Design principles of heterointerfacial redox chemistry for highly reversible lithium metal anode.

High electrochemical reversibility is required for the application of high-energy-density lithium (Li) metal batteries; however, inactive Li formation and SEI (solid electrolyte interface)-instability-induced electrolyte consumption cause low Coulombic efficiency (CE). The prior interfacial chemical designs in terms of alloying kinetics have been used to enhance the CE of Li metal anode; however, the role of its redox chemistry at heterointerfaces remains a mystery. Herein, the relationship between heterointerfacial redox chemistry and electrochemical transformation reversibility is investigated. It is demonstrated that the lower redox potential at heterointerface contributes to higher CE, and this enhancement in CE is primarily due to the regulation of redox chemistry to Li deposition behavior rather than the formation of SEI films. Low oxidation potential facilitates the formation of the surface with the highly electrochemical binding feature after Li stripping, and low reduction potential can maintain binding ability well during subsequent Li plating, both of which homogenize Li deposition and thus optimize CE. In particular, Mg hetero-metal with ultra-low redox potential enables Li metal anode with significantly improved CE (99.6%) and stable cycle life for 700 cycles at 3.0 mA cm-2. This work provides insight into the heterointerfacial design principle of next-generation negative electrodes for highly reversible metal batteries.

Tailoring Li Deposition by Regulating Structural Connectivity of Electrochemical Li Reservoir in Li-metal Batteries.

Irregular Li deposition is the major reason for poor reversibility and cycle instability in Li metal batteries, even leading to safety hazards, the causes of which have been extensively explored. The structural disconnection induced by completely dissolving Li in the traditional testing protocol is a key factor accounting for irregular Li growth during the subsequent deposition process. Herein, the critical role played by the structural connectivity of electrochemical Li reservoir in subsequent Li deposition behaviors is elucidated and a morphology-performance correlation is established. The structural connection and resultant well-distributed morphology of the in situ electrochemical Li reservoir ensure efficient electron transfer and Li+ diffusion pathway, finally leading to homogenized Li nucleation and growth. Tailoring the geometry of Li reservoir can improve the coulombic efficiency and cyclability of anode-free Li metal batteries by optimizing Li deposition behavior.

Regulation of Interfacial Lattice Oxygen Activity by Full-Surface Modification Engineering towards Long Cycling Stability for Co-Free Li-Rich Mn-Based Cathode.

The construction of a protective layer for stabilizing anion redox reaction is the key to obtaining long cycling stability for Li-rich Mn-based cathode materials. However, the protection of the exposed surface/interface of the primary particles inside the secondary particles is usually ignored and difficult, let alone the investigation of the impact of the surface engineering of the internal primary particles on the cycling stability. In this work, an efficient method to regulate cycling stability is proposed by simply adjusting the distribution state of the boron nickel complexes coating layer. Theoretical calculation and experimental results display that the full-surface boron nickel complexes coating layer can not only passivate the activity of interface oxygen and improve its stability but also play the role of sharing voltage and protective layer to gradually activate the oxygen redox reaction during cycling. As a result, the elaborately designed cobalt-free Li-rich Mn-based cathode displays the highest discharge-specific capacity retentions of 91.1% after 400 cycles at 1 C and 94.3% even after 800 cycles at 5 C. In particular, the regulation strategy has well universality and is suitable for other high-capacity Li-rich cathode materials.

Artificial Post-Cycled Structure Modulation Towards Highly Stable Li-Rich Layered Cathode.

High-capacity Li-rich layered oxides (LLOs) suffer from severe structure degradation due to the utilization of hybrid anion- and cation-redox activity. The native post-cycled structure, composed of progressively densified defective spinel layer (DSL) and intrinsic cations mixing, is deemed as the hindrance of the rapid and reversible de/intercalation of Li+ . Herein, the artificial post-cycled structure consisting of artificial DSL and inner cations mixing is in situ constructed, which would act as a shield against the irreversible oxygen emission and undesirable transition metal migration by suppressing anion redox activity and modulating cation mixing. Eventually, the modified DSL-2% Li-rich cathode demonstrates remarkable electrochemical properties with a high discharge capacity of 187 mAh g-1 after 500 cycles at 2 C, and improved voltage stability. Even under harsh operating conditions of 50 °C, DSL-2% can provide a high discharge capacity of 168 mAh g-1 after 250 cycles at 2 C, which is much higher than that of pristine LLO (92 mAh g-1 ). Furthermore, the artificial post-cycled structure provides a novel perspective on the role of native post-cycled structure in sustaining the lattice structure of the lithium-depleted region and also provides an insightful universal design principle for highly stable intercalated materials with anionic redox activity.

