A long-wavelength mitochondria-targeted fluorescent probe for imaging of peroxynitrite during dexamethasone treatment.

Peroxynitrite (ONOO-), as a strong oxidizing reactive nitrogen substance (RNS), is generated endogenously by cells. Its visualization research is crucial to understand relevant disease processes. Herein, we reported a long-wavelength mitochondria-targeted fluorescence "turn on" probe TL. The probe TL could react with ONOO- by using 4-(Bromomethyl)benzeneboronic as a reactive site, which exhibited outstanding characteristics for detection of ONOO-, thus improving response time (about 50 s), sensitivity (DL, 10.1 nM), and emission wavelength (667 nm). Besides, TL displayed well mitochondria targeting and biological visualizing of exogenous and endogenous ONOO- in biological systems. Finally, TL was used to monitor high concentration of dexamethasone-induced an up-regulation of ONOO-. This indicated that TL has excellent potential to study the fluctuation of ONOO- in the physiological and pathological system.

Boosting performance of Co-free Li-rich cathode material through regulating the anionic activity by means of the strong TaO bonding.

Benefiting from the extra contribution of O redox, Co-free Li-rich layered oxides (LRNMO) can satisfy the requirement of high specific capacities. However, during the high-voltage charging process, lattice oxygen being oxidized to O- or O2 leads to a gradual transition of the structure from layered to spinel phase, capacity and voltage decline, hindering the practical application of LRNMO in the lithium-ion battery. Here, a surface modification strategy of Li1.2Ni0.32Mn0.48O2-δ doped with Ta5+ ions is proposed, in which the Ta5+ ions occupy the lithium sites of the lattice structure on the surface layer of LRNMO and form a Ta2O5 coating layer. The modified electrode exhibits excellent rate performance and cycling stability, with 94.9% and 85.5% capacity retention rate and voltage retention rate, respectively, after 200 cycles at 1C. Moreover, the initial coulomb efficiency and ionic conductivity of the modified electrode are also apparently enhanced. Simultaneously, the decreased Li/Ni mixing degree of the modified electrode reflects the improvement of the structural stability. Therefore, the modification strategy through strong metal-oxygen bonding to integrate the surface structure to regulate the oxygen activity provides a new direction for the design of high energy density Co-free Li-rich cathode materials.

Insight into the Catalytic Role of Defect-Enriched Vanadium Sulfide for Regulating the Adsorption-Catalytic Conversion Behavior of Polysulfides in Li-S Batteries.

The performance promotion of Li-S batteries relies primarily on inhibition of the shuttle effect and improvement of the catalytic-conversion reaction kinetics of polysulfides. Herein, we prepare defect-enriched VS2 nanosheets (VS2-x) as catalysts for Li-S batteries and further study the catalytic mechanism of VS2-x via ex situ X-ray diffraction and in situ UV-vis spectroscopy. A multifunctional S cathode was also obtained by assembling VS2-x on a C cloth to achieve high S loading for Li-S batteries. It was found that VS2-x catalysts undergo a lithiation process in the work voltage of Li-S batteries, and the triggered LiyVS2-x intermediates reciprocate VS2-x with a high catalytic activity so as to enhance the performance of Li-S batteries by promoting the dissociation process of S62- to S3•-. Consequently, Li-S batteries with a C/VS2-x/S cathode deliver a high reversible capacity (1471 mAh g-1 at 0.1 C) and good cycling performance (low fading rate of 0.064% per cycle after 400 cycles). Meanwhile, the CC@VS2-x/S cathode with a high S areal loading of 5.6 mg cm-2 can render a satisfactory areal capacity of 4.22 mAh cm-2 at 0.2 C and a cycle stability of over 100 cycles. Therefore, the study on the catalysis of LiyVS2-x intermediates provides a scientific view for revealing the catalysis mechanism of a sulfide-based electrocatalyst and boosting the development of an electrocatalyst for Li-S batteries.

Multifunctional Surface Construction for Long-Term Cycling Stability of Li-Rich Mn-Based Layered Oxide Cathode for Li-Ion Batteries.

