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To gain better insight into the influence of the anion size and symmetry on the transport properties and thermal stability of an electrolyte based on lithium (fluorosulfonyl)(trifluoromethanesulfonyl)-imide (FTFSI) salt, we performed the physical and electrochemical characterization of an electrolyte based on FTFSI incorporated in standard binary (3EC/7EMC) and ternary (EC/PC/3DMC) alkylcarbonate mixtures. By applying the Jones-Dole-Kaminsky (JDK), Eyring and Arrhenius empirical models to the electrolyte viscosity we show that the activation enthalpy and entropy energy barriers ( Δ H ≠ , Δ S ≠ ) for viscous flow are between 12 and 15 kJ·mol−1. They are strongly dependent on the solvent nature and are significantly lower than their symmetric anions LiFSI and LiTFSI (19–20 kJ·mol−1) in the binary mixture. Furthermore, the hydrodynamic radius, rs, calculated by JDK, and the ionicity behavior illustrated by the Walden role, showed that the FTFSI anion is outside the solvation sphere (rs > 0.6 nm) which is smaller in the case of an EC/EMC solvent base. In the 3EC/7EMC solvent mixture, LiFTFSI is less conductive than in the ternary mixture i.e., σmax = 8.9 mS cm−1 at Cmax = 1.1 mol L−1 for 3EC/7EMC and, σmax = 10.5 mS cm−1 at max = 0.7 mol L−1 for EC/PC/3DMC, due to a strong solvation and a greater association of FTFSI ions in the binary solvent mixture. The thermal stability of FTFSI based electrolytes was determined by the shift of the evaporation temperature of the volatile solvents (DMC, EMC) in the presence of salt, towards the higher temperatures. This feature is visible on the thermograms obtained by DSC both with the liquid electrolyte and with charged LMO cathodes in presence of electrolytes. The consequences of these properties on the electrochemical behavior of a graphite (Gr) half-cell, a lithium metal (Li) anode and a manganese lithium oxide (LMO) cathode demonstrated on the one hand the formation of a thick solid electrolyte interphase (SEI) on graphite that consumed a significant amount of lithium i.e., 18% of total capacity of the first charge. Furthermore, LiFTFSI delivered 95% of the initial capacity C = 360 mAh g−1 at C/10 with EC/PC/3DMC versus 91% when it was combined with 3EC/7EMC C = 348 mAh g−1, while the capacities obtained for LiTFSI in EC/PC/3DMC were the lowest (C = 275 mAh g−1) compared to those of the other salts. After 10 cycles, the capacity loss at C/20 is

Equipped with a fully lithiated cathode with a bare anode current collector, the anode-free lithium cell architecture presents remarkable advantages in terms of both energy density and safety compared with conventional lithium-ion cells. However, it is challenging to realize high Li reversibility, especially considering the limited Li reservoir (typically zero lithium excess) in the cell configuration. In this study we have introduced Li2O as a preloaded sacrificial agent on a LiNi0.8Co0.1Mn0.1O2 cathode, providing an additional Li source to offset the irreversible loss of Li during long-term cycling in an initial-anode-free cell. We show that O2− species, released through Li2O oxidation, are synergistically neutralized by a fluorinated ether additive. This leads to the construction of a LiF-based layer at the cathode/electrolyte interface, which passivates the cathode surface and restrains the detrimental oxidative decomposition of ether solvents. We have achieved a long-life 2.46 Ah initial-anode-free pouch cell with a gravimetric energy density of 320 Wh kg–1, maintaining 80% capacity after 300 cycles. Anode-free batteries offer high-energy prospects but suffer from poor cycling stability due to limited lithium sources. Here, the authors preload lithium oxide onto a high-energy cathode in initial-anode-free cells, which substantially improves the cyclability while maintaining high energy density.

In this work, metal foam current collectors (CCs, i.e. nickel [Ni] and copper [Cu]) were treated by thermal oxidation to create a lithiophilic oxide surface that exhibited enhanced electrochemical performances of lithium anodes such as the cyclic stability of Coulombic efficiency at different current densities for various capacities compared to pristine CCs. The oxidized CCs facilitated much increased diffusivities of ions for lithium growth than pristine CCs. It was found that an inhomogeneous solid electrolyte interphase (SEI) formed on pristine CCs while a uniform SEI formed on oxidized CCs. Uniform lithium (Li) deposition can be achieved on oxidized CCs owing to the lithiophilic oxide surface containing metal nanoparticles and the ionic compound lithium oxide (Li 2O) matrix that led to a uniform SEI film and many nucleation sites. In addition, the porous and non-porous composite anodes exhibited different electrochemical performances. The porous composite anodes showed initial lower voltage hysteresis but shorter lifetime with carbonate-based electrolyte than non-porous composite anodes. The porous composite anodes showed better rate performances in full-cell measurements while the non-porous composite anodes displayed better stability. The interfacial modification of porous hosts by lithiated oxides and the effects of porous structure on battery performances can be also useful for designing other electrodes (e.g. sodium [Na], potassium [K], zinc [Zn]).

A parametric study of the electrolytic reduction of uranium dioxide in molten lithium chloride – lithium oxide using carbon anodes was conducted to determine the operational parameter values necessary for high yields. Operational parameters evaluated in this study include anode and cathode current densities, anodic polarization, UO2 batch size, and method of electrochemical control. Seven oxide reduction experiments were conducted with between 25 g and 100 g UO2. The current density on the cathode was the critical parameter, which indicates the reduction process is kinetically controlled by cathodic reactions. High cell currents were achieved without the application of high anodic potentials by using a large anode surface area. This approach facilitates efficient reduction at high throughput without production of chlorine or other corrosive gasses.