Stainless Steel-Like Passivation Inspires Persistent Silicon Anodes for Lithium-Ion Batteries.

Passivation of stainless steel by additives forming mass-transport blocking layers is widely practiced, where Cr element is added into bulk Fe-C forming the Cr2 O3 -rich protective layer. Here we extend the long-practiced passivation concept to Si anodes for lithium-ion batteries, incorporating the passivator of LiF/Li2 CO3 into bulk Si. The passivation mechanism is studied by various ex situ characterizations, redox peak contour maps, thickness evolution tests, and finite element simulations. The results demonstrate that the passivation can enhance the (de)lithiation of Li-Si alloys, induce the formation of F-rich solid electrolyte interphase, stabilize the Si/LiF/Li2 CO3 composite, and mitigate the volume change of Si anodes upon cycling. The 3D passivated Si anode can fully retain a high capacity of 3701 mAh g-1 after 1500 cycles and tolerate high rates up to 50C. This work provides insight into how to construct durable Si anodes through effective passivation.

Challenge and Strategies in Room Temperature Sodium-Sulfur Batteries: A Comparison with Lithium-Sulfur Batteries.

Metal-sulfur batteries exhibit great potential as next-generation rechargeable batteries due to the low sulfur cost and high theoretical energy density. Sodium-sulfur (Na-S) batteries present higher feasibility of long-term development than lithium-sulfur (Li-S) batteries in technoeconomic and geopolitical terms. Both lithium and sodium are alkali metal elements with body-centered cubic structures, leading to similar physical and chemical properties and exposing similar issues when employed as the anode in metal-sulfur batteries. Indeed, some inspiration for mechanism researches and strategies in Na-S systems comes from the more mature Li-S systems. However, the dissimilarities in microscopic characteristics determine that Na-S is not a direct Li-S analogue. Herein, the daunting challenges derived by the differences of fundamental characteristics in Na-S and Li-S systems are discussed. And the corresponding strategies in Na-S batteries are reviewed. Finally, general conclusions and perspectives toward the research direction are presented based on the dissimilarities between both systems. This review attempts to provide important insights to facilitate the assimilation of the available knowledge on Li-S systems for accelerating the development of Na-S batteries on the basis of their dissimilarities.

In Situ Induced Lattice-Matched Interfacial Oxygen-Passivation-Layer Endowing Li-Rich and Mn-Based Cathodes with Ultralong Life.

The high capacity of Li-rich and Mn-based (LRM) cathode materials is originally due to the unique hybrid anion- and cation redox, which also induces detrimental oxygen escape. Furthermore, the counter diffusion of released oxygen (into electrolyte) and induced oxygen vacancies (into the interior bulk phase) that occurs at the interface will cause uncontrolled phase collapse and other issues. Therefore, due to its higher working voltage (>4.7 V) than the activation voltage of lattice oxygen in LRM (≈4.5 V), the anion-redox-free and structurally consistent cobalt-free LiNi0.5 Mn1.5 O4 (LNMO) is selected to in situ construct a robust, crystal-dense and lattice-matched oxygen-passivation-layer (OPL) on the surface of LRM particles by the electrochemical delithiation to protect the core layered components. As expected, the modified sample displays continuously decreasing interfacial impedance and high specific capacity of 135.5 mAh g-1 with a very small voltage decay of 0.67 mV per cycle after 1000 cycles at 2 C rate. Moreover, the stress accumulation during cycling is mitigated effectively. This semicoherent OPL strengthens the surface stability and interrupts the counter diffusion of oxygen and oxygen vacancies in LRM cathode materials, which would provide guidance for designing high-energy-density layered cathode materials.

