Interfacial Engineering of Zn Metal via a Localized Conjugated Layer for Highly Reversible Aqueous Zinc Ion Battery.

Aqueous zinc-ion batteries are regarded as promising and efficient energy storage systems owing to remarkable safety and satisfactory capacity. Nevertheless, the instability of zinc metal anodes, characterized by issues such as dendrite growth and parasitic side reactions, poses a significant barrier to widespread applications. Herein, we address this challenge by designing a localized conjugated structure comprising a cyclic polyacrylonitrile polymer (CPANZ), induced by a Zn2+-based Lewis acid (zinc trifluoromethylsulfonate) at a temperature of 120 °C. The CPANZ layer on the Zn anode, enriched with appropriate pyridine nitrogen-rich groups (conjugated cyclic -C=N-), exhibits a notable affinity for Zn2+ with ample deposition sites. This zincophilic skeleton not only serves as a protective layer to guide the deposition of Zn2+ but also functions as proton channel blocker, regulating the proton flux to mitigate the hydrogen evolution. Additionally, the strong adhesion strength of the CPANZ layer guarantees its sustained protection to the Zn metal during long-term cycling. As a result, the modified zinc electrode demonstrates long cycle life and high durability in both half-cell and pouch cells. These findings present a feasible approach to designing high performance aqueous anodes by introducing a localized conjugated layer.

CuOx/Cu nanorod skeleton supported Ru-doped CoO/NC nanocomposites for overall water splitting.

High overpotential and low stability are major challenges for hydrogen evolution reaction (HER)/oxygen evolution reaction (OER). Tuning the electronic structure of catalysts is regarded as a core strategy to enhance catalytic activity. Herein, we report CuOx/Cu nanorod skeleton supported Ru doped cobalt oxide/nitrogen-doped carbon nanocomposites (Ru-CoO/NC/CuOx/Cu, denoted as RCUF) as bifunctional catalysis. The one-dimensional/three-dimensional (1D/3D) nanostructure and defect-rich amorphous/crystalline phases of RCUF facilitates active site exposure and electron transport. Experimental characterization and density functional theory (DFT) calculation results indicate that Ru doping can optimize the electronic structure, which accelerates the water dissociation process and reduces the Gibbs free energy of the reaction intermediates. As expected, the optimal RCUF-900 exhibits low overpotential (25/205 mV at 10 mA cm-2) and high stability (100/100 h) for HER/OER. RCUF-900 has low voltage (1.54 V at 10 mA cm-2) and high stability (100 h) for overall water splitting. This work provides new insights into the design of advanced catalysts for overall water splitting.

Oxygen vacancies enhanced electrocatalytic water splitting of P-FeMoO4 initiated via phosphorus doping.

Transition metal oxides (TMOs) are abundant and cost-effective materials. However, poor conductivity and low intrinsic activity limit their application in electrolyzed water catalysts. Herein, we prepared P-FeMoO4 in situ on nickel foam (P-FMO@NF) by phosphorylation-modified FeMoO4 to optimize its electrocatalytic properties. Interestingly, phosphorus doping is accompanied by the generation of oxygen vacancies and surface phosphates. Oxygen vacancies accelerated Mo dissolution during the oxygen evolution reaction (OER), leading to the rapid reconfiguration of P-FMO@NF to FeOOH and regulating the electronic structure of P-FMO@NF. The formation of phosphates is caused by the substitution of some molybdates with phosphates, which further increases the amount of oxygen vacancies. Hence, the OER overpotential of P-FMO@NF at a current density of 10 mA cm-2 is only 206 mV, and the hydrogen evolution reaction (HER) overpotential is 154 mV. It was assembled into a water splitting cell with a voltage of just 1.59 V at 10 mA cm-2 and shows excellent stability over 50 h. These excellent electrocatalytic properties are mainly attributed to the oxygen vacancies, which improve the interfacial charge transfer properties of the catalysts. This study provides new insights into phosphorus doping and offers a new perspective on the design of electrocatalysts.

Insights into the SiO2 Stress Effect on the Electrochemical Performance of Si anode.

