Electrodes For Rechargeable Lithium Batteries Research Articles

Two‐dimensional materials and synthesis, energy storage, utilization, and conversion applications of two‐dimensional MXene materials

Owing to the first-rate residences of graphene, the research had been achieved on novel two-dimensional (2D) materials. The MXene is a 2D inorganic compound that consists of transition metal carbides, nitrides, and carbonitrides. Ti₃C₂, the primary 2D-layered MXene, was reported in 2011. This material that is a layered bulk material analogous to graphite, changed into derived from its 3D phase, is Ti₃AlC₂ MAX. The start of this review through reviewing the structures and morphologies and their fabrication routes. After this, the discussion converts to the mechanical, electrical, and electronic properties of MXenes. The awareness then turns to their thrilling capacity in energy storage, conversion, and utilization. Energy storage programs encompass electrodes in rechargeable lithium batteries and supercapacitors. In phrases of energy conversion and utilization, photocatalytic hydrogen evolution, solar steam manufacturing, photothermal therapies, photovoltaic devices are presented. Highlights The study shows that transition metal carbides and nitrides (MXenes), own circle of two-dimensional (2D) inorganic compounds. The substances composed of some atomic layers of transition metal carbides, nitrides, or carbonitrides. Ti₃C₂, the primary 2D-layered MXene, were remote in 2011 This material that is a layered material analogous to graphite, changed into derived from its 3D phase, is Ti₃AlC₂ MAX Conversion of mechanical, electrical, and electronic properties of MXenes which turns to their thrilling capacity in energy storage, conversion, and utilization

A low-cost and high-loading viologen-based organic electrode for rechargeable lithium batteries.

Organic active materials are regarded as a very promising choice for lithium batteries because of several outstanding advantages such as low-cost, flexible tunability and pollution-free sources. Viologen compounds are attractive two-electron storage materials with low redox potentials, which are mainly used as anolytes in redox flow batteries (RFBs) considering their high solubility in electrolytes. However, due to their relatively large molecular weight and low density, it is difficult to prepare high-loading and stable-cycling electrodes for lithium battery application. In this research, by adopting 4,4′-bipyridine as the raw material and combining salification with a high-energy ball milling method, a low-solubility and high-stability viologen carbon-coated composite, ethyl viologen dihexafluorophosphate-Ketjen black (EV-KB), is synthesized. Then, by optimizing the electrode preparation process, a high-loading viologen-based electrode is successfully prepared. Salification effectively reduces the solubility of viologen compounds in the electrolyte so that the EV-KB composite can be used in lithium batteries. At the same time, it is pointed out that current collectors and slurry solvents play an important role in achieving the high-loading electrode. By deliberately selecting carbon paper as the current collector and ethanol as the solvent, the EV-KB composite organic electrode with a loading up to 1.5–9 mg cm−2 can achieve a specific capacity of 106–79 mA h g−1 for 400 stable cycles with a coulombic efficiency of 96% as well as a good rate capability. The synthesis method and electrode preparation optimization process introduced in this paper provide a reference for other types of organic active materials to be used in high-loading lithium batteries.

Dealloyed nanoporous materials for rechargeable lithium batteries

Dealloying has been recognized as a universal strategy to fabricate various functional electrode materials with open networks, nanoscale ligaments, tunable pore sizes and rich surface chemistry, all of which are very attractive characteristics for rechargeable lithium batteries. In particular, lithium ion insertion/extraction in metal anodes is naturally associated with the alloying/dealloying mechanism. The past decade has witnessed rapid growth of this research field with enormous progress. In this review article, we first summarize the recent development and microstructural regulation of dealloyed materials. Next, we focus on the rational design of nanoporous electrodes for rechargeable lithium batteries and related structure-performance correlations. Finally, some critical issues and perspectives are presented to guide the future development directions of such promising technology for high-energy batteries. This review systematically summarizes the recent progress of dealloyed nanoporous materials and their application in rechargeable lithium batteries.

