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Anti-perovskite type Li2 OHCl was previously studied as a solid-state Li+ conductor. Here, we report that the Li2 OHCl can be electrolyzed at 3.3 V or 4.0 V, with the creation of O2 /HCl gases and the release of 2 equiv. Li+ via two different decomposition routes, depending on the acidity of electrolyte. In the electrolyte with trace acid, the Li2 OHCl is oxidized at a constant voltage of 3.3 V. In neutral electrolyte, the oxidization of Li2 OHCl starts at 4.0 V, but the produced HCl will increase the acidity of electrolyte and lead to a voltage drop to 3.3 V for the electrolysis of Li2 OHCl. The electrolysis of Li2 OHCl delivers a lithium releasing capacity as high as 810 mAh g-1 , with an equivalent Li-deposition or Li-intercalation on anode, making it a promising candidate as a Li reservoir for prelithiation of anode. Using Li2 OHCl as the lithium source, silicon-carbon (Si@C) composite anode can be effectively prelithiated. The full cells composed of LiNi0.8 Mn0.1 Co0.1 O2 (NMC811) cathode and prelithiated Si@C anode exhibited increased capacities with the increment of prelithiation dosages.

The application of flexible, robust, and low-cost solid polymer electrolytes in next-generation all-solid-state lithium metal batteries has been hindered by the low room-temperature ionic conductivity of these electrolytes and the small critical current density of the batteries. Both issues stem from the low mobility of Li+ ions in the polymer and the fast lithium dendrite growth at the Li metal/electrolyte interface. Herein, Mg(ClO4)2 is demonstrated to be an effective additive in the poly(ethylene oxide) (PEO)-based composite electrolyte to regulate Li+ ion transport and manipulate the Li metal/electrolyte interfacial performance. By combining experimental and computational studies, we show that Mg2+ ions are immobile in a PEO host due to coordination with ether oxygen and anions of lithium salts, which enhances the mobility of Li+ ions; more importantly, an in-situ formed Li+-conducting Li2MgCl4/LiF interfacial layer homogenizes the Li+ flux during plating and increases the critical current density up to a record 2 mA cm-2. Each of these factors contributes to the assembly of competitive all-solid-state Li/Li, LiFePO4/Li, and LiNi0.8Mn0.1Co0.1O2/Li cells, demonstrating the importance of surface chemistry and interfacial engineering in the design of all-solid-state Li metal batteries for high-current-density applications.

By increasing the charging voltage, a cell specific energy of >400 W h kg−1 is achievable with LiNi0.8Mn0.1Co0.1O2 in Li metal batteries. However, stable cycling of high-nickel cathodes at ultra-high voltages is extremely challenging. Here we report that a rationally designed sulfonamide-based electrolyte enables stable cycling of commercial LiNi0.8Co0.1Mn0.1O2 with a cut-off voltage up to 4.7 V in Li metal batteries. In contrast to commercial carbonate electrolytes, the electrolyte not only suppresses side reactions, stress-corrosion cracking, transition-metal dissolution and impedance growth on the cathode side, but also enables highly reversible Li metal stripping and plating leading to a compact morphology and low pulverization. Our lithium-metal battery delivers a specific capacity >230 mA h g−1 and an average Coulombic efficiency >99.65% over 100 cycles. Even under harsh testing conditions, the 4.7 V lithium-metal battery can retain >88% capacity for 90 cycles, advancing practical lithium-metal batteries. Charging at high voltages in principle makes batteries energy dense, but this is often achieved at the cost of the cycling stability. Here the authors design a sulfonamide-based electrolyte to enable a Li metal battery with a state-of-the-art cathode at an ultra-high voltage of 4.7 V while maintaining cyclability.

Sulfide solid electrolytes (e.g., lithium thiophosphates) have the highest room-temperature ionic conductivity (∼10−2 S cm−1) among solid Li-ion conductors so far, and thus have attracted ever-increasing attention for high energy-density and safety all-solid-state batteries (ASSBs). However, interfacial issues between sulfide electrolytes and electrodes have been the main challenges for their applications in ASSBs. The interfacial instabilities would occur due to side reactions of sulfides with electrodes, poor solid-solid contact, and lithium dendrites during charge/discharge cycling. In this review, we analyze the interfacial issues in ASSBs based on sulfide electrolytes, and in particular, discuss strategies for solving these interfacial issues and stabilize the electrode-electrolyte interfaces. Moreover, a perspective of the interfacial engineering for sulfide-based ASSBs is provided.

Patterning graphene with a spatially periodic potential provides a powerful means to modify its electronic properties1–3. In particular, in twisted bilayers, coupling to the resulting moire superlattice yields an isolated flat band that hosts correlated many-body phases4,5. However, both the symmetry and strength of the effective moire potential are constrained by the constituent crystals, limiting its tunability. Here, we have exploited the technique of dielectric patterning6 to subject graphene to a one-dimensional electrostatic superlattice (SL)1. We observed the emergence of multiple Dirac cones and found evidence that with increasing SL potential the main and satellite Dirac cones are sequentially flattened in the direction parallel to the SL basis vector, behaviour resulting from the interaction between the one-dimensional SL electric potential and the massless Dirac fermions hosted by graphene. Our results demonstrate the ability to induce tunable anisotropy in high-mobility two-dimensional materials, a long-desired property for novel electronic and optical applications7,8. Moreover, these findings offer a new approach to engineering flat energy bands where electron interactions can lead to emergent properties9. Dielectric patterning allows tunable anisotropy in high-mobility one-dimensional graphene electrostatic superlattices.