Li-rich Mn-based layered oxides (LMLOs) are promising cathode material candidate for the next-generation Li-ion batteries (LIBs) of high energy density. However, the fast capacity fading and voltage decay as well as low Coulombic efficiency caused by irreversible oxygen release and phase transition during the electrochemical process hinder their practical application. To solve these problems, in the present study, a multifunctional surface construction involving a coating layer, spinel-layered heterostructure, and rich-in oxygen vacancies is successfully conducted by a facile thermal reduction of the LMLO particles with potassium borohydride (KBH4 ) as the reducing agent. The multifunctional surface structure plays synergistic effects on suppressing the interface side reaction, reducing the dissolution of transition metal, increasing electron conductivity and lithium diffusion rate. As a result, electrochemical performances of the LMLO cathode are effectively enhanced. With optimization of the addition of KBH4 , the electrode delivers a reversible capacity of 280 mAh g-1 at 0.1 C, which maintains after 100 cycles. The capacity retention with respect to the initial capacity is as high as 98% at 1 C after 400 cycles. The present work provides insights into designing a highly effective functional surface structure of LMLO cathode materials for high-performance LIBs.

A Redox Couple Strategy Enables Long-Cycling Li- and Mn-Rich Layered Oxide Cathodes by Suppressing Oxygen Release.

Li- and Mn-rich layered oxides (LMROs) are considered the most promising cathode candidates for next-generation high-energy lithium-ion batteries. The poor cycling stability and fast voltage fading resulting from oxygen release during charging, however, severely hinders their practical application. Herein, a strategy of introducing an additional redox couple is proposed to eliminate the persistent problem of oxygen release. As a proof of concept, the cycling stability of Li1.2 Ni0.13 Co0.13 Mn0.54 O2 , which is a typical LMRO cathode, is substantially enhanced with the help of the S2- /SO3 2- redox couple, and the capacity shows no decay with a retention of 100% after 700 cycles at 1C, far superior to the bare counterpart (61.7%). The surface peroxide ions (O2 2- ) are readily chemically reduced back to immobile O2- by S2- during charging, accompanied by the formation of SO3 2- , which plays a critical role in stabilizing the oxygen lattice and eventually inhibiting the release of oxygen. More importantly, the S2- ions are regenerated during the following discharging process and participate in the chemical redox reaction again. The findings shed light on a potential direction to tackle the poor cycling stability of high-energy anion-redox cathode materials for rechargeable metal-ion batteries.

Boosting Electrochemical Performance of Lithium-Rich Manganese-Based Cathode Materials through a Dual Modification Strategy with Defect Designing and Interface Engineering.

Low Coulombic efficiency, severe capacity fading and voltage attenuation, and poor rate performance are currently great obstacles for the industrial application of lithium-rich manganese-based cathode materials (LRMCs) in lithium-ion batteries (LIBs). Herein, a dual modification strategy combining defect designing with interface engineering is reported to solve the above problems synchronously. Oxygen vacancies, a carbon nitride protective layer, and a fast ion conductor are simultaneously introduced in the LRMCs. It has been found that oxygen vacancies can suppress the release of irreversible oxygen, which is in favor of improving the initial Coulombic efficiency, the carbon nitride protective layer can improve the structural stability and alleviate the attenuation of capacity and voltage, and the fast ion conductor can promote the diffusion rate of Li+ and electron conductivity and thus enhance the rate capability. The modified material exhibits significantly enhanced electrochemical performances, including a favorable capacity retention rate of 94.2% over 120 cycles at 1C (1C = 200 mAh g-1) and excellent rate capabilities of 173.1 and 136.9 mAh g-1 can be maintained at 5 and 10C after 100 cycles, respectively. Hence, the well-designed dual modification strategy with defect design and interface engineering provides significant exploration for the development and industrialization of LRMCs with high performance.

Design and Facile Synthesis of Highly Efficient and Durable Bifunctional Oxygen Electrocatalyst Fe-Nx/C Nanocages for Rechargeable Zinc-Air Batteries.

Looking for a high-efficiency, durabile, and low-cost dual-functional oxygen electrocatalyst as the air electrode catalyst in rechargeable zinc-air batteries (ZABs) is urgently desirable but faces many challenges. Herein, we propose the preparation strategy of effectively using a bifunctional electrocatalyst (Fe-Nx/C) based on the zeolite imidazole organic framework-8 (ZIF-8) as the template agent, with surface modification coated by ferrocene (Fc) molecules followed by pyrolysis at high temperature under inert atmosphere. Benefiting from the surface modification of ZIF-8 with Fc molecules, more abundant multiple catalytic Fe/Fe-Nx/FeCx sites with high intrinsic activity are derived, the resultant Fe-Nx/C exhibits excellent potential gap (ΔE = 0.63 V) and durability, which is obviously superior to the Pt/C + IrO2 benchmark (ΔE = 0.77 V) and other state-of-the-art electrocatalysts. Furthermore, the assembled rechargeable ZABs employing the Fe-Nx/C as an air-electrode show a reduced charging-discharging potential difference of 0.603 V, high power density of 214.8 mW cm-2, and long-term cycling stability of more than 290 h at 2.0 mA cm-2. Therefore, this work presents a feasible strategy to prepare a high-efficiency and durability ORR/OER bifunctional electrocatalyst toward high performance ZABs and next-generation energy storage devices.

