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Several spent Li-ion batteries were manually dismantled and their components were uncurled and separated. The chemical composition of each battery's component was determined by atomic absorption spectroscopy. Among several ways to separate cathode material from the collector, the alkali dissolution treatment was selected as the most effective one. After both complete separation and acid leaching steps, the co-precipitation method, followed by a thermal treatment (700 °C or 850 °C), was used to resynthesize cathode material LiCo 0.415 Mn 0.435 Ni 0.15 O 2 . Its structure and morphology were characterized by XRD, Raman spectroscopy and SEM-EDS methods. The electrochemical behavior of recycled cathode materials was examined by cyclic voltammetry and chronopotentiometry in both LiNO 3 and NaNO 3 aqueous solutions. High sodium storage capacity, amounting to 93 mAh g −1 , was measured galvanostatically at a relatively high current of ∼100 mA g −1 . Initial lithium intercalation capacity of ∼64 mAh g −1 , was determined potentiodynamically at very high scan rate of 20 mV s −1 (∼40 C). Somewhat lower initial capacity of ∼30 mAh g −1 , but much lower capacity fade on cycling, was found for sodium intercalation at the same scan rate. The differences in the Li and Na charge storage capability were explained in terms of ion rearrangement during charging/discharging processes. [ABSTRACT FROM AUTHOR]

In this work, lithium plating is investigated by means of voltage relaxation and in situ neutron diffraction in commercial lithium-ion batteries. We can directly correlate the voltage curve after the lithium plating with the ongoing phase transformation from LiC 12 to LiC 6 according to the neutron diffraction data during the relaxation. Above a threshold current of C/2 at a temperature of −2 °C, lithium plating increases dramatically. The results indicate that the intercalation rate of deposited lithium seems to be constant, independent of the deposited amount. It can be observed that the amount of plating correlates with the charging rate, whereas a charging current of C/2 leads to a deposited amount of lithium of 5.5% of the charge capacity and a current of 1C to 9.0%. [ABSTRACT FROM AUTHOR]

We test the stability of pre-lithiated graphite anodes for Li-ion batteries in a dry room battery processing room. The reaction between LiC x and laboratory air was followed using operando NMR and x-ray diffraction, as these methods are sensitive to change in Li stoichiometry in graphite. There is minimal reactivity between LiC 6 and N 2 , CO 2 or O 2 ; however, LiC 6 reacts with moisture to form lithium (hydr)oxide. The reaction rate follows zero-order kinetics with respects to intercalated lithium suggesting that lithium transport through the graphite is fast. The reaction occurs by sequential formation of higher stages–LiC 12 , then LiC 18 , and then LiC 24 –as the hydrolysis proceeds to the formation of Li x OH y and graphite end products. Slowing down the formation rate of the Li x OH y passivation layer stabilizes of the higher stages. [ABSTRACT FROM AUTHOR]

The electrochemical reaction with lithium of a vanadium-based metal-organic framework V IV (O)(bdc) [MIL-47], which is isostructural to the iron compound MIL-53(Fe), was investigated. The large open channels which can accommodate small guest species, such as Li + ions, together with the redox properties of the tetravalent vanadium ions make this material of potential interest as a rechargeable intercalation electrode for lithium batteries. The electrochemical properties were investigated in Li|1 M LiPF 6 in ethylene carbonate (EC) and dimethyl carbonate (DMC)|V(O)(bdc) cells between 4.0 and 1.5 V vs. Li/Li + . V(O)(bdc) cathodes can be reversibly cycled in Li cells with good rate capability and specific capacity. At a current density of C /12, Li/V(O)(bdc) cells can be cycled between 0 ≤ x ≤ 0.7 in Li x V(O)(bdc) with ∼100% coulombic efficiency corresponding to 82 mAh g −1 which is a higher capacity than that found for MIL-53(Fe). The cell performance and electrochemical profiles at various current conditions are discussed. Structural evolution taking place during lithium intercalation was monitored by powder X-ray diffraction on phases of Li x V(O)(bdc) (0 < x ≤ 2) chemically prepared by using n-BuLi. Previous studies of the reaction of lithium with metal-organic frameworks are briefly reviewed for comparison with the data presented for Li x V(O)(bdc). [ABSTRACT FROM AUTHOR]