Despite of the good stability with Li-metal, Li6.75 La3 Zr1.75 Ta0.25 O12 (LLZTO) suffers from large interfacial resistance and severe Li-metal penetration. Herein, a dual layer ceramic electrolyte of Ti-doped LLZTO(Ti-LLZTO)/LLZTO was developed, with the reducible Ti-LLZTO layer contacting Li-metal and the LLZTO layer contacting cathode. The identical crystal structures of Ti-LLZTO and LLZTO enables a seamless contact and a barrierless Li+ transport between them. The densities of Ti-LLZTO pellets are higher than that of LLZTO. With an in situ reduction of Ti-LLZTO by Li-metal, the interfacial wettability was improved and a mixed ion-electron conducting layer was created. Both features help to reduce defects/pores on interface and homogenize the interfacial ionic/electronic flux, facilitating the reduction of interfacial resistance and suppression of dendrites. With the help of Ti-LLZTO layer, long-term stable lithium plating/stripping was reached in an areal capacity of 3.0 mAh cm-2 .

Most Li+/Na+-conducting solid electrolytes are unstable in moisture, and the formed hydroxides and carbonates on their surfaces result in the increase of the interfacial resistance between solid el...

Controllable synthesis of atomically ordered intermetallic nanoparticles (NPs) is crucial to obtain superior electrocatalytic performance for fuel cell reactions, but still remains arduous. Herein, we demonstrate a novel and general hydrogel-freeze drying strategy for the synthesis of reduced graphene oxide (rGO) supported Pt3 M (M=Mn, Cr, Fe, Co, etc.) intermetallic NPs (Pt3 M/rGO-HF) with ultrasmall particle size (about 3 nm) and dramatic monodispersity. The formation of hydrogel prevents the aggregation of graphene oxide and significantly promotes their excellent dispersion, while a freeze-drying can retain the hydrogel derived three-dimensionally (3D) porous structure and immobilize the metal precursors with defined atomic ratio on GO support during solvent sublimation, which is not afforded by traditional oven drying. The subsequent annealing process produces rGO supported ultrasmall ordered Pt3 M intermetallic NPs (≈3 nm) due to confinement effect of 3D porous structure. Such Pt3 M intermetallic NPs exhibit the smallest particle size among the reported ordered Pt-based intermetallic catalysts. A detailed study of the synthesis of ordered intermetallic Pt3 Mn/rGO catalyst is provided as an example of a generally applicable method. This study provides an economical and scalable route for the controlled synthesis of Pt-based intermetallic catalysts, which can pave a way for the commercialization of fuel cell technologies.

Li+ -conducting oxides are considered better ceramic fillers than Li+ -insulating oxides for improving Li+ conductivity in composite polymer electrolytes owing to their ability to conduct Li+ through the ceramic oxide as well as across the oxide/polymer interface. Here we use two Li+ -insulating oxides (fluorite Gd0.1 Ce0.9 O1.95 and perovskite La0.8 Sr0.2 Ga0.8 Mg0.2 O2.55 ) with a high concentration of oxygen vacancies to demonstrate two oxide/poly(ethylene oxide) (PEO)-based polymer composite electrolytes, each with a Li+ conductivity above 10-4 S cm-1 at 30 °C. Li solid-state NMR results show an increase in Li+ ions (>10 %) occupying the more mobile A2 environment in the composite electrolytes. This increase in A2-site occupancy originates from the strong interaction between the O2- of Li-salt anion and the surface oxygen vacancies of each oxide and contributes to the more facile Li+ transport. All-solid-state Li-metal cells with these composite electrolytes demonstrate a small interfacial resistance with good cycling performance at 35 °C.

The unclear Li+ local environment and Li+ conduction mechanism in solid polymer electrolytes, especially in a ceramic/polymer composite electrolyte, hinder the design and development of a new composite electrolyte. Moreover, both the low room-temperature Li+ conductivity and large interfacial resistance with a metallic lithium anode of a polymer membrane limit its application below a relatively high temperature. Here we have identified the Li+ distribution and Li+ transport mechanism in a composite polymer electrolyte by investigating a new solid poly(ethylene oxide) (PEO)-based NASICON-LiZr2(PO4)3 composite with 7Li relaxation time and 6Li → 7Li trace-exchange NMR measurements. The Li+ population of the two local environments in the composite electrolytes depends on the Li-salt concentration and the amount of ceramic filler. A composite electrolyte with a [EO]/[Li+] ratio n = 10 and 25 wt % LZP filler has a high Li+ conductivity of 1.2 × 10-4 S cm-1 at 30 °C and a low activation energy owing to the additional Li+ in the mobile A2 environment. Moreover, an in situ formed solid electrolyte interphase layer from the reaction between LiZr2(PO4)3 and a metallic lithium anode stabilized the Li/composite-electrolyte interface and reduced the interfacial resistance, which provided a symmetric Li/Li cell and all-solid-state Li/LiFePO4 and Li/LiNi0.8Co0.1Mn0.1O2 cells a good cycling performance at 40 °C.

In this work, a thin-film transistor gas sensor based on the p-N heterojunction is fabricated by stacking chemical vapor deposition-grown tungsten disulfide (WS2) with a sputtered indium–gallium–zi...

Two-dimensional (2D) hybrid perovskite sandwiched between two long-chain organic layers is an emerging class of low-cost semiconductor materials with unique optical properties and improved moisture stability. Unlike conventional semiconductors, ion migration in perovskite is a unique phenomenon possibly responsible for long carrier lifetime, current–voltage hysteresis, and low-frequency giant dielectric response. While there are many studies of ion migration in bulk hybrid perovskite, not much is known for its 2D counterparts, especially for ion migration induced by light excitation. Here, we construct an exfoliated 2D perovskite/carbon nanotube (CNT) heterostructure field effect transistor (FET), not only to demonstrate its potential in photomemory applications, but also to study the light induced ion migration mechanisms. We show that the FET I–V characteristic curve can be regulated by light and shows two opposite trends under different CNT oxygen doping conditions. Our temperature-dependent study indicates that the change in the I–V curve is probably caused by ion redistribution in the 2D hybrid perovskite. The first principle calculation shows the reduction of the migration barrier of I vacancy under light excitation. The device simulation shows that the increase of 2D hybrid perovskite dielectric constant (enabled by the increased ion migration) can change the I–V curve in the trends observed experimentally. Finally, the so synthesized FET shows the multilevel photomemory function. Our work shows that not only we could understand the unique ion migration behavior in 2D hybrid perovskite, it might also be used for many future memory function related applications not realizable in traditional semiconductors., A two-dimensional perovskite/carbon nanotube heterostructure was constructed not only to study light induced ion migration mechanisms, but also to demonstrate its potential in photomemory applications.