Silicon (Si) is regarded as the most potential anode material for next-generation lithium-ion batteries (LIBs). However, huge volume expansion hinders its commercial application. Here, a yolk-shell structural nitrogen-doped carbon coated Si@SiO2 is prepared by SiO2 template and HF etching method. The as-prepared composite exhibits superior cycling stability with a high reversible capacity of 577 mA h g-1 at 1 A g-1 after 1000 cycles. The stress effect of SiO2 on stabilizing the electrochemical performance of Si anode is systematically investigated for the first time. In situ thickness measurement reveals that the volume expansion thickness of Si@SiO2 upon charge-discharge is obviously smaller than Si, demonstrating the electrode expansion can be effectively inhibited to improve the cyclability. The density functional theory (DFT) calculation further demonstrates the moderate young's modulus and enhanced hardness after SiO2 coating contribute significantly to the mechanical reinforcement of overall Si@SiO2@void@NC composite. Various post-cycling electrode analyses also address the positive effects of inner stress from the Si core on effectively relieving the damage to electrode structure, facilitating the formation of a more stable inorganic-rich solid electrolyte interphase (SEI) layer. This study provides new insights for mechanical stability and excellent electrochemical performance of Si-based anode materials.

Surface reconstruction of RuO2/Co3O4 amorphous-crystalline heterointerface for efficient overall water splitting.

The rational construction of amorphous-crystalline heterointerface can effectively improve the activity and stability of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, RuO2/Co3O4 (RCO) amorphous-crystalline heterointerface is prepared via oxidation method. The optimal RCO-10 exhibits low overpotentials of 57 and 231 mV for HER and OER at 10 mA cm-2, respectively. Experimental characterization and density functional theory (DFT) results show that the optimized electronic structure and surface reconstruction endow RCO-10 with excellent catalytic activity. DFT results show that electrons transfer from RuO2 to Co3O4 through the amorphous-crystalline heterointerface, achieving electron redistribution and moving the d-band center upward, which optimizes the adsorption free energy of the hydrogen reaction intermediate. Moreover, the reconstructed Ru/Co(OH)2 during the HER process has low hydrogen adsorption free energy to enhance HER activity. The reconstructed RuO2/CoOOH during the OER process has a low energy barrier for the elementary reaction (O*→*OOH) to enhance OER activity. Furthermore, RCO-10 requires only 1.50 V to drive 10 mA cm-2 and maintains stability over 200 h for overall water splitting. Meanwhile, RCO-10 displays stability for 48 h in alkaline solutions containing 0.5 M NaCl. The amorphous-crystalline heterointerface may bring new breakthroughs in the design of efficient and stable catalysts.

Ultrastable Dendrite-Free Potassium Metal Batteries Enabled by Weakly-Solvated Electrolyte.

Potassium (K) metal is considered one of the most promising anodes for potassium metal batteries (PMBs) because of its abundant and low-cost advantages but suffers from serious dendritic growth and parasitic reactions, resulting in poor cyclability, low Coulombic efficiency (CE), and safety concerns. In this work, we report a localized high-concentration electrolyte (LHCE) consisting of potassium bis(fluorosulfonyl)imide (KFSI) in a cosolvent of 1,2-dimethoxyethane (DME) and 1,1,2,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) to solve the problems of PMBs. TTE as a diluent not only endows LHCE with advantages of low viscosity, good wettability, and improved conductivity but also solves the dendrite problem pertaining to K metal anodes. Using the formulation of LHCE, a CE of 98% during 800 cycles in the K||Cu cell and extremely stable cycling of over 2000 h in the K||K symmetric cell are achieved at a current density of 0.1 mA cm-2. In addition, the LHCE shows good compatibility with a Prussian Blue cathode, allowing almost 99% CE for the K||KFeIIFeIII(CN)6 full cell during 100 cycles. This promising electrolyte design realizes high-safety and energy-dense PMBs.

Synthesis of Ni3 B/Ni via Vacuum-Induced for Ultrahigh Stable and Efficient Methanol Oxidation.

Designing efficient catalysts to promote the electrochemical oxidation of anodes is the core of the development of electrochemical synthesis technologies, such as HER and CO2 RR. Here, a novel vacuum induction strategy is used to synthesize nickel boride/nickel (Ni3 B/Ni) heterostructure catalyst for electrochemical oxidation of methanol into formic acid. The catalyst has extremely high reactivity (only 146.9 mV overpotential at 10 mA cm-2 , the maximum current density reaches 555.70 mA mg-1 and 443.87 mA cm-2 ), ultra-high selectivity (Faraday efficiency of methanol conversion to formic acid is close to 100%), and ultra-long life (over 50 h at 100 mA cm-2 ). In-suit electrochemical impedance spectroscopy proved that MeOH is oxidized first and inhibits the phase transition of the electrocatalyst to the high-valent electrooxidation products, which not only enables the high selectivity of MeOH oxidation but also ensures high stability of the catalyst. The mechanism studies by density functional theory calculations show that the potential determining step, the formation of *CH2 O, occurs most favorably in the Ni3 B/Ni heterostructure. These results provide references for the development of MeOH oxidation catalysts with high activity, high stability, high selectivity, and low cost.