Abstract: Lithium battery performances degrade even at rest time that means when electric/hybrid electric vehicles are in the parking. This phenomenon is well known as calendar aging. In this paper, the kinetic of the CC–CV charge at 1 C and mainly kinetic of the voltage regulation, CV step, is investigated as an indicator of battery state-of-health through calendar aging. In fact, CV step is responsible in a major part of lithium intercalation into negative electrode and revealed to give signification on cyclable lithium loss which is the major cause of calendar aging according to literature and post mortem analysis. Comparison from the aging of four battery technologies is presented. Through aging, results show a difference in battery behavior even if the time for CC charge is decreasing for all the battery. According to battery technology, the current during CV charge phase has been useful for lithium–nickel–manganese–cobalt-oxide, lithium–nickel–cobalt–aluminum-oxide and lithium-ion–manganese battery state-of-health determination. However, in the case of the lithium–iron–phosphate battery, simple calculation of the duration of the CV step revealed to be very accurate compared to the classic discharged capacity measurement. [Copyright &y& Elsevier]

Abstract: Layered sulfides, 2H-Li0.7NbS2 (s.g.: P63 /mmc) and 3R-NbS2 (s.g: R3m) were synthesized and characterized as electrode materials for a lithium-ion battery. 2H-NbS2 has been known as a poor electrode material for Li+-intercalation. However, both 2H-Li0.7NbS2 and 3R-NbS2 show reversible charge/discharge reactions based on the Nb(IV)/Nb(III) redox couple. They present distinctive differences in the voltage curves as a result of local structural differences. Galvanostatic charge/discharge tests between 1.0 and 3.0 V versus Li showed that discharge capacities were 169.5 mAh g−1 for 2H-Li x NbS2 and 169.0 mAh g−1 for 3R-Li x NbS2 at 0.05 C rate and room temperature. At 10 C rate, 2H-Li x NbS2 delivered a discharge capacity of 84.0 mAh g−1 while 3R-Li x NbS2 kept 74.9 mAh g−1. After 200 cycles at 1 C, 9% of capacity fade was observed for 2H-Li x NbS2 (from 141.5 to 129.4 mAh g−1) and 3R-Li x NbS2 showed 14% fade from 139.4 to 120.1 mAh g−1. The key to improvement of the electrochemical performance of the 2H-Li x NbS2 electrode is an initial synthesis of Li0.7NbS2. [Copyright &y& Elsevier]

Abstract: A new material, LiRu2O4, has been synthesized by ion-exchange reaction from NaRu2O4 that has been prepared by solid state reaction at 950 °C under Ar flow. The crystal structure of LiRu2O4, isostructural with the parent NaRu2O4, has been refined by an X-ray Rietveld method (Pnma, a = 9.13940(5) Å, b = 2.80070(9) Å, c = 11.0017(1) Å, Z = 4, R p = 5.30%, wR p = 6.73%, χ 2 = 0.41, 23 °C). The structure belongs to CaFe2O4-type, where double chains of edge-sharing octahedral RuO6 share the corners with neighboring double chains and form tunnels in between them parallel to the shortest b-axis so that the one-dimensional Li array is placed inside each of the tunnels. Detailed structural analysis indicates that the tunnel inside has more than enough space to be filled with the Li atoms. The electrochemical tests of LiRu2O4 demonstrates a reversible Li intercalation reaction at 3.2–3.5 V vs. Li/Li+ with a capacity of ∼80 mAhg−1. The material exhibits excellent high-rate characteristics (93% capacity retention at 10C/1C) as well as high capacity retention with cycles (99% at 50 cycles). [Copyright &y& Elsevier]

