Reversible Lithium Intercalation Research Articles

Lithium electrochromism of atmospheric pressure plasma jet-synthesized NiO x C y thin films

Reversible lithium intercalation and deintercalation behavior of atmospheric pressure plasma jet (APPJ)-synthesized organonickel oxide (NiO x C y ) thin films under various substrate distances is testified in an electrolyte (1 M LiClO4–propylene carbonate solution) at low driving voltages from −0.5 to 1.5 V. Fast responses of 2 s bleaching at −0.5 V and 6 s coloration at +1.5 V are accomplished for the nano-porous NiO x C y thin films. This study reveals that a rapid synthesis of electrochromic NiO x C y thin films in a single process via APPJ by 21 s is investigated. This study presents a noteworthy electrochromic performance in a light modulation with up to 43% of transmittance variation and a coloration efficiency of 36.3 cm2/C at a wavelength of 830 nm after 200 cycles of cyclic voltammetry measurements.

Success and serendipity on achieving high energy density for rechargeable batteries

Rechargeable lithium batteries that use non-aqueous electrolytes may not be suitable for electric vehicle applications, which require safe, inexpensive, and high energy density. In this paper, we showed that reversible lithium intercalation can occur in MnO2 cathode coupled with Zn anode while using LiOH aqueous electrolyte. This new Zn|LiOH|MnO2 aqueous rechargeable cell could operate around 1.5 V for multiple cycles and possibly be used in battery packs, are of low cost, and environmentally benign. However, higher energy density, power density, and cycling life of the Zn|LiOH|MnO2 system are required for exploiting this technology to better compete with the lithium battery counterparts. Serendipitously, high energy density (270 Wh/Kg) that was achieved with physically mixed additives (Bi2O3 and TiB2) on MnO2 is reported. Physically modified cathode containing multiple additives is shown to be superior in energy density and capacity retention compared to that of the additive-free MnO2 or carbon-coated MnO2 using polyvinylpyrrolidone as the source. The role of the additives (Bi2O3 and Bi2O3 + TiB2) in the MnO2 electrode is found to avoid the formation of unwanted (non-rechargeable) products and to decrease the polarization of the electrode.

Structural characteristics of olivine Li(Mg0.5Ni0.5)PO4 via TEM analysis

The structural characteristics of olivine-type lithium orthophosphate Li(Mg0.5Ni0.5)PO4 synthesized via solid-state reaction have been studied using X-ray diffraction, ion beam technique, scanning electron microscopy, infrared spectroscopy, transmission electron microscopy and energy dispersive X-ray analysis. The parent LiNiPO4 compound can be synthesized in olivine structure without any evidence of secondary phases as impurities. The structural quality of the parent LiNiPO4 in the absence of secondary component phases resulted in the formation of hexagonal closed packed structure. The olivine analogue compound containing mixed M (M = Mg, Ni) cations, Li(Mg0.5Ni0.5)PO4 contained Li3PO4 as a second phase upon synthesis, however a carbothermal reduction method produced a single-phase compound. The redox behaviour of carbon-coated Li(Mg0.5Ni0.5)PO4 cathode in aqueous lithium hydroxide as the electrolyte showed reversible lithium intercalation.

Structure and reversible lithium intercalation in a new P′3-phase: Na2/3Mn1−yFeyO2 (y = 0, 1/3, 2/3)

In this contribution, new data on the reversible Li+ intercalation in iron substituted sodium manganates are provided. Novel Na2/3Mn1−yFeyO2 (y = 0, 1/3 and 2/3) compounds with a P′3-type structure are prepared from freeze-dried citrate precursors at 500 °C. A new structural element is the development of three-layer oxygen stacking contrary to the well-known P2-type Na2/3MnO2 with a two-layer sequence. The effect of Fe additives on the structure of Na2/3MnO2 was examined by XRD powder diffraction and TEM analysis. The oxidation state and the distribution of transition metal ions in Na2/3Mn1−yFeyO2 were analysed using electron paramagnetic resonance spectroscopy. The lithium intercalation in Na2/3Mn1−yFeyO2 was investigated in two-electrode lithium cells of the type Li|LiPF6 (EC:DMC)|Na2/3Mn1−yFeyO2. The stability of the layered phases during lithium intercalation was studied by ex situ Raman spectroscopy. It was found that the intermediate Na2/3Mn2/3Fe1/3O2 composition is able to intercalate Li+ reversibly in high amounts. Details of the structure and its stability during the Li+ intercalation are discussed.