High energy storage of Li-ions on keggin-type polyoxometalate as electrodes for rechargeable lithium batteries

In the result of increasing energy demand, rechargeable Li-ion batteries with high energy density are suitable sustainable power sources for the energy storage generations. Keggin-type polyoxometalates (POM) are being regarded as an electrode material for energy storage devices, though advanced improvement is adaptable for futuristic applications. Consequently, we demonstrate [PMo10V2O40]−5 POM with hydrogen and lithium as counter cations for anode and cathode synthesize by simple and cost-effective method, with the average energy densities of 230 Wh g−1 and 329.4 Wh g−1. The material with lithium cation deliver high initial specific capacity 1414 mAh g−1 for anode and 332 mAh g−1 for cathode at 0.1C than the material with the hydrogen cation. Among which, the cathode seems favorable with long and stable cycle life. The structural, compositional, morphological and electrochemical studies are explored from the various physical and electrochemical techniques. Also the geometry optimization of POM with hydrogen and lithium clusters is studied from the computational studies. In these cluster with lithium cation acts as a promising electrodes for Li-ion rechargeable batteries.

Homogeneous Interface Conductivity for Lithium Dendrite-Free Anode

Dendrite growth is one of the major problems that hinder the practical application of lithium metal electrodes in rechargeable lithium batteries. Herein, we report that the thin-film Cu3N coating can greatly suppress the lithium dendrite growth on the Cu current collector. Li|Cu and LiFePO4|Cu cells using thin-film Cu3N-modified Cu foil as electrode exhibit improved cyclic stability and low charge–discharge overpotential. A multifaceted investigation demonstrates that Cu3N can convert to Li3N/Cu nanocomposite after initial lithium plating, forming in situ a highly homogeneous conductive network. The peak-force tunneling atomic force microscopy experiments enable the direct measurement of the surface conductivity, confirming the improved distribution uniformity for the Cu3N-modified Cu. These findings suggest that the uniformity of surface electronic conductivity is an important factor for homogeneous lithium plating–stripping, and in situ formation of a nanoconductive network via conversion reaction could...

Lithium Molybdenum Oxyfluorides As High-Capacity Positive Electrodes for Rechargeable Lithium Batteries

The demand for the increase in energy density of rechargeable lithium batteries are still growing. Recently, the use of two-electron redox of vanadium ions coupled with a high electronegativity anion in the crystal lattice is proposed as an effective strategy to enhance the energy density of positive electrode materials.[1] Theoretical capacities of lithium insertion materials depend on both total extractable lithium ions and electron numbers in the structure of positive electrodes. Therefore, in addition to the lithium-enrichment in the structure, the use of multi-electron redox processes for transition metals is expected to be an important strategy to further increase energy density of positive electrode materials. We have recently proposed a new lithium-excess oxide, Li9/7Nb2/7Mo3/7O2, which delivers a large reversible capacity of ca. 290 mAh g-1 based on highly reversible three-electron redox of Mo3+/Mo6+.[2] Three-electron redox of molybdenum ions is expected to be a promising system to further increase energy density of positive electrode materials with less transition metal ions. Nevertheless, redox potential of Mo3+/Mo6+in the oxide framework structure is relatively low for positive electrodes. In this study, to increase in the redox potential of three-electron redox reaction of Mo3+/Mo6+, a mixed anion system, oxyfluorides, is targeted. Crystal structures and electrode performance of a new series of xLiF–LiMoO2 binary system, Li1+x MoO2F x , as oxyfluoride positive electrodes are systematically examined. The highest theoretical capacity based on Mo3+/Mo6+ is expected for x = 2 (Li3MoO2F2) in this binary system. Li3MoO2F2 was prepared by mechanical milling from LiMoO2 and LiF. A mixture of LiMoO2 and LiF was mechanically milled with a ZrO2 container and balls. Li3MoO2F2 is found to crystallize into an anion-/cation-disordered rocksalt structure with low crystallinity. Electrochemical properties of Li3MoO2F2 before and after mechanical milling are compared in Figure 1. The sample after mechanical milling delivers a large reversible capacity of ca. 280 mAh g-1, which nearly corresponds to that of theoretical capacity based on the two-electron redox reaction of Mo3+/Mo5+. However, higher average voltage for the molybdenum oxyfluoride is evidenced compared with those of oxides.[2] From these results together with structural and electrochemical data of Li1+x MoO2F x (x= 0.5, 1, and 1.5), we will discuss the feasibility of molybdenum oxyfluoride materials with multi-electron redox reactions as positive electrode materials for rechargeable lithium batteries.