Abstract: H2V3O8 nanobelts have been successfully synthesised from commercial V2O5 powder through a fast and environmental friendly microwave-hydrothermal method. X-ray diffraction, field-emission scanning electron microscopy, thermogravimetric analysis, infrared spectroscopy, high-resolution transmission electron microscopy and ICP spectroscopy were used to characterise the morphology and structure–microstructure details. Nanobelts about 100 nm wide and several micrometres long are easily prepared in no more than 2 h. The electrochemical study reveals the reversible insertion of ca. 4 Li per formula unit (400 mAh g−1), through several pseudo-plateaus in the 3.75–1.5 V vs Li+/Li voltage range showing the interest of this material produced by a “green” route as an electrode for lithium rechargeable batteries. After the first cycle a significant capacity loss is observed, though a high capacity, ca. 300 mAh g−1, remains upon cycling. Furthermore, the similarity of discharge and charge curves, pointing to the absence of hydrogen displacement during lithium insertion in H2V3O8, shows that not all protonated systems must be discarded as prospective electrode materials. On the other hand, further reduction down to 1 V is possible to insert up to 5 Li per formula unit (480 mAh g−1). Interestingly it corresponds to full reduction of vanadium to V3+ as it is also confirmed by EELS experiments. However, the full reduction to V3+ is associated with a fast decay of the extra capacity developed at low voltage with increasing current rate. Then for practical use we may consider only the capacity obtained down to 1.5 V. [Copyright &y& Elsevier]

Abstract: We report single-crystalline TiO2 nanowires (TiO2-NWs) synthesized by hydrothermal process without any surfactant and template with enhanced lithium intercalation properties. The single-crystalline nature of rutile TiO2-NWs was clearly observed by field-emission transmission electron microscopy and fast Fourier transform pattern demonstrating that the nanowire growth is along the [001] direction. The single-crystalline rutile TiO2-NWs showed much higher charge capacity and excellent high-rate performance as compared to typical rutile TiO2 nanoparticles. The improved lithium-ion intercalation properties of TiO2-NWs may be attributed to relatively large specific surface area, short transport distance of 1-D nanostructure, and freedom for volume change accompanied by lithium-ion intercalation. [Copyright &y& Elsevier]

Abstract: As a new molecular cluster cathode material for lithium batteries, K5.72H3.28[PV14O42] (KPV), a hetero polyoxovanadate with a bi-capped Keggin structure, was synthesized. Its crystal structure was refined by X-ray Rietveld analysis, and its electrochemical properties were examined. The symmetry space group of KPV was assigned to FM3-M. The [PV14O42]9− bi-capped Keggin units are connected sharing K+ ions. KPV contains many cation site vacancies and has tunnels facing various directions. The polycrystalline KPV powder becomes amorphous when dried at 80 °C, while the molecular cluster structure of KPV, identified by Raman scattering method, is maintained. KPV showed higher discharge capacity with higher discharge voltage than K3[PMo12O40] (KPM) with Keggin-type structure. The most improved property of KPV compared with KPM was cycle stability. KPV kept 95% of its initial discharge capacity after 50 cycles of discharge–charge, whereas KPM kept only 35%. The presence of bi-capped Keggin unit is confirmed by ex situ EXAFS measurement, even though a rapid amorphization of KPV was observed at the beginning of the discharge–charge process in ex situ X-ray diffraction (XRD) measurements. The results of ex situ EXAFS measurement and the reversible charge transfer resistance of KPV estimated from the AC-impedance measurement during the discharge–charge process also indicate that the cycle stability of KPV is attributable to the stability of the KPV cluster ion unit. [Copyright &y& Elsevier]

Abstract: The electrochemical property of Keggin type hetero polyoxomolybdate K3[PMo12O40] (KPM) as the cathode electrode material for lithium battery was examined. KPM showed charge–discharge performance in the potential region from 4.2V to 1.5V with capacity of over 200mAhg−1. From the result of the ex situ XRD measurement, it is presumed that the electrochemical reaction of KPM proceeds via the lithium (de-)intercalation. The cycle performance of KPM is largely dependent on the charge–discharge potential range. The capacity fade caused by deep discharging seems to be concerned to the 〈 to ® isomerization of KPM. [Copyright &y& Elsevier]

Abstract: 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 300mAhg−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. [Copyright &y& Elsevier]

Abstract: Graphite electrodes were modified by polyacrylic acid (PAA), polymethacrylic acid (PMA), and polyvinyl alcohol (PVA). Their electrochemical properties were examined in 1moldm−3 LiClO4 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. 0.8V 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. [Copyright &y& Elsevier]