Silicon is touted as a replacement for the commercially utilized carbon anode in lithium ion batteries. However, two drawbacks have hindered its use: low electronic conductivity and significant volume changes during lithiation/delithiation. Numerous studies have examined ways to improve silicon thin films with doped and reactive (i.e., oxidized, nitrated, and hydrogenated) forms summarized herein. Factors affecting electrochemical performance and cycling stability are compared against pure silicon, with the two alternatives generally showing better results. Most of the improvements for doped silicon have been attributed to higher electronic conductivity. Treatment gases such as: oxygen, nitrogen, and hydrogen, have been used to produce reactive silicon films. For oxidized silicon reaction products (i.e., lithium silicate, lithiated silicon, and lithium oxide) during cycling were found to serve as a buffer layer and/or matrix, helping to negate volume changes during charge/discharge. Improvements in nitrated silicon films were attributed to large lithiation capacity, high lithium ion conductivity, and mechanical stability. The improvement in cyclability performance for hydrogenated silicon films has yet to be fully developed and further systematic investigations are warranted Refereed/Peer-reviewed

Realization of an outermost layer on the surface of metallic lithium is performed via reactive exposure of a thin lithium foil to a constant flow of pure O2 gas in a controlled, airtight environment to form spontaneously a ceramic-type, Li-ion conductive film for use in rechargeable lithium metal batteries with a liquid electrolyte. This layer acts as possible intermediate ‘buffer’ between the underlying lithium and solid electrolyte interphase (SEI) formed in contact with the electrolyte. The impact of this oxygen-containing layer on the cycle performances of thin lithium anodes and associated surface evolution are studied here in cells having LiFePO4 as stable cathode. The influence of this protective layer on 30 μm-thick lithium metal anodes and related effects on the electrochemical behaviour of corresponding cells are investigated with both standard LiPF6 electrolyte and lithium bis-oxalato-borate (LiBOB) as F-free alternative. Combining lithium oxide coating and LiBOB appears to play a key role in extending cell cycling and hindering dendrite formation, although a clear surface roughening of the cycled lithium is observed too. This protected lithium cycled against LiFePO4 with LiBOB provides good capacity retention at different C-rates, displaying adequate Coulombic and round-trip efficiencies and simultaneously enhancing the number of charge-discharge cycles.

Silicon suboxide (SiOx) is a promising anode material for lithium ion batteries (LIBs), due to its high specific capacity, small volume variation and superior cycle performance. Herein, we demonstrated the determining roles of oxygen contents on the behavior of SiOx upon lithium by means of thin-film type electrodes. The SiOx thin-film anodes with different oxygen contents were prepared by sputtering with Cu foil as substrates. XRD and Raman investigations reveal that these SiOx films are amorphous. As anodes, it is found that increasing oxygen contents in SiOx endows an enhanced cycle stability, but does harm to their initial Coulombic efficiency and capacity. Among all the a-SiOx film anodes (x = 0.4, 0.7, 1.1 and 1.5), the SiO0.7 electrode with a thickness of 450 nm exhibits excellent cycle performance and rate capability, with a high initial discharge capacity of 463 μAh cm−2 μm−1 at the current density of 64 μA cm−2 and a high capacity retention of 90% after 300 cycles. This superior performance is ascribed to that the in-situ formed lithium oxide/silicates compounds during discharge effectively alleviates the large volume change of Si components, but also suppresses the electron leakage from the surface of active particles, shutting down the further decomposition of electrolytes and then the formation of thick solid interphase layer. These results will provide inspirations for designing high-performance Si based anodes for lithium ion batteries.

An elevated lithium battery Batteries based on lithium metal and oxygen could offer energy densities an order of magnitude larger than that of lithium ion cells. But, under normal operation conditions, the lithium oxidizes to form peroxide or superoxide. Xia et al. show that, at increased temperatures, the formation of lithium oxide is favored, through a process in which four electrons are transferred for each oxygen molecule (see the Perspective by Feng et al. ). Reversible cycling is achieved through the use of a thermally stable inorganic electrolyte and a bifunctional catalyst for both oxygen reduction and evolution reactions. Science , this issue p. 777 ; see also p. 758

Electrochemical reduction of CO2 to value-added carbon and oxygen in molten carbonates is a promising approach to the efficient and economical utilization of CO2. Fully understanding the electrode kinetics is crucial to scaling up the process. Herein, the reduction kinetics were studied by cyclic voltammetry, linear sweep voltammetry and potentiostatic electrolysis. The electrolytic products prepared at selected potentials were characterized by X-ray diffraction. It was found that the cathode surface was partially covered by insoluble lithium oxide and that the sluggish diffusion of the O2– ion was the rate-determining step during carbon deposition at 723 K. When the temperature is increased to 923 K, the reaction kinetics are accelerated around 100-fold with a limiting current density of 1.5 A/cm2. Knowledge of this mechanism should prove useful in the design of a pilot cell based on molten salt CO2 capture and electrochemical transformation (MSCC-ET) technology. Keywords: Carbon dioxide utilization, Molten carbonates, Electrochemical reduction, Electrode kinetics, Rate-determining step

The structural and morphological changes occurred during the molten salt treatment of ilmenite (FeTiO3) are investigated by a variety of techniques including X-ray diffraction, scanning and transmission electron microscopy, as well as Raman and photoelectron spectroscopy. The phase evolution of ilmenite in molten LiCl under humid atmosphere leads to the facile formation of Li-containing phases such as Li0.8Ti2.2O4 and LiFeO2. Moreover, graphene nanosheets are successfully incorporated in the molten salt produced material through ball milling, and the Li-storage performance of the electrode made of the hybrid material is investigated. Unlike ilmenite, the hybrid structure exhibit an excellent electrochemical performance with a stable capacity of around 300 mAh g−1 after 500 successive discharge/charge cycles. This enhanced electrochemical performance is attributed to the presence of lithium oxide in the molten salt product that reduces the overall volume changes taking place during the lithiation/delithiation of the material, increasing the structural stability of the electrode. Furthermore, the presence of graphene nanosheets not only provides the electrical conductivity for the electrode, but also contributes to the structural stability of electrode by agglomerating the nanoparticles formed during cycling of the electrode. This article suggests a green and low-cost approach for the facile conversion of ilmenite into materials applicable for energy storage systems.

