Coin Cell Research Articles

Characterization of identical lithium-ion battery electrodes before and after charge/discharge cycles via in-plane large-area polishing

As an effective method to fabricate a large-area cross-sectional sample for lithium-ion battery electrodes, we perform in-plane polishing of LiNi0.8Co0.15Al0.05O2(NCA) cathode samples and obtain a large cross-sectional area with a diameter of 1.5 mm. The polished cross-sections of NCA cathode particles are sufficiently flat to perform the atomic force microscopy (AFM) measurements on each cathode particle. Following AFM-based Kelvin probe force microscopy and scanning spreading resistance microscopy measurements, an identical in-plane polished NCA sample is assembled into a coin cell for the charge and discharge processes. After 90 charge/discharge cycles, the in-plane-polished sample is successfully disassembled from the coin cell without causing critical damage. In addition, a microcrack structure, which is a typical degradation feature of the cycles of NCA particles, is observed for the identical in-plane polished NCA sample. This indicates that the in-plane polishing method is effective for investigating identical NCA electrode samples before and after the charge/discharge process. Furthermore, the in-plane polishing method can be successfully applied to the large-area polishing of a Si-based anode which is a mixture of Si carbon complexes and graphite particles. This study presents a novel methodology for analyzing the degradation of lithium-ion battery electrode materials.

Button battery exposure in children: a systematic review and meta-analysis

BackgroundThere is a rising burden of severe and fatal outcomes resulting from button battery exposures (ingestions or insertions). We summarised current evidence following button battery exposures in children and provided...

Searching for thermal shutdown separators in lithium-ion batteries: Paradigm and practice

This paper focuses on the thermal shutdown separators for thermal runaway control in lithium-ion batteries (LIB). In electrical cars (EV), thermal runaway is the most catastrophic and life-threatening failure mode. Here we reexamined 17 reported phase-change-based thermal shutdown separators and suggested a new design paradigm for thermal shutdown separators of EV level batteries. Through accelerating rate calorimeter (ARC), we have obtained the thermal response curves of three typical EV level batteries: LFP 18,650 battery, NCM 18,650 battery and NCM pouch battery and summarized their critical temperatures. Taking NCM pouch battery as an example, we formed a searching zone for the 17 phase-change-based thermal shutdown separators and found that only 7 of them falling into the promising zone. After analysis on these 7 composite materials, we designed a new trial composite material PBS/PI, which turned out successful in all the following thermal and electrochemical tests. Moreover, we are aware from the beginning that all the reported materials are only tested in button batteries and may not as well apply to EV level batteries. Our own practice has also shown this discrepancy. Thereby we employed thermal simulation to help mapping the discrepancy between the button battery and pouch battery. The results shows that the thermal shutdown happens much earlier in the button battery when elevating the temperature, which tricks researchers into misjudging the material feasibility. This work offers avenues for the searching of thermal shutdown separators in EV level batteries.

Investigation of polypyrrole based composite material for lithium sulfur batteries

With the rising demand for electricity storage devices, the performance requirements for such equipment have become increasingly stringent. Lithium-sulfur (Li-S) batteries are poised to be among the next generation of energy storage systems. However, before they can be commercially viable, several challenges must be addressed, including low sulfur conductivity and the shuttle effect. Herein, polypyrrole based sulfur composite was prepared by simple method in hydrothermal teflon lined autoclave for Li-S battery. The S/SP/ppy/PVDF electrode exhibited the initial discharge capacity of 662 mAh g− 1 at 0.5 C and 637 mAh g− 1 after 100 cycles. The Coulombic efficiency was 96% all along charge/discharge cycling. Moreover, Li-S coin cells were assembled and tested to demonstrate the potential application and scale-up of the polypyrrole-sulfur composite.