MXenes have attracted great attention for their potential applications in electrochemical and electronic devices due to their excellent characteristics. Traditional sound sources based on the thermoacoustic effect demonstrated that a conductor needs to have an extremely low heat capacity and high thermal conductivity. Hence, a thin MXene film with a low heat capacity per unit area (HCPUA) and special layered structure is emerging as a promising candidate to build loudspeakers. However, the use of MXenes in a sound source device has not been explored. Herein, we have successfully prepared sound source devices on an anodic aluminum oxide (AAO) and a flexible polyimide (PI) substrates by using the prepared Ti3C2 MXene nanoflakes. Due to the larger interlayer distance of MXene, the MXene-based sound source device has a higher sound pressure level (SPL) than that of graphene of the same thickness. High-quality Ti3C2 MXene nanoflakes were fabricated by selectively etching the Ti3AlC2 powder. The as-fabricated MXene sound source device on an AAO substrate exhibits a higher SPL of 68.2 dB (f = 15 kHz) and has a very stable sound spectrum output with frequency varying from 100 Hz to 20 kHz. A theoretical model has been built to explain the mechanism of the sound source device on an AAO substrate, matching well with the experimental results. Furthermore, the MXene sound source device based on a flexible PI substrate has been attached to the arms, back of the hand, and fingers, indicating an excellent acoustic wearability. Then, the MXene film is packaged successfully into a commercial earphone case and shows an excellent performance at high frequencies, which is very suitable for human audio equipment.

Lithium-sulfur (Li-S) batteries have been explored extensively for high-capacity electric-power storage, but their practical application has been prevented by severe issues stemming from the use of a lithium anode and an organic-liquid electrolyte in which Li2Sx intermediates of the cell discharge reaction are soluble and shuttle to the anode. Both problems are addressed using bis(4-nitrophenyl) carbonate as an additive in the organic-liquid electrolyte. The soluble Li2Sx polysulfides react with the additive to create insoluble polysulfides with a lithium byproduct; this byproduct reacts with the Li-metal anode to create an anode passivation layer that is a good Li+ conductor, which allows for safe and rapid plating/stripping of lithium metal with a low impedance.

A self-standing, flexible and lithium dendrite growth-suppressing composite gel polymer electrolyte membrane was designed for the use of room-temperature lithium ion batteries. The multi-functional composite semi-interpenetrating polymer network (referred to as “Cs-IPN”) electrolyte membrane was fabricated by combining a UV-cured ethoxylated trimethylolpropane triacrylate (ETPTA) macromer with alumina nanoparticles in the presence of liquid electrolyte and thermoplastic linear poly(ethylene oxide) (PEO). The polymer electrolyte membrane exhibits a semi-interpenetrating polymer network structure and a higher room temperature ionic conductivity, which impart the electrolyte with a significant cycling (120 mAh g−1 after 200 cycles) and a remarkable rate (137 mAh g−1 at 0.1 °C, 130 mAh g−1 at 0.5 °C, 119 mAh g−1 at 1 °C and 100 mAh g−1 at 2 °C) performance in Li/LiFePO4 battery. More importantly, the polymer electrolyte possesses superior ability to inhibit the growth of lithium dendrites, which makes it promising for next generation lithium ion batteries. Keywords: Gel polymer electrolytes, Semi-interpenetrating polymer network, UV-Cured reaction, Ionic conductivity, Lithium ion batteries

A porous material composed of nano-columnar Tetra-β-(4-nitro) yttrium phthalocyanine (TNY-Pc) with a sandwich-type layered structure is synthesized and characterized as a negative electrode for rechargeable lithium-ion batteries. The X-ray diffraction and transmission electron microscopy measurement confirmed that the sandwich layer structure has a stable interlayer spacing of 3.07 A. The TNY-Pc negative electrode is stable during charge/discharge, and the lithium cell with the TNY-Pc negative electrode exhibits a high reversible capacity of 730 mAh g−1 with a high initial coulombic efficiency of 96%; the capacity remains 610 mAh g−1 after 1150 cycles. The cell shows a good rate performance with a capacity of 370 mAh g−1 at 3 A g−1. The XRD, TEM and XPS analysis results suggest that N=O double bond on a substituted nitro group of phthalocyanine ring and C=C double bond on phthalocyanine conjugate structure are the two major contributors to the large capacity of lithium intercalation.

Lithium metal has long been regarded as one of the most promising anode materials for future rechargeable batteries. However, the severe reaction of Li with carbonate electrolytes and the rapid growth of Li-dendrites at high current densities hinder its practical application in Li-metal batteries. Here we report a polar polymer protective layer to suppress highly corrosive cyclic carbonates by tuning polymer–solvent interactions. The CN groups of polyacrylonitrile (PAN) polymer chains in the polar polymer network can effectively reduce high reactivity of the CO groups of carbonate solvents leading to a stable solid electrolyte interphase (SEI) layer with higher inorganic components. In situ optical and electron microscopes demonstrate that the polar polymer network effectively restrained the formation and growth of Li-dendrites, which helps to stabilize the plating/stripping behavior of Li in a symmetric Li|Li cell and a Li|LiNi1/3Co1/3Mn1/3O2 cell. This study provides a useful perspective of controlling electrolyte coordination to form a stable SEI layer in carbonate electrolytes for Li-metal batteries.