Anode-supported micro-tubular solid oxide fuel cell (MT-SOFC) made from lithium (Li) doped cerium gadolinium oxide (CGO) electrolyte was prepared via phase inversion based co-extrusion/co-sintering technique. In this study, the co-sintering temperature of CGO electrolyte with anode layer was reduced by adding Li that acts as sintering additive. The prepared Li doped CGO (Li-CGO) were characterized by shrinkage analysis, atomic resolution analytical microscope (ARM) observation and X-ray photoelectron spectroscopy (XPS) spectra. Meanwhile, the developed half-cell of MT-SOFC which was co-sintered at 1350–1500 °C with interval of 50 °C were characterized by its mechanical strength, gas tightness and microstructural analysis. The electrochemical performances of the cells were tested in anode-supported MT-SOFCs with configuration of Ni-CGO anode, Li-CGO electrolyte and LSCF-CGO cathode using humidified hydrogen as fuel and oxygen air as oxidant. MT-SOFCs fabricated with Li-CGO electrolyte were found to exhibit maximum power density of 60 Wm − 2 at 500 °C compared to 200 Wm − 2 for cells with unmodified CGO electrolyte. The poor performance of cell with Li-CGO electrolyte is probably due to the combined effects of (i) moderately dense electrolyte layer and (ii) appearance of electronic conductivity in Li-CGO electrolyte. Nevertheless, lowering the sintering temperature has shown good properties of the electrolyte materials, which allows the electrolyte materials and anode can be co-sintered together at lower temperature.

Li 2 ZnTi 3 O 8 @C anode material has been synthesized by a facile solid-state reaction method, in which C 6 H 5 Li 3 O 7 ·4H 2 O is used as the lithium source, as well as the single-source carbon. With the formation of carbon-wrapped lithium oxide by the thermolysis of single-component precursor C 6 H 5 Li 3 O 7 ·4H 2 O, Li 2 ZnTi 3 O 8 particles are produced in a limited area, which could effectively hinder their growth/agglomeration. Moreover, the carbon layer coating on the outer surface of Li 2 ZnTi 3 O 8 is also beneficial to the transfer of both Li + and electrons, then an enhanced electrochemical performance is expected to achieve. From the electrochemical test results, a reversible capacity of 227.4 mAh g −1 could be delivered by Li 2 ZnTi 3 O 8 @C after 100 cycles at the current rate of 2 C.

Hematite (Fe2O3) nanoparticles and reduced graphene oxide (rGO) were supersonically sprayed onto copper current collectors to create high-performance, binder-free lithium ion battery (LIB) electrodes. Supersonic spray deposition is rapid, low-cost, and suitable for large-scale production. Supersonic impact of rGO sheets and Fe2O3 nanoparticles on the substrate produces compacted nanocomposite films with short diffusion lengths for Li+ ions. This structure produces high reversible capacity and markedly improved capacity retention over many cycles. Decomposition of lithium oxide generated during cycling activates the solid electrolyte interface layer, contributing to high capacity retention. The optimal composition ratio of rGO to Fe2O3 was 9.1 wt.%, which produced a reversible capacity of 1242 mAh g−1 after N = 305 cycles at a current density of 1000 mA g−1 (1C).

Lithium oxide (Li2O) is activated in the presence of a layered composite cathode material (HEM) significantly increasing the energy density of lithium-ion batteries. The degree of activation depends on the current rate, electrolyte salt, and anode type. In full-cell tests, the Li2O was used as a lithium source to counter the first-cycle irreversibility of high-capacity composite alloy anodes. When Li2O is mixed with HEM to serve as a cathode, the electrochemical performance was improved in a full cell having an SiO-SnCoC composite as an anode. The mechanism behind the Li2O activation could also explain the first charge plateau and the abnormal high capacity associated with these high energy cathode materials.

Herein, we describe a new simple method to improve the irreversible performance of a SiO anode during the initial cycle. The solid state-reacted SiO material was synthesized from bare SiO and lithium powders (three samples with weight ratios of 7:1, 8:1, and 9:1 were prepared) using a heat treatment process at 600 °C. Irreversible phases such as lithium silicates (Li4SiO4 and Li2SiO3) and Li2O were formed upon the solid state reaction with SiO. Electrochemical tests using half-cells were performed to confirm the effects of the solid state-reacted SiO material. The initial Coulombic efficiencies of the three samples were 82.12% (7:1), 79.81% (8:1), and 78.95% (9:1), which were far higher than that of a bare SiO cell (58.52%). Furthermore, the electrochemical performance of a full cell using a 7:1 wt% SiO anode and a lithium cobalt oxide cathode was evaluated. The full cell exhibited an initial Coulombic efficiency of 93.62% and a capacity retention of 74.70% after 15 cycles, which were also far higher than those of a bare SiO cell (66.4% and 55.72%, respectively). A comparison of the solid state-reacted and bare SiO electrodes demonstrated that the pre-formed irreversible phases prevented the consumption of lithium ions during the 1st cycle.

Liquid-cell in situ transmission electron microscopy (TEM) observations of the charge/discharge reactions of nonaqueous Li-oxygen battery cathode were performed with ∼5 nm spatial resolution. The discharging reaction occurred at the interface between the electrolyte and the reaction product, whereas in charging, the reactant was decomposed at the contact with the gold current collector, indicating that the lithium ion diffusivity/electronic conductivity is the limiting factor in discharging/charging, respectively, which is a root cause for the asymmetry in discharging/charging overpotential. Detachments of lithium oxide particles from the current collector into the liquid electrolyte are frequently seen when the cell was discharged at high overpotentials, with loss of active materials into liquid electrolyte ("flotsam") under minute liquid flow agitation, as the lithium peroxide dendritic trees are shown to be fragile mechanically and electrically. Our result implies that enhancing the binding force between the reaction products and the current collector to maintain robust electronic conduction is a key for improving the battery performance. This work demonstrated for the first time the in situ TEM observation of a three-phase-reaction involving gold electrode, lithium oxides, DMSO electrolyte and lithium salt, and O2 gas. The technique described in this work is not limited to Li-oxygen battery but also can be potentially used in other applications involving gas/liquid/solid electrochemical reactions.