Fe3O4/f‐MWCNTs Nanocomposite: Efficient Electrode Material for Symmetric Hybrid Supercapacitors with 25 k Cycle Stability

AbstractFe3O4 with acid functionalized multiwalled carbon nanotubes (f‐MWCNTs) was synthesized using a simple ultrasonic‐assisted co‐precipitation method. The structural, morphological, and elemental composition of the composite material were determined using P‐XRD, FT‐IR, SEM‐EDS, and BET analysis. The electrochemical properties of the composite were analysed by CV, CP and EIS techniques. In a three‐electrode system setup, a specific capacitance (Cs) of 509 Fg−1 at 2 mVs−1 and 116 Fg−1 at 2.5 Ag−1 was achieved in 1 M KOH solution. The composite material was utilized in the design of a symmetric supercapacitor coin cell (CR2032) device. The coin cell exhibited Cs of 49 Fg−1 at 2 mVs−1 (0 to 1.8 V) and 19.2 Fg−1 at 1 Ag−1 (0 to 1.75 V) in 1 M KOH electrolyte, with a Cs retention of 80 % at the end of 25,000 charge‐discharge cycles at a high current density of 20 Ag−1. The coin cell demonstrated a maximum energy density of 8.2 Whkg−1 and power density of 17.5 kWkg−1. This study highlights an inexpensive, environmentally benign hybrid supercapacitor composite material synthesized by a facile method as a promising candidate for high‐performance supercapacitor applications.

Fabrication and performance assessment of coin cell supercapacitors with multiwalled carbon nanotube-supported mixed metal oxide nanocomposites and redox additive electrolyte

In the realm of supercapacitor applications, the fabrication of coin cell supercapacitors with superior performances played a crucial role. In this work, an asymmetrical type coin supercapacitor was fabricated with multiwalled carbon nanotube supported mixed metal oxide (CuO/CoO@MWCNT - CCM) nanocomposites (NCs) and potassium ferrocyanide incorporated KOH based redox additive electrolyte (RAE). The synergistic effect and the enhanced conductivity by the mixed metal oxides and MWCNT, respectively, were acted as the performance enhancer for electrode performances. On the other hand, RAE with optimized concentration provided additional redox active sites for superior performances. The combined effect of CCM NCs and RAE, were responsible for the superior performances. CCM NCs were prepared by one-pot hydrothermal technique and characterized. Working electrodes with CCM NCs were fabricated by doctor blade method and evaluated in KOH and RAE. It exhibited 1838.55 Fg−1 of specific capacitance (Csp) in RAE. Assembled asymmetrical supercapacitors with CCM NCs modified working electrode and activated carbon based anode, delivered 123.91 Fg−1 of Csp at 2.75 Ag−1 in RAE. The assembled supercapacitors delivered the highest energy density of 27.53 Wh kg−1 and power density of 1875 W kg−1 in RAE with an impressive 82.89 % of cyclic retention after 5000 GCD cycles. Finally, an asymmetric coin cell supercapacitor (CR2302) was fabricated with CCM NCs and RAE. The fabricated coin cell delivered the charge and discharge capacities of 157.72 and 55.99 mAh g−1, respectively in KOH, whereas these values were significantly improved 172.46 and 126.2 mAh g−1 respectively, in RAE. It proved that the fabricated coin cell supercapacitors performed well in terms of maximum charge and discharge performances in RAE compared to conventional KOH.

Evaluation and Upscaling of Impregnated La0.20Sr0.25Ca0.45TiO3 Fuel Electrodes for Solid Oxide Electrolysis Cells

Recent research into Rh and Ce0.80Gd0.20O1.90-impregnated La0.20Sr0.25Ca0.45TiO3 fuel electrodes for solid oxide fuel cells has demonstrated the high-stability of these material sets to a variety of harsh operating conditions at small scales (1 cm2 active area button cells), as well as commercial scales (100 cm2 cells) in short stacks (5 cells) and full micro-combined heat and power systems (60 cells). In this work, the authors present a comprehensive evaluation of the ability of these novel titanate-based materials to function as fuel electrodes in solid oxide electrolysis cells (SOECs). Short-term and durability testing of button cell scale SOECs highlighted the limited stability of lanthanum strontium manganite-based air electrodes, under CO2 and steam electrolysis conditions, with lanthanum strontium cobaltite ferrite-based air electrodes offering improved degradation characteristics. Upscaling of this optimized cell chemistry to a 16 cm2 active area SOEC and testing under CO2, CO2/H2O and H2O electrolysis conditions demonstrated encouraging performance over a period of ∼600 h, with stable co-electrolysis performance at ∼−7.5 A at 1.47 V for the first 100 h.

