FeS 2 particles with rich interfaces can provide facile ion/electron transfer paths, ensure boosted reaction kinetics, and help maintain the structural integrity, thereby resulting in a high reversible capacity (457 mA h g -1 at 1 A g -1 ), excellent rate performance (350 mA h g -1 at 5 A g -1 ), and outstanding long-term cycling stability (93.5% retention after 1100 cycles). This work provides a facile and efficient synthetic strategy to develop TMS-based heterostructured anode materials with high-rate and stable sodium storage properties.