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Abstract: Rechargeable lithium-ion batteries (LIBs) are currently accepted to be one of the most suitable energy storage resources in portable electronic devices because of their high gravimetric and volumetric energy density. To understand the behavior of Li+ ions on electrochemical lithium extraction/insertion process, we performed in situ 7Li nuclear magnetic resonance (NMR) measurements for LiCoO2 cathode in a plastic cell battery, and the spectral evolutions of the 7Li NMR signal of Li x CoO2 (0≤ x ≤1) were well investigated. Very narrow solid solution region of Li x CoO2 (∼0.99≤ x <1) was explicitly defined from the large intensity reduction of LiCoO2 signal at ∼0ppm, which is related to the localized nature of the electronic spin of paramagnetic Co4+ ion formed at the very early delithiation stage. With further decreasing the signal intensity of LiCoO2, a Knight-shifted signal corresponding to an electrically conductive Li x CoO2 phase emerged at x =0.97, which then monotonously decreased in intensity for x <0.75 in accordance with the electrochemical lithium de-intercalation from Li x CoO2. These observations acquired in situ fully confirm the earlier studies obtained in ex situ measurements, although the present study offers more quantitative information. Moreover, it was shown that the peak position of the NMR shift for Li x CoO2 moved as a function of lithium content, which behavior is analogous to the change in its c lattice parameter. Also, the growth and consumption of dendritic/mossy metallic lithium on the counter electrode was clearly observed during the charge/discharge cycles. [Copyright &y& Elsevier]

Highlights: [•] Cation-incorporated Li3V2(PO4)3/C have been systematically investigated. [•] Cation incorporation in Li3V2(PO4)3 does not change the monoclinic structure but form solid solution. [•] Fe-incorporation shows the best electrochemical performance whereas Ni-incorporation shows the poorest performance. [•] A clear profile of cation incorporation with Fe, Co, Ni, Mn ions in Li3V2(PO4)3/C is obtained. [ABSTRACT FROM AUTHOR]

• Amorphisation and recrystallisation technique was employed for simulated synthesis. • Composite nanosheets (2D) and nanoporous (3D) materials were generated. • XRDs and microstructures showed presence of layered-spinel intergrowths. • Bulk and nanoporous LiMn 2 O 4 can withstand stresses associated with cycling. Mechanical stresses originate from various factors, such as mechanical load, operational vibration, diffusion during cycling, and thermal expansion coefficients. Li-ion intercalation causes lattice expansion that will impart stress on neighbouring regions and ion mechanical degradation within the layers, which leads to weaker battery performance and eventual failure. The current study reports on the advances in the simulated synthesis of nanosheet, nanoporous, and bulk ternary LiMn 2 O 4 spinel from an atomic perspective, during which amorphisation and recrystallisation techniques were employed and the microstructures reflect the spinel and layered heterostructures. Analysis of mechanical and structural properties is carried out via stress-strain, x-ray diffraction (XRD), radial distribution functions (RDF) graphs, and molecular graphics systems before and after subjection to strain. Subsequently, molecular graphics for the nanoporous material indicated a rigid tunnel framework, whilst the bulk framework showed tilting upon compression. These structural deformations within the bulk might prevent efficient Li transport into/out of the electrode materials. [ABSTRACT FROM AUTHOR]

Highlights: [•] Li2+x Mn1−x P x Si1−x O4/C are novel cathode materials for lithium ion batteries. [•] Single phase Li2+x Mn1−x P x Si1−x O4/C is formed when x is not higher than 0.05. [•] Li2.05Mn0.95P0.05Si0.95O4/C (x =0.05) has the best electrochemical properties. [ABSTRACT FROM AUTHOR]

Abstract: Zn2V2O7 nanorods were successfully synthesized by a hydrothermal route for the application in the Lithium ion batteries. The effects of the reacting time on the Zn2V2O7 nanorods as well as the corresponding electrochemical properties were investigated. Results show that the obtained sample under the optimum condition possesses high crystallinity; the width and the thickness are in the range of 40–60nm and 20–40nm, respectively. Based on the observations, a possible growth mechanism of Zn2V2O7 nanorods could be described as a reacting–exfoliating–splitting process. Besides, the Zn2V2O7 nanorods used as anode materials in rechargeable lithium-ion battery can exhibit a highly reversible discharge/charge capacity and excellent rate property at a current density as high as 0.1Ag−1. This might be attributed to the intrinsic characteristics of the layered structure of Zn2V2O7 nanorods. [Copyright &y& Elsevier]