Characterisation of Cu2O, Cu4O3, and CuO mixed phase thin films produced by microwave-activated reactive sputtering

Copper readily forms three oxides, CuO, Cu4O3 and Cu2O, widely recognised as the most promising p-type oxides because of their desirable optical and electrical properties and potential use in solar cells, transparent electronics as well as other specialised applications such as electrodes for rechargeable lithium batteries, catalysis and memristors. For large-scale implementation of devices, magnetron sputtering is a practical method of producing metal oxides; however, sputtered copper oxides tend to form as a mixture of the oxides, with Cu2O being particularly difficult to produce reliably in pure form. Here, nanostructured thin films of copper oxides were prepared by a variation on reactive sputtering known as microwave-activated reactive sputtering under various rates of oxygen flow. Microwave-activated reactive sputtering was shown to be a suitable technique for the inexpensive production of large areas of copper oxide thin films at near room temperature, facilitating deposition on a wide variety of substrates including polymers. Furthermore, it was demonstrated that the sputtered films develop through CuO, Cu4O3 and Cu2O mixed phases as oxygen flow rate is increased. The preparation of a given stoichiometry for a particular application can be achieved by varying the flow rate of oxygen during the microwave-activated reactive sputtering process.

Isolation and characterization of lignins from wheat straw: Application as binder in lithium batteries

Three different lignin-rich fractions have been used as binder material for electrodes in rechargeable lithium batteries. Lignin samples were obtained through three different pulping processes; kraft, soda and organosolv pulping processes, using wheat straw as raw material. Physico-chemical characterization of three types of lignins was evaluated. Characterization has been performed using Fourier transform infrared spectroscopy (FTIR) and 31P NMR Spectroscopy to analyse the functional groups; gel permeation chromatography (GPC) for determining molar mass distribution (MWD), and thermogravimetric analysis (TGA) to follow the thermal behaviour. Electrodes containing lignin or poly vinylidene fluoride (PVDF) were tested electrochemically. The three different lignin samples exhibited excellent performance as binder, retaining the specific capacity after 50 cycles at a current density of 100mAg‐1. These results show that lignin could be used as a low-cost and environmental binder, replacing the PVDF polymer in electrodes for energy storage applications.

Combining electrospinning and sputtering to improve rechargeable lithium battery cathodes: coating carbon fibre felt with nickel sulfide

Various nickel sulfide nanostructures have been developed for the fabrication of high surface area electrodes for rechargeable lithium batteries. In this study, we fabricated a nickel sulfide covered carbon fibre felt with high uniformity, high density, and large area for cathode materials for use in rechargeable lithium batteries, by using a combined electrospinning and sputtering deposition technique. In particular, the nickel sulfide/carbon fibre felt is a multi-functional material that can act as a conducting electrode itself without the use of binders and conductive materials owing to the high conductivity of the interlinked carbon fibre structures. A Li/nickel sulfide cell with current density of 100 mA g−1 exhibits good cycle performance and high first discharge capacity (970.46 mAh g−1) and good coulombic efficiency of 99% at 20 cycles. This electrode has good structural and electrochemical properties and has a potential to be commercialized when the properties are matured.