Characterization and Pharmacokinetic Profile of Herbs and Spices' Phytochemicals over 24 h after Consumption in Overweight/Obese Adults.

SCOPE: This study aims to characterize the phytochemicals in commonly consumed herbs/spices (H/S) in the United States and their pharmacokinetic profile (PK) over 24 h in humans after consumption. METHOD AND RESULTS: The clinical trial is a randomized, single-blinded, four-arm, 24 h, multi-sampling, single-center crossover design (Clincaltrials.gov NCT03926442) conducted in obese/overweight adults (n = 24, aged 37 ± 3 years, BMI = 28.4 ± 0.6 kg m-2 ). Study subjects consume a high-fat high-carbohydrate meal with salt and pepper (control) or the control meal with 6 g of three different H/S mixtures (Italian herb: rosemary, basil, thyme, oregano, and parsley in the same ratio; cinnamon; and pumpkin pie spice containing cinnamon, ginger, nutmeg, and allspice, the ratio is unknown). Three H/S mixtures are analyzed and 79 phytochemicals are tentatively identified and quantified. Following H/S consumption, 47 metabolites are tentatively identified and quantified in plasma samples. The PK data suggest that some metabolites appear in blood as early as 0.5 h while others can extend up to 24 h. CONCLUSION: Phytochemicals from H/S include in a meal are absorbed and undergo phase I and phase II metabolism and/or catabolized to phenolic acids peaking at different times.

Surface-Diluted LiMn6 Superstructure Units Utilizing PO4 3- Confined Ni-Doping Sites to Stabilize Li-Rich Layered Oxides.

Serious capacity and voltage degradation of Li-rich layered oxides (LLOs) caused by severe interfacial side reactions (ISR), structural instability, and transition metal (TM) dissolution during charge/discharge need to be urgently resolved. Here, it is proposed for the inaugural time that the confinement effect of PO4 3- dilutes the LiMn6 superstructure units on the surface of LLOs, while deriving a stable interface with phosphate compounds and spinel species. Combining theoretical calculations, diffraction, spectroscopy, and micrography, an in-depth investigation of the mechanism is performed. The results show that the modified LLO exhibits excellent anionic/cationic redox reversibility and ultra-high cycling stability. The capacity retention is increased from 72.4% to 95.4%, and the voltage decay is suppressed from 2.48 to 1.29 mV cycle-1 after 300 cycles at 1 C. It also has stable long cycling performance, with capacity retention improved from 40.2% to 81.9% after 500 cycles at 2 C. The excellent electrochemical performance is attributed to the diluted superstructure units on the surface of LLO inhibiting the TM migration in the intralayer and interlayer. Moreover, the stable interfacial layers alleviate the occurrence of ISR and TM dissolution. Therefore, this strategy can give some important insights into the development of highly stable LLOs.

Having Your Cake and Eating It Too: Electrode Processing Approach Improves Safety and Electrochemical Performance of Lithium-Ion Batteries.

A layered Li[NixCoyMn1-x-y]O2 (NCM)-based cathode is preferred for its high theoretical specific capacity. However, the two main issues that limit its practical application are severe safety issues and excessive capacity decay. A new electrode processing approach is proposed to synergistically enhance the electrochemical and safety performance. The polyimide's (PI) precursor is spin-coated on the LiNi0.5Co0.2Mn0.3O2 (NCM523) electrode sheet, and the homogeneous sulfonated PI layer is in situ produced by thermal imidization reaction. The PI-spin coated (PSC) layer provides improvements in capacity retention (86.47% vs 53.77% after 150 cycles at 1 C) and rate performance (99.21% enhancement at 5 C) as demonstrated by the NCM523-PSC||Li half-cell. The NCM523-PSC||graphite pouch full cell proves enhanced capacity retention (76.62% vs 58.58% after 500 cycles at 0.5 C) as well. The thermal safety of the NCM523-PSC cathode-based pouch cell is also significantly improved, with the critical temperature of thermal safety T1 (the beginning temperature of obvious self-heating temperature) and thermal runaway temperature T2 increased by 60.18 and 44.59 °C, respectively. Mechanistic studies show that the PSC layer has multiple effects as a passivation layer such as isolation of electrode-electrolyte contact, oxygen release suppression, solvation structure tuning, and the decomposition of carbonate solvents as well as LiPF6 inhibition. This work provides a new path for a cost-effective and scalable design of electrode decoration with synergistic safety-electrochemical kinetics enhancement.