Synergistic Structural Integrity and Remarkable Structural Stability of NC@Si Anodes for Lithium-ion Batteries

The silicon-based anode has attracted wide attention because of its high theoretical specific capacity, which is expected to greatly improve the batteries’ energy density. However, during the charge-discharge cycles, the great volume expansion of the anode active silicon seriously restricts its electrochemical stability. Herein, N-doping carbon-coated silicon microsphere was prepared for lithium-ion batteries. Benefit from the core-shell structure formed from silicon carbon, the volume change of silicon anode during the cycle is well coordinated. What's more, N-doping carbon reduces the reaction energy barrier between silicon and lithium and accelerates the electrochemical reaction, which improves the cycling performance of the battery. The specific capacity of the prepared button battery is as high as 2913.13 mAh g−1 at the current density of 0.21 mA g−1, and the average coulomb efficiency is higher than 99.84% during the cycling. And the capacity of NC@SiO2 anode gradually stabilizes after 500 cycles.

Numismedica II: Health Problems Caused by Coins.

Coins occasionally cause health problems. These problems have a wide range of presentations and can affect multiple organ systems. This article updates a 2009 review of the medical literature addressing health problems caused by coins in several ways. The spectrum of clinical findings is expanded by describing new entities associated with coin ingestion, including laryngeal impaction in adults, gastric perforation, and pancreatic disease. Guidelines for differentiating swallowed coins from the potentially life-threatening mimic of swallowed button batteries are summarized. Multiple new case series better define outcomes and management approaches in coin ingestion. Metal toxicity from coins remains rarely reported. The evidence that systemic allergic reactions can result from ingested coins is strengthened by new case reports. Maintaining the perspective that coin ingestion can cause obscure symptoms may lead to both a diagnosis of the cause of such symptoms and the description of clinical findings not yet reported.

A seaweed-inspired separator for high performance Zn metal batteries: Boosting kinetics and confining side-reactions

Uncontrolled dendrite growth, sluggish reaction kinetics, and drastic side reactions on the anode-electrolyte interface are the main obstacles that restrict the application prospect of aqueous zinc-ion batteries. Traditional glass fiber (GF) separator with chemical inertness is almost ineffective in restricting these challenges. Herein, inspired by the ionic enrichment behavior of seaweed plants, a facile biomass species, anionic sodium alginate (SA), is purposely decorated on the commercial GF separator to tackle these issues towards Zn anode. Benefiting from the abundant zincophilic functional groups and superior mechanical strength properties, the as-obtained SA@GF separator could act as ion pump to boost the Zn2+ transference number (0.68), reduce the de-solvation energy barrier of hydrated Zn2+, and eliminate the undesired concentration polarization effect, which are verified by experimental tests, theoretical calculations, and finite element simulation, respectively. Based on these efficient modulation mechanisms, the SA@GF separator can synchronously achieve well-aligned Zn deposition and the suppression of parasitic side-reactions. Therefore, the Zn||Zn coin cell integrated with SA@GF separator could yield a prolonged calendar lifespan over 1230 h (1 mA cm−2 and 1 mAh cm−2), exhibiting favorable competitiveness with previously reported separator modification strategies. Impressively, the Zn-MnO2 full and pouch cell assembled with the SA@GF separator also delivered superior cycling stability and rate performance, further verifying its practical application effect. This work provides a new design philosophy to stabilize the Zn anode from the aspect of separator.

A Comparison of Standard SEI Growth Models in the Context of Battery Formation

Growth of the Solid Electrolyte Interphase (SEI) layer on negative electrode particles during the formation cycle is one of the most complex and least understood steps of lithium-ion battery manufacturing. This initial SEI formation significantly impacts battery performance, lifetime, and degradation. Zero-dimensional models, which reduce the complexity of SEI’s morphology, material, and structure, are commonly used to study long-term SEI growth rates and capacity fade. These models are derived based on limiting mechanisms. We aim to compare the most common SEI growth models, focusing on the first few cycles at low C-rates representing formation protocols. Using consistent parameters across models, we seek to understand if they can capture the dynamics of SEI formation. We conducted qualitative comparisons with experimental measurements of Coulombic efficiency in 2032-type coin cells at low C-rate. Our analysis shows that the models predict SEI growth in the first cycle to be higher than in subsequent cycles. However, the difference between cycles in these models is insufficient to explain the experimental results, which indicate a capacity fade during the first cycle that is two orders of magnitude higher than in later cycles. This suggests new models are needed to accurately describe the physics of the formation cycle.