The Effect of Interactions and Reduction Products of LiNO3, the Anti-Shuttle Agent, in Li-S Battery Systems

Sulfur cathodes have excellent theoretical properties for use as positive electrodes in rechargeable lithium batteries. However they suffer from an internal redox shuttle process which limit their capacity because the sulfur reduction products, LixSy species, cannot be fully re-oxidized. In order to overcome this problem, lithium nitrate is commonly used as an additive to the electrolyte solution, suppressing the shuttle phenomena in Li-sulfur batteries. We rigorously studied the electrochemical behavior of LiNO3 in electrolyte solutions and with electrodes relevant to Li-S cells. EQCM UV-Vis and XPS spectroscopies were used in conjunction with standard electrochemical measurements, in order to determine the stability limits of this additive. An irreversible reduction of the nitrate species occurs in Li-S cells resulting in a precipitation of electrolyte solutions decomposition products such as LiF and oxygen-containing polymeric species formed by reactions of the ethereal solutions due to nitrate reduction on the cathode side below 1.9 V vs. Li .We showed that both the reversible capacity and the voltage profile of Li-S cells are significantly improved when the limiting cutoff potentials for the sulfur cathodes is set above the red-ox potential of LiNO3.

Thermal and Structural Behavior of Surface-Modified Li[Ni0.7Co0.2Mn0.1]O2 As a Positive Electrode for Rechargeable Lithium Batteries

Lithium secondary battery is promising as a power backup for energy storage system. In this respect, studies towards improvement in performances of electrode are being progressed to assure long cycling performances, thermal stability, safety, and so on. In particular, positive electrode materials are need to be further investigated to accomplish the above- mentioned properties. Several kinds of 4 V class positive electrode materials are commercially available. Among them, LiCoO2 is one of the most common electrode materials in rechargeable lithium batteries. Although the LiCoO2 has many advantages, this material has poor capacity retention because of dissolution of Co and structural instability at deeply charged state. To improve the nature of active material, surface modification is effective to overcome those limited properties of active materials. Actually, Metal oxides as coating materials have been extensively studied. In this study, Metal phosphate coatings are applied on the surface of Li[Ni0.7Co0.2Mn0.1]O2. We, here, report the resulting structural, electrochemical and thermal properties of the surface-modified Li[Ni0.7Co0.2Mn0.1]O2.H3PO4 and metal salts were selected as starting materials for surface modification of Li[Ni0.7Co0.2 Mn0.1]O2. A solution anhydrous ethanol containing metal phosphates was stirred at 30 oC for 5 hours. Then, active materials were added into the solution. And the solution was evaporized at 80 oC in air and the resulting precipitates were then heated at 500 oC in air. Also, the coated powders were characterized by XRD, SEM, and HR-TEM. Electrochemical properties of coated powders were examined by galvanostatic cycle test and electrochemical impedance spectroscopy.Metal phosphates coatings shows uniform coating layers, as observed by TEM. TG and DSC analyses were conducted for the materials. Electrochemical test with half cells in voltage range of 3 - 4.3 V at 25 oC indicates that coated materials have better capacity retention and coulombic efficiency, rate capability and thermal properties. Thin coating layers were effective in improvement of the electrochemical, structural and thermal properties. Also, metal phosphates coatings give decrease in the residual lithium content and byproduct on the surfaces of particles, as confirmed by ToF-SIMS. And the materials were analyzed into XPS and ToF-SIMS to confirm surface byproducts of the materials itself at high temperature. Details will be mentioned at the conference site.

Synthesis of Nickel-Cobalt Difluoride [NixCo(1-x)F2] for Lithium Ion Batteries Application