Extraction and determination of tussilagone from Farfarae Flos with online solid-phase extraction-high-performance liquid chromatography using a homemade monolithic cartridge doped with porous organic cage material.

A solid-phase extraction cartridge was fabricated using diallyl isophthalate as the monomer with the addition of porous organic cage material via in situ free-radical polymerization in a stainless-steel column. The resulting monolithic adsorbent exhibited a relatively uniform porous structure, a high specific surface area of 113.98 m2 /g, and multiple functional chemical groups according to the characterization results. An online solid-phase extraction-high-performance liquid chromatography procedure was fabricated to extract and determine tussilagone from Farfarae Flos. The results show that the complex sample matrices can be removed in the solid-phase extraction procedure. Simultaneously, tussilagone can remain, which can be subsequently switched to an octadecylsilane bonded analytical column. The methodological validation showed that the correlation coefficient was 0.9999 with a linear range of 0.6-200.0 µg/mL, the limit of detection was 0.2 µg/mL, the limit of quantification was 0.6 µg/mL, accuracy was 100.3-100.6%, and relative standard deviation of precision was ≤1.9%. The present monolithic cartridge exhibits good reusability of not more than 100 times. The real sample of Farfarae Flos was determined with a tussilagone content of 0.74 mg/g.

Fabrication of a cycloalkyl-monolith for on-line solid-phase extraction and determination of four polyphyllins in plasma.

A cycloalkyl-based polymer monolithic column for solid-phase extraction was prepared via radical polymerization using cyclohexyl methacrylate as the monomer. The preparative conditions such as crosslinker/monomer ratio and the amount of the porogens were optimized and the resulting monoliths were characterized by scanning electron microscopy and nitrogen adsorption-desorption method. On-line solid-phase extraction-high-performance liquid chromatography was performed to quantitatively analyse polyphyllin I, II, VI and VII contained in herbal medicine of paridis rhizome in mouse plasma using the homemade optimized monolithic SPE column combined with a C18 column, in which water was used to remove the plasma matrix while the polyphyllins in the mouse plasma were eluted by acetonitrile-water (42:58, V/V). Results obtained from the method validation show that the present method is feasible for the quantitative analysis of the four polyphyllins in plasma. The developed method was further applied for the real mouse plasma sample. These results show that the homemade cycloalkyl-based polymer monolithic SPE column has good ability for clean-up of the interfering bio-matrix and simultaneously extracting the four polyphyllins from mouse plasma. Furthermore, the present method is a promising method for quantitative determination of saponins compounds from complex bio-samples with the advantages of simple and efficient.

A rapid method for on-line solid-phase extraction and determination of dioscin in human plasma using a homemade monolithic sorbent combined with high-performance liquid chromatography.

A phenyl-based polymer monolithic column was prepared via free radical polymerization in a stainless steel column with the size of 4.6 mm i.d. × 50 mm, using ethylene glycol phenyl ether acrylate as the monomer. The resulting monolithic column shows high porosity of 73.42% and relative uniform pore structure, as characterized by mercury porosimetry and scanning electron microscopy, respectively. The optimized polymer monolith column was used for on-line solid-phase extraction prior to the reversed phase mode HPLC-UV analysis for the determination of dioscin in human plasma, using a COSMOSIL C18 column (4.6 mm × 150 mm, 4.5 µm). Water was used to wash non-retained components from the SPE sorbent, and methanol water (80:20, V/V) was used as the mobile phase for isocratic elution of dioscin. The maximum adsorbed quantity of dioscin to the SPE column is 6.79 mg/g, which is high enough for the quantitative analysis of dioscin in plasma, due to the low content of dioscin in plasma. The method was validated by assessing the linearity, lower limit of quantification, intra- and inter-day precision, accuracy, and repeatability. The developed method was applied for the analysis of dioscin in plasma from a volunteer who had orally administered an aqueous extract of dioscorea nipponica rhizome, showing the method capable of detecting dioscin in the plasma. These results show that the developed method is a rapid method for on-line solid-phase extraction and determination of dioscin from plasma, exhibiting good selectivity with hydrogen bond interaction and hydrophobic interaction, good clean-up ability, cost-saving, and time-saving. Graphical abstract.