Abstract: LiNi1/3Co1/3Mn1/3O2 (LNCM) with a well-ordered layered structure, confirmed by X-ray diffraction, was synthesized by the chemical-wet synthesis incorporated with (i) a pulse microwave-assisted heating of LNCM precursors and (ii) a carbon coating technique. The microwave irradiation periods (i.e., 5–20min) and amount of carbon additive (i.e., glucose content: 0.1–0.75%) served as key factors in modifying as-prepared LNCM powders. The electrochemical performance of as-prepared LNCM cathodes was well characterized by cyclic voltammetry and charge–discharge cycling at 0.1–5C. Both appropriate microwave heating and carbon coating significantly improve discharge capacity, rate capability, and cycling stability of LNCM cathodes. This improved performance can be attributed to the facts that an appropriate microwave heating of LNCM precursors induces low cation mixing of the layered lattices and the carbon coating enables the creation of outer circuit of charge-transfer pathway, preventing cathode corrosion from direct contact to the electrolyte. The C-coated LNCM cathode shows the increased capacity retention from 70.2 to 93.3% after 50 cycles at 1C. On the basis of the experimental results, both the microwave heating and the carbon coating provide a feasible potential way to improve the electrochemical performance of LNCM cathode, benefiting the development of Li-ion batteries. [Copyright &y& Elsevier]

Highlights: [•] Polymer-derived SiCN and SiOC ceramics are studied as anode for Li-ion batteries. [•] Ceramic precursors are modified in order to increase the carbon content. [•] Ceramic matrix stabilizes free carbon phase. [•] Stabilizing role is lost once the amount of carbon exceeds a threshold value. [Copyright &y& Elsevier]

Abstract: Li2MnSiO4 cathode materials doped with various cationic ions, Ga3+, Al3+, and Mg2+, are synthesized and their microstructure and electrochemical properties are investigated. The samples doped with trivalent ions, especially Ga3+, lead to a higher charge/discharge capacity and initial efficiency with well-dispersed nanoparticle formation. We can realize that the enhanced electrochemical performance of the specific ion doped Li2MnSiO4 cathodes originated from the uniformly distributed nanoparticles rather than the additional lithium insertion/extraction of the given cathode materials induced by the charge compensation. [Copyright &y& Elsevier]

Abstract: Lithium-rich layered cathode Li1.2Mn0.54Ni0.13Co0.13O2 is synthesized by a co-precipitation method followed by high-temperature treatment and surface coated with different amount of amorphous FePO4. The microstructure and electrochemical performance of the as-prepared cathode materials are investigated systematically. It is demonstrated that the Li1.2Mn0.54Ni0.13Co0.13O2 particles are uniformly coated with amorphous FePO4. With proper amount of amorphous FePO4 coating layer, significant improvements in discharge capacity, initial Coulombic efficiency, rate capability, cycle performance, and thermal stability are achieved at room temperature. Specifically, the 3 wt.% FePO4-coated cathode exhibits the highest discharge specific capacities (271.7 mAh g−1 at C/20), improved initial Coulombic efficiency (85.1%), and best cyclability (discharge capacity of 202.6 mAh g−1 at C/2 after 100 cycles), while the 1 wt.% FePO4-coated cathode displays the best rate capability (194.3 mAh g−1 at 1 C rate and 167.9 mAh g−1 at 2 C rate). The charge–discharge curves and electrochemical impedance spectra reveal that the improved electrochemical performances are due to the suppression of both the oxygen vacancy elimination at the end of the first charge and side reactions of the cathode with the electrolyte, as well as the decrease in charge transfer polarization by the FePO4 coating layer. [Copyright &y& Elsevier]

Abstract: The cobalt sulfides/graphene nanosheets (GNS) composite is prepared by a facile one-pot solvothermal route in the presence of graphene oxide sheets (GOS). XRD, SEM and TEM characterizations show that sphere-like cobalt sulfides particles with an average size of about 150 nm, which are complicated phases of CoS2, CoS and Co9S8, are highly dispersed on or wrapped in the creasy graphene. The selective nucleation and growth of cobalt sulfides particles on GOS make the particles more uniform in morphology and size. The as-fabricated cobalt sulfides/GNS composite exhibits very high electrochemical lithium storage reversible capacity of about 1018 mAh g−1. Moreover, the cobalt sulfides/GNS composite still remains reversible capacity of above 950 mAh g−1 after 50 cycles at a current density of 100 mA g−1 as well as at the different current densities from 100 to 1000 mA g−1, proving its excellent cycling durability and high-rate capability. The superior electrochemical performances of the composite may be attributed to the robust composite structure and superior conductivity, high charger mobility, large surface area and good flexibility of graphene. [Copyright &y& Elsevier]