(NH 4) 0.5V 2O 5 nanobelt with good cycling stability as cathode material for Li-ion battery

(NH 4) 0.5V 2O 5 nanobelt is synthesized by sodium dodecyl benzene sulfonate (SDBS) assisted hydrothermal reaction as a cathode material for Li-ion battery. The as-prepared (NH 4) 0.5V 2O 5 nanobelts are 50–200 nm in diameter and several micrometers in length. The reversible lithium intercalation behavior of the nanobelts has been evaluated by cyclic voltammetry, galvanostatic discharge–charge cycling, and electrochemical impedance spectroscopy. The (NH 4) 0.5V 2O 5 delivers an initial specific discharge capacity of 225.2 mAh g −1 between 1.8 and 4.0 V at 15 mA g −1, and still maintains a high discharge capacity of 197.5 mAh g −1 after 11 cycles. It shows good rate capability with a discharge capacity of about 180 mAh g −1 remaining after 40 cycles at various rates and excellent cycling stability with the capacity retention of 81.9% after 100 cycles at 150 mA g −1. Interestingly, the excess 120 mAh g −1 capacity in the first charge process is observed, most of which could be attributed to the extraction of NH 4 + group, verified by Fourier transform Infrared (FT-IR) and X-ray diffraction (XRD) results.

BDMI+양이온을 함유한 이온성 액체로부터 흑연으로의 전기화학적 리튬 삽입

흑연과 1-buthyl-2,3-dimethylimidazolium(BDMI)계 이온성 액체의 계면 반응을 이해하기 위하여 lithium bis(fluorosulfonyl)imide(LiTFSI)가 용해된 BDMI-TFSI 용액 중에서 전기화학 원자간력 현미경(electrochemical atomic force microscopy, ECAFM)을 이용하여 순환 전압전류법 전후에 있어서의 고배향성 열분해 흑연(highly oriented pyrolytic graphite, HOPG)의 표면을 in-situ로 관찰하였다. HOPG 전극에서 리튬의 가역적인 삽입과 탈리반응은 진행되지 않았으며, <TEX>$BDMI^+$</TEX> 양이온의 삽입에 의한 blister의 형성 및 그라펜 층의 파괴만이 관찰되었다. 한편, <TEX>$BDMI^+$</TEX> 양이온의 삽입 반응은 농도가 4.90 mol/kg인 LiTFSI-propylene carbonate(PC)를 15 wt% 함유하고 있는 BDMI-TFSI계에서는 일어나지 않았으며, 이 경우에는 가역적인 리튬의 삽입과 탈리반응이 진행 되었다. ECAFM 결과는 고농도의 PC계 용액이 solid electrolyte interface(SEI)를 형성함으로 인해 <TEX>$BDMI^+$</TEX> 양이온의 삽입을 막는 매우 효과적인 첨가제임을 나타내었다. In situ electrochemical atomic force microscopy (ECAFM) observations of the surface of highly oriented pyrolytic graphite (HOPG) was performed before and after cyclic voltammetry in lithium bis(fluorosulfonyl)imide (LiTFSI) dissolved in 1-buthyl-2,3-dimethylimidazolium (BDMI)-TFSI to understand the interfacial reactions between graphite and BDMI-based ionic liquids. The formation of blisters and the exfoliation of graphene layers by the intercalation of <TEX>$BDMI^+$</TEX> cations within HOPG were observed instead of reversible lithium intercalation and de-intercalation. On the other hand, lithium ions are reversibly intercalated into the HOPG and de-intercalatied from the HOPG without intercalation of the <TEX>$BDMI^+$</TEX> cations in the presence of 15 wt% of 4.90 mol/<TEX>$kg^{-1}$</TEX> LiTFSI dissolved in propylene carbonate (PC). ECAFM results revealed that the concentrated PC-based solution is a very effective additive for preventing <TEX>$BDMI^+$</TEX> intercalation through the formation of solid electrolyte interface (SEI).