Due to the abundance of sodium sources and relatively high safety, sodium-ion batteries (SIBs) are considered as a promising candidate for next-generation large-scale energy storage systems. However, currently the lack of suitable anode materials is limiting the development of SIBs. Metal oxides (MOs) which have the advantage of rich material sources and high theoretical capacity have attracted lots of attention as anode for SIBs in scientific community. Nevertheless, due to the low conductivity, large volumetric change during charge/discharge process of SIBs, the material often demonstrates unsatisfactory cycling stability and capacity rate. Construction of material composites through incorporation of graphene to MOs with tailored nanostructure and composition has demonstrated promising performance in SIBs. In this review, we attempt to provide a comprehensive summary of the research development on the low-cost metal oxides/graphene composites (MOs/G) as anode materials for SIBs. The characteristics of different morphology, composition, crystal phases of MOs/G composites and their electrochemical properties in SIBs are demonstrated. The correlation of the morphological and structural properties of the MOs materials with their performance in SIBs is discussed. This timely review sheds light on the path towards achieving cost effective, safe SIBs with high energy density and long cycling life using MOs/G as anode materials.

In this study, the structural, electronic and optical properties of a tungsten disulfide (WS2) hybrid with indium-gallium-zinc-oxide (IGZO) heterostructures were investigated based on density functional theory (DFT) calculations. According to the results of binding energy, charge density difference and electron localization function of heterostructures, we found that the WS2 and IGZO monolayers were bound to each other via non-covalent interactions with large binding energy. The calculated results illustrate that the AAii stacking pattern has an indirect band gap of 1.643 eV, while AAi and AB stacking patterns have maximum direct-gaps of 1.102 eV and 1.234 eV, respectively. Under an external E-field and mechanical strain, the response of the energy gap of the WS2/IGZO heterostructure monotonically decreased over a wide range, even with a semiconductor-metal transition. In addition, we investigated the optical properties of the heterostructure and found that it exhibits a much broad spectral responsivity (from visible light to deep UV light) and a more pronounced optical absorption than WS2 and IGZO monolayers. Moreover, the tensile strain could weaken the photoresponse of the heterostructure to the UV light and enhance the response for the visible light; under compressive strain, the heterostructure showed a strong absorption peak in the UV light. Meanwhile, a red-shift was observed under an external strain. All these unique and tunable properties indicate that the WS2/IGZO heterostructure is a good candidate for nanoelectronic and photoelectronic devices, such as field-effect transistors, flexible sensors, photodetectors and photonic devices.

Recently, soft electrothermal actuators have attracted tremendous attentions. Large deformation under low driving voltage has long been the design concerns for scholars. However, in practice, apart from larger deformation, higher requirements are put forward for higher deformation speed in repeated cycles to achieve efficient and agile actuation. Herein, a soft electrothermal actuator is fabricated based on laser reduced graphene oxide and silver nanowire composite with polydimethylsiloxane substrate, which completely realizes the above required advantages. Besides, a concept of periodic curvature rate is proposed to accurately evaluate the deformation speed, which is more normalized than time alone to reflect before. The soft electrothermal actuator here can achieve a large curvature of 2.5 cm-1 with a high periodic curvature rate of up to 8.93×10-2 cm-1/s under low power density input of 0.8W•cm-2 (driving voltage of 28V), which shows obvious advantages in both deformation quantity and speed compared with most reported electrothermal actuators till now. Finally, a bionic hand consisting of five U-shaped electrothermal actuators is demonstrated to achieve gesture following and restoring, showing its promising prospects in the emerging bionics field.

Quasi-solid-state potassium-ion batteries (QSPIBs) are regarded as one of the most promising safety-enhanced energy storage devices. Herein, a facile method for preparing a potassium-ion composite electrolyte membrane on a large scale is presented for the first time. The as-synthesized membrane displays excellent electrochemical stability, good mechanical flexibility, and high ionic conductivity (9.31 × 10-5 S cm−1 at 25 °C). Furthermore, QSPIBs prepared with this membrane and commercial raw material-based electrodes show superior electrochemical performance even at low temperatures (99.7 mAh g−1 at −20 °C for half QSPIBs and 90.7 mAh g−1 at −15 °C for full QSPIBs), and a promising rate performance (115.6 mAh g−1 for half QSPIBs and 90.9 mAh g−1 for full QSPIBs at 800 mA g−1). The reaction mechanism and structure evolution of a 3,4,9,10-perylene-tetracarboxylicacid-dianhydride (PTCDA) cathode is also systematically studied. The promising characteristics of the prepared low-cost quasi-solid-state potassium-ion batteries in this work open up new possibilities for safer and more durable batteries and a wide range of practical applications in the electronics industry.

Single-crystal (SC) perovskite is currently a promising material due to its high quantum efficiency and long diffusion length. However, the reported perovskite photodetection range ( 10 μs) are still limited. Here, to promote the development of perovskite-integrated optoelectronic devices, this work demonstrates wider photodetection range and shorter response time perovskite photodetector by integrating the SC CH3NH3PbBr3 (MAPbBr3) perovskite on silicon (Si). The Si/MAPbBr3 heterojunction photodetector with an improved interface exhibits high-speed, broad-spectrum, and long-term stability performances. To the best of our knowledge, the measured detectable spectrum (405-1064 nm) largely expands the widest response range reported in previous perovskite-based photodetectors. In addition, the rise time is as fast as 520 ns, which is comparable to that of commercial germanium photodetectors. Moreover, the Si/MAPbBr3 device can maintain excellent photocurrent performance for up to 3 months. Furthermore, typical gray scale face imaging is realized by scanning the Si/MAPbBr3 single-pixel photodetector. This work using an ultrafast photodetector by directly integrating perovskite on Si can promote advances in next-generation integrated optoelectronic technology.

International audience; Sodium layered oxide cathodes for rechargeable batteries suffer from Na+ ordering and transition-metal layer gliding that lead to several plateaus in their voltage profile. This characteristic hinders their competitiveness as a viable option for commercial rechargeable batteries. In O′3-layered Na3Ni1.5TeO6 (Na5/6[Na1/6Ni3/6Te2/6]O2), Rietveld refinement and solid-state nuclear magnetic resonance spectroscopy show that there is sodium in the transition-metal layer. This sodium within the transition-metal layer provides cation disorder that suppresses Na+ ordering in the adjacent sodium layers upon electrochemical insertion/extraction of sodium. Although this material shows a reversible O′3 to P′3 phase transition, its voltage versus composition profile is typical of traditional lithium layered compounds that have found commercial success. A Ni2+/3+ redox couple of 3.45 V versus Na+/Na is observed with a specific capacity as high as 100 mAh g–1 on the first discharge at a C/20 rate. This material shows good retention of specific capacity, and its rate of sodium insertion/extraction can be as high as a 2C-rating with particle sizes on the order of several micrometers. The structural nuances of this material and their electrochemical implications will serve as guidelines for designing novel sodium layered oxide cathodes.