A novel hierarchical book-like structured sodium manganite for high-stable sodium-ion batteries.

As one of the most promising cathodes for rechargeable sodium-ion batteries (SIBs), Layered transition metal oxides with high energy density show poor cycling stability. Judicious design/construction of electrode materials plays a very important role in cycling performance. Herein, a P2-Na0.7MnO2.05 cathode material with hierarchical book-like morphology combining exposed (100) active crystal facets is synthesized by hydrothermal method. Owing to the superiority of the unique hierarchical structure, the electrode delivers a high reversible capacity of 163 mA h g-1 at 0.2C and remarkable high-rate cyclability (88.8% capacity retention after 300 cycles at 10C). Its unique oriented stacking nanosheet constructed hierarchical book-like structure is the origin of the high electrochemical performance, which is able to shorten the diffusion distances of Na+ and electrons, and a certain gap between the nanosheets can also relieve the stress and strain of volume generated during the cycle. In addition, the exposed (100) active crystal facets can provide more channels for the efficient transfer of Na+. Our strategy reported here opens a door to the development of high-stable oxide cathodes for high energy density SIBs.

Mesoporous MgO enriched in Lewis base sites as effective catalysts for efficient CO2 capture.

Capturing CO2 has become increasingly important. However, wide industrial applications of conventional CO2 capture technologies are limited by their slow CO2 sorption and desorption kinetics. Accordingly, this research is designed to overcome the challenge by synthesizing mesoporous MgO nanoparticles (MgO-NPs) with a new method that uses PEG 1500 as a soft template. MgO surface structure is nonstoichiometric due to its distinctive shape; the abundant Lewis base sites provided by oxygen vacancies promote CO2 capture. Adding 2 wt % MgO-NPs to 20 wt % monoethanolamine (MEA) can increase the breakthrough time (the time with 90% CO2 capturing efficiency) by ∼3000% and can increase the CO2 absorption capacity within the breakthrough time by ∼3660%. The data suggest that MgO-NPs can accelerate the rate and increase CO2 desorption capacity by up to ∼8740% and ∼2290% at 90 °C, respectively. Also, the excellent stability of the system within 50 cycles is verified. These findings demonstrate a new strategy to innovate MEA absorbents currently widely used in commercial post-combustion CO2 capture plants.

Empowering Zn Electrode Current Capability Along Interfacial Stability by Optimizing Intrinsic Safe Organic Electrolytes.

Metallic Zn is one of the most promising anodes, but its practical application has been hindered by dendritic growth and serious interfacial reactions in conventional electrolytes. Herein, ionic liquids are adopted to prepare intrinsically safe electrolytes via combining with TEP or TMP solvents. With this synergy effect, the blends of TEP/TMP with an IL fraction of ≈25 wt% are found to be promising electrolytes, with ionic conductivities comparable to those of standard phosphate-based electrolytes while electrochemical stabilities are considerably improved; over 1000 h at 2.0 mA cm-2 and ≈350 h at 5.0 mA cm-2 with a large areal capacity of 10 mAh cm-2 . The use of functionalized IL turns out to be a key factor in enhancing the Zn2+ transport due to the interaction of Zn2+ ions with IL-zincophilic sites resulting in reduced interfacial resistance between the electrodes and electrolyte upon cycling leading to spongy-like highly porous, homogeneous, and dendrite-free zinc as an anode material.

P-Doped Cotton Stalk Carbon for High-Performance Lithium-Ion Batteries and Lithium-Sulfur Batteries.

Biomass as a carbon material source is the characteristic of green chemistry. Herein, a series of hierarchical P-doped cotton stalk carbon materials (HPCSCMs) were prepared from cheap and abundant biowaste cotton stalk. These materials possess a surface area of 3463.14 m2 g-1 and hierarchical pores. As lithium-ion battery (LIB) anodes, the samples exhibit 1100 mAh g-1 at 0.1 A g-1 after 100 cycles and hold 419 mAh g-1 at 1 A g-1 after 1000 cycles, with nearly 100% capacity retention. After HPCSCMs are loaded with sulfur (S/HPCSCMs), the samples (S/HPCSCMs-2) deliver a discharge capacity of 413 mAh g-1 at 0.1 A g-1 after 100 cycles as lithium-sulfur (Li-S) battery cathodes. This excellent electrochemical performance can be attributed to P in carbon networks, which not only provides more active sites, but also improves electrical conductivity.

