Lithium Ion Deintercalation Research Articles

Understanding the electrochemical superiority of 0.6Li[Li1/3Mn2/3]O2-0.4Li[Ni1/3Co1/3Mn1/3]O2 nanofibers as cathode material for lithium ion batteries

Solid solution cathode materials 0.6Li[Li1/3Mn2/3]O2-0.4Li[Ni1/3Co1/3Mn1/3]O2 with different morphologies were synthesized by electrospinning and coprecipitation method respectively. The field-emission scanning electron microscope images verified the successful formation of nanofibers for electrospinning and nanoparticles for coprecipitation and the nanofibers showed larger specific surface area according to the Brurauer Emmerr Teller procedure. The X-ray powder diffraction patterns and the corresponding lattice parameter refinements showed that both samples can be indexed to hexagonal α-NaFeO2 layered structure with space group of R-3m. And the material prepared by electrostatic spinning method has a tight atomic arrangement in the layer yet the different dimensions do not influence the intercalation and deintercalation of lithium ion through the interlayer. The discharge capacity of nanofibers electrode is 302.3mAhg−1 at 0.05C and the initial columbic efficiency is 76.2%, which are higher than 282.7mAhg−1 and 68.2% of the nanoparticles electrode. The nanofibers electrode also presented better cycleability and rate capability, especially performed capacity of 126.6mAhg−1 at 5C, much higher than that of 109.4mAhg−1 for nanoparticles electrode. The step-by-step cyclic voltammetry revealed that the nanofibers electrode performs higher discharge voltage platform and enhanced discharge energy density. The excellent electrochemical performance of nanofibers electrode is ascribed to the better conductivity and superior lithium ion diffusion ability according to the electrochemical impedance spectrum measurement.

Studies on LiMn1.5Ni0.4Cr0.1O4 Cathode Spinel Combined with Graphene for Lithium Ion Batteries

The low-cost development of rechargeable lithium ion batteries is of considerable technological importance. In this context, the use of active cathode LiMn1.5Ni0.4Cr0.1O4 material has attracted much attention due to its stable structure while intercalation and de-intercalation of lithium ions. The necessity of such battery material is that the energy density stored electrochemically in the electrodes is quite high. They combine high theoretical energy storage capability with low weight and good mechanical strength. Here we report the development of a rechargeable lithium ion battery with homogeneous mixing of graphene powder (with 10, 15 and 20%) in active cathode materials for high energy applications. The reduced graphene oxide was synthesized using modified Hummers method with high purity concentrated of H2SO4 (50 ml), oriented pyrolytic graphite, KMnO4 (7 g) and H2O2 (30 wt %). The resultant mixture was stirred well and then filtered with the help of a glass filter. The obtained precipitates were dried for 30 h in a vacuum oven at room temperature. Highly conducting reduced graphene powder was obtained using hydrazine treatment. The redox behavior of the cell, which is normally too slow for practical applications, is accelerated with highly conductive powder of the graphene (which itself functions as an active cathode material). Intimate mixing of the two materials is achieved by a slurry maker using an organic solution for a cathode paste. The resulting electrode can be repeatedly charged to near its theoretical limit and discharged. The gravimetric energy density of our composite cathode materials exceeds that of the LiMn1.5Ni0.4Cr0.1O4 oxide electrodes in lithium-ion batteries, a feature that is likely to prove advantageous in applications where weight, rather than volume, is a critical factor. The aforementioned results will be discussed.