Solid-state electrolytes provide excellent electrochemical stability, mechanical strength and safety as compared to conventional liquid electrolytes for lithium ion batteries. Recent developments of polymer electrolytes mixed with nanofillers have enhanced ionic conductivity and stability owing to the interaction between nanoscale fillers and polymer matrix/lithium salt. However, the agglomeration of the nanofillers limits the concentration of the filler, thereby preventing the composite electrolyte from further improving the conductivity and stability. In this study, we first report three-dimensional (3D) nanostructured garnet framework as 3D nanofillers for composite polymer electrolyte. The well-percolated structure of garnet framework enables a high weight ratio of 62 wt% in composite electrolyte and improves conductivity to 8.5 × 10−5 S cm−1 at 25 °C with ~ 10−3 S cm−1 at 60 °C. The excellent conductivity and high garnet content of composite electrolyte also lead to enhanced electrochemical and thermal stability as well as interfacial stability with lithium metal. Our 3D interconnected garnet framework design represents a useful strategy for developing high-performance composite polymer electrolytes for next-generation lithium batteries.

Garnet electrolytes having a room-temperature Li+ conductivity of 10−3 S cm−1 suffer from adsorbents that prevent wetting by a lithium anode; formation and growth of lithium-anode dendrites into grain boundaries and a huge interfacial resistance to anode plating and stripping result. A thin coating of a garnet surface by a Li+-conducting polymer with a transfer number of 0.9 is shown to suppress dendrite formation and to reduce greatly the interfacial resistance. A coulombic efficiency near 100% with a single thin polymer coat can provide Li/garnet/LiFePO4 all-solid-state cell with a long cycle life.

Lithium carbonate on the surface of garnet blocks Li+ conduction and causes a huge interfacial resistance between the garnet and electrode. To solve this problem, this study presents an effective strategy to reduce significantly the interfacial resistance by replacing Li2CO3 with Li ion conducting Li3N. Compared to the surface Li2CO3 on garnet, Li3N is not only a good Li+ conductor but also offers a good wettability with both the garnet surface and a lithium metal anode. In addition, the introduction of a Li3N layer not only enables a stable contact between the Li anode and garnet electrolyte but also prevents the direct reduction of garnet by Li metal over a long cycle life. As a result, a symmetric lithium cell with this Li3N-modified garnet exhibits an ultralow overpotential and stable plating/stripping cyclability without lithium dendrite growth at room temperature. Moreover, an all-solid-state Li/LiFePO4 battery with a Li3N-modified garnet also displays high cycling efficiency and stability over 300 cycles even at a temperature of 40 °C.

A selective CO evolution from photoreduction of CO2 in water was achieved on a noble-metal-free, carbide-based composite catalyst, as demonstrated by a CO selectivity of 98.3% among all carbon-containing products and a CO evolution rate of 29.2 μmol h–1, showing superiority to noble-metal-based catalyst. A rapid separation of the photogenerated electron–hole pairs and improved CO2 adsorption on the surface of the carbide component are responsible for the excellent performance of the catalyst. The high CO selectivity is accompanied by a predominant H2 evolution, which is believed to provide a proton-deficient environment around the catalyst to favor the formation of hydrogen-deficient carbon products. The present work provides general insights into the design of a catalyst with a high product selectivity and also the carbon evolution chemistry during a photocatalytic reaction.

Practical, high-yield mesoporous organic polymer (MOP) spheres were successfully synthesized by a novel self-template method, which can be used as fillers to prepare poly (ethylene oxide) (PEO)-based polymer electrolytes membranes. The result shows that both the electrical conductivity and lithium-ion conductivity of PEO-based electrolytes can be improved effectively by adding the MOP filler. The electrolyte membranes are mechanically robust, thermally stable to over 270 °C, and can effectively block dendrites penetrating from metallic-lithium anode to cathode. The Li+ transfer conductivity of composite electrolyte membrane increases to 4.4 × 10−4 S cm−1 at 63 °C. All-solid-state LiFePO4/MOP-PEO-LiTFSI/Li cell shows excellent cycling (144 mAh g−1 after 300 cycles) and rate (167 mAh g−1 at 0.2 C, 170 mAh g−1 at 0.5 C, 160 mAh g−1 at 1 C and 145 mAh g−1 at 2 C) performance.

Synthesis of α-MnO2 nanorods grown on porous graphitic carbon nitride (g-C3N4) sheets via a facile hydrothermal treatment gives a porous composite exhibiting higher activity for an air cathode than the individual component of α-MnO2 or porous g-C3N4 for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The porous g-C3N4/α-MnO2 composite also exhibits better performance in a Li-air battery than pure α-MnO2 or XC-72 carbon catalysts, which includes superior discharge capacity, low voltage gap and high cycle stability. The α-MnO2 nanorods catalyze the OER and the porous g-C3N4 sheets catalyze the ORR.

Summary Lithium-ion batteries with high energy density are being intensively pursued to meet the ever-growing demand for energy storage. However, the increase in energy density often comes with an elevated instability of electrode materials, causing major concerns about the reliability and safety of lithium-ion batteries. Here, we report a strategy for stabilizing cathode materials by modulating the vacant lattice sites on the particle surface. Using the high-voltage Li[Ni0.5Mn1.5]O4 as an example, we demonstrate that introduction of a 10-nm epitaxial surface layer with Al3+ in the empty 16c octahedral sites of the spinel Li[Ni0.5Mn1.5]O4 suppresses structural degradation during cycling by increasing the surface stability without interfering with the Li+ diffusion around the Al3+ sites. Control of the Al3+ concentration in the surface region was shown to be a facile process. The process was shown to stabilize long-term cycling of Li[Ni0.5Mn1.5]O4 to 5 V versus Li+/Li0.