Abstract: This study examines the electrochemical reactions occurring at graphite negative electrodes of lithium-ion batteries in a propylene carbonate (PC) electrolyte that contains different concentrations of lithium salts such as, LiClO4, LiPF6 or LiN(SO2C2F5)2. The electrode reactions are significantly affected by the electrolyte concentration. In concentrated solutions, lithium ions are reversibly intercalated within the graphite to form stage 1 lithium–graphite intercalation compounds (Li–GICs), regardless of the lithium salt used. On the other hand, electrolyte decomposition and exfoliation of the graphene layers occur continuously in the low-concentration range. In situ analysis with atomic force microscopy reveals that a thin film (thickness of ∼8nm) forms on the graphite surface in a concentrated solution, e.g., 3.27molkg−1 LiN(SO2C2F5)2/PC, after the first potential cycle between 2.9 and 0V versus Li+/Li. There is no evidence of the co-intercalation of solvent molecules in the concentrated solution. [Copyright &y& Elsevier]

Abstract: Two tin–graphite composites (“core-shell” structures) with different metal content (80wt% and 20wt%) as well as their structural and electrochemical characteristics are presented. Mitsubishi''s synthetic carbon was used as starting material for the modification experiments. Chemical reduction was applied for the coating process, which was carried out under inert argon atmosphere. Although a homogeneous film of the nanoscale tin particles (∼60nm) have been achieved, the electrochemical performance improvement strongly depends on the thickness of the “shell’ layer and the progressively increased active surface area together with the tin metal contents. The electrode with low metal concentration displayed both improved cycling performance and stable discharge capacity of 435Ahkg−1 compared with untreated graphite electrode. The tin-rich composite shows a higher medial discharge capacity (540mAhg−1) but increased capacity fading, while higher metal contents lead to bulk-coated film with disassociated and agglomerated tin nanoparticles as well as higher surface area and likely presence of oxide impurities. The obtained electrochemical results lead to the assumption, that there is a critical metal ratio up to which good cycling behavior can be achieved. Moreover, the properties of the coating film are closely related with the synthesis conditions and the type of the graphite. In this case, the optimal amount for tin–graphite composite with improved electrochemical performance is about 20wt%. [Copyright &y& Elsevier]

Abstract: Cyclic voltammetry, XPS, RBS and AFM have been combined to study the ageing mechanism of Li intercalation in V2O5 thin films prepared by thermal oxidation of vanadium metal. Multi-cycling tests were performed in 1M LiClO4-PC in the potential range E ∈[3.8, 2.8V] versus Li/Li+, corresponding to the α-to-δ phase transition. XPS and AFM were performed using direct anaerobic and anhydrous transfer. Capacity fading remains inferior to 20% during ∼2500 cycles. XPS shows slight modifications of the oxide composition with a V4+ concentration increasing from ∼5% prior to cycling to ∼16–27% after cycling, due to Li trapped in the oxide film and to the loss of V2O5 active material. The presence of lithium carbonate and lithium-alkyl carbonate species evidences the formation of the so-called SEI layer. AFM evidences the loss of crystalline material by grain exfoliation from the outer V2O5 layer of the oxide film. By further exfoliation, the inner VO2 layer of the oxide film is reached and pits are formed, occupying ∼9–13% of the surface. This de-cohesion at grain boundaries is attributed to the strain generated by repeated lattice distortions. After 3300 cycles, the disappearance of lithium carbonates, whereas Li-alkyl carbonates and/or Li-alkoxides remain on the surface, indicates the dissolution and/or conversion of the SEI layer. After 4500 cycles, the oxide film became very labile and could be stripped away by rinsing to reveal the vanadium metal substrate. [Copyright &y& Elsevier]

Abstract: The electrochemical reactivity of the layered titanium hydrogeno phosphate Ti(HPO4)2·H2O versus lithium has been studied. Lithium intercalation occurs at ∼2.5V with low polarization, leading to a new lithiated Ti(III) phase, LiTi(HPO4)2·H2O. Ti(HPO4)2·H2O exhibits a reversible capacity of 80mAhg−1 in the voltage window 1.8–3.5V at C/10 rate. The stable reversible capacity reveals that the presence of H2O lattice is not affecting the electrochemical reaction. The reversibility of the reaction is demonstrated by extracting lithium from LiTi(HPO4)2·H2O and the host structure is intact. The electrochemical behaviour of dehydrated phases Ti(HPO4)2 and TiP2O7 has also been investigated. [Copyright &y& Elsevier]