Electronic structure and transport properties of cathode material Li2FeSiO4 for lithium-ion battery

The electronic structure and properties of silicate polyanion Li2FeSiO4 in the orthorhombic crystal structure with Pmn21 symmetry and the relevant delithiated system LiFeSiO4 are investigated by the first principles method in the framework of the density functional theory with the generalized gradient approximation. The WIEN2k software is used for the self-consistent calculation of the crystal structure to obtain the energy band, density of states, and charge density. Boltzmann transport theory is further used to obtain the values of ratio σ /τ of Li2FeSiO4 and LiFeSiO4 based on the results of the first-principles calculations. The structural stability of Li2FeSiO4 system is demonstrated by calculating and analyzing the lattice parameter and the bond length. The results indicate that Li2FeSiO4 crystal has only 2.7% volume variation in the lithiation/delithiation process and the change of the Si–O bond length is very small, which suggests that the bonding nature between silicon and oxygen atoms remains unchanged. The results of charge density analysis show that the structural stability of Li2FeSiO4 crystal during lithium deintercalation is actually a consequence of a strong covalent interaction between silicon and oxygen atoms. An analysis of density of states shows that the density in the high-energy range near the Fermi level mainly comes from Fe-3d electron states. The Fermi level moves towards the lower energy end during the deintercalation of lithium ions and the electronic conductivity decreases with the decreasing of lithium ions, indicating that the conductive properties of Li2FeSiO4 are better than those of LiFeSiO4. It suggests that Li2FeSiO4 could be modified by doping atoms to affect the electrons in orbital Fe-3d and enhance conductive properties in future research. The calculations of transport properties show that the electronic conductivity of Li2FeSiO4 is not sensitive to temperature in a range from 300 to 800 K, and Li2FeSiO4 material is a potential candidate for heat-resisting cathode material. It also indicates that Li2FeSiO4 owns a better electronic conductivity than LiFeSiO4, which is consistent with the analyses of band structure and density of states. This research reveals the microscopic mechanism such as electronic structure and electronic transport properties of Li2FeSiO4 crystal in theoretical calculations, and provides a theoretical basis for the further improvement of electrochemical properties of lithium-ion battery.

A novel silicon/carbon nanocomposite anode for high performance lithium-ion micro-battery

This paper reports a novel nanocomposite anode for lithium-ion battery, with high initial specific capacity (1200mAh/g) and good capacity retention (850mAh/g remaining after 30 cycles). Sufficient silicon nanoparticles (SiNPs) at anode make a significant contribution to specific capacity increase. Moreover, nano void space between SiNPs and carbon scaffold provide enough space for expansion and contraction of SiNPs during the process of lithium ion intercalation and deintercalation to ensure a long cycle life. The porous carbon scaffold is obtained from Si/SiO2-templated SU-8 photoresist. As such, this design and fabrication makes it possible to implement direct prototyping of three dimensional (3D) micro-battery on chip.

Nanoscale visualization of redox activity at lithium-ion battery cathodes.

Intercalation and deintercalation of lithium ions at electrode surfaces are central to the operation of lithium-ion batteries. Yet, on the most important composite cathode surfaces, this is a rather complex process involving spatially heterogeneous reactions that have proved difficult to resolve with existing techniques. Here we report a scanning electrochemical cell microscope based approach to define a mobile electrochemical cell that is used to quantitatively visualize electrochemical phenomena at the battery cathode material LiFePO4, with resolution of ~100 nm. The technique measures electrode topography and different electrochemical properties simultaneously, and the information can be combined with complementary microscopic techniques to reveal new perspectives on structure and activity. These electrodes exhibit highly spatially heterogeneous electrochemistry at the nanoscale, both within secondary particles and at individual primary nanoparticles, which is highly dependent on the local structure and composition.

Review of Electrochemical Performance of LiNiO2 and their Derivatives as Cathode Material for Lithium-ion Batteries

Lithium-ion battery which widely used as portable power sources with high energy density is greatly being increased due to the development and popularity of portable electronic device and vehicle. Lithium nickel oxide (LiNiO2) and their derivatives are promising positive cathode materials for next generation of lithium-ion batteries. LiNiO2 potentially offers a higher capacity at about 200 mAh/g. However it is more difficult to synthesized stoichiometric LiNiO2 because of the loss of lithium from host structure during high temperature calcination due the high vapor pressure of lithium and capacity fade when charging up to a high voltage (> 4.0V vs Li+/Li) during deintercalation of lithium ion that affected cycling. The review is focused the electrochemical performance by substitution or effect doping of LiNiO2 and their derivative by other metals as a cathode materials for lithium ion batteries.

