1,720,981 research outputs found
Electrochemical features of LiMnPO4 olivine prepared by sol-gel pathway
No full textLiMnPO4 is a potential cathode for lithium-ion battery of high thermal stability, low cost, environmental sustainability and high theoretical energy density. However, this intriguing olivine material suffers from intrinsic sluggish kinetics of lithium (de-)insertion, which limits the reversible reaction in practical lithium cells. Herein we report a careful study of the impedance features of LiMnPO4 during electrochemical reaction in lithium cell. The LiMnPO4 material is prepared by sol-gel method and fully characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The material shows suitable galvanostatic cycling with a working voltage of about 4.1 V, which is higher than the 3.5 V value expected from the most common olivine material, i.e., LiFePO4. Hence, electrochemical impedance spectroscopy (EIS) is used to study the lithium (de-)insertion within the LiMnPO4 structure. The results indicate an impedance behavior depending on the state of charge and a lithium diffusion coefficient trend slightly decreasing during cell operation within the 10−14 − 10−13 cm2 s−1 range. The electrochemical study in lithium cell reveals remarkable enhancement of the electrode kinetics at 70 °C, which suggests preferred application of LiMnPO4 materials at the higher temperatures
Lithium transport properties in LiMn1−αFeαPO4 olivine cathodes
No full textWe report a comparative study of the electrochemical lithium diffusion properties within the olivine structure of LiMn0.5Fe0.5PO4, LiFePO4, and LiMnPO4 materials prepared by the solvothermal pathway. The study includes careful analysis performed by potentiodynamic cycling with galvanostatic acceleration (PCGA), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and the galvanostatic intermittent titration technique (GITT), carried out in order to investigate the features of the Fe3+/Fe2+ and Mn3+/Mn2+ redox processes and the lithium ion transport within the olivine structure. The electrochemical investigation reveals a shift of the redox potential of Fe3+/Fe2+ and Mn3+/Mn2+ couples toward higher and lower values, respectively, in LiMn0.5Fe0.5PO4 with respect to the bare materials. Interestingly, the study shows the dependence of the lithium diffusion coefficients on the state of charge of the materials as well as on the adopted technique. Accordingly, CV leads to lithium diffusion coefficients of the order of 10−12 cm2 s
−1 for LiMnPO4, 10−9 cm2 s −1 for LiFePO4, and 10−11 cm2 s −1 for LiMn0.5Fe0.5PO4. EIS mainly indicates lower values of lithium diffusion coefficients, i.e., 10−13 cm2 s −1 for LiMnPO4, 10−12 cm2 s −1 for LiFePO4, and 10−13 cm2 s −1 for LiMn0.5Fe0.5PO4. GITT provides a wide range of Li+ diffusion coefficient, depending on the Li1−xMePO4 stoichiometry, that is, 10−14−10−10 cm2 s −1 for LiMnPO4 and LiFePO4 and 10−13−10−10 cm2 s −1 for LiMn0.5Fe0.5PO4. The wide diffusion coefficient window obtained by changing the state of charge and the adopted technique sheds light on the complex trend of the lithium diffusion in olivines and indicates that the technique may actually influence the materials evaluation
Lithium Metal Battery Using LiFe0.5Mn0.5PO4 Olivine Cathode and Pyrrolidinium-Based Ionic Liquid Electrolyte
Get PDFIonic liquids (ILs) represent the most suitable electrolyte media for a safe application in high-energy lithium metal batteries because of their remarkable thermal stability promoted by the room-temperature molten salt nature. In this work, we exploit this favorable characteristic by combining a pyrrolidinium-based electrolyte and a LiFe0.5Mn0.5PO4 mixed olivine cathode in a lithium metal cell. The IL solution, namely N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) dissolving LiTFSI, is designed as viscous electrolyte, particularly suited for cells operating at temperatures higher than 40 °C, as demonstrated by electrochemical impedance spectroscopy. The olivine electrode, characterized by remarkable structural stability at high temperature, is studied in the lithium metal cell using the Pyr14TFSI–LiTFSI medium above the room temperature. The Li/Pyr14TFSI–LiTFSI/LiFe0.5Mn0.5PO4 cell delivers a capacity of about 100 mA h g–1 through two voltage plateaus at about 3.5 and 4.1 V, ascribed to the iron and manganese redox reaction, respectively. The cycling stability, satisfactory levels of the energy density, and a relevant safety content suggest the cell studied herein as a viable energy storage system for future applications
Rechargeable lithium battery using non-flammable electrolyte based on tetraethylene glycol dimethyl ether and olivine cathodes
Get PDFWe propose lithium metal cells employing LiCF3SO3-tetraethylene glycol dimethy ether (TEGDME)
electrolyte solution with LiFePO4 and LiMn0.5Fe0.5PO4 cathodes. The electrolyte is selected due to its nonflammability, herein demonstrated, and considered as a key requirement for application cells employing
high energy lithium metal anode. The selected olivine cathodes, i.e., stable materials prepared by solvothermal
pathway, have regular submicrometrical morphology suitable for cell operation and homogeneous
composition, as confirmed by electron microscopy and energy dispersive X-ray spectroscopy.