Amylopectin-Assisted Fabrication of In Situ Carbon-Coated Na3V2(PO4)2F3 Nanosheets for Ultra-Fast Sodium Storage.

Na3V2(PO4)2F3 is one of the most studied polyanion type cathode materials for sodium-ion batteries (SIBs) and offers great promises. However, the inferior rate capability induced by its sluggish diffusion of electrons and ions greatly limits the practical application of electrode materials in SIBs. Herein, we develop an efficient method to fabricate in situ carbon-coated Na3V2(PO4)2F3 nanosheets by using cost-effective amylopectin. The amylopectin not only could induce the nucleation of Na3V2(PO4)2F3 along its backbone to form a 2D nanostructure, but also act as a source of amorphous carbon for in situ coating on the active material surface. The composite exhibits extraordinary rate capability (104 mA h g-1 at 40 C, 51 mA h g-1 at 150 C) and desirable cycling stability. Such satisfactory achievements, especially the superior rate performance, should be ascribed to its unique 2D nanostructure which shortens the Na+ diffusion length, and the in situ carbon coating endows the composites with effective electron transport. Even applied to full cells, the obtained devices still display an exceptionally high energy density (94.8 W h kg-1), high power density (7295 W kg-1), and excellent cyclic stability.

Fe2O3/MoO3@NG Heterostructure Enables High Pseudocapacitance and Fast Electrochemical Reaction Kinetics for Lithium-Ion Batteries.

Transition metal oxides (TMOs) hold great potential for lithium-ion batteries (LIBs) on account of the high theoretical capacity. Unfortunately, the unfavorable volume expansion and low intrinsic electronic conductivity of TMOs lead to irreversible structural degradation, disordered particle agglomeration, and sluggish electrochemical reaction kinetics, which result in perishing rate capability and long-term stability. This work reports an Fe2O3/MoO3@NG heterostructure composite for LIBs through the uniform growth of Fe2O3/MoO3 heterostructure quantum dots (HQDs) on the N-doped rGO (NG). Due to the synergistic effects of the "couple tree"-type heterostructures constructed by Fe2O3 and MoO3 with NG, Fe2O3/MoO3@NG delivers a prominent rate performance (322 mA h g-1 at 20 A g-1, 5.0 times higher than that of Fe2O3@NG) and long-term cycle stability (433.5 mA h g-1 after 1700 cycles at 10 A g-1). Theoretical calculations elucidate that the strong covalent Fe-O-Mo, Mo-N, and Fe-N bonds weaken the diffusion energy barrier and promote the Li+-ion reaction to Fe2O3/MoO3@NG, thereby facilitating the structural stability, pseudocapacitance contribution, and electrochemical reaction kinetics. This work may provide a feasible strategy to promote the practical application of TMO-based LIBs.

Endothelial Function and Postprandial Glucose Control in Response to Test-Meals Containing Herbs and Spices in Adults With Overweight/Obesity.

Objectives: Herbs and Spices (H/S) contain bioactive compounds with purported health benefits. This study investigated the effect of H/S intake on indicators of vascular and metabolic health over 24 h using a test-meal challenge paradigm in adults with overweight or obesity. Methods: In a randomized, single-blinded, 4-arm, 24 h, multi-sampling, crossover clinical trial, adults (n = 25) aged 36.6 ± 3.1 years with BMI 28.5 ± 0.6 kg/m2 (mean ± SEM) consumed a high-fat, high-carbohydrate challenge meal (~810 kcal) with salt/pepper only (control) or control with one of three different H/S combinations: Italian herb (rosemary, basil, thyme, oregano, and parsley), cinnamon, or pumpkin pie spice mix (cinnamon, ginger, nutmeg, and allspice) on four separate visits at least 3 days apart. Meals provided 35% of subjects' energy to maintain weight and ~1 g H/S per 135 kcal of the meal. Flow-mediated dilation (FMD) and blood samples were collected at 0, 1, 2, 4, 5.5, 7, and 24 h for endpoint analysis (additional blood draw at 0.5 h for insulin/glucose). Mixed-model analysis of repeated measures via PROC MIXED PC-SAS 9.4 was performed on the primary outcome (FMD) and secondary outcome variables. This study was registered at ClinicalTrials.gov (NCT03926442). Results: Italian herb and pumpkin spice meals significantly increased %FMD at 24 h compared to the control meal (P = 0.048 and P = 0.027, respectively). The cinnamon meal reduced postprandial glycemia (Δ) compared to control (P = 0.01), and pumpkin pie spice mix and cinnamon meals reduced postprandial insulin at 0.5 h compared to the control meal (P = 0.01 and P = 0.04, respectively). IL-6 and triglycerides increased in response to all meals (Time, P < 0.0001) but were not significantly different between meals. Conclusions: The test-meal challenge study design coupled with multiple sampling over 24 h provides insights into time-course bioactivity of H/S on vascular function and metabolic indices in overweight/obese adults. Clinical Trial Registration: ClinicalTrials.gov, identifier: NCT03926442.