Preparation and Conductivity Analysis of LLTO Nanofiber‐Incorporated PEO‐PVDF‐HFP‐LiClO4 Solid Polymer Electrolytes for High‐Voltage Lithium Metal Batteries

ABSTRACTThis work focuses on the development of a composite polymer electrolyte (CPE) for all‐solid‐state lithium metal batteries (ASSLMBs), integrating LLTO nanofibers into a PEO (polyethylene oxide)‐PVDF‐HFP (poly(vinylidene fluoride‐cohexafluoropropylene)) matrix with LiClO4 as the lithium salt. The PEO has high ionic conductivity and flexibility, and the PVDF‐HFP has high mechanical strength and electrochemical stability. Therefore, the resulting composite has improved electrochemical performance and mechanical properties. Incorporating LLTO nanofibers enhances ionic conductivity due to the one‐dimensional ion transport pathways provided by the nanofibers while maintaining mechanical integrity and air stability, overcoming the challenges associated with conventional fillers. The prepared CPE demonstrates exceptional electrochemical stability up to 5.1 V versus Li/Li+, making it suitable for high‐voltage applications over traditional polymer electrolytes. The optimized CPE with 15 wt% LLTO provides the ionic conductivity of 1.1 × 10−5 S cm−1 at room temperature and reaches 1.46 × 10−4 S cm−1 at 80°C. The assembled LiNi1/3Mn1/3Co1/3PO4||PEO‐PVDF‐HFP‐LiClO₄‐LLTO||Li based 2032 coin cell worked in between 3 and 4.8 V versus Li/Li+ potential window without any electrolyte decomposition from 0.5 to 5 mV/s scan rates. Similarly, the fabricated LiFePO₄||PEO‐PVDF‐HFP (1:2)‐LiClO4‐LLTO (15 wt%)||Li cell provides an initial capacity of 149 mAh g−1 at 0.1 C and 85 mAh g−1 at 0.5 C, exploring its potential for lithium metal batteries. Overall, this work offers a promising pathway for developing advanced solid polymer electrolytes for next‐generation lithium metal batteries, which combine high ionic conductivity, excellent electrochemical performances, and robust mechanical properties.

Synthesis and performance evaluation of bio-derived and synthetic carbon as lithium-sulfur battery cathode

The next-generation of batteries need be both energy dense and environment friendly. Lithium sulfur batteries (LSBs) satisfy both criteria but their practical implementation is marred by the highly resistive nature of sulfur. Carbon-based cathodes play a vital role in mitigating the issue because their high conductivity allows for effective electron transfer during electrochemical cycling. Synthesis and electrochemical evaluation of carbon-based cathodes from two different sources for LSBs was carried out. Herein, two kinds of carbon, namely bio-derived carbon from coconut shells (CC500) and N-doped carbon (NC) from polyacrylonitrile fibers were synthesized and sulfur was incorporated via the melt diffusion route. The composites are characterized by PXRD and TGA, which determined 80 wt% mass loading of sulfur. The higher intensity of G-band over D-band in Raman spectroscopy indicates greater graphitic character for CC500 compared to NC. SEM images show large macro-pore like tunnels in CC500 while NC appears are irregular chunks. EDAX spectra showed 20 wt% N content in NC while CC500 is largely carbon with some minor surface oxygen. In galvanostatic charge–discharge cycling of coin cells, bare CC500/S shows better specific capacity compared to NC/S samples but the trend flips once a separator modified with 4 mg of graphene oxide (GO) is introduced (indicated as NC/S/GO4 and CC500/S/GO4). This points towards synergy between N-doped carbon and GO layer in retaining the soluble polysulfides in the catholyte region. NC/S/GO4 exhibited better capacity i.e., 1453, 1024, 866, 787, 697 mAh/g versus 1016, 779, 672, 551, 441 mAh/g offered by CC500/S/GO4 when discharged at 50, 100, 200, 300 and 500 mA/g, respectively.