In Situ Mössbauer Effect Study of Lithium Intercalation in LiFe2F6

A sample of with a disordered trirutile structure was prepared by high energy ball milling, and reversible lithium intercalation in this material was investigated using in situ Mössbauer spectroscopy. During the first discharge to 2.0 V (adding lithium), the percentage of decreased linearly with lithium content from 46 to 11%, while the percentage of increased linearly from 54 to 89%. No evidence of was observed in this potential range indicating that displacement reactions do not occur above 2.0 V. During the first charge (removing lithium) to 4.5 V, the percentage of increased from 11 to 68%, while the percentage of decreased from 89 to 32%. The change in the Fe oxidation state showed a 1:1 correlation with in between 2.0 and 4.5 V. When cells were charged to voltages higher than 4.5 V, the percentage of did not increase linearly with the cell capacity, indicating that side reactions occur above 4.5 V.

Determination of lithium diffusion coefficient in LiFePO 4 electrode by galvanostatic and potentiostatic intermittent titration techniques

A new model of lithium-ion transport processes in the LiFePO 4 electrode is proposed. This model takes into account the phase transition LiFePO 4 ↔ FePO 4 accompanying reversible lithium intercalation into the electrode during potential or current steps. The diffusion coefficient of Li + ion and its dependence on the LiFePO 4/FePO 4 phase ratio have been determined by means of processing of experimental potential and current transients in accordance with the model's equations. The results of galvanostatic and potentiostatic intermittent titration techniques are in good agreement. The value of diffusion coefficient varies within 10 −10–10 −16 cm 2 s −1 depending on the lithium content in solid solution Li X FePO 4 and Li 1− X FePO 4 ( X < 0.02) or the LiFePO 4/FePO 4 phase ratio.

Functional binders for reversible lithium intercalation into graphite in propylene carbonate and ionic liquid media

Poly(acrylic acid) (PAA), poly(methacrylic acid) (PMA), and poly(vinyl alcohol) (PVA), which have oxygen species as functional groups, were utilized as a binder for graphite electrodes, and the electrochemical reversibility of lithium intercalation was examined in PC medium and ionic liquid electrolyte, lithium bis(trifluoromethanesulfonyl)amide dissolved in 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide (BMP-TFSA). Columbic efficiency of 75–80% with more than 300 mAh g −1 was achieved upon first reduction/oxidation cycle in both electrolytes using these binding polymers, which were significantly improved in comparison to a conventional PVdF binder (less than 45% of columbic efficiency for the first cycle). For the graphite-PVdF electrode, co-intercalation and/or decomposition of PC molecules solvating to Li ions were observed by the electrochemical reduction, resulting in the cracking of graphite particles. In contrast, the co-intercalation and decomposition of PC molecules and BMP cations for the first reduction process were completely suppressed for the graphite electrodes prepared with the polymers containing oxygen atoms. It was proposed that the selective permeability of lithium ions was attained by the uniform coating of the graphite particles with PAA, PMA, and PVA polymers, because the electrostatic interaction between the positively charged lithium ions and negatively charged oxygen atom in the polymer should modulate the desolvation process of lithium ions during the lithium intercalation into graphite, showing the similar functions like artificial solid-electrolyte interphase.

New ramsdellites LiTi 2−yV yO 4 (0≤ y≤1): Synthesis, structure, magnetic properties and electrochemical performances as electrode materials for lithium batteries

The new ramsdellite series LiTi 2− y V y O 4 (0≤ y≤1) has been prepared by conventional solid state chemistry techniques and was characterized by X-ray powder diffraction and electron diffraction. To our knowledge, this is the first report on ramsdellites containing vanadium. The magnetic behaviour of these ramsdellites is strongly influenced by its vanadium content. In this sense, LiTi 2O 4 ( y=0) exhibits metallic-like temperature independent paramagnetism, but d electrons tend to localize with increasing V content. LiTiVO 4, though also paramagnetic, follows then the Curie–Weiss law. The crossover from delocalized to localized electrons is observed between compositions y=0.6 and 0.8. For y≥0.8 the magnetic results evidence an isovalent substitution mechanism of trivalent Ti by V. The electrochemical lithium intercalation and deintercalation chemistry of LiTi 2− y V y O 4 is grouped into two different operating voltage regions. Reversible lithium deintercalation of vanadium-substituted ramsdellite titanates LiTi 2− y V y O 4 in the high voltage range 2–3 V vs. Li occurs in two main steps, one at about 2 V and the other at about 3 V. The 3 V process capacity increases with the vanadium content, while the 2 V capacity decreases at the same time. The vanadium to titanium substitution rate in LiTi 2O 4 was found to be beneficial to the specific energy in as much as a 50% increase (1 V) of the working voltage is observed. On the other hand, reversible lithium intercalation in vanadium-substituted ramsdellite titanates LiTi 2− y V y O 4 in the low voltage range 1–2 V vs. Li occurs in one main single step, in which the capacity is not affected by the vanadium content, although vanadium-doping produces an improved capacity retention with an excellent cycling behaviour observed for y≤0.6.