Composite polyethylene-oxide/garnet electrolytes containing LiTFSI as the lithium salt have a Li+ conductivity σLi > 10−4 S cm−1 at 55 °C and a low plating/stripping impedance of a dendrite-free Li-metal anode; they have been developed for a safe solid-state Li-metal rechargeable battery. Composites consisting of “ceramic-in-polymer” to “polymer-in-ceramic” that are flexible and mechanically robust are fabricated by hot-pressing. Safe pouch cells with a remarkable flexibility have been fabricated. Solid-state LiFePO4|Li batteries with electrolytes of “ceramic-in-polymer” and “polymer-in-ceramic” deliver excellent cycling stability with high discharge capacities (139.1 mAh g–1 with capacity retention of 93.6% after 100 cycles) and high capacity retention (103.6% with coulombic efficiency of 100% after 50 cycles) at 0.2 C and 55 °C. Both kinds of electrolytes can be applied to solid-state lithium batteries.

Summary Transition metal oxide catalysts with high oxygen reduction activity and durability are highly desirable for use in fuel cells and metal-air batteries. Herein we report, for the first time, the oxygen reduction activity of hollow porous spinel AB 2 O 4 microspheres, where A = Zn 2+ and B = Mn 3+ and/or Co 3+ (i.e., ZnMn x Co 2−x O 4 ). Among them, ZnMnCoO 4 ( x = 1) microspheres exhibit the best oxygen reduction activity with a half-wave-potential only 50 mV lower than that of the Pt/C counterpart and an excellent durability in the alkaline solution. Importantly, the electronic transition of Co 3+ ions from low-spin state in commercial Co 3 O 4 catalyst to a mixed high-spin and low-spin state in ZnMnCoO 4 catalyst was found to weaken the Co 3+ -OH bond and facilitate the O 2− /OH − displacement. The density functional theory calculation substantiated that ZnMnCoO 4 displayed a more favorable binding energy with O 2 and oxygenated species, thereby enabling the fast reaction kinetics in the oxygen reduction reaction process.

In this work, nitrogen-doped LaNiO3 perovskite was prepared and studied, for the first time, as a bifunctional electrocatalyst for oxygen cathode in a rechargeable lithium–oxygen battery. N doping was found to significantly increase the Ni3+ contents and oxygen vacancies on the bulk surface of the perovskite, which helped to promote the oxygen reduction reaction and oxygen evolution reaction of the cathode and, therefore, enabled reversible Li2O2 formation and decomposition on the cathode surface. As a result, the oxygen cathodes loaded with N-doped LaNiO3 catalyst showed an improved electrochemical performance in terms of discharge capacity and cycling stability to promise practical Li–O2 batteries.

Solid-state electrolytes have emerged as a promising alternative to existing liquid electrolytes for next generation Li-ion batteries for better safety and stability. Of various types of solid electrolytes, composite polymer electrolytes exhibit acceptable Li-ion conductivity due to the interaction between nanofillers and polymer. Nevertheless, the agglomeration of nanofillers at high concentration has been a major obstacle for improving Li-ion conductivity. In this study, we designed a three-dimensional (3D) nanostructured hydrogel-derived Li0.35 La0.55 TiO3 (LLTO) framework, which was used as a 3D nanofiller for high-performance composite polymer Li-ion electrolyte. The systematic percolation study revealed that the pre-percolating structure of LLTO framework improved Li-ion conductivity to 8.8×10-5 S cm-1 at room temperature.

Natural energy haversting devices serve as an alternative candidate for power supply in many micro-/nano-systems. However, traditional nanogenerators based on piezoelectricity or triboelectric power generation face challenges in terms of biocompatibility and stability in various biological systems. The bacteriorhodopsin (bR) protein in Halobacterium halobium is an ideal biocompatible material for photoelectric conversion. Conventional bR systems based on ion transport or enhanced light absorption layers have a limited light power conversion speed. On the other hand, bR-based biohybrid devices have a great potential for sensitive light power conversion as compared to conventional nanogenerators. Herein, we present a biohybrid nanogenerator made of bR and horizontally aligned-long carbon nanotubes (CNTs) with electron–ion interaction for the first time for sensitive light power conversion. The bR layer serves as the proton pump, whereas CNTs are utilized to enhance the photocurrent; thus, the photocurrent frequency response improves significantly because of the effect of the electron–ion interaction. The photocurrent shows a linear relationship with the intensity of light and can still obtain a stable signal at a light intensity of 0.03 mW cm−2. With regard to the influence of the light on–off period, the photocurrent initially increases and then decreases with an increase in flickering frequency up to 360 Hz; this can be ascribed to the combinational influence of light switch speed and photocycle decay time. The photocurrent shows highest value (99 nA cm−2) at a frequency of about 50 Hz at a light intensity of 0.43 mW cm−2, which matches well with the frequency standard of the electrical power supply system. Moreover, we found that a higher density of CNTs contributed to improve performance of the nanogenerators. Furthermore, a H+ ion releasing model was proposed to interpret the operating mechanism of the biohybrid nanogenerator. The biohybrid nanogenerator shows great potential for applications as a power source for bio-nanosystems.

Organic carbon-coated LiNi0.5Mn0.3Co0.2O2 materials are prepared by mixing 2 or 5% starch or bagasse evenly with the synthesized LiNi0.5Mn0.3Co0.2O2 material and calcining for 10 h at 750 °C. The microstructures and electrochemical performance are investigated by X-ray diffraction, scanning electron microscopy, carbon/sulfur analysis, transmission electron microscopy and electrochemical testing. The results indicate that the organic carbon coated on the surface of LiNi0.5Mn0.3Co0.2O2 material does not change the surface morphology and crystal structure, but greatly improves the conductivity, rate and cycle performance of the LiNi0.5Mn0.3Co0.2O2 cathode in a Li-ion battery. The initial discharge capacity of the synthesized LiNi0.5Mn0.3Co0.2O2 material is 147.8 mAh g−1, which increases to 152.4 and 153.3 mAh g−1 for 2% starch and bagasse, respectively. After 100 cycles, the capacity retention rates are 70.7% (uncoated), 83.3% (coated with 2% starch), 90.1% (coated with 2% bagasse), 83.1% (coated with 5% starch) and 91.1% (coated with 5% bagasse). The influence of the percentage of coated carbon and its dispersion uniformity on the performance of the battery is analyzed. A small coating capacity and uniform carbon film can achieve better performance. Rational organic carbon coating technology is an effective way to improve the electrochemical performance of LiNi1−x−y Mn x Co y O2-based material.