Flotation separation of lithium–ion battery electrodes predicted by a long short-term memory network using data from physicochemical kinetic simulations and experiments

Anode and cathode active materials from spent lithium–ion batteries may be recovered and potentially used in new batteries to promote recycling and resource circulation. Froth flotation was applied to pristine active materials and the black mass obtained from pretreated spent batteries. Flotation kinetics was simulated with the use of computational fluid dynamics and surface chemistry. Bubble surface coverage and entrainment in the flotation kinetics model were selected and optimized by systematic fitting to experimental data. Entrainment influences the recovery and grade of the active materials. The optimized flotation kinetics model was used for generating additional data that, along with the fitted data, were used to train a deep learning neural network. The trained network was validated using anode–cathode and black mass flotation experiments, and its predictions showed a maximum residual error of 0.18 ± 0.11 recovery. The simulation framework was developed into a desktop application that predicts the flotation behavior of active materials. It provides information for estimating results following operational and physicochemical changes and for optimizing flotation processes. Finally, recovered anode active materials from black mass were selected for coin cell tests. The coulombic efficiency of these coin cells was initially lower (86.8 %) than that of cells made with pristine graphite particles (98.4 %).

Bidirectional pH Buffer Effect Facilitates High-Reversible Aqueous Zinc Ion Batteries.

Aqueous zinc ion batteries (AZIBs) stand out from the crowd of energy storage equipment for their superior energy density, enhanced safety features, and affordability. However, the notorious side reaction in the zinc anode and the dissolution of the cathode materials led to poor cycling stability has hindered their further development. Herein, ammonium salicylate (AS) is a bidirectional electrolyte additive to promote prolonged stable cycles in AZIBs. NH4 + and C6H4OHCOO- collaboratively stabilize the pH at the interface of the electrolyte/electrode and guide the homogeneous deposition of Zn2+ at the zinc anode. The higher adsorption energy of NH4 + compared to H2O on the Zn (002) crystal plane mitigates the side reactions on the anode surface. Moreover, NH4 + is similarly adsorbed on the cathode surface, maintaining the stability of the electrode. C6H4OHCOO- and Zn2+ are co-intercalation/deintercalation during the cycling process, contributing to the higher electrochemical performance of the full cell. As a result, with the presence of AS additive, the Zn//Zn symmetric cells achieved 700h of highly reversible cycling at 5mA cm-2. In addition, the assembled NH4V4O10(NVO)//Zn coin and pouch batteries achieved higher capacity and higher cycle lifetime, demonstrating the practicality of the AS electrolyte additive.

Clinical features, management, and complications of paediatric button battery ingestions in Canada: an active surveillance study using surveys of Canadian paediatricians and paediatric subspecialists

Clinical features, management, and complications of paediatric button battery ingestions in Canada: an active surveillance study using surveys of Canadian paediatricians and paediatric subspecialists

Manipulation of Zn Deposition Behavior to Achieve High-Rate Aqueous Zinc Batteries via High Valence Zirconium Ions.

Aqueous zinc ion batteries are excellent energy storage devices with high safety and low cost. However, the corrosion reaction and zinc dendrite formation occurring on the surface of zinc anodes are hindering their further development. To solve the problems, zirconium acetate (ZA) was used as an electrolyte additive in the ZnSO4 electrolyte. Attributing to the higher electro-positivity of Zr4+ than Zn2+, these high valence metal cations preferentially adsorb onto the surface of metallic zinc, shielding parasitic reactions between zinc and electrolyte, reshaping the electric field distribution, and directing preferential homogeneous deposition of Zn-ions on the Zn (002) crystal plane. Furthermore, the adsorption of Zr4+ on the Zn metal after electrochemical cycles can enhance the energy barrier of zinc atom diffusion, resulting in high resistance of corrosion and manipulation of the Zn2+ nucleation configuration. Attributing to these properties, the Zn//Zn symmetric cell with an electrolyte additive of ZA was able to cycle for 400 h under an extremely high current density of 40 mA cm-2 with an area capacity of 2 mAh cm-2. Meanwhile, the MnO2//Zn coin cell still had 81.7 mAh g-1 (85% retention of capacity) after 850 cycles under a current density of 1 A g-1.