Electrochemical Performances of Carbon Electrode Materials Depending on Electrode Density for Hybrid Capacitors

Supercapacitors are of practical interest owing to their high power electrical energy storage and exceptionally long cycle life. Also, it has been used and developed such as memory back up for electric home appliance and information transport devices, renewable energy and power assist for transportation and machinery, voltage sag and renewable energy sources for stable electric power. Significantly, electric double layer capacitor (EDLC) consist of stacked activated carbon shows superior high power characteristics whereas it has low energy density as a drawback. Therefore, hybrid capacitor is one of possible candidates and is developing for high energy density.The hybrid capacitor is made up with activated carbon electrode for electric double layer capacity and anode for intercalation and de-intercalation of lithium ions. Although it shows inevitable increase of energy density [1-3], the total output power is lower than that the EDLC due to chemical reaction on the anode. To increase the power density, the decrease of intercalation length for low diffusion resistance is necessary. The hybridization of activated materials with carbon nanotubes, carbon nanofiber, and graphene is intriguing for the application of highly conductive cathode electrode.Here, we introduce the preparation of carbon electrodes to enhance the output power on the anode without high-dimensional and high cost method. In general, high density electrode has high power characteristics because of low contact resistance. However, in this study, the decrease of electrode density can be increase dramatically the output power in the high current density. This result may give rise to the decrease of diffusion resistance due to the low electrode density and the stable surface electrolyte interface at the reacting surfaces.

Low temperature process modified MCMB for lithium ion batteries

The negative electrode of a lithium-ion battery should have the characteristics of large charge capacity, excellent charge and discharge cycle, steady discharge voltage, low irreversible charge capacity, and stable electrolyte. Natural graphite and mesocarbon microbeads (MCMB) are the most common materials used for the negative electrodes of such batteries. This study examines the effect of the use of homemade non-modified MCMB (HMM), modified MCMB (HMMQ), and natural graphite (NG) to produce electrodes on the batteries' high current charge–discharge behavior. In this experiment, the charge–discharge results showed that the voltage plateaus of HMM and HMMQ sloped due to short-range structural order, which enabled the intercalation and deintercalation of lithium ions to occur at different voltages. When HMMQ was charging and discharging high current at a rate of 2C, the battery's charge capacity reached 160mAh·g−1 and the coulometric efficiency exceeded 96%. Following the start of charging and discharging, a stable solid electrolyte interface (SEI) layer formed on HMMQ. The charge capacity of HMMQ was approximately 167mAh·g−1 after 100 charge–discharge cycles at 1C, and the cycles were stable. According to FTIR analysis, the content of the SEI layer produced within HMMQ consisted of Li2CO3 and (CH2OCOLi)2, and was stable, non-soluble, and passive. Negative electrodes made using modified material displayed good stability throughout many cycles when charging and discharging at a high current.