Abstract: Vanadium oxide/polyaniline nanotubes were produced by cationic exchange between hexadecylamine and polyaniline after the synthesis of vanadium oxide nanotubes by sol–gel method followed by hydrothermal treatment. The local structure of this hybrid material was studied by high-resolution transmission electron microscopy, infrared and Raman spectroscopy and small angle X-ray diffraction technique. The results show that polyaniline is intercalated in the interlamellar space of the vanadium oxide nanotube forming a hybrid material with defined morphology. Electrochemical impedance spectroscopy experiments have shown that the apparent diffusion coefficient for nanotubes with template was approximately 1×10−9 cm2 s−1. Nanotubes with polyaniline presented an apparent diffusion coefficient at least one order in magnitude higher than the parent material “with template”, comparable with other vanadium oxide described in the literature, revealing a promising material for utilization as cathode for ion-Li batteries. [Copyright &y& Elsevier]

Abstract: LiNi0.5Mn0.5O2, LiNi0.475Al0.05Mn0.475O2, and LiNi0.5Mn0.45Ti0.05O2 were prepared via the emulsion drying method. The as-prepared materials showed different degrees of cation mixing. Rietveld refinement of X-ray diffraction data revealed that Al and Ti doping in LiNi0.5Mn0.5O2 was significantly effective to decrease the cation mixing in the octahedral Li layers. The cation mixing consequently affected to the charge and discharge capacities. The irreversible capacity was the smallest for the Al doped LiNi0.5Mn0.5O2, which showed the smallest cation mixing. Al and Ti doped LiNi0.5Mn0.5O2 delivered a stable capacity of about 175mAhg−1 with high reversibility. Such higher capacities were possible to be obtained by the achievement of structural stabilization and enhancement of structural integrity by Al and Ti doping in LiNi0.5Mn0.5O2. [Copyright &y& Elsevier]

Abstract: Electrochemical performance of a graphite electrode for lithium ion batteries are easily improved by sodium ion dissolved in an electrolyte solution as reported recently by our group. On the contrary, when potassium ions were added by dissolving 0.2moldm−3 KPF6 into a 1moldm−3 LiPF6 ethylene carbonate–diethyl carbonate (1:1, v/v) electrolyte solution prior to charge–discharge cycle, an electrochemical performance of a graphite electrode was deteriorated compared to that tested in an additive free electrolyte; larger irreversible capacity at the first cycle and worse retention of discharge capacities on successive cyclings. During the first charge in a potassium additive system, ex situ XRD observation of graphite electrodes revealed that lithium intercalation hardly proceeded in the lower potential region less than 0.1V versus Li though lithium ions were intercalated at >0.1V. Electroreduction of potassium ions on the electrode occurred instead of lithium intercalation into graphite in the lower potential region. Furthermore, the electrode surface morphology observed by electron microscopes after charge–discharge tests got less uniform in the potassium added electrolyte. [Copyright &y& Elsevier]

Using a novel electrodeposition/thermal process, V6O13+y, 0, bronzes were directly fabricated into a coin cell without the use of binders or electronic conductors. Transport properties of lithium insertion and removal from V2O5 and nonstoichiometric (ns) V6O13+y bronzes, were examined by electrochemical methods in asymmetrical Li/LixV6O13+y cells. Diffusion coefficients in the range 0.2–5.0×10-8 cm2 s-1 were found for insertion and removal steps in the range, x=0–1.0. The transport of lithium ions from the vanadium oxides is similar to the insertion process. These bronze cathodes have similar transport properties to composite cathodes, making them potentially useful for electrochromic displays and microbatteries. [Copyright &y& Elsevier]