A Novel Tin-Bonded Silicon Anode for Lithium-Ion Batteries.

Poor cyclic stability and low rate performance due to dramatic volume change and low intrinsic electronic conductivity are the two key issues needing to be urgently solved in silicon (Si)-based anodes for lithium-ion batteries. Herein, a novel tin (Sn)-bonded Si anode is proposed for the first time. Sn, which has a high electronic conductivity, is used to bond the Si-anode material and copper (Cu) current collector together using a hot-pressed method with a temperature slightly above the melting point of Sn. The cycling performance of the electrode is studied using a galvanostatic method. Nanoindentation and peeling tests are conducted to measure the mechanical strength of the electrodes. Direct current polarization and galvanostatic intermittent titration techniques are applied to assess the conductivity of the composites. Electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy are conducted to evaluate the effect of the coating layer on the cycling ability of the composites. The Sn-bonded Si anodes show superior cycling stability and high rate performance with an improved initial Coulombic efficiency. Analyses reveal that the low-melting-point Sn helps to markedly improve the electronic conductivity of the electrodes and serves as a metallic binder as well to enhance the adhesive strength of the electrode. It is hopeful that this novel Sn-bonded Si anode provides a new insight for the development of advanced Si-based anodes for LIBs.

Opening MXene Ion Transport Channels by Intercalating PANI Nanoparticles from the Self-Assembly Approach for High Volumetric and Areal Energy Density Supercapacitors.

Two-dimensional (2D) MXene materials have attracted great attention as advanced energy storage devices. A Ti3C2 MXene film can be used as a high-performance electrode material for flexible supercapacitors owing to its high specific capacitance, excellent conductivity, and remarkable flexibility. Unfortunately, self-stacking of MXene nanosheets makes them hard to balance the volumetric and areal capacitance performance. Herein, high conductive polyaniline nanoparticles (PANI NPs, ∼10 nm) are proposed as intercalators to regulate the MXene nanosheet interlayer by the self-assembly method. Interlayered PANI NPs not only restrain MXene self-stacking but also enable more ion transport routes, and conductive PANI NPs filled in MXene interlayer are in the form of nanoparticles that can build interconnected conductive channels. Meanwhile, PANI NPs slightly changes the thickness of the MX/PANI NPs hybrid film, thus bringing a high volumetric capacitance. As a result, the freestanding MX/PANI NPs-10% electrode displays an excellent areal capacitance of 1885 mF cm-2 (377 F g-1), meanwhile maintains a high volumetric capacitance of 873 F cm-3 even when the load of MXene reaches 5 mg cm-2. Moreover, the symmetric supercapacitor assembled by MX/PANI NPs hybrid film demonstrates high areal energy density (90.3 µWh cm-2) and volumetric energy density (20.9 Wh L-1) compared to MXene-based symmetric supercapacitors reported in the literature. This rational design balancing areal and volumetric energy densities provides another approach for solving the inherent problems of MXene and further exploiting MXene materials toward application in advanced energy storage devices.

Suppressing the Voltage Decay Based on a Distinct Stacking Sequence of Oxygen Atoms for Li-Rich Cathode Materials.