Density functional theory calculations are performed to investigate the role of lithium salts regarding the oxygen reduction reaction (ORR) occurred in non-aqueous electrolyte in Li-air batteries. This study is useful to elucidate the influence of ion-conducting lithium salts on ORR kinetics. The Li + -O bonding, binding energy, Gibb's free energy, heat of formation energy, and IR spectra with increase in dimethyl sulfoxide (DMSO) solvent molecules in the primary solvation shell reveal that lithium trifluoromethanesulfonate (LiCF 3 SO 3 ) is the most stable in dimethyl sulfoxide (DMSO) as compared to lithium hexafluorophosphate (LiPF 6 ) and lithium bis(trifluoromethanesulfonimide (LiN(CF 3 SO 2 ) 2 ). Infrared spectroscopic (IR) data confirm the formation of lithium peroxide (Li 2 O 2 ), lithium oxide (Li 2 O), and lithium carbonate (Li 2 CO 3 ) as discharge products on the micro-electrode surface in non-aqueous electrolyte containing lithium salts. The infrared (IR) analysis reveals that the lithium trifluoromethanesulfonate/dimethyl sulfoxide (LiCF 3 SO 3 /DMSO) electrolyte is primarily assumed to be the most favorable for ORR kinetics. In order to study the kinetics of oxygen reduction reaction at the oxygen cathode of non-aqueous Li-air battery with three Li salts in dimethyl sulfoxide (DMSO), we calculate thermodynamic properties of the reactions held during the formation of lithium peroxide (Li 2 O 2 ) and lithium oxide (Li 2 O). The Gibb's energy and heat of formation of these reactions indicate that lithium trifluoromethanesulfonate/dimethyl sulfoxide (LiCF 3 SO 3 /DMSO) electrolyte plays a key role in oxygen reduction reaction mechanism compared to other two.

Silica based materials are important candidates as anodes for lithium ion batteries due to their high specific capacity, low production and material cost and abundance in the earth crust. Silica lithiation leads to reversible and irreversible reactions to produce silicon, lithium oxide and lithium silicates. The final composition of these products confers a variety of electrochemical performances, particularly concerning their specific capacity and stability/cyclability of the electrodes. Knowledge on the thermochemistry of these reactions is relevant to analyze the thermodynamic stability and potential occurrence of the different phases. In this work, the free energy of reaction for the lithiation of silica is calculated for different products. The present first principles studies indicate that the formation of products is a highly exothermic and endergonic process in all cases. In the case of SiO2 lithiation, the free energy shows that the reaction to form Li2Si2O5 is highly exothermic, having the greatest probability of formation. The lithiation potentials and stability of different products are analyzed in the context of experimental results from the literature. Fil: Lener, German. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina Fil: Otero, Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina Fil: Barraco Diaz, Daniel Eugenio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina Fil: Leiva, Ezequiel Pedro M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina

The graphene/cubic cobaltite oxide nanosheets (rGO/Co 3 O 4 ) with a face centered cubic crystalline structure are synthesized and are exploited as effective cathode catalysts in high performance Lithium-air batteries. The morphological images enunciate that 220 nm average diameter of Co 3 O 4 nanosheets are effectively anchored over the graphene sheets and the diameter of individual nanoparticles that construct the cubic nanosheets is 5 nm. The growth and composite formation mechanisms of prepared nanostructures are identified from Raman and FT-IR spectroscopic techniques. rGO/Co 3 O 4 composite exhibits a lower voltage, high discharge capacity of 4150 mAh g −1 and displays superior cyclability without any capacity losses, signifying the excellent rechargeability of the fabricated electrodes. The post mortem analysis of electrodes specify the existence of lithium peroxide (Li 2 O 2 ), lithium oxide (Li 2 O) and lithium carbonate (Li 2 CO 3 ) discharge products, revealing the involved electrochemical reaction of Lithium-air batteries. The excellent electrochemical properties of rGO/Co 3 O 4 composite is due to the combination of rapid electrokinetics of electron transport and high electrocatalytic activity toward oxygen reduction reaction given via the synergetic effects of rGO and cubic Co 3 O 4 nanosheets. These findings provide fundamental knowledge on understanding the influence of morphological and structural properties of graphene based nanostructures toward Lithium-air battery performances.

Over-lithiated oxides are promising cathode materials for 5V-class high-voltage batteries, however, their widespread adoption has been seriously restricted owing to their complicated chemical and electrochemical limitations. To resolve both of these issues at once, we suggest a multi-functional additive, tris(trimethylsilyl)phosphite (TMSP), with a comprehensive working mechanism that is demonstrated by systematic spectroscopic analyses combined with first-principles calculations. First, TMSP remarkably reduces the internal pressure because trivalent phosphorus effectively scavenges the oxygen gas in the cell. Second, TMSP greatly enhances the overall chemical stability of electrolytes because electrophilic phosphorus and silicon readily remove nucleophilic lithium oxide species by means of a chemical scavenging reaction. Third, TMSP affords a phosphite component in the protection layer on the electrode surface, inhibiting additional electrolyte decomposition under a high working potential. Finally, TMSP provides a silyl ether component in the protection layer, which is responsible for preventing transition metal dissolution through a fluoride scavenging reaction. Based on these verified effects, TMSP-controlled cells offer remarkable cycle performance with 90.2% capacity retention for 100 cycles.

Sulfated zirconia was successfully synthesized and uniformly coated onto a nickel-rich layered lithium oxide (LiNi0.8Co0.1Mn0.1O2), and investigated with a view to its potential use as a cathode material in Li-ion batteries. The uniformity of this sulfated zirconia coating was confirmed through electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. Furthermore, the electrochemical properties of the sulfated-zirconia-coated LiNi0.8Co0.1Mn0.1O2 electrode were found to be greatly improved compared to those of pristine LiNi0.8Co0.1Mn0.1O2 and zirconia-coated LiNi0.8Co0.1Mn0.1O2, especially at elevated temperature (60 °C). These results are directly attributed to the sulfated zirconia coating, which is effective in reducing side reactions by preventing direct contact between the active materials and electrolyte solutions, as well as forming a more stable solid electrolyte interphase (SEI) layer on the active material surface.

Despite their technological challenges, non-aqueous rechargeable lithium–oxygen cells offer extremely high theoretical energy densities and are therefore attracting much attention in a rapidly emerging area of electrochemical research. Early results have suggested that, among the transition metal oxides, alpha manganese dioxide (α-MnO2) appears to offer electrocatalytic properties that can enhance the electrochemical properties of Li–O2 cells, particularly during the early cycles. In this study, we have investigated the hybrid Li-ion/Li–O2 character of α-MnO2 electrodes in Li–O2 coin cells by in situ high-energy synchrotron X-ray diffraction, and compared the results with conventional Li/α-MnO2 coin cells assembled under argon. Complementary first principles density functional theory calculations have been used to shed light on competing lithium insertion and lithium and oxygen insertion reactions within the α-MnO2 tunnel structure during discharge, relative to lithium peroxide or lithium oxide formation.