The electrochemical tests reveal promising cycling performances in terms of delivered capacity, stability
and rate capability. The Li/LiCF3SO3-TEGDME/LiFePO4 cell operates at 3.5 V with capacity ranging from
150 mAh g-1 at C/10 to 110 mAh g-1 at 2C, while the Li/LiCF3SO3-TEGDME/LiFe0.5Mn0.5PO4 cell performs
following two plateaus at 4.1 V and 3.5 V with capacity ranging from 160 mAh g-1 at C/10 to
75 mAh g-1 at 2C. Hence, the results demonstrate the suitability of TEGDME-based electrolytes in
combination with LiFePO4 and LiFe0.5Mn0.5PO4 cathodes for high performances lithium battery
A Gel-Polymer Sn-C/LiMn<inf>0.5</inf>Fe<inf>0.5</inf>PO<inf>4</inf> Battery Using a Fluorine-Free Salt
No full textSafety and environmental issues, because of the contemporary use of common liquid electrolytes, fluorinated salts, and LiCoO2-based cathodes
in commercial Li-ion batteries, might be efficiently mitigated by employing alternative gel−polymer battery configurations and new electrode materials. Herein we study a lithium-ion polymer cell formed by combining a LiMn0.5Fe0.5PO4 olivine cathode, prepared by simple solvothermal pathway, a nanostructured Sn−C anode, and a LiBOB-containing PVdF-based gel electrolyte. The polymer electrolyte, here analyzed in terms of electrochemical stability by impedance spectroscopy (EIS) and voltammetry, reveals full compatibility for cell application. The LiBOB electrolyte salt and the electrochemically delithiaded Mn0.5Fe0.5PO4 have a higher thermal stability compared to conventional LiPF6 and Li0.5CoO2, as confirmed by thermogravimetric analysis (TGA) and by galvanostatic cycling at high temperature. LiMn0.5Fe0.5PO4 and Sn−C, showing in lithium half-cell a capacity of about 120 and 350 mAh g−1, respectively, within the gelled electrolyte configuration are combined in a full Li-ion polymer battery delivering a stable capacity of about 110 mAh g−1, with working voltage ranging from 2.8 to 3.6 V
Lithium-ion batteries for sustainable energy storage: recent advances towards new cell configurations
Get PDFThe recent advances in the lithium-ion battery concept towards the development of sustainable energy storage systems are herein presented. The study reports on new lithium-ion cells developed over the last few years with the aim of improving the performance and sustainability of electrochemical energy storage. Alternative chemistries involving anode, cathode and electrolyte components are herein recalled in order to provide an overview of state-of-the-art lithium-ion battery systems, with particular focus on the cell configurations currently proposed at the laboratory scale. Hence, the review highlights the main issues related to full cell assembly, which have been tentatively addressed by a limited number of reports, while many papers describe materials investigation in half-cells, i.e., employing lithium metal anodes. The new battery prototypes here described are evaluated in terms of their electrochemical performances, cell balance, efficiency and cycle life. Finally, the applicability of these suitable energy storage systems is evaluated in the light of their most promising characteristics, thus outlining a conceivable scenario for new generation, sustainable lithium-ion batteries
A high voltage olivine cathode for application in lithium-ion batteries
No full textA new olivine composition (i.e., LiFe0.25Mn0.5Co0.25PO4) is proposed as electrode material with increased energy density for application in lithium-ion batteries. The new formulation increases the working voltage and induces different electrochemical behavior with respect to bare olivine materials based on Fe. The study provides deep insight into the features of the Fe3+/Fe2+, Mn3+/Mn2+, and Co3+/Co2+ redox couples within the olivine lattice in terms of electrochemical activity, Li+ transport properties, and Li-cell behavior. The electrochemical characterization clearly reveals the voltage signatures corresponding to the various metals; however, the Mn3+/Mn2+ process has higher intrinsic polarization with respect to Fe3+/Fe2+ and Co3+/Co2+. This issue is efficiently mitigated by carbon coating the material, resulting in enhanced electrochemical performances
Insight on the Enhanced Reversibility of a Multimetal Layered Oxide for Sodium-Ion Battery