Lithium Deficiencies Engineering in Li-Rich Layered Oxide Li1.098Mn0.533Ni0.113Co0.138O2 for High-Stability Cathode.

Li-rich layered oxides have been in focus because of their high specific capacity. However, they usually suffer from poor kinetics, severe voltage decay, and capacity fading. Herein, a long-neglected Li-deficient method is demonstrated to address these problems by simply reducing the lithium content. Appropriate lithium vacancies can improve dynamics features and induce in situ surface spinel coating and nickel doping in the bulk. Therefore, the elaborately designed Li1.098Mn0.533Ni0.113Co0.138O2 cathode possesses improved initial Coulombic efficiency, excellent rate capability, largely suppressed voltage decay, and outstanding long-term cycling stability. Specifically, it shows a superior capacity retention of 93.1% after 500 cycles at 1 C (250 mA g-1) with respect to the initial discharge capacity (193.9 mA h g-1), and the average voltage still exceeds 3.1 V. In addition, the discharge capacity at 10 C can be as high as 132.9 mA h g-1. More importantly, a Li-deficient cathode can also serve as a prototype for further performance enhancement, as there are plenty of vacancies.

High-Performance Na-O2 Batteries Enabled by Oriented NaO2 Nanowires as Discharge Products.

Na-O2 batteries are emerging rechargeable batteries due to their high theoretical energy density and abundant resources, but they suffer from sluggish kinetics due to the formation of large-size discharge products with cubic or irregular particle shapes. Here, we report the unique growth of discharge products of NaO2 nanowires inside Na-O2 batteries that significantly boosts the performance of Na-O2 batteries. For this purpose, a high-spin Co3O4 electrocatalyst was synthesized via the high-temperature oxidation of pure cobalt nanoparticles in an external magnetic field. The discharge products of NaO2 nanowires are 10-20 nm in diameter and ∼10 µm in length, characteristics that provide facile pathways for electron and ion transfer. With these nanowires, Na-O2 batteries have surpassed 400 cycles with a fixed capacity of 1000 mA h g-1, an ultra-low over-potential of ∼60 mV during charging, and near-zero over-potential during discharging. This strategy not only provides a unique way to control the morphology of discharge products to achieve high-performance Na-O2 batteries but also opens up the opportunity to explore growing nanowires in novel conditions.

3D Graphene Encapsulated Hollow CoSnO3 Nanoboxes as a High Initial Coulombic Efficiency and Lithium Storage Capacity Anode.

3D Graphene sheets encapsulated amorphous hollow CoSnO3 nanoboxes (H-CoSnO3 @reduced graphene oxide [RGO]) are successfully fabricated by first preparing 3D graphene oxides encapsulated solid CoSn(OH)6 nanocubes, followed by an alkaline etching process and subsequent heating treatment in Ar. The hollow CoSnO3 nanoboxes with average particle size of 230 nm are uniformly and tightly encapsulated by RGO sheets. As an anode material for Li-ion batteries, H-CoSnO3 @RGO displays high initial Coulombic efficiency of 87.1% and large reversible capacity of 1919 mA h g-1 after 500 cycles at the current density of 500 mA g-1 . Moreover, excellent rate capability (1250, 1188, 1141, 1115, 1086, 952, 736, and 528 mA h g-1 at 100, 200, 300, 400, 500, 1000, 2000, and 5000 mA g-1 , respectively) is acquired. The reasons for excellent lithium storage properties of H-CoSnO3 @RGO are discussed in detail.

Phase-controlled synthesis and magnetic properties of cubic and hexagonal CoO nanocrystals.