As a potential solution to concerns on sustainable energy, the wide spread commercialization of fuel cell has long been hindered by limited reserves and relatively high costs of metal catalysts. 3D graphene, a carbon-only catalyst prepared by reduction of carbon monoxide with lithium oxide, is found to electrochemically catalyze carbohydrazide oxidation reaction efficiently. A prototype of a completely metal-catalyst-free anion exchange membrane fuel cell (AEMFC) with a 3D graphene anode catalyst and an N-doped CNT (N-CNT) cathode catalyst generate a peak power density of 24.9 mW cm(-2) . The average number of electrons electrochemically extracted from one carbohydrazide molecule is 4.9, indicating the existence of CN bond activation, which is a key factor contributing to high fuel utilization efficiency.

In order to confirm reasons that deteriorate cathode performances, Ni-rich Li[Ni0.7Mn0.3]O2 is modified by lithium isopropoxide to artificially provide lithium excess environment by forming Li2O on the surface of active materials. X-ray diffraction patterns indicate that the lithium oxide coating does not affect structural change comparing to the bare material. Scanning electron microscopy and transmission electron microscopy data show the presence of coating layers on the surface of Li[Ni0.7Mn0.3]O2. Electrochemical tests demonstrate that the Li2O-coated Li[Ni0.7Mn0.3]O2 exhibits a greater irreversible capacity with a small capacity because of the presence of insulating layers composed of lithium compounds on the active materials since these layers delay facile Li+ diffusion. Also, the Li2O layer forms byproducts such as Li2CO3, LiOH, and LiF, as are proved by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. The presence of residual lithium tends to bond with hydrocarbons induced from decomposition of electrolytic salt during electrochemical reactions. And the reaction, accelerated by the decomposition of electrolytic salt that produces the byproducts, causes the formation of passive layers on the surface of active material. As a result, the new layers consequently impede diffusion of lithium ions that deteriorate electrochemical properties.

Silicon as the negative electrode material of lithium ion batteries has a very large capacity, the exploitation of which is impeded by the volume changes taking place upon electrochemical cycling. A Si electrode displaying a controlled porosity could circumvent the difficulty. In this perspective, we present a preparative method that yields ordered arrays of electrochemically competent silicon nanotubes. The method is based on the atomic layer deposition of silicon dioxide onto the pore walls of an anodic alumina template, followed by a thermal reduction with lithium vapor. This thermal reduction is quantitative, homogeneous over macroscopic samples, and it yields amorphous silicon and lithium oxide, at the exclusion of any lithium silicides. The reaction is characterized by spectroscopic ellipsometry for thin silica films, and by nuclear magnetic resonance and X-ray photoelectron spectroscopy for nanoporous samples. After removal of the lithium oxide byproduct, the silicon nanotubes can be contacted electrically. In a lithium ion electrolyte, they then display the electrochemical waves also observed for other bulk or nanostructured silicon systems. The method established here paves the way for systematic investigations of how the electrochemical properties (capacity, charge/discharge rates, cyclability) of nanoporous silicon negative lithium ion battery electrode materials depend on the geometry.

Results of a study of how the density and electrical conductivity of a Li7La3Zr2O12 ceramic depends on the sintering temperature were used to determine the optimal conditions for formation of the system under study as a solid electrolyte with a conductivity of 3.7 × 10−2 S cm−1 at 185°C for electrochemical devices.

Secondary Lithium/air batteries are of great interest because of their considerably larger theoretical energy densities (~ 11,000 Wh/kg) compared to conventional battery systems like NiCd, Ni metal hydride or Li ion accumulators (~ 300 Wh/kg) in combination with larger power densities. The current main limitation of the aprotic Lithium/air system is given by the stability of the electrolyte, which is generally based on organic media like carbonates and ethers. Recent results by Bruce et al. show the decomposition and irreversible side product formation of these organic solvents in Lithium ion-containing solutions. They suggest that the reversible Lithium oxide formation during discharge is almost completely suppressed by several side reactions, resulting in a blockage of the air cathode pores and a decrease of capacity. Moreover, the performance of the Lithium/air cell is strongly dependent on the structure and composition of the air cathode as well as on the addition of catalysts. Here, the development of bifunctional catalysts, i.e. one catalyst for the discharge (oxygen reduction) as well as for the charge (oxygen evolution) reaction, is of special interest. Therefore the colloidal synthesis of nanometerscale manganese oxide particles and their electrochemical characterization in the Lithium/air system will be discussed. Fig. 1) indicates that the use of noble metals as catalysts results in reduced stability of the electrolyte, as larger currents are measured at the Pt electrode of the RRDE in a LiTFSI/acetonitrile system than at the carbon electrode (representing the air cathode without catalyst). We report on a systematic study on the stability of different aprotic electrolyte systems containing a variety of conducting salts (e.g. LiPF6, LiTFSI), solvents (acetonitrile, DMSO, ionic liquids) and additives via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and rotating ring-disk electrode (RRDE) analysis (see Fig. 1). Furthermore the replacement of noble metal nanoparticles as catalysts for ORR/OER by considerably less expensive side group metal oxide nanoparticles will be discussed. There special attention lies on the different catalytic pathways of metal and metal oxide systems. In particular the mechanisms of side group metal oxide catalysts will be evaluated for their use in future secondary Lithium/air batteries.

Film model electrodes of silicon oxide (SiOx) with various oxygen content (x = 0.4, 0.85, 1.0 and 1.3) have been studied for the effects of oxygen content and interfacial reaction behavior on cycling ability. IR and XPS analyses on the origin of initial charge plateau in 1M LiPF6/EC:DEC indicate that the contribution of electrolyte reduction to the plateau is far larger than the formation of lithium silicates, lithium oxide and silicon. Higher oxygen content of SiOx induces to decrease initial electrolyte reduction, whereas larger fraction of oxides is subjected to dissolution by acid (e.g., HF)-etching. Cycling ability at higher oxygen content however is remarkably improved when constructing a surface protective siloxane network at the electrodes using silane electrolyte additive. The SiO1.0 electrode exhibits superior capacity retention of 84% at the 200th cycle delivering discharge capacity of 1206–1017 mAh/g. The SEI layer formed over surface siloxane network consists of a plenty of organic compounds and lithium carbonate, in contrast to mainly inorganic salts and organic phosphorus fluoride compounds upon cycling without silane adidtive. A better protection and passivation of electrode surface should be of the effects of siloxane network, and in that fashion cycling ability is greatly stabilized.