Sodium manganese hexacyanoferrate (NaMnHCF) with low cost and high energy density is a promising cathode in Na-ion batteries (NIBs); however, the Jahn-teller effect of Mn3+ and large amounts of Fe(CN)64− defects significantly reduces the cycling life of the battery. Here, we introduce a chemically less soluble and structurally more stable layer to the NaMnHCF surface with a simple ion-exchange method to mitigate the irreversible structural change and side reactions associated with both the low-spin FeII/FeIII and the high-spin MnII/MnIII redox. The NaMnHCF cathode treated in Cu2+ solution shows much better cycling stability (80 vs. 30 mA h g−1 after 1000 cycles at 1 C) and rate performance than the unmodified NaMnHCF. The as-proposed chemical ion-exchange is a well-compatible and low-cost technology to realize surface modification of NaMnHCF and other hexacyanoferrates, which is of great significance for the development of high-performance NIB cathodes.

Flexible gas sensing is attracting more attention with the development of machine learning and Internet of Things (IoT). Herein, we report flexible and foldable high-performance hydrogen (H2) sensor on all textiles substrate-fabricated by inkjet–printing of reduced graphene oxide (rGO) and its application to wearable environmental sensing. The inkjet-printing process provides the advantages of the compatibility with various substrates, the capability of non-contact patterning and cost-effectiveness. The sensing mechanism is based on the catalytic effect of palladium (Pd) nanoparticles (NPs) on the wide bandgap rGO, which allows facile adsorption and desorption of the nonpolar H2 molecules. The graphene textile gas sensor (GT-GS) demonstrates about six times higher sensing response than the graphene polyimide membrane gas sensor due to the large surface area of the textile substrate. An analysis of the temperature influence on the GT-GS shows better H2 gas response at room temperature than at high temperature (e.g., 120 °C). In addition, with the machine learning-enabled technology and triboelectric-textile to power IoT (temperature and humidity for gas calibration), H2 is well identified for wearable applications with a robust mechanical performance (e.g., flexibility and foldability).

Electrocatalysts for both the oxygen reduction and evolution reactions (ORR and OER) are vital for the performances of rechargeable metal–air batteries. Herein, we report an advanced bifunctional oxygen electrocatalyst consisting of porous metallic nickel-iron nitride (Ni3FeN) supporting ordered Fe3Pt intermetallic nanoalloy. In this hybrid catalyst, the bimetallic nitride Ni3FeN mainly contributes to the high activity for the OER while the ordered Fe3Pt nanoalloy contributes to the excellent activity for the ORR. Robust Ni3FeN-supported Fe3Pt catalysts show superior catalytic performance to the state-of-the-art ORR catalyst (Pt/C) and OER catalyst (Ir/C). The Fe3Pt/Ni3FeN bifunctional catalyst enables Zn–air batteries to achieve a long-term cycling performance of over 480 h at 10 mA cm−2 with high efficiency. The extraordinarily high performance of the Fe3Pt/Ni3FeN bifunctional catalyst makes it a very promising air cathode in alkaline electrolyte.

The garnet-type solid Li-ion conductor, Li6.4La3Zr1.4Ta0.6O12, is viewed as a promising solid-state electrolyte for the next-generation high-performance Li-ion battery because of its high ionic conductivity and stability. The previous researches, in order to avoid Li volatilization loss during solid-state reaction of sintering, mother powder with the same composition as green bodies was usually used to cover the samples, it would waste the expensive raw materials and increase the fabrication cost. In this study, a new method was proposed to prepare the Li6.4La3Zr1.4Ta0.6O12 ceramic solid-state electrolyte where the Li loss is compensated by the outside Li2CO3. Samples prepared by this method have pure garnet phase and compact micromorphology with few pores. These samples have a high Li-ion conductivity of 2.9×10−4 S/cm and a low activation energy of 0.37 eV at room temperature. The electronic conductivity is 1.08×10−8 S/cm, which can be neglected for solid-state electrolyte.

Potassium has as rich an abundance as sodium in the earth, but the development of a K-ion battery is lagging behind because of the higher mass and larger ionic size of K+ than that of Li+ and Na+, which makes it difficult to identify a high-voltage and high-capacity intercalation cathode host. Here we propose a cyanoperovskite KxMnFe(CN)6 (0 ≤ x ≤ 2) as a potassium cathode: high-spin MnIII/MnII and low-spin FeIII/FeII couples have similar energies and exhibit two close plateaus centered at 3.6 V; two active K+ per formula unit enable a theoretical specific capacity of 156 mAh g–1; Mn and Fe are the two most-desired transition metals for electrodes because they are cheap and environmental friendly. As a powder prepared by an inexpensive precipitation method, the cathode delivers a specific capacity of 142 mAh g–1. The observed voltage, capacity, and its low cost make it competitive in large-scale electricity storage applications.

Here, a class of organometallic compounds, metallocenes, are explored to serve as both catholyte and anolyte redox species for non-aqueous lithium-based redox flow battery (Li-RFB) applications. The prototype of all-metallocene-based Li-RFB exploits ferrocene (FeCp2) and cobaltocene (CoCp2) as the redox-active cathode and anode, respectively. The reaction rate constants of metallocenes are determined to be as high as 10−3 cm s−1, two orders greater than most redox-active materials applied in conventional redox flow batteries. This designed Li-RFB yields a working potential of 1.7 V, and by introduction of methyl groups on the ligand rings of CoCp2, the working potential can be further increased to 2.1 V. The fabricated full cell shows capacity retention of over 99% per cycle with a coulombic efficiency (CE) of >95% and an energy efficiency of >85%. These results demonstrate a generic design route towards high performance non-aqueous RFBs via rational screening and functionalization of metallocenes.