We report facile solution approaches for the phase-controlled synthesis of rock-salt cubic CoO (c-CoO) and wurtzite-type hexagonal CoO (h-CoO) nanocrystals. In the syntheses, the cobalt precursor cobalt (II) stearate is decomposed in 1-octadecene at 320 °C, and the crystalline phase of synthesized products depend critically on the amounts of H2O. While the presence of small amounts of H2O promotes the generation of c-CoO, h-CoO is obtained in the absence of H2O. The as-prepared c-CoO nanocrystals exhibit a multi-branched morphology with several short rods growing on the 〈100〉 direction interlaced together whereas the h-CoO nanocrystals show a multi-rod structure with several rods growing on the same base facet along the c-axis. The formation mechanisms are discussed on the basis of FTIR spectrometry data and color changes of the reaction mixture. Finally the magnetic properties of as-prepared CoO nanocrystals are measured and the results show that c-CoO nanocrystals are intrinsically antiferromagnetic with a Néel temperature of about 300 K but the antiferromagnetic ordering is not distinct for the h-CoO nanocrystals. Weak ferromagnetic contributions are also observed for both c-CoO and h-CoO nanocrystals with obvious magnetic hysteresis at 5 and 300 K. The uncompensated spins that can be induced by crystalline defects such as cation-vacancy may account for the observed weak ferromagnetism.

Nanoring Arrays on Fe Coated Substrate: Formation and Guidance for the Growth of Hierarchical CNTs.

In this article, we report the formation of nanoring structures on Fe coated substrate and their application in guiding the growth of carbon nanotube (CNT) patterns with hierarchical structures. The formation of nanorings involves the etching of polystyrene (PS) monolayer colloidal crystals (MCCs) under reactive ion etching (RIE), and the redeposition and cross-linkage of the active degradation products at the contact line between the MCCs and the substrate. After washing out the MCCs, insoluble nanorings with hexagonal order on the substrate are developed. The RIE process can control the morphology of the nanorings, as well as the distribution of the Fe element on the substrate; thus, a continuous Fe layer and separated Fe discs on the substrate are created on substrate after washing, depending on the etching time and the shield of MCCs. The surviving Fe element can work as the catalyst to initiate the in situ growth of aligned CNTs in the following chemical vapor deposition (CVD) process, while the Fe element underneath the nanorings keep its inactivity. Eventually, CNT patterns with hierarchical structures are formed. One level originates from the surviving Fe layer; the other level is templated from the nanoring structures, which cause the blank area in the CNT bundles.

Enhanced anomalous Hall effect in Fe nanocluster assembled thin films.

An enhanced anomalous Hall effect is observed in heterogeneous uniform Fe cluster assembled films with different film thicknesses (ta = 160-1200 nm) fabricated by a plasma-gas-condensation method. The anomalous Hall coefficient (Rs) at ta = 1200 nm reaches its maximum of 2.4 × 10(-8) Ω cm G(-1) at 300 K, which is almost four orders of magnitude larger than bulk Fe. The saturated Hall resistivity (ρ(A)xy) first increases and then decreases with the increase of temperature accompanied by a sign change from positive to negative. Analysis of the results revealed that ρ(A)xy decreases with increasing longitudinal resistivity (ρxx) on a double-logarithmic scale and obeys a new scaling relation of log(ρ(A)xy/ρxx) = a0 + b0 log ρxx.

Bi-magnetic Mn3O4@Ni core-shell binary superparticles: Self-assembly preparation and magnetic behaviors.

Binary superparticles formed by self-assembling two different types of nanoparticles may utilize the synergistic interactions and create advanced multifunctional materials. Bi-magnetic superparticles with a core-shell structure have unique properties due to their specific spatial configurations. Herein, we built Mn3O4@Ni core-shell binary superparticles via an emulsion self-assembly technique. The superparticles are generated with a spherical morphology, and have a typical average size of about 240 nm. By altering the ratio of the two magnetic nanoparticles, the thickness of Ni shells can be adjusted. Oleic acid ligands are crucial for the formation of core-shell structure. Magnetic analysis suggests that core-shell superparticles display dual-phase magnetic interactions, contrasting with the single-phase magnetic behaviors of commonly core-shell magnetic nanoparticles. The calculation on the effective magnetic anisotropy constants indicates that the presence of Ni shell layers reduces the dipole interactions among the Mn3O4 core particles. Due to the presence of Ni nanoparticle shells, the blocking temperature of Mn3O4 is reduced, while the Curie temperature of Mn3O4 is independent on Ni content. Tunable magnetic properties can be achieved by modulating the Ni nanoparticle shell thickness. This study offers insights for the development of core-shell superparticles with varied magnetic characteristics.