Well-formed Li 1.131 Mn 0.504 Ni 0.243 Co 0.122 O 2 cathode materials are synthesized via freeze drying followed by a solid state reaction at temperatures of 750–900 °C. Among these oxides, the one synthesized at 800 °C delivers the highest initial discharge capacity of 246.5 mAh g −1 at 0.1 C (1 C = 200 mA g −1 ) between 2.5 V and 4.8 V. Enhancing the discharge rate to 1 C, initial capacity of 197.8 mAh g −1 is obtained, and 78.8% capacity is retained after 50 cycles. Furthermore, the diffusion coefficients of Li + in the lithium-rich layered oxide are about 10 −14 cm 2 s −1 and 10 −15 cm 2 s −1 for the initial charge platform at 3.90 V and 4.55 V, respectively, determined by galvanostatic intermittent titration technique (GITT). The Li 1.131 Mn 0.504 Ni 0.243 Co 0.122 O 2 prepared by freeze drying is a promising cathode material for lithium ion batteries.

Sn-based oxide materials as an anode of lithium ion batteries (LIBs) suffer from the unavoidable mechanical stress originated from huge volume changes during lithiation/delithiation reactions. We synthesized the hierarchical SnO nanobranches (NBs) decorated with Sn nanoparticles on Cu current collector using a vapor transport method. The Sn-decorated SnO NBs as an anode of LIB showed good electrochemical performance with high reversible capacity retention of as high as 502 mAh/g and rate capability of 455 mAh/g at a current density of 2.0 A/g after 50 cycles. Through the morphological and crystal structure analyses after the charge and discharge processes, it was found that the morphology of Sn-decorated SnO NBs was transformed to nanoporous layered-structure, composed of Sn and lithium oxide, during the repeated lithiation/delithiation reactions. The free-volume of Sn-decorated SnO NBs and nanoporous layered-structure effectively accommodate the huge volume changes and enhance the electrochemical cyclability by facilitating the diffusion of Li-ions. Electronic supplementary material The online version of this article (doi:10.1186/s40580-016-0070-1) contains supplementary material, which is available to authorized users.

Loss of lithium in the initial cycles appreciably reduces the energy density of lithium-ion batteries. Anode prelithiation is a common approach to address the problem, although it faces the issues of high chemical reactivity and instability in ambient and battery processing conditions. Here we report a facile cathode prelithiation method that offers high prelithiation efficacy and good compatibility with existing lithium-ion battery technologies. We fabricate cathode additives consisting of nanoscale mixtures of transition metals and lithium oxide that are obtained by conversion reactions of metal oxide and lithium. These nanocomposites afford a high theoretical prelithiation capacity (typically up to 800 mAh g−1, 2,700 mAh cm−3) during charging. We demonstrate that in a full-cell configuration, the LiFePO4 electrode with a 4.8% Co/Li2O additive shows 11% higher overall capacity than that of the pristine LiFePO4 electrode. The use of the cathode additives provides an effective route to compensate the large initial lithium loss of high-capacity anode materials and improves the electrochemical performance of existing lithium-ion batteries. There is an intensive research effort in suppressing the first-cycle lithium loss in lithium-ion batteries. Now, a cathode prelithiation method with nanocomposites of conversion materials is demonstrated to compensate the initial lithium loss and improve the battery performance.

An ether based electrolyte containing TEGDME/LiPF6 was optimized, which possessed low viscosity and high ionic conductivity, under dry argon atmosphere in a glove box. In order to prevent air breathing cathode clogging by lithium oxide and provide stability of Li metal anode, different types in varying quantities of polymeric additives such as PEO and PVDF were added into TEGDME/LiPF6. These additives are thought to promote the dissolution of lithium peroxide precipitates formed in course of discharge process and protect the anode. Graphene/alpha-MnO2 nanocomposite air breathing structure coated on nickel mesh was used as cathode. A lithium disk was used as anode while glass fiber was used as the separator in ECC-Air test cells. The cells were cyclically tested using 0.1 mA/cm(2) current density over a voltage range of 2.15-4.25 V. Electrochemical impedance spectroscopy (EIS) measurements was applied to investigate the effect of the polymeric additives on the resistivity of the electrolyte. Results revealed that polymer contained electrolyte structures with PVDF addition provided not only good discharge capacity but also excellent stability. After the electrochemical cycling test, the morphologies of the cathodes were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and Raman spectroscopy to determine the reaction products. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

{AA2099-T8} aluminium alloy was anodized at a current density of 5 {mA/cm} 2 to selected voltages in 0.1 M ammonium pentaborate electrolyte at 293 K. It was found that the growth of barrier-type anodic film on the alloy was accompanied by oxidation of intermetallics, formation and rupture of oxygen gas-filled voids in the anodic film and healing of the anodic film at the sites of rupture. It was revealed that the formation of oxygen gas-filled voids was related to the oxidation of copper-rich nanoparticles in the copper-enriched layer at the film/alloy interface, and that the oxidation process of copper-rich nanoparticles depended on grain orientation. Further, the significantly reduced Pilling-Bedworth ratio for formation of anodic lithium oxide compared with that for formation of anodic alumina resulted in the formation of fine voids at the alloy/film interface and sequentially, detachment of the anodic film from the alloy surface. ?? 2012 Elsevier Ltd.

This work demonstrates that structural defects in amorphous metal oxide electrodes can serve as a reversible Li+ storage site for lithium secondary batteries. For instance, molybdenum dioxide electrode in amorphous form (a-MoO2) exhibits an unexpectedly high Li+ storage capacity (up to four Li per MoO2 unit), which is larger by a factor of four than that for the crystalline counterpart. The conversion-type lithiation is discarded for this electrode from the absence of Mo metal and lithium oxide (Li2O) in the lithiated a-MoO2 electrode and the retention of local structural framework. The sloping voltage profile in a wide potential range suggests that Li+ ions are inserted into the structural defects that are electrochemically nonequivalent. This electrode also shows an excellent cycle stability and rate capability. The latter feature is seemingly due to a rather opened Li+ diffusion pathway provided by the structural defects. A high Li+ mobility is confirmed from nuclear magnetic resonance study.