聚3, 4-乙撑二氧噻吩(PEDOT)在锂氧电池中的电催化性能

In this work, poly(3,4-ethylenedioxythiophene)(PEDOT) powders were successfully synthesized by chemical polymerization. PE-DOT/acetylene black/poly(tetrafluoroethylene)(PTFE) and acetylene black/PTFE were mixed in weight ratios of 4.5/4.5/1 and 9/1, respectively. The composites were made into slurries and spread on a nickel foam, which acted as the air electrode in lithium–air batteries. The structures were determined using fourier-transform infrared spectroscopy. The electrical conductivities and electrochemical performances of acetylene black and PEDOT/acetylene black were investigated using the four-probe method, cyclic voltammetry(CV), the constant current charge/discharge method, and electrochemical impedance spectroscopy(EIS). The reduction potentials of acety-lene black/PTFE(9/1) and PEDOT/acetylene black/PTFE(4.5/4.5/1) were 2.20 and 2.57 V, respectively. The first discharge capacity of acetylene black/PTFE(9/1) was 2812 mA h/g. However, the first discharge capacity of PEDOT/acetylene black/PTFE(4.5/4.5/1) was 4056 mA h/g. In addition, PEDOT modification reduced the charge transfer resistance by about 7.85%, compared with that of acetylene black. PEDOT lowered the polarization between lithium ion intercalation and de-intercalation. The CV, constant current charge/discharge, and EIS results show that PEDOT can effectively enhance the electrocatalytic properties of acetylene black.

Improvement of High Voltage Cyclic Performance By Novel Binder for High Energy Lithium Ion Battery Application

Introduction Lithium-ion batteries (LIB) have been used as high density storage devices for several kinds of applications. Higher energy density and higher durability are required for use of high-performance energy devices. Among various attempts to improve energy density of LIB, technologies which increase battery voltage have emerged as a viable solution.Binder affects electrochemical performance reaction directly because it exists near the active materials. In a previous report, Co-ion dissolution and Co3O4 formation were observed in the electrode with PVdF (Polyvinylidene fluoride) [1].In this study, we clarified the degradation mechanism of cathode electrode that contain PVdF binder. Experimental The cathode electrodes consisted of LiCoO2, acetylene black, and PVdF. The performance tests were investigated in 40mAh laminate type lithium ion cells. The cycle life test was performed at 4.2V or 4.4V. Solid F-NMR of electrode was used for the analysis of binder degradation after cycle test.Thin-film electrode of LiCoO2 was fabricated on Au substrate by rf-sputtering method [2]. X-ray diffraction pattern indicated that high crystalline LiCoO2 thin-film electrode was prepared. Binders were spin-coated on the thin-film electrode. Three-electrode cell was used for electrochemical measurements of LiCoO2 thin-film electrode. The electrochemical properties of LiCoO2 thin films were investigated by cyclic voltammetry (CV) Results Figure 1 shows cycle performance at each cut-off voltage. Cycle performance was dramatically decreased at high cut-off voltage. Figure 2 shows the cyclic voltammograms of LiCoO2 thin-film electrode coated with PVdF in LiClO4/EC/DEC at 60°C. Around 3.9 V, peaks of lithium-ion de-intercalation /intercalation were observed. With cycling, redox currentsgradually decreased and redox voltage shifted. This result suggested the degradation of LiCoO2.We evaluated the structure change of LiCoO2 after cycle test by TEM spectroscopy. From the TEM spectroscopy, degradation of surface structure was observed at the electrode after cycle test. From the F-NMR, structure of PVdF was slightly changed after the cycle test. It is suggested that PVdF increased the reactivity of active material. From ICP measurements, the amount of metal precipitation on anode was also increased after cycle test. And adhesion strengths wassignificantly decreased after cycle test.In our presentation, we will show a new type of water-based binder developed by Zeon which can contribute to improvement of cell performance, such as improved cycling performance.

Li[Li0.2Mn0.54Ni0.13Co0.13]O2–LiMn1.5Ti0.5O4 composite cathodes with improved electrochemical performance for lithium ion batteries

Layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2–Spinel LiMn1.5Ti0.5O4 composite cathodes have been prepared by mechanically mixing process and investigated in this work. The unoccupied 16c sites of spinel LiMn1.5Ti0.5O4 can be used as a reservoir to store the Li+ ions that are lost during the activation of Li2MnO3 component in lithium-rich Li[Li0.2Mn0.54Ni0.13Co0.13]O2 material. As a consequence, the initial irreversible capacity loss (ICL) of lithium-rich Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is significantly reduced in the presence of spinel LiMn1.5Ti0.5O4. When mixed with 35.7 wt% of LiMn1.5Ti0.5O4, the lithium-rich material shows an initial ICL of only 17 mAh g−1, and could still deliver an initial discharge capacity as high as 220 mAh g−1. More importantly, the composite materials show better cycling performance and rate capability as compared with the pristine Li[Li0.2Mn0.54Ni0.13Co0.13]O2. The material with 35.7 wt% LiMn1.5Ti0.5O4 shows the best cycling stability, retaining 90% of the initial discharge capacity at the current density of 20mAg−1 after 40 cycles. The improved cycling stability and rate performance can be ascribed to the good conductivity of spinel LiMn1.5Ti0.5O4 with 3D fast Li+ diffusion path, which ensures the timely lithium ion intercalation and de-intercalation.

Enhanced electrochemical performance of Mg-doped LiCoO2 synthesized by a polymer-pyrolysis method

LiCo1−xMgxO2(x=0, 0.01, 0.03, and 0.05) was synthesized by a polymer-pyrolysis method. The effect of Mg doping on the structure and electrochemical properties of LiCoO2 was investigated. XRD analysis showed that all the samples obtained had the well-ordered layer structure. SEM image showed that the powders consist of well-crystallized particles with hexagonal form. The charge–discharge tests showed that the increase of Mg content in LiCoO2 pronouncedly improved the cycling performance of samples although it slightly decreased the initial discharge capacity. LiCo0.97Mg0.03O2 demonstrated an initial discharge capacity of 169.2mAhg−1 and the best cyclic performance as it retained 91.1% of the initial capacity after 50 cycles when cycled at 50mAg−1 between 3.0 and 4.5V. Cyclic voltammagram demonstrated that the Mg doping can distinctly stabilize the crystal structure of LiCoO2 by suppressing the phase transition of the cathode during lithium ion deintercalation and intercalation.

Influence of structure and atom sites on Sn-based anode materials for lithium ion batteries: a first-principle study

To understand the influence of structure and atom sites on the electrochemical properties of Sn-based anode materials, the lithium intercalation–deintercalation mechanisms into SnNi2Cu and SnNiCu2 phases were studied using the first-principle plane wave pseudo-potential method. Calculation results showed that both SnNi2Cu and SnNiCu2 were unsuitable anode materials for lithium ion batteries. The Sn-based anode structure related to the number of interstitial sites, theoretical specific capacity, and volume expansion ratio. Different atom sites led to different forces at interstitial sites, resulting in variations in formation energy, density of states, and hybrid orbital types. In order to validate the calculated model, the SnNi2Cu alloy anode material was synthesized through a chemical reduction-codeposition approach. Experimental results proved that the theoretical design was reasonable. Consequently, when selecting Sn-based alloy anodes, attention should be paid to maximizing the number of interstitial sites and distributing atoms reasonably to minimize forces at these sites and facilitate the intercalation and deintercalation of lithium ion.

Study of sulfonated polyether ether ketone with pendant lithiated fluorinated sulfonic groups as ion conductive binder in lithium-ion batteries

In an attempt to reduce the Li+ concentration polarization and electrolyte depletion from the electrode porous space, sulfonated polyether ether ketone with pendant lithiated fluorinated sulfonic groups (SPEEK-FSA-Li) is prepared and attempted as ionic conductivity binder. Sulfonated aromatic poly(ether ether ketone) exhibits strong adhesion and chemical stability, and lithiated fluorinated sulfonic side chains help to enhance the ionic conductivity and Li+ ion diffusion due to the charge delocalization over the sulfonic chain. The performances are evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, charge–discharge cycle testing, 180° peel testing, and compared with the cathode prepared with polyvinylidene fluoride binder. The electrode prepared with SPEEK-FSA-Li binder forms the relatively smaller resistances of both the SEI and the charge transfer of lithium ion transport. This is beneficial to lithium ion intercalation and de-intercalation of the cathode during discharging–charging, therefore the cell prepared with SPEEK-FSA-Li shows lower charge plateau potential and higher discharge plateau potential. Compared with PVDF, the electrode with ionic binder shows smaller decrease in capacity with the increasing of cycle rate. Meanwhile, adhesion strength of electrode prepared with SPEEK-FSA-Li is more than five times greater than that with PVDF.