Li-rich cathode materials possess a much higher theoretical energy density than all intercalated cathode materials currently reported and thus are considered as the most promising candidate for next-generation high-energy density Li-ion batteries. However, the rapid voltage decay and the irreversible phase transition of O3-type Li-rich cathode materials often lessen their actual energy density and limit their practical applications, and thus, effectively suppressing the voltage decay of Li-rich cathodes becomes the hotspot of the current research. Herein, the F-doped O2-type Li-rich cathode materials Li1.2Mn0.54Ni0.13Co0.13O2+δ-xFx (F-O2-LRO) are designed and prepared based on the P2-type sodium-ion cathode materials Na5/6Li1/4(Mn0.54Ni0.13Co0.13)3/4O2+δ (Na-LRO) by ion exchange. It has been found that the as-prepared F-O2-LRO exhibits excellent electrochemical performance, for example, a high discharge specific capacity of 280 mA h g-1 at 0.1 C with an initial Coulombic efficiency of 94.4%, which is obviously higher than the original LRO (77.2%). After 100 cycles, the F-O2-LRO cathode can still maintain a high capacity retention of 95% at a rate of 1 C, while the capacity retention of the original LRO is only 69.1% at the same current rate. Furthermore, the voltage difference (ΔV) of F-O2-LRO before and after cycling is only 0.268 V after 100 cycles at 1 C, which is less than that of the LRO cathode (0.681 V), indicating much lower polarization. Besides, even at a high current rate of 5 C, F-O2-LRO still displays a satisfactory discharge capacity of 210 mA h g-1 with a capacity retention of 90.1% after 100 cycles. Therefore, this work put forward a new strategy for the development and industrial application of Li-rich cathode materials in high-energy Li-ion batteries.

A Novel Perovskite Electron-Ion Conductive Coating to Simultaneously Enhance Cycling Stability and Rate Capability of Li1.2 Ni0.13 Co0.13 Mn0.54 O2 Cathode Material for Lithium-Ion Batteries.

Poor cycling stability and rate capability are two key issues needing to be solved for Li- and Mn-rich oxide cathode material for lithium-ion batteries (LIBs). Herein, a novel perovskite electron-ion mixed conductor Nd0.6 Sr0.4 CoO3 (NSCO) is used as the coating layer on Li1.2 Ni0.13 Co0.13 Mn0.54 O2 (LNCMO) to simultaneously enhance its cycling stability and rate capability. By coating 3 wt% NSCO, LNCMO-3NSCO exhibits an optimal cycling performance with a capacity retention of 99% at 0.1C (1C = 200 mA g-1 ) after 60 cycles, 91% at 1C after 300 cycles, and 54% at 20C after 1000 cycles, much better than 78%, 63%, and 3% of LNCMO, respectively. Even at a high charge and discharge rate of 50C, LNCMO-3NSCO exhibits a discharge capacity of 53 mAh g-1 and a mid-point discharge voltage of 2.88 V, much higher than those of LNCMO (24 mA h g-1 and 2.40 V, respectively). Benefiting from the high electronic conductivity (1.46 S cm-1 ) and ionic conductivity (1.48 × 10-7  S cm-1 ), NSCO coating not only suppresses transition metals dissolution and structure transformation, but also significantly enhances electronic conductivity and Li+ diffusion coefficient of LNCMO by an order of magnitude.

A novel self-supported structure of Ce-UiO-66/TNF in a redox electrolyte with high supercapacitive performance.

A novel self-supported structure of Ce-UiO-66/TNF was firstly synthesized by growing Ce-UiO-66 on a TNF substrate. This novel Ce-UiO-66/TNF material was proved to possess a high supercapacitive performance in the redox electrolyte of Fe(CN)63-/4-, and it was also the first study for Ce-UiO-66 material on the supercapacitor application. High specific capacitances of 6.9 and 2.5 Fcm-2 can be achieved at large current densities of 20 and 80 mAcm-2, respectively. After 10,000 charge-discharge cycles, the capacitance retention can be kept at 95% and the coulomb efficiency can be maintained over 98%. Such outstanding electrochemical performance may be related to the redox property of the electrolyte, high specific surface area of the Ce-UiO-66 material, porous characteristic of the TNF substrate and self-supported structure of the whole electrode.

Photo-induced self-catalysis of nano-Bi2MoO6 for solar energy harvesting and charge storage.

Efficient, sustainable, and integrated energy systems require the development of novel multifunctional materials to simultaneously achieve solar energy harvesting and charge storage. Bi-based oxysalt aurivillius phase materials are potential candidates due to their typical photovoltaic effect and their pseudo-capacitance charge storage behavior. Herein, we synthesized nano-Bi2MoO6 as a material for both solar energy harvesting and charge storage due to its suitable band gap for absorption of visible light and its well-defined faradaic redox reaction from Bi metal to Bi3+. The irradiation of visible light significantly affected the electrochemical processes and the dynamics of the Bi2MoO6 electrode. The photo-induced self-catalytic redox mechanism was carefully explored by adding sacrificial agents in photocatalysis reaction. In accordance with the rule of energy matching, the photo-generated holes oxidized the Bi metal to Bi3+, and the corresponding peak current increased by 79.5% at a scanning rate of 50 mV s-1. More importantly, the peak current retention rate remained higher than 92.5% during the entire 200 cycles. The photo-generated electrons facilitated a decrease of 184 mV in the overpotential of the reduction process. Furthermore, the irradiation of visible light also accelerated the ionic diffusion of the electrolyte. These investigations provide a unique perspective for the design and development of new multifunctional materials to synergistically realize solar energy harvesting and charge storage.

