Facet-Dependent Ni Segregation in a Micron-Sized Single-Crystal Li1.2Ni0.2Mn0.6O2 Cathode.

Elemental surface segregation in cathode materials is critical for determining the phase and interfacial reaction between the electrode and electrolyte, which consequently affects the electrochemical properties. Single-crystal cathodes of Li1.2Ni0.2Mn0.6O2 and Li1.2Ni0.2Mn0.6O1.95F0.05 with octahedral morphologies of (102)- and (003)-dominated facets have been manifested to show enhanced electrochemical properties. However, the surface structural features of such single crystals have not been investigated. Herein, using scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, and electron energy loss spectroscopy, we probe the elemental surface segregation characteristics in these single-crystal cathodes. We reveal that Ni surface segregation shows dependence on the crystal facet such that it occurs on crystal facets with a mix of cations and anions but not on the facets with only cations or anions. Furthermore, facet-dependent surface reconstructions are observed, featuring a spinel-like structure at the Ni-rich facet but a rock-salt structure at the facet without Ni segregation. The commonly known Mn reduction appears at the single-crystal surfaces and is more pronounced at the facet without Ni segregation. We further reveal that fluorination leads to stabilization of surface oxygens. This study provides detailed structural and chemical information about the facet-dependent Ni surface segregation and the resulting phase formation in the rather less explored micron-sized octahedral Li1.2Ni0.2Mn0.6O2 and Li1.2Ni0.2Mn0.6O1.95F0.05 single crystals, which is key to further exploration of the electrochemical properties of the cathodes in the form of microsized single crystals.

Fluorination Effect on Lithium- and Manganese-Rich Layered Oxide Cathodes.

Lithium- and manganese-rich (LMR) layered oxides are promising high-energy cathodes for next-generation lithium-ion batteries, yet their commercialization has been hindered by a number of performance issues. While fluorination has been explored as a mitigating approach, results from polycrystalline-particle-based studies are inconsistent and the mechanism for improvement in some reports remains unclear. In the present study, we develop an in situ fluorination method that leads to fluorinated LMR with no apparent impurities. Using well-defined single-crystal Li1.2Ni0.2Mn0.6O2 (LNMO) as a platform, we show that a high fluorination level leads to decreased oxygen activities, reduced side reactions at high voltages, and a broadly improved cathode performance. Detailed characterization reveals a particle-level Mn3+ concentration gradient from the surface to the bulk of fluorinated-LNMO crystals, ascribed to the formation of a Ni-rich LizNixMn2-xO4-yFy (x > 0.5) spinel phase on the surface and a "spinel-layered" coherent structure in the bulk where domains of a LiNi0.5Mn1.5O4 high-voltage spinel phase are integrated into the native layered framework. This work provides fundamental understanding of the fluorination effect on LMR and key insights for future development of high-energy Mn-based cathodes with an intergrown/composite crystal structure.

A Solid-State Electrolyte Based on Li0.95 Na0.05 FePO4 for Lithium Metal Batteries.

Solid-state electrolytes (SSEs) play a crucial role in developing lithium metal batteries (LMBs) with high safety and energy density. Exploring SSEs with excellent comprehensive performance is the key to achieving the practical application of LMBs. In this work, the great potential of Li0.95 Na0.05 FePO4 (LNFP) as an ideal SSE due to its enhanced ionic conductivity and reliable stability in contact with lithium metal anode is demonstrated. Moreover, LNFP-based composite solid electrolytes (CSEs) are prepared to further improve electronic insulation and interface stability. The CSE containing 50 wt% of LNFP (LNFP50) shows high ionic conductivity (3.58 × 10-4 S cm-1 at 25 °C) and good compatibility with Li metal anode and cathodes. Surprisingly, the LMB of Li|LNFP50|LiFePO4 cell at 0.5 C current density shows good cycling stability (151.5 mAh g-1 for 500 cycles, 96.5% capacity retention, and 99.3% Coulombic efficiency), and high-energy LMB of Li|LNFP50|Li[Ni0.8 Co0.1 Mn0.1 ]O2 cell maintains 80% capacity retention after 170 cycles, which are better than that with traditional liquid electrolytes (LEs). This investigation offers a new approach to commercializing SSEs with excellent comprehensive performance for high-performance LMBs.

2D Conjugated Metal-Organic Frameworks Embedded with Iodine for High-Performance Ammonium-Ion Hybrid Supercapacitors.