Get PDFSodium-ion layered cathodes range along a vast variety of structures and chemical compositions that influence the physical–chemical characteristics and the electrochemical features in battery. In this work, we show that the synergistic effects of various metals, enhanced structure, and optimal morphology of Na₀.₄₈AI₀.₀₃Co₀.₁₈Ni₀.₁₈Mn₀.₄₇O₂ material lead to remarkable reversibility in a sodium cell. X-ray diffraction refinement evidences that the electrode has a P3/P2-type layered structure, whereas scanning electron microscopy study shows a morphology consisting of primary layers with nanometric thickness regularly stacked into uniform micrometric particles. In-depth investigation combining ex situ X-ray diffraction, galvanostatic intermittent titration, and voltammetry measurements reveals solid-solution Na⁺ intercalation into the layered oxide between 1.4 and 4.6 V versus Na+/Na with relevant lattice stability. Furthermore, the study shows the absence of phase transitions during Na⁺ exchange within the material framework, which advantageously leads to enhanced reversibility, benefiting from minor lattice change upon Na+ intercalation, fast diffusion, improved electrode/electrolyte interphase, and smooth voltage profile. Hence, the electrode delivers a maximum capacity of about 175 mAh g⁻¹ with suitable cycling stability and a Coulombic efficiency approaching 99% in a sodium cell. Therefore, we believe that the study reported herein may shed light on important characteristics of this attractive class of electrodes, allowing efficient operation in next-generation sodium-ion batteries
Lithium sulfur battery exploiting material design and electrolyte chemistry: 3D graphene framework and diglyme solution
No full textHerein we investigate a lithium sulfur battery suitably combining alternative cathode design and relatively safe, highly conductive electrolyte. The composite cathode is formed by infiltrating sulfur in a N-doped 3D graphene framework prepared by a microwave assisted solvothermal approach, while the electrolyte is obtained by dissolving lithium bis(trifluoromethane)sulfonimide (LiTFSI) in diethylene glycol dimethyl ether (DEGDME), and upgraded by addition of lithium nitrate (LiNO3) as a film forming agent. The particular structure of the composite cathode, studied in this work by employing various techniques, well enhances the lithium-sulfur electrochemical process leading to very stable cycling trend and specific capacity ranging from 1000 mAh g−1at the highest rate to 1400 mAh g−1at the lowest one. The low resistance of the electrode/electrolyte interphase, driven by an enhanced electrode design and a suitable electrolyte, is considered one of the main reasons for the high performance which may be of interest for achieving a promising lithium-sulfur battery. Furthermore, the study reveals a key bonus of the cell represented by the low flammability of the diglyme electrolyte, while comparable conductivity and interface resistance, with respect to the most conventional solution used for the lithium sulfur cell
Effect of the iron doping in LiCoPO4 cathode materials for lithium cells
No full textLiCoPO4 (LCP) is a promising candidate as alternative cathode for high-voltage lithium-ion batteries.
However, its practical electrochemical performances are still far from the theoretical data likely due to
the low electronic and ionic conductivities. Moreover LCP typically suffers a rapid capacity fading upon
cycling, probably due to structural degradations and electrolyte decomposition at 5 V vs. Li+/Li. Previous
studies showed that carbon coating and metal doping may improve LCP electrochemical properties. In
this work we report: (a) the
fine tuning of a novel synthetic route at low temperature to obtain
micrometric LCP crystallites morphologically homogeneous and crystallographically pure; (b) the
analysis of the effect of iron doping on LCP structural features and electrochemical properties in lithium
cell; (c) the beneficial simultaneous effect of iron doping and post-synthesis high-temperature annealing
on the electrochemical performances in Li cells. The optimized material shows a reversible capacity of
120 mAh g1 at 0.1C rate and a capacity retention of 78% after 20 cycles
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