1,720,994 research outputs found
A High-Voltage, Multi-Metal LiNi0.35Cu0.1Mn1.45Fe0.1O4Spinel Cathode for Lithium Batteries
No full textA LiNi0.35Cu0.1Mn1.45Fe0.1O4 spinel cathode exploiting the multi-metal approach and operating in a lithium battery at 4.7 V is prepared by co-precipitation of metal oxalates followed by annealing. Our investigation demonstrates that the designed electrode formulation including Ni, Cu, Mn and Fe may actually ensure suitable structural and morphological characteristics, as well as an extended stability in cells operating at 25 C and 55 C. Indeed, the LiNi0.35Cu0.1Mn1.45Fe0.1O4 cathode shows reversible capacities of 108 mAh g-1 at 0.75C and 91 mAh g-1 at 1.5C (where 1C is 147 mA g-1), with a retention between 84% and 80% after 200 cycles and coulombic efficiency values of about 99%. Notably, optimal cathode composition in terms of metals nature and content avoids material degradation upon cycling and enables stable operation in the lithium cell even at a temperature higher than 25 C, with satisfactory retention of the initial capacity of 110 mAh g-1, i.e., 77%, after 200 cycles at 0.5C. Therefore, the strategy adopted herein is considered adequate for allowing practical battery application of the high-voltage spinel cathode
Investigation of Mn and Fe Substitution Effects on the Characteristics of High-Voltage LiCo1- xMxPO4 (x = 0.1, 0.4) Cathodes Prepared by Sol-gel Route
No full textHerein, we provide a fundamental study revealing the substantial changes promoted by manganese and iron substitution for cobalt in a high-voltage LiCoPO4 olivine cathode. Therefore, LiCoPO4, LiCo0.9Fe0.1PO4, LiCo0.6Fe0.4PO4, LiCo0.9Mn0.1PO4, and LiCo0.6Mn0.4PO4 are synthesized by a sol-gel pathway and comparatively investigated in terms of structure, morphology, and electrochemical features in lithium battery. Besides the observed effects on structure, particle size, and metals distribution, the work reveals a gradually enhancing electrode reaction by increasing the Fe content in LiCo0.9Fe0.1PO4 and LiCo0.6Fe0.4PO4, with Co3+/Co2+ and Fe3+/Fe2+ signatures at 4.8 and 3.5 V vs Li+/Li, respectively. On the other hand, the introduction of Mn leads to a progressive electrode deactivation in LiCo0.9Mn0.1PO4 and LiCo0.6Mn0.4PO4 due to an intrinsic hindering of the Mn3+/Mn2+ process at 4.1 V vs Li+/Li. The reasons accounting for such an intriguing behavior are investigated in detail using electrochemical impedance spectroscopy within the potential range of the redox processes. The study reveals that manganese and iron substitutions in the high-voltage olivine have opposite effects on the charge transfer resistance, i.e., detrimental for the former while beneficial for the latter, with remarkable enhancement of the reversible capacity, the Coulombic efficiency, and the cycle life. Such results provide to the scientific community useful information on possible strategies to enhance the emerging LiCoPO4 high-voltage electrode by transition metal substitution
Novel Lithium-Sulfur Polymer Battery Operating at Moderate Temperature
No full textA safe lithium-sulfur (Li−S) battery employs a composite polymer electrolyte based on a poly(ethylene glycol) dimethyl ether (PEGDME) solid at room temperature. The electrolyte membrane enables a stable and reversible Li−S electrochemical process already at 50 °C, with low resistance at the electrode/electrolyte interphase and fast Li+ transport. The relatively low molecular weight of the PEGDME and the optimal membrane composition in terms of salts and ceramic allow a liquid-like Li−S conversion reaction by heating at moderately high temperature, still holding the solid-like polymer state of the cell. Therefore, the electrochemical reaction of the polymer Li−S cell is characterized by the typical dissolution of lithium polysulfides into the electrolyte medium during discharge and the subsequent deposition of sulfur at the electrode/electrolyte interphase during charge. On the other hand, the remarkable thermal stability of the composite polymer electrolyte (up to 300 °C) suggests a lithium-metal battery with safety content significantly higher than that using the common, flammable liquid solutions. Hence, the Li−S polymer battery delivers at 50 °C and 2 V a stable capacity approaching 700 mAh gS−1, with a steady-state coulombic efficiency of 98 %. These results suggest a novel, alternative approach to achieve safe, high-energy batteries with solid polymer configuration
Triglyme-based electrolyte for sodium-ion and sodium-sulfur batteries