Ammonium ions (NH4 + ) are emerging non-metallic charge carriers for advanced electrochemical energy storage devices, due to their low cost, elemental abundance, and environmental benignity. However, finding suitable electrode materials to achieve rapid diffusion kinetics for NH4 + storage remains a great challenge. Herein, a 2D conjugated metal-organic framework (2D c-MOF) for immobilizing iodine, as a high-performance cathode material for NH4 + hybrid supercapacitors, is reported. Cu-HHB (HHB = hexahydroxybenzene) MOF embedded with iodine (Cu-HHB/I2 ) features excellent electrical conductivity, highly porous structure, and rich accessible active sites of copper-bis(dihydroxy) (Cu─O4 ) and iodide species, resulting in a remarkable areal capacitance of 111.7 mF cm-2 at 0.4 mA cm-2 . Experimental results and theoretical calculations indicate that the Cu─O4 species in Cu-HHB play a critical role in binding polyiodide and suppressing its dissolution, as well as contributing to a large pseudocapacitance with adsorbed iodide. In combination with a porous MXene anode, the full NH4 + hybrid supercapacitors deliver an excellent energy density of 31.5 mWh cm-2 and long-term cycling stability with 89.5% capacitance retention after 10 000 cycles, superior to those of the state-of-the-art NH4 + hybrid supercapacitors. This study sheds light on the material design for NH4 + storage, enabling the development of novel high-performance energy storage devices.

Largely Pseudocapacitive Two-Dimensional Conjugated Metal-Organic Framework Anodes with Lowest Unoccupied Molecular Orbital Localized in Nickel-bis(dithiolene) Linkages.

Although two-dimensional conjugated metal-organic frameworks (2D c-MOFs) provide an ideal platform for precise tailoring of capacitive electrode materials, high-capacitance 2D c-MOFs for non-aqueous supercapacitors remain to be further explored. Herein, we report a novel phthalocyanine-based nickel-bis(dithiolene) (NiS4)-linked 2D c-MOF (denoted as Ni2[CuPcS8]) with outstanding pseudocapacitive properties in 1 M TEABF4/acetonitrile. Each NiS4 linkage is disclosed to reversibly accommodate two electrons, conferring the Ni2[CuPcS8] electrode a two-step Faradic reaction with a record-high specific capacitance among the reported 2D c-MOFs in non-aqueous electrolytes (312 F g-1) and remarkable cycling stability (93.5% after 10,000 cycles). Multiple analyses unveil that the unique electron-storage capability of Ni2[CuPcS8] originates from its localized lowest unoccupied molecular orbital (LUMO) over the nickel-bis(dithiolene) linkage, which allows the efficient delocalization of the injected electrons throughout the conjugated linkage units without inducing apparent bonding stress. The Ni2[CuPcS8] anode is used to demonstrate an asymmetric supercapacitor device that delivers a high operating voltage of 2.3 V, a maximum energy density of 57.4 Wh kg-1, and ultralong stability over 5000 cycles.

Study on the relationship among typhoon, climate change, and acute Stanford type A aortic dissection in southern of Zhejiang in China.

BACKGROUND: The aim of this study was to investigate the relationship between typhoon, climate change, and acute Stanford type A aortic dissection (TAAD) in southern of Zhejiang Province in China. METHOD: 371 patients with TAAD were admitted to three hospitals (the aortic dissection center) in southern of Zhejiang Province, China from January 2015 to December 2020, and data were retrospectively collected, the data included (1) the number of patients admitted in different months and seasons, (2) daily meteorological data in southern of Zhejiang Province, and (3) typhoon information were retrospectively analyzed. RESULTS: The number of TAAD occurred in winter was the highest and in summer was the lowest. The incidence of TAAD was correlated with minimum temperature, maximum wind speed, mean wind speed, and water vapor pressure (P < 0.05). Maximum wind speed (RR 0.37; 95% CI 0.17 to 0.80, P = 0.01) and water vapor pressure (RR 0.96; 95% CI 0.92 to 1, P = 0.03) were the protective factor. The occurrence incidence of TAAD under the influence of typhoon climate was less than that during the period not affected by typhoon (P < 0.05). CONCLUSION: There was a correlation between typhoon, climate change, and the occurrence of TAAD in southern Zhejiang Province. Wind speed, vapor pressure, and typhoon may be protective factors.

Advanced Three-Dimensional Microelectrode Architecture Design for High-Performance On-Chip Micro-Supercapacitors.