Oxygen Vacancy Enhanced Two-Dimensional Lithium Titanate for Ultrafast and Long-Life Bifunctional Lithium Storage.

Boosting sufficient Li+ ion mobility in Li4Ti5O12 (LTO) is crucial for high-rate performance lithium storage. Here, an ultrafast charge storage oxygen vacancy two-dimensional (2D) LTO nanosheet was successfully fabricated through a one-pot hydrothermal method. The selectively doped Al3+ into octahedron Li+/Ti4+ 16d sites not only provide bulk oxygen vacancy and appropriate distorted TiO6 octahedra to facilitate Li+ ions diffusion, but also serve as a "pillar" to stabilize the Ti-O framework. The oxygen vacancy lowers Li+ ion diffusion energy barrier. Moreover, the 2D structure provides open diffusion channels for fast Li+ ion transport. As a result, the sample shows excellent electrochemical performance for bifunctional lithium storage. As a lithium-ion battery anode, the capacity retention reaches 112.8 mA h g-1 after 5000 cycles at 40 C with a fading rate of 0.288% per 100 cycles. Meanwhile, as a lithium-ion capacitor anode, it exhibits an excellent rate capacity of 120 mA h g-1 after 5000 cycles at 500 C with nearly 100% Coulombic efficiency. The produced LTO shows much higher rate capacity and longer lifetime than the reported LTO. Density functional theory calculations also demonstrate that oxygen vacancy can facilitate Li+ ion diffusion kinetics. The relationship between oxygen vacancy content and Li+ ions diffusion energy barrier in LTO is quantified. This work pioneers a defect engineering strategy for synthesized high-performance electrode materials.

Enhancing lithium ion diffusion kinetic in hierarchical lithium titanate@erbium oxide from coating to doping via facile one-step co-precipitation.

Hierarchical lithium titanate@erbium oxide (Li4Ti5O12@Er2O3) microspheres from coating to doping were successfully synthesised by a simple and scalable one-step co-precipitation method. Microscopic observations revealed that the Li4Ti5O12@Er2O3 microspheres present a well-defined hierarchical structure and that Li4Ti5O12 is coated by the Er2O3 layer. The X-ray photoelectron spectroscopy (XPS) results demonstrate that partial Ti4+ is reduced to Ti3+ and induces oxygen vacancy because partial Er3+ dope into octahedral 16d Li+/Ti4+ sites of Li4Ti5O12. Owing to the hierarchical microsphere structure, Er2O3 coating, and Er3+ doping, the material exhibits excess rate capacity (183.7 mAh g-1 at 30C). The hierarchical microsphere structure shortens the diffusion pathways for Li+ ions. The Er2O3 coating on the surface reduces the adverse interface reaction. Importantly, oxygen vacancy induced by Er3+ doping enhances Li+ ion diffusion kinetics and offers extra space to store Li+ ions, which endows this sample with excess rate capacity.

Bifunctional separator with sandwich structure for high-performance lithium-sulfur batteries.

Severe "Shuttle effect" and uncontrollable lithium-dendrite growth are ongoing challenges that hinder the practical application of Lithium-sulfur (Li-S) batteries. Herein, a bifunctional separator was modified by Al2O3 and carbon nanotubes (CNTs) via a facile method. Li-S battery assembled with the modified separator shows excellent cycling stability (760.4 mA h g-1 at 0.2 C after 100 cycles) and promising rate performance. The reason is ascribed to synergistic effect of CNTs and Al2O3 double coating layers, the strong physicochemical interaction between Al2O3 and the polysulfides could alleviate the shuttle effect, and the high conductivity of CNTs can facilitate the reaction kinetics of sulfur and its corresponding discharge products, respectively, which can improve the utilization ratio of sulfur. In addition, the double protection layers improve the hardness of the separator, as well as regulate Li+ ion deposition, which can effectively prevent the formation of lithium dendrites, thus the safety of the batteries are significant improved.