The practical use of lithium-sulfur batteries for the next-generation energy storage, especially the automobiles, was hindered by low electronic conductivity of sulfur and the resulting poor rate capabilities. Here, we report a sulfur-carbon composite by confining S into a graphene sandwiched in mesoporous carbon nanosheets with a two-dimensional ultrathin morphology, suitable mesopore size and large pore volume, and excellent electronic conductivity. Serving as cathode material for a Li-S battery, the elaborately designed S/C composite leads to "kinetically stable" transmissions of Li ions and electrons, triggering a stable electrochemistry and a record-breaking rate performance. In this way, the S/C composite has been proved a promising cathode material for high-rate Li-S batteries targeted at automobile storage.

Inspired by the turbinate structure in the olfaction system of a dog, a biomimetic artificial nose based on 3D porous laser-induced graphene (LIG) decorated with palladium (Pd) nanoparticles (NPs) has been developed for room-temperature hydrogen (H2) detection. A 3D porous biomimetic turbinate-like network of graphene was synthesized by simply irradiating an infrared laser beam onto a polyimide substrate, which could further be transferred onto another flexible substrate such as polyethylene terephthalate (PET) to broaden its application. The sensing mechanism is based on the catalytic effect of the Pd NPs on the crystal defect of the biomimetic LIG turbinate-like microstructure, which allows facile adsorption and desorption of the nonpolar H2 molecules. The sensor demonstrated an approximately linear sensing response to H2 concentration. Compared to chemical vapor-deposited (CVD) graphene-based gas sensors, the biomimetic turbinate-like microstructure LIG-gas sensor showed ∼1 time higher sensing performance with much simpler and lower-cost fabrication. Furthermore, to expand the potential applications of the biomimetic sensor, we modulated the resistance of the biomimetic LIG sensor by varying laser sweeping gaps and also demonstrated a well-transferred LIG layer onto transparent substrates. Moreover, the LIG sensor showed good mechanical flexibility and robustness for potential wearable and flexible device applications.

Nano energy 83, 105841 (2021). doi:10.1016/j.nanoen.2021.105841, Rechargeable potassium (K) batteries are a promising next-generation technology for low-cost grid scale energy storage applications. Nevertheless, the undesirable interfacial instabilities originating from the interplay between the employed separators and electrodes largely compromise the battery’s performance, and the underlying mechanism of which remains elusive. Herein, the interfacial stability between three types of commercial separators (Celgard 2325, Celgard 2400 and GF/D) and the K electrodeposits is investigated in K|K symmetric cells via in-situ Synchrotron X-ray tomography technique. It is demonstrated that the cell built with a Celgard 2400 separator can achieve a stable cycling performance due to its high mechanical strength and integrity along the thickness direction, thus alleviating the K dendrites growth. In contrast, a GF/D membrane of low mechanical cohesion and excessive porosity is found to be easily deformed and filled with deciduous potassium dendritic aggregates during battery cycling. Similarly, the tri-layer Celgard 2325 separators, which are weakly bonded by interlaminar forces, are found to be severely delaminated by the overgrowth of K dendrites. Furthermore, it is revealed that the delamination failure behaviors of Celgard 2325 is driven by the local stress induced by the spatially and heterogeneously formed "dead" K dendrites. Our work provides direct visualization of morphological evolvement of the separators in presence of potassium dendrites in K|K symmetric cells and highlights the significance of mechanical cohesion, porosity distribution and mechanical integrity of separators in dictating the battery’s performance under realistic battery operation conditions. As a result, these discoveries provide an in-depth understanding that is needed to design next-generation high performance separators to mitigate the formation of potassium dendrite in KMBs., Published by Elsevier, Amsterdam [u.a.]

NASICON (Na+ super ionic conductor) structures of NaxMV(PO4)3 (M = Mn, Fe, Ni) were prepared, characterized by aberration-corrected STEM and synchrotron radiation, and demonstrated to be durable cathode materials for rechargeable sodium-ion batteries. In Na4MnV(PO4)3, two redox couples of Mn3+/Mn2+ and V4+/V3+ are accessed with two voltage plateaus located at 3.6 and 3.3 V and a capacity of 101 mAh g–1 at 1 C. Furthermore, the Na4MnV(PO4)3 cathode delivers a high initial efficiency of 97%, long durability over 1000 cycles, and good rate performance to 10 C. The robust framework structure and stable electrochemical performance makes it a reliable cathode materials for sodium-ion batteries.

Sodium extraction behavior in the rhombohedral Na3MnTi(PO4)3 with the NASICON structure was investigated and shown to have a 0.5 eV separation of the localized-electron Mn3+/Mn2+ and Mn4+/Mn3+ redox energies. Used as a cathode in a sodium-ion half-cell, the redox couples of Mn3+/Mn2+ and Mn4+/Mn3+ exhibit two voltage plateaus located at about 3.6 and 4.1 V vs Na+/Na, respectively. Na3MnTi(PO4)3 also exhibits a small volume change after the extraction of two sodium ions, and the NASICON structure is well-maintained after repeated extraction and insertion of sodium ions.

Two-dimensional bismuth oxychloride (BiOCl) ultrathin nanoplates with a thickness of 10–20 nm are synthesized by a simple hydrothermal method. The as-prepared product is explored as an anode material for sodium-ion batteries for the first time. It shows BiOCl ultrathin nanoplates with two very suitable discharge voltage plateaus (0.6 V and 0.4 V) for sodium ion batteries. Furthermore, a two-step sodiation mechanism including an intercalation reaction and a conversion reaction is proposed. This work reveals a novel electrode material for sodium-ion batteries beyond conventional materials (such as transition metal oxides, carbon materials and alloys) and encourages more researchers to further investigate BiOCl.