Introduction Transition metal fluorides have been gaining interest as reversible positive electrodes for rechargeable lithium batteries in the recent years due to their high theoretical e.m.f values and their ability to transfer more than 1 electron per formula unit.1 Among the metal difluorides, CoF2 and NiF2 have the highest calculated theoretical discharge voltage1. However, previous experimental work conducted has shown that nanostructured CoF2 has a discharge voltage of about 1.4V and an initial discharge capacity of about 550 mAhg-1. 2 The discharge capacity of 550 mAhg-1 relates to a 2 electron transfer per formula unit of CoF2. As for NiF2, it has previously been reported to have a discharge voltage of about 1.5 V with an initial discharge capacity of about 700 mAhg-1.3 Comparison of their effective ionic radius shows that Ni2+ has an effective ionic radius of 0.70 angstroms while Co2+ with an octahedral coordination has an effective ionic radius of 0.745 angstroms4. This indicates the possibility of the presence of a mixed nickel-cobalt difluoride [NixCo(1-x)F2]. However, the presence of [NixCo(1-x)F2] has never been reported. Our recent work presents the synthesis and the electrochemical properties of nanostructured mixed nickel-cobalt difluoride [NixCo(1-x)F2] in the sizes from 15 nm to 80 nm. Bond valance sum analysis conducted shows that Ni and Co are still in the oxidation state of +2. EDX mapping demonstrated a homogeneous mixing of nickel, cobalt and fluorine which confirms the successful synthesis of [NixCo(1-x)F2] with no phase seperation. Bond length calculations show a decrease in the metal-fluorine bond length as the nickel content was increased, hence leading to a smaller unit cell with smaller crystallites. Lattice parameters calculations conducted on the [NixCo(1-x)F2] show a slight positive deviation from Vegard’s law. Lastly, the possibility of voltage tuning via having a mixed nickel-cobalt difluoride [NixCo(1-x)F2] was also demonstrated in the work.

Li-S Cathodes with Extended Cycle Life By Sulfur Encapsulation in Disordered Micro-Porous Carbon Powders

Sulfur cathodes have excellent theoretical properties for use as positive electrodes in rechargeable lithium batteries, but lack long-term stability required of practical secondary battery systems. To deal with this issue, high capacity Lithium-Sulfur cathodes with extended cycle life were prepared through thermal encapsulation of sulfurat 155°C in disordered micro-porous carbon powders that have high specific surface-area of ~ 2000 m2/g. The electrodes have been characterized using X-ray diffraction (XRD), Scanning electron microscopy/energy-dispersive X-ray (SEM/EDX), Raman spectroscopy, Thermal Gravimetric Analysis (TGA) and Gas adsorption technique. By using microporous carbon as matrices for sulfur cathodes and lithium nitrate as an additive to the electrolyte solution, that suppresses the shuttle phenomena in Li-sulfur batteries, we managed to achieve a reversible capacity of over 500mAh/g after 1000 cycles (Figure 1) with a Columbic efficiency approaching 100% throughout cycling. The sulfur composite cathodes of 14mm in diameter (area of ~1.54 cm2) and active material load of more than 1mg/cm2were tested in a two electrodes configuration with coin-type cells (2523,NRC, Canada). Electrolyte solution was DOL and DME (1:1 ratio) with 10% LiTFSI and 2% of LiNO3(by weight).The influence of the volume of the electrolyte solutions in Li-S cells was further evaluated by analyzing their voltage profiles during cycling.

Effect of the Carbonization on the LiFePO4 Particles of Positive Electrode for Rechargeable Lithium Batteries

In addition of the poor intrinsic conductivity of LiFePO4 particle, surface effects become increasingly important, and can eventually dominate the physical and the chemical properties when the size decreases below 100 nm. Carbon coating appeared to overcome the drawback of highly resistive LiFePO4 powders and to cure the disordered surface layer that reduces the electrochemical performance of non-coated sample. Here, we analyze the effect of the carbon coating on the LiFePO4 particles that meets a worldwide success as a positive electrode for commercial Li-ion batteries.

Li-S Cathodes with Extended Cycle Life by Sulfur Encapsulation in Disordered Micro-Porous Carbon Powders

Sulfur cathodes have excellent theoretical properties for use as positive electrodes in rechargeable lithium batteries, but lack long-term stability required of practical secondary battery systems. To deal with this issue, high capacity Lithium-Sulfur cathodes were prepared through sulfur impregnation of disordered micro-porous carbon powders that have high surface-area. By using microporous carbon as a matrix for sulfur cathodes and lithium nitrate as an additive to the electrolyte solution, that suppresses the shuttle phenomena in Li-sulfur batteries, we managed to achieve a reversible capacity of over 500 mAh/g for 1000 cycles with a Columbic efficiency approaching 100% throughout cycling. The influence of the volume of the electrolyte solutions in Li-S cells was further evaluated by analyzing their voltage profiles during cycling.