The rapid development of miniaturized electronic devices has greatly stimulated the endless pursuit of high-performance on-chip micro-supercapacitors (MSCs) delivering both high energy and power densities. To this end, an advanced three-dimensional (3D) microelectrode architecture design offers enormous opportunities due to high mass loading of active materials, large specific surface areas, fast ion diffusion kinetics, and short electron transport pathways. In this review, we summarize the recent advances in the rational design of 3D architectured microelectrodes including 3D dense microelectrodes, 3D nanoporous microelectrodes, and 3D macroporous microelectrodes. Furthermore, the emergent microfabrication strategies are discussed in detail in terms of charge storage mechanisms and structure-performance correlation for on-chip MSCs. Finally, we conclude with a perspective on future opportunities and challenges in this thriving field.

Descriptor-Driven Computational Design of Bifunctional Double-Atom Hydrogen Evolution and Oxidation Reaction Electrocatalysts for Rechargeable Hydrogen Gas Batteries.

Rechargeable hydrogen gas batteries (RHGBs) have been attracting much attention as promising all-climate large-scale energy storage devices, which calls for low-cost and high-activity hydrogen evolution/oxidation reaction (HER/HOR) bifunctional electrocatalysts to replace the costly platinum-based catalysts. Based on density functional theory (DFT) computations, herein we report an effective descriptor-driven design principle to govern the HER/HOR electrocatalytic activity of double-atom catalysts (DACs) for RHGBs. We systematically investigate the d-band center variation of DACs and their correlations with HER/HOR free energies. We construct activity maps with the d-band center of DACs as a descriptor, which demonstrate that high HER/HOR electrocatalytic activity can be achieved with an appropriate d-band center of DACs. This work not only broadens the applicability of d-band center theory to the prediction of bifunctional HER/HOR electrocatalysts but also paves the way to fast screening and design of efficient and low-cost DACs to promote practical applications of RHGBs.

Porous Polymer Cubosomes with Ordered Single Primitive Bicontinuous Architecture and Their Sodium-Iodine Batteries.

Bicontinuous porous materials, which possess 3D interconnected pore channels facilitating a smooth mass transport, have attracted much interest in the fields of energy and catalysis. However, their synthesis remains very challenging. We report a general approach, using polymer cubosomes as the template, for the controllable synthesis of bicontinuous porous polymers with an ordered single primitive (SP) cubic structure, including polypyrrole (SP-PPy), poly-m-phenylenediamine (SP-PmPD), and polydopamine (SP-PDA). Specifically, the resultant SP-PPy had a unit cell parameter of 99 nm, pore diameter of 45 nm, and specific surface area of approximately 60 m2·g-1. As a proof of concept, the I2-adsorbed SP-PPy was employed as the cathode materials of newly emerged Na-I2 batteries, which delivered a record-high specific capacity (235 mA·h·g-1 at 0.5 C), excellent rate capability, and cycling stability (with a low capacity decay of 0.12% per cycle within 400 cycles at 1 C). The advantageous contributions of the bicontinuous structure and I3- adsorption mechanism of SP-PPy were revealed by a combination of ion diffusion experiments and theoretical calculations. This study opens a new avenue for the synthesis of porous polymers with new topologies, broadens the spectrum of bicontinuous-structured materials, and also develops a novel potential application for porous polymers.

An Efficient Rechargeable Aluminium-Amine Battery Working Under Quaternization Chemistry.

Rechargeable aluminium (Al) batteries (RABs) have long-been pursued due to the high sustainability and three-electron-transfer properties of Al metal. However, limited redox chemistry is available for rechargeable Al batteries, which restricts the exploration of cathode materials. Herein, we demonstrate an efficient Al-amine battery based on a quaternization reaction, in which nitrogen (radical) cations (R3 N.+ or R4 N+ ) are formed to store the anionic Al complex. The reactive aromatic amine molecules further oligomerize during cycling, inhibiting amine dissolution into the electrolyte. Consequently, the constructed Al-amine battery exhibits a high reversible capacity of 135 mAh g-1 along with a superior cycling life (4000 cycles), fast charge capability and a high energy efficiency of 94.2 %. Moreover, the Al-amine battery shows excellent stability against self-discharge, far beyond conventional Al-graphite batteries. Our findings pave an avenue to advance the chemistry of RABs and thus battery performance.

Dual-Redox-Sites Enable Two-Dimensional Conjugated Metal-Organic Frameworks with Large Pseudocapacitance and Wide Potential Window.