Synthesis of ribbon type carbon nanostructure using LiFePO 4 catalyst and their electrochemical performance

Ribbon type of carbon nanostructure has been synthesized by chemical vapor deposition using a new catalyst (LiFePO 4) introduced for the first time and its electrochemical behavior has been determined from charge/discharge characteristics. The synthesized material characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and by Raman spectroscopy confirms the graphitic structure and ribbon type morphology of material. The performance of the single cell using purified carbon nanoribbon as the anode has been studied and the reversible lithium intercalation capacity has been found about 345 mAh/g, of which 335 mAh/g remain after 14th cycle. The columbic efficiency has been stabilized at approximately 98% from the 5th cycle.

Polyacrylate Modifier for Graphite Anode of Lithium-Ion Batteries

Polyacrylates were applied as a binder of graphite electrode in a lithium-ion cell to modify the interface. Compared to a conventional binder, poly(vinylidene fluoride), the efficiency at the initial cycle was improved by poly(acrylic acid) and alkali polyacrylates in an ethylene carbonate (EC)-based electrolyte with highly reversible lithium intercalation. In a LiClO 4 propylene carbonate (PC) solution, the poly(vinylidene fluoride) electrode showed a huge irreversible capacity as is generally known. However, the polyacrylate-modified graphite demonstrated highly reversible lithium intercalation in the PC electrolyte containing no film-forming additives as well as in the EC electrolyte due to the interfacial modification with polyacrylates.

Functional interface of polymer modified graphite anode

Graphite electrodes were modified by polyacrylic acid (PAA), polymethacrylic acid (PMA), and polyvinyl alcohol (PVA). Their electrochemical properties were examined in 1 mol dm −3 LiClO 4 ethylene carbonate:dimethyl carbonate (EC:DMC) and propylene carbonate (PC) solutions as an anode of lithium ion batteries. Generally, lithium ions hardly intercalate into graphite in the PC electrolyte due to a decomposition of the PC electrolyte at ca. 0.8 V vs. Li/Li +, and it results in the exfoliation of the graphene layers. However, the modified graphite electrodes with PAA, PMA, and PVA demonstrated the stable charge–discharge performance due to the reversible lithium intercalation not only in the EC:DMC but also in the PC electrolytes since the electrolyte decomposition and co-intercalation of solvent were successfully suppressed by the polymer modification. It is thought that these improvements were attributed to the interfacial function of the polymer layer on the graphite which interacted with the solvated lithium ions at the electrode interface.

Polyacrylate as Modifier for Graphite/Electrolyte Interface

Polyacrylate anion was used as binder of graphite electrode in lithium-ion cell to modify the interface. Compared with polyvinylidene fluoride, the coulombic efficiency at the initial cycle was improved by polyacrylic acid and alkali polyacrylates in an ethylene carbonate (EC) based electrolyte. Although the polyvinylidene fluoride electrode showed a huge irreversible capacity in propylene carbonate (PC) electrolyte, the polyacrylate modified graphite demonstrated highly reversible lithium intercalation in a PC electrolyte as well as in an EC based electrolyte.

Impedance spectroscopy of lithium-carbon electrodes

The methods of coulometric titration and electrode impedance spectroscopy are used in studying the behavior of carbon film electrodes free of binding and conducting additives in the course of reversible lithium intercalation from nonaqueous electrolytes. The electrodes with the high and low degrees of graphitization are studied. The measurements are performed in the frequency range from 105 to 10−2 Hz with the lithium concentration in intercalate varied from 0.025 mol/cm3 (corresponds to LiC6) to a state free of lithium. The factors responsible for the hysteresis in charge-discharge curves, the versions of equivalent circuits (EC) suitable for modeling the impedance spectra of LixC6 electrodes, the dependence of EC parameters and the lithium diffusion coefficient on the concentration are discussed. It is shown that all experimental impedance spectra can be adequately modeled by a common general EC. The concentration dependences are consistent with the earlier data of pulse methods. The diffusion coefficient varies approximately from 10−12 to 10−13 cm2/s.