LiMn 1.5− x M 2 x Ni 0.5− x O 4 (M = Co or Cr, 0.0 ≤ x ≤ 0.2) compounds were synthesized by the sol–gel method. It is found from X-ray diffraction analysis that single spinel phases are obtained for both Cr 3+ - and Co 3+ -substitution, but a small cation mixing between the 8a and 16d sites is found only in the Co 3+ -substitution case. All of the compounds exhibit M – T curves characteristic of ferromagnetic materials. As the substitution degree is raised, the saturation magnetization at 4.2 K decreases and the Curie temperature shifts lower, irrespective of the kind of the substituent. That is, the cation substitution yields a reduction of the ferromagnetism. Additionally, both Cr 3+ - and Co 3+ -substitution have a large influence on the electrochemical properties. The Cr 3+ -substitution induces a rise in the average operating potential without a loss of redox capacity, while both the average operating potential and the redox capacity decrease with an increase in the Co 3+ -substitution degree.

Nano-sized LiMn 2 O 4 spinel with well crystallized homogeneous particles (60 nm) is synthesized by a resorcinol–formaldehyde route. Micro-sized LiMn 2 O 4 spinel with micrometric particles (1 μm) is prepared by a conventional solid-state reaction. These two samples are characterized by XRD, SEM, TEM, BET, and electrochemical methods. At current rate of 0.2 C (1 C = 148 mA g −1 ), a discharge capacity of 136 mAh g −1 is obtained on the nano-sized LiMn 2 O 4 , which is higher than that of micro-sized one (103 mAh g −1 ). Furthermore, compared to the micro-sized sample, nano-sized LiMn 2 O 4 shows much better rate capability, i.e. a capacity of 85 mAh g −1 , 63% of that at 0.2 C , is realized at 60 C . The excellent high rate performance of nano-sized LiMn 2 O 4 spinel may be attributed to its impurity-free nano-sized particles, higher surface area and well crystalline. The outstanding electrochemical performances demonstrate that the nano-sized LiMn 2 O 4 spinel will be the promising cathode materials for high power lithium-ion batteries used in hybrid and electric vehicles.

We fabricate LiCoO 2 /helical nanocarbon (HCN) composites by forming HCNs on LiCoO 2 on which iron oxides (Fe 2 O 3 or Fe 3 O 4 ) are dispersed (LiCoO 2 (Fe 2 O 3 ) or LiCoO 2 (Fe 3 O 4 )) as catalysts for HCN formation, and estimate their electrochemical properties. Granular nanocarbons form on LiCoO 2 (Fe 2 O 3 ) and LiCoO 2 (Fe 3 O 4 ) at 350 °C although HCNs of about 100 nm in diameter form on LiCoO 2 (Fe 2 O 3 ) at 450 °C. Transmission electron microscopy and energy dispersive X-ray spectroscopy measurements show that HCNs consist of stacked graphene layers for LiCoO 2 (Fe 2 O 3 )/HCN composites fabricated at 450 °C. On the other hand, several-nm-thick tetragonal layer exists on the LiCoO 2 substrate and amorphous nanocarbons form on the tetragonal layer for LiCoO 2 (Fe 2 O 3 )/HCN and LiCoO 2 (Fe 3 O 4 )/HCN composites fabricated at 350 °C. X-ray diffraction measurements suggest that Fe 2 O 3 and Fe 3 O 4 do not completely inhibit LiCoO 2 decomposition. Cathodes containing LiCoO 2 (Fe 2 O 3 )/HCN or LiCoO 2 (Fe 3 O 4 )/HCN fabricated at 350 °C improve rate capability of lithium cells. However, this rate capability is not better than that of cathodes containing a mixture of LiCoO 2 and acetylene black.

A Li-air battery can provide a much higher theoretical energy density than a Li-ion battery. The use of aqueous acidic electrolytes may prevent lithium oxide deposition from aprotic electrolytes and lithium carbonate precipitation from alkaline electrolytes. The present communication reports a study on the effect of Li ions on the oxygen reduction reaction (ORR) in sulfuric acid electrolytes. It was found that the Li ions have negligible interactions with the active surface of Pt catalysts. However, significantly lower ORR activities were found when Li ions are present in the sulfuric acid. The intrinsic kinetic activities were found to decrease with the increase of Li ion concentrations, but level off when the Li ion concentrations are larger than 1.0 M. The low activities of Pt catalysts in Li ion containing electrolytes were attributed to a constraining effect of Li ions on the diffusion of oxygen in the electrolyte solution. Keywords: Li-air battery, Lithium cation, Platinum electrocatalyst, Oxygen reduction reaction

Layered LiNi 1/3 Co 1/3 Mn 1/3 O 2 was synthesized by co-precipitation method, and a series of polypyrrole–LiNi 1/3 Co 1/3 Mn 1/3 O 2 composites were then prepared by polymerizing pyrrole monomers on the surface of LiNi 1/3 Co 1/3 Mn 1/3 O 2 . The bare sample and composites were subjected to analysis and characterization by the techniques of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrochemical properties of the composites were investigated with galvanostatic charge–discharge test and AC impedance measurements, which show that the formed coats of polypyrrole (PPy) significantly decrease the charge-transfer resistance of LiNi 1/3 Co 1/3 Mn 1/3 O 2 . And the composite containing 2.0 wt% PPy exhibits a good electrochemical performance, its specific discharge capacity is 182 mAh g −1 at 0.1 C rate and voltage limits of 2.8–4.6 V, while the capacity of the bare sample is only 134 mAh g −1 .

LiNi0.5Mn1.5O4 spinel samples were synthesized by a two-step solid-state reaction method. Manganese acetate and nickel acetate were mixed together in a molar ratio of 3:1 and reacted at 500 °C to form a mixed Ni-Mn oxide, which reacted subsequently with lithium acetate at 900 °C to form a LiNi0.5Mn1.5O4 powder. For comparison, manganese acetate, nickel acetate and lithium acetate were mixed together in a molar ratio of 3:1:2 and directly reacted in one-step at 900 °C. The LiNi0.5Mn1.5O4 powder synthesized from the two-step process shows enhanced conductivity and improved rate performance. X-ray diffraction and Raman spectroscopy analyses indicate that the two-step sample has a space group of F d 3 ¯ m while the one-step sample has a space group of P4332. The cyclic voltammetry test has confirmed that lithium-ion cells with the two-step sample in the positive electrode exhibit lower impedance than those with the one-step sample.