Lithium ion intercalation mechanism for LiCoPO4 electrode

Abstract Recently, there exists a discrepancy on the lithium ion de-intercalation mechanism for LiCoPO4 electrode. In the present work, the study was focused upon exploring the origin of this discrepancy by studying the dependence of the impedance spectrum on the state of charge and the carbon content. For the pure LiCoPO4 electrode, the two plateaus in the charge curve are at 4.82 and 4.92 V. We have also studied the variation of electrochemical impedance spectroscopies (EISs) with the state of charge. The EIS measurement has shown that the total interfacial resistance increases as the state of charge increases for the pure LiCoPO4 electrode. If higher content of sucrose was added in the precursor (this implies higher carbon content in the synthesized sample), only one potential plateau can be found in the charge curve. For this electrode, the total interfacial resistance decreases with the state of charge. Especially, the total interfacial resistance has a dramatic decrease when the state of charge increases from 20% to 40%. It is believed that the influence of carbon impurity on the variation tendency of the EIS pattern may reflect the change of the fine structure. For the pure LiCoPO4 electrode, the intermediate phase is Li0.20~0.45CoPO4.

Ultrathin MoS2/Nitrogen‐Doped Graphene Nanosheets with Highly Reversible Lithium Storage

The extensive range of possibilities for using a rechargeable lithium ion battery (LIB) for stationary power storage applications has stimulated signifi cant research to improve its energy, power density and cycling life. The current use of graphite as a commercially available anode material cannot fully meet the energy density requirements for LIB applications in electric vehicles due to its relatively small capacity (372 mAh/g). In the next generation LIB, graphite should be replaced by alternative higher capacity materials and graphene based composite is one of the promising choices. The discovery of graphene has attracted wide-ranging interest due to its unique physical and chemical properties and potential for applications in electronic devices and sensors. [ 1–3 ] This has led to the development of a signifi cant number of graphene-based materials for use as LIB anodes and results have been generally promising due to high specifi c capacity and improvement of its cycling ability. In recent years, chemical substitutional doping has been used to enhance the properties of graphene—further improving its properties beyond just morphology and size control. This includes the use of sulfur, boron, and nitrogen doping, the latter of which is particularly effective in modulating the electronic properties of graphene. [ 4–6 ] Based on these results, we expect that nitrogen-doped (N-doped) graphene will be used as a template for synthesis of active electrode materials. Compared to graphene-based metal oxide materials, some graphene-based transition metal sulfi des possess consummate 2D-layered structures. The matched structure between transition metal sulfi des and graphene avoids the exfoliation of electrode materials and capacity fading during the charge/discharge process. [ 7–9 ] As a typical layered transition metal sulfi de, MoS 2 has a structure similar to graphite, consisting of three atom layers of S-Mo-S stacked together through van der Waals interactions. [ 10 , 11 ] This layered structure enables the effi cient intercalation and deintercalation of lithium ions. In recent years, many published reports have articulated various processes for preparing MoS 2 or MoS 2 composites as LIB anodes, which

Oxalic Dihydrazide Assisted Novel Combustion Synthesized Li3V2(PO4)3 and LiVP2O7 Compounds for Rechargeable Lithium Batteries

A novel oxalic dihydrazide (ODH) has been identified as a fuel for solution combustion synthesis to prepare LixMy(PO4)z compounds as a cathode material for lithium battery applications. These compounds have been synthesized at 850°C using a mixture of Ar:H2 (90:10) atmosphere, wherein oxalic dihydrazide acts both as a combustible fuel and a carbon source. This resulted in a higher carbon content weighing ca. 12 and 8% for poly (Li3V2(PO4)3/C) and pyrophosphate (LiVP2O7/C) composites as opposed to the in-situ added super P carbon was only 5 wt.%. The electrochemical behavior of these cathodes showed reversible intercalation and de-intercalation of lithium ions while exhibiting specific capacities of 168 and 100 mAh/g with good capacity retention. The role of ODH assisted combustion synthesis (ODHAC) on the physical and electrochemical behavior of the title compounds has been demonstrated.