There is a renewal of interest in the use of metals that are capable of alloying with lithium as negative-electrode materials for lithium-ion batteries. These metals can supply larger capacities than graphite but their main disadvantage consists in their very limited cycle life.Indeed, they present considerable volume variations during alloying, which lead to a mechanical degradation of the electrode. The concept of an active phase stabilizing matrix was introduced. We propose in this study to associate a metal able to alloy lithium to graphite by using new preparation methods involving graphite intercalation compounds (GICs) as precursors.In one case, antimony pentachloride SbCl5 was reduced by the stage I KC8 GIC. In another case, C12SbCl5 and C24SbCl5 GICs were reduced either by gaseous caesium or by activated sodium hydride NaH. Actually, these methods led to the attention of antimony-based graphite composites in which antimony particles are deposited on the surface and edges of graphite layers or embedded in an organic matrix. Both morphological and structural characteristics of such composites were studied by transmission electron microscopy. Examination of their electrochemical properties as regards lithium insertion showed that they present interesting performances because the reversible capacity is increased by comparison with that of pure graphite and the stability of the metal is preserved throughout the cycling. The combination of graphite and antimony prevents the metal against cracking and pulverization that occur generally during alloying/dealloying cycles. Antimony-graphite composites prepared via SbCl5 reduction by KC8, via C12SbCl5 reduction by gaseous caesium or via C24SbCl5 reduction by activated NaH display improved reversible capacities of 420, 490 and 440 mAh g-1, respectively. [Copyright &y& Elsevier]

Ternary oxides with general formula MMoO4 (where M is a 3d-transitional metal) were characterized as cathode materials for lithium rechargeable batteries by galvanostatic charge–discharge technique and cyclic voltammetry. The significant capacity fading after the first cycle of lithium insertion/removal takes place for different copper molybdates (α-CuMoO4 and high-pressure modification CuMoO4-III) corresponding to the irreversible copper reduction and formation of Li2MoO4 during the first discharge. X-ray powder diffraction data reveal the decomposition of pristine ZnMoO4 by electrochemical reaction, lithium zinc oxide with the NaCl-type structure and Li2MoO3 seem to be formed. Lithium intercalation into nickel and iron molybdates is shown to proceed without phase transitions, but at unsatisfactory low operating voltages. [Copyright &y& Elsevier]

The intercalation rate of Li+-ions in flake natural graphite (two-dimensional) with particle size from 2 to 40 μm and sphere-like graphite (three-dimensional), 12 to 40 μm in particle size, was investigated. The amount of Li+ ions that intercalate at different rates was determined from measurement of the reversible capacity during de-intercalation in 1 M LiClO4/1:1 (volume ratio) ethylene carbonate—dimethyl carbonate. The key issues in this study are the role of the particle size and fraction of edge sites on the rate of intercalation and de-intercalation of Li+ ions. At low specific current (15.5 mA/g carbon), the composition of lithiated graphite approaches the theoretical value, x=1 in LixC6, except for the natural graphite with the largest particle size. However, x decreases with an increase in specific current for all particle sizes. This trend suggests that slow solid-state diffusion of Li+ ions limits the intercalation capacity in graphite. The 3D natural graphite with a particle size of 12 μm may provide the optimum combination of reversible capacity and irreversible capacity loss in the electrolyte and discharge rates used in this study. [Copyright &y& Elsevier]

Quasi-equilibrium potential profiles of stoichiometric LiMn2O4 spinel in charge–discharge process have been recorded to investigate temperature dependence in lithium ions intercalation. Temperature of electrodes has been controlled within 273≤T≤298 K in this research. Discharge curve reveals anomalous stepwise features when both charge and discharge processes are carried out at low temperature (T≤278 K). However, discharge curve at 273 K immediately after charge at 298 K does not show stepwise shape but gently slope as potential curve in charge at 298 K. In contrast to this, discharge curve at 298 K immediately after charge at 273 K shows stepwise anomaly. Temperature at discharge does not affect on shape of potential profile at next charge process. This temperature hysteresis has been confirmed repeatedly in several charge–discharge cycles. Temperature at Li ions de-intercalation has a large effect on next intercalation in LiMn2O4 spinel. [Copyright &y& Elsevier]

The phase diagram of LixNiO2 (0) and the evolution of the monoclinic distortion as a function of the lithium content are calculated using a combination of first-principles energy methods and statistical–mechanics techniques. As a function of the temperature different ordered LixNiO2 structures appear in the phase diagram at x=0.25, 0.33, 0.4, 0.5 and 0.75. Noteworthy, a new and unsuspected phase, Li0.4NiO2, dominates the low-lithium region of the phase diagram. In agreement with experimental results, maxima in monoclinicity (am/bm) are predicted to occur near Li0.75NiO2 and Li0.4NiO2. The coupling between the Li-vacancy ordering and the Jahn–Teller activity of Ni3+ ions plays a crucial role in the stability of ordered LixNiO2 structures and is at the origin of the monoclinic distortion. As a result, the different electrochemical behavior of LixNiO2 versus LixCoO2 lies in the electronic nature of the involved transition metal cation. [Copyright &y& Elsevier]