Full text linkHerein, we investigate a lowly flammable electrolyte formed by dissolving sodium trifluoromethanesulfonate (NaCF₃SO₃) salt in triethylene glycol dimethyl ether (TREGDME) solvent as suitable medium for application in Na-ion and Na/S cells. The study, performed by using various electrochemical techniques, including impedance spectroscopy, voltammetry, and galvanostatic cycling, indicates for the solution high ionic conductivity and sodium transference number (t⁺), suitable stability window, very low electrode/electrolyte interphase resistance and sodium stripping/deposition overvoltage. Direct exposition to flame reveals the remarkable safety of the solution due to missing fire evolution under the adopted experimental setup. The solution is further investigated in sodium cells using various electrodes, i.e., mesocarbon microbeads (MCMBs), tin-carbon (Sn–C), and sulfur-multiwalled carbon nanotubes (S-MWCNTs). The results show suitable cycling performances, with stable reversible capacity ranging from 90 mAh g⁻¹ for MCMB to 130 mAh g⁻¹ or Sn–C, and to 250 mAh g⁻¹ for S-MWCNTs, thus suggesting the electrolyte as promising candidate for application in sustainable sodium-ion and sodium-sulfur batteries
Spinel Cathode and Their Combination in a Li-Ion Battery
No full textA Li-conversion α-Fe2O3@C nanocomposite anode and a high-voltage LiNi0.5Mn1.5O4 cathode are synthesized in parallel, characterized, and combined in a Li-ion battery. α-Fe2O3@C is prepared via annealing of maghemite iron oxide and sucrose under an argon atmosphere and subsequent oxidation in air. The nanocomposite exhibits a satisfactory electrochemical response in a lithium half-cell, delivering almost 900 mA h g-1, as well as a significantly longer cycle life and higher rate capability compared to the bare iron oxide precursor. The LiNi0.5Mn1.5O4 cathode, achieved using a modified co-precipitation approach, reveals a well-defined spinel structure without impurities, a sub-micrometrical morphology, and a reversible capacity of ca. 120 mA h g-1 in a lithium half-cell with an operating voltage of 4.8 V. Hence, a lithium-ion battery is assembled by coupling the α-Fe2O3@C anode with the LiNi0.5Mn1.5O4 cathode. This cell operates at about 3.2 V, delivering a stable capacity of 110 mA h g-1 (referred to the cathode mass) with a Coulombic efficiency exceeding 97%. Therefore, this cell is suggested as a promising energy storage system with expected low economic and environmental impacts
Glyme-based electrolytes: Suitable solutions for next-generation lithium batteries
No full textThe concept of green in a battery involves the chemical nature of electrodes and electrolytes as well as the economic sustainability of the cell. Although these aspects are typically discussed separately, they are deeply interconnected: indeed, a new electrolyte can allow the use of different cathodes with higher energy, lower cost or more pronounced environmental compatibility. In this respect, we focus on an alternative class of electrolyte solutions for lithium batteries formed by dissolving LiX salts in glyme solvents, i.e., organic ethers with the molecular formula CH3O[CH2CH2O]nCH3 differing by chain length. The advantages of these electrolytes with respect to the state-of-the-art ones are initially illustrated in terms of flammability, stability, toxicity, environmental compatibility, cell performances and economic impact. A particular light is shed on the stability of these systems, particularly in the polymer state, and in various environments including oxygen, sulfur and high-energy lithium metal. Subsequently, the most relevant studies on the chemical-physical features, characteristic structures, favorable properties, and electrochemical behavior of glyme-based solutions are discussed, and the most recent technological achievements in terms of cell design and battery performance are described. In the final sections, the use of glyme-based electrolytes in high-energy cells arranged by coupling a lithium-metal anode with conventional insertion cathodes as well as in alternative and new batteries exploiting the Li-S and Li-O2 conversion processes is described in detail. The various paragraphs actually reveal the advantages, including safety, low cost and sustainability, which can be achieved by employing the glyme-based electrolytes with respect to the commercially available ones, in particular taking into account future and alternative applications. Particular relevance is given to the glymes with long chains that show remarkable stability, high safety and very low toxicity. Therefore, this review is expected to shed light on the potentialities, the actual advantages compared to the state-of-the-art batteries, and the possible applications of electrolytes based on glyme solvents in next-generation energy storage systems
Structural and Morphological Tuning of LiCoPO4 materials Synthesized By SolvoThermal Methods for LiCell Applications
No full textThe role of synthesis pathway on the microstructural characteristics of sulfur-carbon composites: X-ray imaging and electrochemistry in lithium battery