Synthesis and electrochemical performance of Li1+xV3O8 as cathode material prepared by citric acid and tartaric acid assisted sol–gel processes

Lithium-ion battery cathode material Li1+xV3O8 is synthesized by a citric acid/tartaric acid assisted sol–gel method and sintered at 350 °C, 450 °C and 550 °C for 3 h for the formation of Li1+xV3O8 phase. The synthesized samples were fully characterized by FTIR, TG/DTA, XRD, SEM, EIS and charge–discharge tests. Li1+xV3O8 material synthesized by tartaric acid assisted route and sintered at 450 °C for 3 h shows best electro-chemical performance. It shows a high initial capacity of 249 mAh g−1 and still reserves a discharge capacity of 260 mAh g−1 after 50 cycles. Moreover, in the case of tartaric assisted products, no capacity decadence is observed in 50 cycles. XRD together with TG/DTA measurements reveal that compared with citric acid assisted products, the adoption of tartaric acid as chelating agent effectively lowers the crystallization temperature of amorphous Li1+xV3O8. Therefore, precursors obtained by tartaric acid route calcinated at 450 °C for 3 h exhibit lower crystallinity and smaller grain size, which contributes to the better electrochemical performance of the cathode electrodes. From EIS measurements, the bulk resistance is reduced, which favors the intercalation and de-intercalation of lithium ions while cycling.

Carbon Nanomaterials with Different Dimensions for Anode of Li-Ion Batteries

In this article, the structure and morphology of the carbon anode materials with different dimensions have been characterized through SEM and TEM. The performances of electrochemical intercalation and deintercalation of lithium-ions have been studied. The results show that graphene as the two dimensional nanomaterials possess more advantages of microstructure and better Li-ions intercalation performances than carbon nanotubes (CNTs) and graphite. The superior abilities of Li-ions intercalation and deintercalation are attributed to increasing lithium storage space, decreasing Li diffusion distance, and higher specific surface area for Li-ions.

Electrochemical behavior of Li[Li0.2Co0.3Mn0.5]O2 as cathode material in Li2SO4 aqueous electrolyte

Layered, lithium-rich Li[Li0.2Co0.3Mn0.5]O2 cathode material is synthesized by reactions under autogenic pressure at elevated temperature (RAPET) method, and its electrochemical behavior is studied in 2 M Li2SO4 aqueous solution and compared with that in a non-aqueous electrolyte. In cyclic voltammetry (CV), Li[Li0.2Co0.3Mn0.5]O2 electrode exhibits a pair of reversible redox peaks corresponding to lithium ion intercalation and deintercalation at the safe potential window without causing the electrolysis of water. CV experiments at various scan rates revealed a linear relationship between the peak current and the square root of scan rate for all peak pairs, indicating that the lithium ion intercalation–deintercalation processes are diffusion controlled. The corresponding diffusion coefficients are found to be in the order of 10−8 cm2 s−1. A typical cell employing Li[Li0.2Co0.3Mn0.5]O2 as cathode and LiTi2(PO4)3 as anode in 2 M Li2SO4 solution delivers a discharge capacity of 90 mA h g−1. Electrochemical impedance spectral data measured at various discharge potentials are analyzed to determine the kinetic parameters which characterize intercalation–deintercalation of lithium ions in Li[Li0.2Co0.3Mn0.5]O2 from 2 M Li2SO4 aqueous electrolyte.