Sn/Li 2 O composite coatings on stainless steel substrate, as anodes of thin-film lithium battery are carried out in SnCl 2 and LiNO 3 mixed solutions by using cathodic electrochemical synthesis and subsequently annealed at 200 °C. Through cathodic polarization tests, three major regions are verified: (I) O 2 + 4H + + 4e − → 2H 2 O (∼0.25 to −0.5 V), (II) 2H + + 2e − → H 2 , Sn 2+ + 2e − → Sn, and NO 3 − + H 2 O + 2e − → NO 2 − + 2OH − (−0.5 to −1.34 V), and (III) 2H 2 O + 2e − → H 2 + 2OH − (−1.34 to −2 V vs. Ag/AgCl). The coated specimens are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and charge/discharge tests. The nano-sized Sn particles embedded in Li 2 O matrix are obtained at the lower part of region II such as −1.2 V, while the micro-sized Sn with little Li 2 O at the upper part, such as −0.7 V. Charge/discharge cycle tests elucidated that Sn/Li 2 O composite film showed better cycle performance than Sn or SnO 2 film, due to the retarding effects of amorphous Li 2 O on the further aggregation of Sn particles. On the other hand, the one tested for cut-off voltage at 0.9 V (vs. Li/Li + ) is better than those at 1.2 and 1.5 V since the incomplete de-alloy at lower cut-off voltage may inhibit the coarsening of Sn particles, revealing capacity 587 mAh g −1 after 50 cycle, and capacity retention ratio C50/C2 81.6%, higher than 63.5% and 49.1% at 1.2 and 1.5 V (vs. Li/Li + ), respectively.

A 50-μm thick lithium manganese oxide (parent material LiMn2O4) battery electrode (positive electrode; cathode) was charged, slightly discharged and then sliced with a scotch tape test-type method. A selected number of slices was then subject to synchrotron soft X-ray emission spectroscopy near the Mn Lα,β emission lines in order to determine changes in the oxidation state of the manganese as a function of sampling depth. The emission spectra showed a minute yet noticeable and systematic chemical shift of up to 0.25 eV between the layer near the current collector and the layer near the electrolyte separator. The average manganese oxidation state near the separator was smaller than the average oxidation state in the interior of the electrode, or near the current collector. Since the data provide an oxidation state depth profile of the cathode, a Li+ depth profile can be inferred. This method provides information on the spatial chemical inhomogeneity of electrodes prior to and after electrochemical cycling, and thus can aid in degradation studies.

LiMn 1.5 Ni 0.5 O 4 materials coated with AlPO 4 are prepared by a sol–gel method with citric acid to improve their electrochemical performance; the physical and electrochemical properties are characterized by various analytical techniques. The coated AlPO 4 layer completely covers the surfaces of the LiMn 1.5 Ni 0.5 O 4 particles and the thickness of the coated layer is ∼15 nm. 1 wt.% AlPO 4 -coated LiMn 1.5 Ni 0.5 O 4 has much lower surface and charge-transfer resistances and shows a higher lithium diffusion rate in comparison with the pristine sample. The modified material demonstrates dramatically enhanced electrochemical reversibility and stability under elevated temperature conditions. This is because the coated AlPO 4 layer reduces the contact area between the electrode and electrolyte and suppresses the formation of undesirable solid electrolyte interface films.

A new two-step solid-state process was developed for synthesis of a pure phase 4.7 V LiMn 1.5 Ni 0.5 O 4− δ (LMNO) spinel of good electrochemical properties. This process which was based on formation of stable Ni 1− x Mn 2 O 4− δ ( x ≤ 0.33) spinel followed by subsequent lithiation, demonstrated the emerging of LiMn 1.5 Ni 0.5 O 4− δ frame work at temperatures of as low as 350 °C. During this lithiation process, migration of metal ions (Ni/Mn) from partially occupied tetrahedral 8a sites (in Ni 0.67 Mn 2 O 4− δ ) toward octahedral 16d site occurred. The resultant spinel material displayed low irreversible loss, a 97% columbic efficiency and 6% loss in discharge capacity after 100 cycles at 60 °C.

In this study, the mechanism of enhanced performance of ZrO2-coated LiCoO2 especially at high potential range is systematically investigated. Firstly, when overcharging to 4.5 V (higher than 4.2 V, the normal cutoff charging potential), phase transformation from H1 to H2 takes place with less volume expansion for ZrO2-coated LiCoO2 (1.2% and 2.2% for as-received one). EIS analysis indicates the growth of interfacial impedance during charging/discharging can be effectively suppressed with ZrO2 coating on the LiCoO2 surface. It is demonstrated as well that cation mixing of the cycled LiCoO2 caused by re-intercalation of dissolved Co2+ is inhibited with the ZrO2 coating on the LiCoO2. Therefore the ZrO2-coated LiCoO2 shows great enhancement in the electrochemical properties with 85% capacity retention after 30 cycles from 3 to 4.5 V at a rate of 0.5C. Nevertheless, under the same evaluation process, the as-received LiCoO2 possesses only 21% capacity retention, which is resulted from the formation of polymeric layers by the electrolyte decomposition on its surface, the higher volumetric changes during charging/discharging and possible cation mixing by re-intercalation of the dissolved Co2+.

The layered LiNi1/3Mn1/3Co1/3O2 materials with good crystalline are synthesized by a novel method of hydrothermal method followed by a short calcination process. The crystalline structure and morphology of the synthesized materials are characterized by XRD, SEM. Their electrochemical performances are evaluated by CV, EIS and galvonostatic charge/discharge tests. The material synthesized at 850 °C for 6 h shows the highest initial discharge capacity of 187.7 mAh g−1 at 20 mA g−1. And the capacity retention of 97.9% is maintained at the end of 40 cycles at 1.0 C. CV test reveals almost no shift of anodic and cathodic peaks after first cycle, which indicates good reversible deintercalation and intercalation of Li+ ions.