Carbon-Coated Yttria Hollow Spheres as Both Sulfur Immobilizer and Catalyst of Polysulfides Conversion in Lithium-Sulfur Batteries.

Li-S battery has tremendous application prospect on account of the high theoretical specific capacity and large energy density, while its large-scale application is impeded by the severe shuttle effect and the slow electrochemical kinetics of polysulfides conversion. Herein, the Lewis acidic yttria hollow spheres (YHS) are rationally designed as both sulfur immobilizer and catalyst of polysulfides conversion for the advanced Li-S batteries. It can be known that the Lewis acidic yttria can effectively capture the Lewis basic polysulfides and thus mitigate the shuttle effect of Li-S battery; besides, yttria shows the enhanced catalytic effect for the kinetics of interconversion reaction from polysulfides to Li2S. As a result, either as a sulfur host or as the separator coating, yttria plays a vital part in realizing the high specific discharge capacity and good cycle stability for Li-S battery. In particular, Li-S battery with YHS@C/S cathode and YHS/CNT-0.6- modified separator (2.1 mg cm-2 active material loading) shows a good specific discharge capacity of 912.5 mAh g-1 at 0.5C. Even after 200 steady cycles, the discharge specific capacity can keep as 842.3 mAh g-1, and the capacity decay rate is only 0.038% per cycle. When active material areal loading is increased to 4.24 mg cm-2, it still maintains a considerable areal capacity of 3.79 mAh cm-2. In consequence, the synergy of polysulfides confinement and catalytic conversion reaction provides a meaningful exploration for achieving the high performance of Li-S batteries.

Preparation and Performance of the Heterostructured Material with a Ni-Rich Layered Oxide Core and a LiNi0.5Mn1.5O4-like Spinel Shell.

The LiNi1- x- yCo xAl yO2 (NCA)-layered materials are regarded as a research focus of power lithium-ion batteries (LIBs) because of their high capacity. However, NCA materials are still up against the defects of cation mixing and surface erosion of electrolytes. Herein, a novel design strategy is proposed to obtain a heterostructured cathode material with a high-capacity LiNi0.88Co0.09Al0.03O2 layer ( R3̅ m) core and a stable LiNi0.5Mn1.5O4-like spinel ( Fd3̅ m) shell, which is prepared through spontaneous redox reaction of the precursor with KMnO4 in an alkaline solution and subsequent calcination procedure. The structure, morphology, element distribution, and electrochemical performances of the as-prepared NCA are studied by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical techniques. The results show that the LiNi0.5Mn1.5O4-like spinel ( Fd3̅ m) shell layer with a robust cubic close-packed crystal structure is uniformly adhered to the surface of the NCA and can availably suppress the side reactions with the electrolyte and surface-phase transformation, which will facilitate insertion/extraction of Li+ ions during cycling. Benefiting from the enhanced structural stability and improved kinetics, the heterostructured NCA delivers a better cycling performance. The discharge specific capacity is as high as 153.7 mA h g-1 at 10 C, and even at high charge voltage of 4.5 V, the capacity retention can still increase 11% at 1 C (200 mA g-1) after 100 cycles. Besides, the material exhibits a prominent thermal stability of 248 °C at 4.3 V. Therefore, this novel structure design strategy can contribute to the development and commercialization of high-performance cathode materials for power LIBs.

A new synthesis of 2-chloro-2'-deoxyadenosine (Cladribine), CdA).

A new efficient route for the synthesis of 2-chloro-2';-deoxyadenosine (Cladribine), CdA) has been developed. The key step of this method was selective deprotection of the acetyl group at the 2' position; the 3', 5' acetyl groups were not affected. This can be accomplished efficiently with hydroxylamine hydrochloride and sodium acetate in pyridine. The 2' hydroxyl group was removed by the Barton-McCombie reaction. Using this strategy, CdA was prepared in five steps and 31.0% yields.