No full textTwo synthesis pathways are adopted to tune the microstructural characteristics of sulfur-carbon (S-C) composites for application in lithium-sulfur (Li-S) batteries. Both methods include intimate mixing of either carbon black or multiwalled carbon nanotubes with elemental sulfur, molten according to the first approach while dispersed in alcohol and heated according to the second one. Nano- and micro-scale X-ray computed tomography supported by X-ray diffraction and electron microscopy shows materials consisting of crystalline sulfur clusters (70 wt%) with size ranging from about 5 to 50 μm, surrounded by carbon. The sulfur cluster size appears limited by direct mixing of molten sulfur and carbons, in particular when carbon black is employed, whilst it is increased by exploiting the alcohol dispersion. Electrochemistry reveals that small sulfur particles lead to an improved rate capability in Li-S cells, whereas large active material domains may favor the capacity retention. The composites using carbon black nanoparticles exhibit the highest reversible capacity, with a maximum value exceeding 1500 mAh gS−1, whereas the composites involving multiwalled carbon nanotubes show the best capacity retention, with values approaching 70% over 150 cycles. Our multi-disciplinary approach will shed light on significant aspects aiming to enhance the Li-S battery and favor a practical application
Characteristics of a gold-doped electrode for application in high-performance lithium-sulfur battery
No full textBulk sulfur incorporating 3 wt% gold nano-powder is investigated as possible candidate to maximize the fraction of active material in the Li-S battery cathode. The material is prepared via simple mixing of gold with molten sulfur at 120 °C, quenching at room temperature, and grinding. Our comprehensive study reports relevant electrochemical data, advanced X-ray computed tomography (CT) imaging of the positive and negative electrodes, and a thorough structural and morphological characterization of the S:Au 97:3 w/w composite. This cathode exhibits high rate capability within the range from C/10 to 1C, a maximum capacity above 1300 mAh gS−1, and capacity retention between 85% and 91% after 100 cycles at 1C and C/3 rates. The novel formulation enables a sulfur fraction in the composite cathode film as high as 78 wt%, an active material loading of 5.7 mg cm−2, and an electrolyte/sulfur (E/S) ratio of 5 μL mg−1, which lead to a maximum areal capacity of 5.4 mAh cm−2. X-ray CT at the micro- and nanoscale reveals the microstructural features of the positive electrode that favor fast conversion kinetics in the battery. Quantitative analysis of sulfur distribution in the porous cathode displays that electrodeposition during the initial cycle may trigger an activation process in the cell leading to improved performance. Furthermore, the tomography study reveals the characteristics of the lithium anode and the cell separator upon a galvanostatic test prolonged over 300 cycles at a 2C rate
Investigating high-performance sulfur-metal nanocomposites for lithium batteries
No full textHerein, for the first time, we study the reversible conversion in a lithium cell of a novel sulfur-metal nanocomposite by combining X-ray computed tomography data at the micro- and nanoscales with the electrochemistry. The electrode is obtained at mild temperatures according to an alternative approach, including metal nanoparticles of either tin or nickel in bulk molten sulfur in the corresponding weight ratio of 85 : 15. We show that this pathway leads to the formation of high-performance electrodes, matching the state-of-the-art results obtained from the best carbonaceous composites. Indeed, lithium-sulfur (Li-S) cells at a working voltage of about 2.2 V ensure sulfur-mass-referred capacity approaching 1400 mA h g−1at a C/3 rate and 740 mA h g−1at a rate as high as 3C (1C = 1675 mA h g−1), with a coulombic efficiency close to 100% and stable cycling trends over 100 cycles. High-resolution imaging sheds light on the characteristic morphological features of the electrode allowing these remarkable performances, and reveals the beneficial effects of the incorporation of metal nanoparticles within the sulfur phase. The various investigation techniques, with a particular focus on three-dimensional imaging, suggest sulfur electrodeposition upon charging, preferentially adjacent to the electron-conductive centers within the electrode support as well as that on metal clusters. A massive microstructural reorganization is observed during the first cycle in lithium cells with concomitant remarkable enhancements in the electrode charge transfer and variation in the reaction potentials. This process is accompanied by substantial electrode amorphization and migration of the active material toward the current-collector bulk. The results obtained in this work, as well as a comprehensive study with anad hocdesign for sulfur electrodes, suggest alternative strategies for ultimately achieving actual Li-S cell improvement
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