Advanced supercapacitor electrodes require the development of materials with dense redox sites embedded into conductive and porous skeletons. Two-dimensional (2D) conjugated metal-organic frameworks (c-MOFs) are attractive supercapacitor electrode materials due to their high intrinsic electrical conductivities, large specific surface areas, and quasi-one-dimensional aligned pore arrays. However, the reported 2D c-MOFs still suffer from unsatisfying specific capacitances and narrow potential windows because large and redox-inactive building blocks lead to low redox-site densities of 2D c-MOFs. Herein, we demonstrate the dual-redox-site 2D c-MOFs with copper phthalocyanine building blocks linked by metal-bis(iminobenzosemiquinoid) (M2[CuPc(NH)8], M = Ni or Cu), which depict both large specific capacitances and wide potential windows. Experimental results accompanied by theoretical calculations verify that phthalocyanine monomers and metal-bis(iminobenzosemiquinoid) linkages serve as respective redox sites for pseudocapacitive cation (Na+) and anion (SO42-) storage, enabling the continuous Faradaic reactions of M2[CuPc(NH)8] occurring in a large potential window of -0.8 to 0.8 V vs Ag/AgCl (3 M KCl). The decent conductivity (0.8 S m-1) and high active-site density further endow the Ni2[CuPc(NH)8] with a remarkable specific capacitance (400 F g-1 at 0.5 A g-1) and excellent rate capability (183 F g-1 at 20 A g-1). Quasi-solid-state symmetric supercapacitors are further assembled to demonstrate the practical application of Ni2[CuPc(NH)8] electrode, which deliver a state-of-the-art energy density of 51.6 Wh kg-1 and a peak power density of 32.1 kW kg-1.

Facile assembly of layer-interlocked graphene heterostructures as flexible electrodes for Li-ion batteries.

Flexible electrodes with robust mechanical properties and high electrochemical performance are of significance for the practical implementation of flexible batteries. Here we demonstrate a general and straightforward co-assembly approach to prepare flexible electrodes, where electrochemically exfoliated graphene (EG) is exploited as the film former/conducting matrix and different binary metal oxides (Li4Ti5O12, LiCoO2, Li2MnO4, LiFePO4) are incorporated. The resultant EG-metal oxide hybrids exhibit a unique layer-interlocked structure, where the metal oxide is conformably wrapped by the highly flexible graphene. Due to numerous contact interphases generated between EG and the intercalated material, the hybrid films show high flexibility and can endure rolling, bending, folding and even twisting. When serving as the anode for Li-ion batteries, the freestanding EG-Li4Ti5O12 hybrid presents a characteristic flat discharge plateau at 1.55 V (vs. Li/Li+), indicating transformation of Li4Ti5O12 to Li7Ti5O12. Small polarization, high rate capability and excellent cycling stability against mechanical bending are also demonstrated for the prepared EG-Li4Ti5O12 hybrid. Finally, full cells composed of EG-Li4Ti5O12 and EG-LiFePO4 hybrids show impressive cycling (98% capacity retention after 100 cycles at 1C) and rate performance (84% capacity retained at 2.5C). The straightforward co-assembly approach based on EG can be extended to other two-dimensional layered materials for constructing highly efficient flexible energy storage devices.

Boosting Capacitive Sodium-Ion Storage in Electrochemically Exfoliated Graphite for Sodium-Ion Capacitors.

Sodium (Na)-ion capacitors possess higher energy density than supercapacitors and higher power density than Na-ion batteries. However, kinetic mismatches between fast capacitive charge storage on the cathode and sluggish battery-type reactions on the anode lead to a poor charge/discharge rate capability and insufficient power output of Na-ion capacitors. Thus, developing suitable anode materials for Na-ion capacitors is urgently desirable. This work demonstrates an electrochemically exfoliated graphite (EEG) anode with enhanced capacitive charge storage, greatly boosting the Na-ion reaction kinetics of co-intercalation. The EEG anode shows a high reversible capacity of 109 mAh g-1 and maintains a good capacity retention of 90% after 1000 cycles. The assembled Na-ion capacitor using the EEG anode can finish the charge/discharge process in less than 10 s, which achieves an ultrahigh power density of 17,500 W kg-1 with an energy density of 17 Wh kg-1. The high capacitive contributions at both the anode and cathode contribute to the fast rate capability and high power output of the fabricated Na-ion capacitors. This work will promote the development of ultrafast charging sodium-ion storage devices.

A Stimulus-Responsive Zinc-Iodine Battery with Smart Overcharge Self-Protection Function.