Impedance spectroscopy of lithium-tin film electrodes

A method of electrochemical impedance spectroscopy was used to study the reversible lithium intercalation from nonaqueous electrolyte into tin films with the thickness of 0.1–1 μm. The impedance spectra of lithium-tin (LixSn) electrodes have a complicated shape depending on the electrode state and prehistory; they reflect the occurrence of several consecutive and parallel processes, including the lithium migration, diffusion, and accumulation. The formation of a solid-electrolyte layer on the surface at Li intercalation into Sn is observed. Equivalent circuits are proposed that adequately model the experimental data on the LixSn electrodes both freshly prepared and after prolonged cycling. Problems associated with the choice of equivalent circuits and determination of their parameters, the accuracy of the diffusion coefficient determination, the trends in the parameters’ variation with electrode potential (composition) are discussed.

Kinetics of electrochemical lithium intercalation into thin tungsten (VI) oxide layers

The methods of galvanostatic intermittent titration, cyclic voltammetry, and electrode impedance spectroscopy are used to study the behavior of tungsten (VI) oxide film electrodes free of binding and conducting additives in the course of reversible lithium intercalation from nonaqueous electrolyte at 25°C. The studies are performed for electrodes with different degrees of crystallinity at the variation of the lithium concentration in intercalate from zero to 0.017 mol/cm3. Lithium diffusion coefficient is in the range of 10−11–10−16 cm2/s. The concentration dependences of the intercalation-layer transport parameters are analyzed, the equivalent circuit versions are discussed, and results obtained by different methods are compared.

Reversible lithium intercalation in disordered carbon prepared from 3,4,9,10-perylenetetracarboxylic dianhydride

The electrochemical properties of the 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA)-based carbon, synthesized by directly pyrolyzing PTCDA under an argon gas flow, have been firstly explored as an anode material for lithium-ion batteries. PTCDA is decomposed in a single-step reaction, which was completed around 650 °C. X-ray diffraction studies indicated a disordered carbon structure, and scanning electron microscopy (SEM) results revealed that this PTCDA-based carbon had a pillar-like morphology with a diameter of approximately 1–4 μm and length of 5–20 μm. Electrochemical measurements showed that it delivered lithium insertion and deinsertion capacities of 496 and 311 mAh g−1, respectively, during the first cycle. The charge capacity retention from the 1st to the 50th is 93.2% with an average capacity fade of 0.14% per cycle. The coulombic efficiency of the Li insertion/deinsertion processes reached 99% after five cycles.

Electrochemistry of Graphite in Li and Na Salt Codissolving Electrolyte for Rechargeable Batteries

Electrochemical reduction and oxidation of a graphite electrode were carried out in nonaqueous electrolytes that consisted of ethylene carbonate/diethyl carbonate (1:1) solvents where and were codissolved. Reversible lithium intercalation into graphite occurred accompanied with no remarkable side reactions in the potential range between 1.5 and vs , that is, no sodium deposition and no sodium intercalation were observed. Comparing to results in a sodium-free electrolyte, i.e., a conventional electrolyte in Li-ion batteries, the initial irreversibility was noticeably suppressed by codissolving sodium ions, and kinetics of the lithium intercalation were enhanced with better capacity retention during cycling. Additionally, the redox behavior of graphite for lithium-ion batteries was improved by sodium ion coexistence, with no inferior influences on the negative and positive electrodes and electrolyte. When the sodium ion concentration increased to , the superior reversibility of lithium intercalation was observed in comparison with that in a sodium-free system; however, the higher concentration of sodium ions deteriorated the lithium intercalation properties. We found that a surface layer formed on graphite electrode got less resistive as a lithium-ion conductor by entrapping sodium during the initial electroreduction with optimal concentration.

On the possibility of using ionic liquids as electrolyte solutions for rechargeable 5 V Li ion batteries

We report herein on the reversible cycling of LiNi 0.5Mn 1.5O 4 spinel electrodes with their reversible lithium intercalation potential of about 4.7–4.8 V vs. Li/Li +, in electrolytes based on 1-methyl-3-methylimidazolium tetrafluoroborate (EMIBF 4) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF 4). In this application, one of the main advantages of room temperature ionic liquids, their high anodic stability, is well exploited.