By using an electrodeposition method to form hexavanadates, followed by a thermal process, a range of bronze stoichiometries, MxV6O13+y, where M: K, Ni, or Mo, 0, 0.2 in the ternary system of V2O4–V2O5–M2O were prepared. These bronzes adhered well to a conducting substrate and could be directly fabricated into a coin cell without the need for binders or electronic conductors. The phase changes on discharge and the lithium insertion ability were influenced by the amount of the guest metal in the bronze structure. When the value of x was small (<0.5) reversible phase changes resembled those of V2O5 or V6O13 depending on the initial O2 content of the bronze after heating. The cycle life was adversely affected by the depth of discharge below 2.2 V for the V2O5 type bronzes. The V6O13 bronze cathodes had better cycle lives at average operating voltages of about 2.5 V and over 350 Ah/kg for their initial cycles. [Copyright &y& Elsevier]

The intercalation of Li ions in natural graphite that was purified by chemical and thermal processes was investigated. A new chemical process was developed that involved a mixed aqueous solution containing 30% H2SO4 and 30% NHxFy heated to 90 °C. The results of this process are compared to those obtained by heating the natural graphite from 1500 to 2400 °C in an inert environment (thermal process). The first-cycle coulombic efficiency of the purified natural graphite obtained by the chemical process is 91 and 84% after the thermal process at 2400 °C. Grinding the natural graphite before or after purification had no significant effect on electrochemical performance at low currents. However, grinding to a very small particle size before purification permitted optimization of the size distribution of the particles, which gives rise to a more homogenous electrode. The impurities in the graphite play a role as microabrasion agents during grinding which enhances its hardness and improves its mechanical properties. Grinding also modifies the particle morphology from a 2- to a 3-D structure (similar in shape to a potato). This potato-shaped natural graphite shows high reversible capacity at high current densities (about 90% at 1C rate). Our analysis suggests that thermal processing is considerably more expensive than the chemical process to obtain purified natural graphite. [Copyright &y& Elsevier]

Nickel substituted lithium–cobalt oxides, LiCo1−xNixO2 (0), have been synthesized in a very short time by a solution combustion method at 350 °C using diformyl hydrazine as a fuel. Pure phases with hexagonal lattice structure have been obtained. These compounds facilitate reversible insertion/extraction of Li+ ions with good discharge capacity between 3.0 and 4.4 V versus Li/Li+. Results of the studies by powder X-ray diffraction, scanning electron microscopy, cyclic voltammetry, galvanostatic charge–discharge cycling and ac impedance measurements are presented. [Copyright &y& Elsevier]

In order to investigate the relation between spinel type structure and anomaly in potential–composition profile of stoichiometric LiMn2O4 spinel at low temperature (T≤278 K), several LiCryMn2−yO4 type spinels (y=0.01–0.25) have been synthesized by conventional solid-state reaction and their potential–composition (φ–x; LixCryMn2−yO4) profiles at 273 K have been recorded. The φ–x profiles of the specimens (y=0.01–0.03) show an anomalous stepwise feature as one that stoichiometric LiMn2O4 shows at low temperature. However, the step at x≒0.7 becomes weak with increase of the value y, and finally disappears. In the specimens, Mn and Cr are considered to occupy only 16d sites of spinel type structure. As compared with the φ–x profiles of lithium-excess type spinels Li1+δMn2−δO4 and lithium-deficient type spinels Li1−δMn2O4, the gradual result suggests that state of Mn lattice strongly affects the appearance of anomalous step at x≒0.7. [Copyright &y& Elsevier]

Graphitized carbons have played a key role in the successful commercialization of Li-ion batteries. The physicochemical properties of carbon cover a wide range; therefore, identifying the optimum active electrode material can be time consuming. The significant physical properties of negative electrodes for Li-ion batteries are summarized, and the relationship of these properties to their electrochemical performance in non-aqueous electrolytes, are discussed in this paper. [Copyright &y& Elsevier]