High-Voltage All-Solid-State Thin-Film Lithium Batteries Enabled by LiF Interlayer.

All-solid-state thin-film lithium batteries (TFBs) with high voltage are crucial for powering microelectronics systems. However, the issues of interfacial instability and poor solid contact of cathode/electrolyte films have limited their application. In this work, the preferentially orientated LiCoO2 (LCO) nanocolumns and the LCO/LiPON/Li TFBs are fabricated by in situ heating sputtering. By introducing the LiF interlayer, the solid contact of the LCO/LiPON interface is improved, enabling the high-voltage TFBs. The elemental diffusion, morphology change, and interfacial deterioration are suppressed, as demonstrated by various in situ and ex situ tests. As a result, the LCO/LiF/LiPON/Li TFB exhibits a more stable and higher capacity compared to other TFBs. This work provides guidance to improve the solid contact of TFBs and increase the performance of all-solid-state lithium batteries.

Fusing Ta-doped Li7La3Zr2O12 grains using nanoscale Y2O3 sintering aids for high-performance solid-state lithium batteries.

Solid-state lithium batteries have advantages of high energy density and usage safety and are considered as promising next-generation power sources. Among them, the garnet-type oxide electrolyte has become a widely studied inorganic electrolyte due to its high ionic conductivity and chemical stability. In this paper, nanoscale Y2O3 (NYO) particles are introduced as sintering aids for fabricating Ta-doped Li7La3Zr2O12 (LLZTO) ceramics, and the sintering effects of various NYO ratios on the properties of LLZTO are investigated. Among the samples, the LLZTO-5%NYO sample exhibits the highest ionic conductivity (7.39 × 10-4 S cm-1) and the lowest activation energy (0.17 eV). At various current densities, the polarization voltage of LLZTO-5%NYO is also the lowest without a short circuit. The full cells of LFP|LLZTO-5%NYO|Li exhibit a high capacity of 163.9 mA h g-1 with a high initial coulombic efficiency of 97.4%, and the capacity retention rate is up to 98.1% after 50 cycles. This work may inspire the development of analogous solid-state electrolytes and lithium batteries.

An autotransferable alloy overlayer toward stable sodium metal anodes.

Sodium (Na) metal anodes receive significant attention due to their high theoretical specific energy and cost-effectiveness. However, the high reactivity of Na foil anodes and the irregular surfaces have posed challenges to the operability and reliability of Na metals in battery applications. In the absence of inert environmental protection conditions, constructing a uniform, dense, and sodiophilic Na metal anode surface is crucial for homogenizing Na deposition, but remains less-explored. Herein, we fabricated a Tin (Sn) nanoparticle-assembled film conforming to separator pores, which provided ample space for accommodating volumetric expansion during the Na alloying process. Subsequently, a seamless Na-Sn alloy overlayer was formed and transferred onto the Na foil during Na plating through a separator-assisted technique, thereby overcoming conventional operational limitations of metallic Na. As compared to traditional volumetrically expanded cracked ones, the present autotransferable, highly sodiophilic, ion-conductive, and seamless Na-Sn alloy overlayer serves as uniform nucleation sites, thereby reducing nucleation and diffusion barriers and facilitating the compact deposition of metallic Na. Consequently, the autotransferable alloy layer enables a high average Coulombic efficiency of 99.9 % at 3.0 mA cm-2 and 3.0 mAh cm-2 in the half cells as well as minimal polarization overpotentials in symmetric cells, both during prolonged cycling 1200 h. Furthermore, the assembled Na||Sn-1.0h-PP||Na3V2(PO4)3@C@CNTs full cell delivers high capacity retention of 97.5 % after 200 cycles at a high cathodic mass loading.