Zinc-iodine aqueous batteries (ZIABs) are highly attractive for grid-scale energy storage due to their high theoretical capacities, environmental friendliness, and intrinsic non-flammability. However, because of the close redox potential of Zn stripping/platting and hydrogen evolution, slight overcharge of ZIABs would induce drastic side reactions, serious safety concerns, and battery failure. A novel type of stimulus-responsive zinc-iodine aqueous battery (SR-ZIAB) with fast overcharge self-protection ability is demonstrated by employing a smart pH-responsive electrolyte. Operando spectroelectrochemical characterizations reveal that the battery failure mechanism of ZIABs during overcharge arises from the increase of electrolyte pH induced by hydrogen evolution as well as the consequent irreversible formation of insulating ZnO at anode and soluble Zn(IO3 )2 at cathode. Under overcharge conditions, the designed SR-ZIABs can be rapidly switched off with capacity degrading to 6% of the initial capacity, thereby avoiding continuous battery damage. Importantly, SR-ZIABs can be switched on with nearly 100% of capacity recovery by re-adjusting the electrolyte pH. This work will inspire the development of aqueous Zn batteries with smart self-protection ability in the overcharge state.

Oligophenyls with Multiple Disulfide Bridges as Higher Homologues of Dibenzo[c,e][1,2]dithiin: Synthesis and Application in Lithium-Ion Batteries.

Higher homologues of dibenzo[c,e][1,2]dithiin were synthesized from oligophenyls bearing multiple methylthio groups. Single-crystal X-ray analyses revealed their nonplanar structures and helical enantiomers of higher meta-congener 6. Such dibenzo[1,2]dithiin homologues are demonstrated to be applicable to lithium-ion batteries as cathode, displaying a high capacity of 118 mAh g-1 at a current density of 50 mA g-1 .

A High-Voltage, Dendrite-Free, and Durable Zn-Graphite Battery.

The intrinsic advantages of metallic Zn, like high theoretical capacity (820 mAh g-1 ), high abundance, low toxicity, and high safety have driven the recent booming development of rechargeable Zn batteries. However, the lack of high-voltage electrolyte and cathode materials restricts the cell voltage mostly to below 2 V. Moreover, dendrite formation and the poor rechargeability of the Zn anode hinder the long-term operation of Zn batteries. Here a high-voltage and durable Zn-graphite battery, which is enabled by a LiPF6 -containing hybrid electrolyte, is reported. The presence of LiPF6 efficiently suppresses the anodic oxidation of Zn electrolyte and leads to a super-wide electrochemical stability window of 4 V (vs Zn/Zn2+ ). Both dendrite-free Zn plating/stripping and reversible dual-anion intercalation into the graphite cathode are realized in the hybrid electrolyte. The resultant Zn-graphite battery performs stably at a high voltage of 2.8 V with a record midpoint discharge voltage of 2.2 V. After 2000 cycles at a high charge-discharge rate, high capacity retention of 97.5% is achieved with ≈100% Coulombic efficiency.

Fully Conjugated Phthalocyanine Copper Metal-Organic Frameworks for Sodium-Iodine Batteries with Long-Time-Cycling Durability.

Rechargeable sodium-iodine (Na-I2 ) batteries are attracting growing attention for grid-scale energy storage due to their abundant resources, low cost, environmental friendliness, high theoretical capacity (211 mAh g-1 ), and excellent electrochemical reversibility. Nevertheless, the practical application of Na-I2 batteries is severely hindered by their poor cycle stability owing to the serious dissolution of polyiodide in the electrolyte during charge/discharge processes. Herein, the atomic modulation of metal-bis(dihydroxy) species in a fully conjugated phthalocyanine copper metal-organic framework (MOF) for suppression of polyiodide dissolution toward long-time cycling Na-I2 batteries is demonstrated. The Fe2 [(2,3,9,10,16,17,23,24-octahydroxy phthalocyaninato)Cu] MOF composited with I2 (Fe2 -O8 -PcCu/I2 ) serves as a cathode for a Na-I2 battery exhibiting a stable specific capacity of 150 mAh g-1 after 3200 cycles and outperforming the state-of-the-art cathodes for Na-I2 batteries. Operando spectroelectrochemical and electrochemical kinetics analyses together with density functional theory calculations reveal that the square planar iron-bis(dihydroxy) (Fe-O4 ) species in Fe2 -O8 -PcCu are responsible for the binding of polyiodide to restrain its dissolution into electrolyte. Besides the monovalent Na-I2 batteries in organic electrolytes, the Fe2 -O8 -PcCu/I2 cathode also operates stably in other metal-I2 batteries like aqueous multivalent Zn-I2 batteries. Thus, this work offers a new strategy for designing stable cathode materials toward high-performance metal-iodine batteries.