VO2·xH2O nanoribbons as high-capacity cathode material for aqueous zinc-ion batteries: Electrolyte selection and performance optimization

In the pursuit of efficient energy storage solutions for renewable energy, aqueous zinc-ion batteries (ZIBs) have emerged as promising contenders, offering high capacity and manufacturability. Among transition metal oxides, vanadium dioxide (VO2) stands out as the synergestic behavior of H+ and Zn2+ ions with the VO2·xH2O ensures high specific capacity in Zn-ion based battery. Here, we present the successful synthesis of hydrated vanadium oxide (VO2·xH2O) nanoribbons via the hydrothermal method, followed by comprehensive characterizations to assess material properties. A systematic study on electrolyte selection, focusing on achieving high capacity and stability, was conducted using varying electrolyte types and concentrations. The superior 3 M Zn(CF3SO3)2 electrolyte was chosen for further electrochemical investigations, leading to the formation of a two-electrode system comprising VO2·xH2O//Zn half-cell ZIB, which lasts more than 1000 cycles at 1 A g−1 in addition to capacity retention of 82.18% while providing a capacity of 235.63 mAh g−1 at 0.1 A g−1, while demonstrating favorable rate capability. Ex-situ XRD analysis unveiled insights into the designed ZIB's charging/discharging mechanism, showcasing variations in cathode crystallinity and the formation of Zn(OH)2 peaks during cycling. To establish the effective usage of this formed ZIB for daily-life applications, the coin cell was effectively used to power an LED and LCD screen, and the subsequently attained value of capacity was compared along with the available literature. This work surpasses existing ZIBs in terms of capacity and cyclability, paving the way for a more sustainable future through efficient energy storage from renewable sources.

Dual action electrochemical bandage operated by a programmable multimodal wearable potentiostat

We have developed electrochemical bandage (e-bandage) prototypes that generate the reactive oxygen species hypochlorous acid (HOCl) or hydrogen peroxide (H2O2) for potential use to treat biofilm-infected wounds in humans. We have shown that both e-bandage-generated HOCl and H2O2 kill biofilms in vitro and in infected wounds on mice, with the former being more active in vitro. The H2O2-generating e-bandage, more so than the HOCl-generating e-bandage, was associated with improved healing of infected wounds. Here, a strategy in which H2O2 and HOCl are alternately generated—for dual action—was explored. The goal was to develop a programmable multimodal wearable potentiostat [PMWP] that can generate HOCl or H2O2, as needed. An ultralow-power microcontroller unit was developed to manage operation of the PMWP. The system was operated with a 260-mAh capacity coin battery and weighed 4.6 g, making it suitable for future small animal experiments (and ultimately, potential evaluation in humans). As assessed using electrochemical parameters, the device functioned comparably to a commercial benchtop potentiostat. To confirm antimicrobial activity, PMWP-controlled e-bandages were tested in vitro against clinical isolates of methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Enterococcus faecium, and Candida auris. When programmed to deliver HOCl followed by H2O2, PMWP-controlled e-bandages exhibited activity against biofilms of all study isolates tested. Finally, we demonstrated the PMWP's usability in a murine wound infection model.

Boosting the potassium storage property of spongia-like copper phosphide anode via nano-in-micro construction

Metal phosphides (MPs) show great promise as anode material in potassium-ion batteries (PIBs) owing to their cost-effectiveness and high theoretical capacity. Despite that, MPs anode usually manifests inferior poor cyclability as a result of dramatic volume fluctuation during discharge–charge cycling. Herein, a scalable salt template-assisted spray-drying method is developed to fabricate the porous carbon microspheres wrapped CuP2 nanoparticles (p-CuP2/C) with a nano-in-micro structure. The combination of the CuP2 nanoparticles, large meso-porous carbon microspheres can simultaneously offer plenty of reactive sites, promote electrolyte penetration, and maintain structural integrity. Additionally, the proposed synthesis strategy is suit for the industrial manufacture. As an anode for PIBs, the p-CuP2/C anode presents a high reversible capacity (494 mAh/g at 0.05 A/g), excellent cycling stability (a capacity degradation rate of 0.04 % per cycle during 2000 cycles at 2 A/g), and superior rate capability (244 mAh/g at 2 A/g). More impressively, pairing with a potassium Prussian blue cathode, the potassium-ion coin cell shows an excellent cycling lifespan with 87.1 % capacity retention after 200 cycles at a current density of 0.1 A/g, the assembled pouch cell also maintains stable cycling at 0.3 A/g over 80 cycles. This research could offer a facile approach to develop other advanced anodes with industrial practicability for alkali ion batteries.