Improved Cycling Stability of Lithium Electrodes in Rechargeable Lithium Batteries

Poly(3,4-ethylenedioxythiophene)-co-poly(ethylene glycol) copolymer was coated onto lithium metal as a protective layer. The thin conductive polymer with strong adhesion to the lithium electrode suppressed the corrosion of the lithium metal and stabilized the interface of the lithium electrode in prolonged contact with the organic electrolyte. The conductive polymer coating on the lithium metal caused the capacity retention of the Li/LiCoO2 cell to increase from 9.3% to 87.3% after 200 cycles compared to the cell with the pristine lithium electrode. The improvement in cycling stability is attributed to the conductive polymer coating suppressing lithium dendrite growth and the deleterious reaction between the lithium electrode and the electrolyte solution during cycling.

Modeling Binder-Free and Carbon-Free High Energy Density LiCoO2 Electrodes for Rechargeable Lithium Batteries

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Surface Modified Li[Ni0.6Co0.2Mn0.2]O2 As a Positive Electrode for Rechargeable Lithium Batteries

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High Capacity Microporous Molybdenum–Vanadium Oxide Electrodes for Rechargeable Lithium Batteries

Microporous Mo2.5+yVO9+δ with channels defined by seven-membered rings of corner-sharing MO6 (M = Mo5+/6+ or V4+/5+) octahedra belongs to the family of isostructural MoVNbTeO compounds, which are very active and selective oxidation catalysts for light alkanes. The large open channels which can accommodate small ions, together with the redox properties of Mo2.5+yVO9+δ, make this material of potential interest as a rechargeable intercalation electrode. Microcrystalline Mo2.5+yVO9+δ was synthesized by hydrothermal reaction of (NH4)6Mo7O24·4H2O and VOSO4·nH2O and exists in the composition range −0.13 ≤ y ≤ 0.05. The electrochemical properties of Mo2.5+yVO9+δ were investigated in Li/1 M LiPF6 in ethylene carbonate (EC) and dimethyl carbonate (DMC)/Mo2.5+yVO9+δ cells. When the cells are discharged between 3.9 and 1.5 V vs Li/Li+, up to 6 Li+ ions per formula unit are electrochemically inserted into the framework. Upon recharge, all of the Li+ ions can be extracted with minimal structural rearrangement. Unit cell dimensions for LixMo2.5+yVO9+δ (0 < x ≤ 6) phases prepared by chemical lithiation with n-BuLi have been determined by powder X-ray analysis and are closely related to those of the parent Mo2.5+yVO9+δ phase with orthorhombic Pba2 symmetry. Lithium cells of Mo2.5+yVO9+δ are rechargeable and exhibit a reversible capacity exceeding 300 mAh/g making Mo2.5+yVO9+δ a potential electrode material for secondary lithium batteries.

Exploring sulfur solubility in ionic liquids for the electrodeposition of sulfide films with their electrochemical reactivity toward lithium

Metal binary sulfides (TiS2, FeS2), in either powder or thin film forms, were the first studied Li insertion electrodes for rechargeable lithium batteries, with thin films made mainly by sputtering. Here we exploit the equilibrium solubility of molecular sulfur into ionic liquids at its melting point (120°C), which we estimated to be at a maximum level of 80mM by both electrochemical and microwave studies, to prepare thin films of both Co9S8 and FeSx showing initial capacities of 559mAhg−1 and 708mAhg−1 versus lithium in coin cells, respectively. We demonstrate that the growth of Co9S8 films involves the reaction of soluble sulfur with the electrodeposited Co metallic layer, while the formation of FeSx films enlists a precipitation between the reduced Fe(II) cations and the electrochemically produced Sxy− species in the ionic liquid bath. Such findings, namely the solubility of sulfur into ionic liquids, open opportunities to electrodeposit sulfur-based compounds as well as capture sulfur from various media enabling a better environment.