Treading on eggshells: WO3 powders are prepared by using a one‐step spray pyrolysis process. Different spray solutions are used (with or without sucrose), and particles with various morphologies (yolk‐shell, hollow, and dense‐structured) are achieved. The yolk‐shell composite demonstrates electrochemical properties that are superior to the particles with dense and hollow structures at a high current density. [ABSTRACT FROM AUTHOR]

Abstract: Carbon coated LiMn0.5Fe0.5PO4 solid solution materials (LiMn0.5Fe0.5PO4/C) are synthesized by rheological phase reaction with stearic acid as carbon source, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET and TG/DTG. The results show that well-crystallized olivine structure LiMn0.5Fe0.5PO4 nanoplatelets with no obvious impurity phase are obtained. The as-synthesized materials are served as cathode of lithium ion battery and investigated by galvanostatic charge/discharge tests. The results demonstrate that, in comparison with the LMFP materials of different Mn:Fe ratio (LiMn0.2Fe0.8PO4/C and LiMn0.8Fe0.2PO4/C) synthesized by the same route of rheological phase reaction, the LiMn0.5Fe0.5PO4/C exhibit excellent rate specific capability, and can deliver discharge capacity of 138, 99, 80, 72, 67 and 55 mAh g−1 at respectively 0.1, 1, 5, 10, 15 and 20C rates. Moreover, the electrode possesses good cycle stability. A specific capacity of 100 mAh g−1 at 1C after 300 cycles of charge–discharge at room temperature is reached, which represents 95% of capacity retention. The significantly improved electrochemical performances of the LiMn0.5Fe0.5PO4/C cathode are attributed to the uniformly distributed particles and the enhancement of conductivity that is originated from the surface coating of carbon on primary particles. [Copyright &y& Elsevier]

Abstract: This paper deals with the problem of estimating the state of charge (SOC) of lithium-ion batteries. Based on the analysis of the impedance spectra obtained by electrochemical impedance spectroscopy (EIS), a simplified battery impedance model is derived with the constant phase element (CPE). To interpret the impedance model, a fractional order calculus (FOC) method is introduced to model the CPE in the impedance model. A new identification method is proposed to identify the impedance model, considering both accuracy and simplicity. The fractional Kalman filter is introduced to estimate the SOC of the lithium-ion battery based on the impedance model. Finally, a battery test bench is established, and the proposed method is verified by a scaled down system on the urban dynamometer driving schedule (UDDS) drive cycle test. [Copyright &y& Elsevier]

Abstract: Electrochemically formed solid electrolyte interfaces (SEIs) are the crucial link between electrolytes and electrodes because they enable several functions in lithium ion batteries, including ionic diffusion, electric conduction, and the safety provided by thermal stability. However, fabricating the electrochemical formed in SEI entails accuracy regarding its architecture to create the specific electrolyte composition that is mutually compatible with the electrode materials. This process, however, is difficult and hinders the industrial application and development of lithium ion batteries. In this study, the atomic layer deposition (ALD) technique is used in artificial SEI fabrication to deposit a metal oxide on the graphite anode''s surface. In addition, the effects of the artificial SEI-applied Al2O3 and TiO2 on the charge–discharge performance and cycling behavior at 55 °C were investigated. Electrochemical performance was analyzed by an impedance and cyclic voltammogram to show that an ALD coating of TiO2 provides crucial functions for graphite. The results indicated that the TiO2 coating increased the graphite capacity by 5% and limited the formation of electrochemically formed SEIs. In addition, the TiO2-coating graphite with ALD improved thermal stability and greatly enhanced long-term cycle ability at 55 °C. [Copyright &y& Elsevier]

Highlights: [•] Loosely arranged decahedral particles formed larger bulk particles on fluorine substitution. [•] At high potentials, fluorine coating reduces surface damage and improves lithium diffusion and thereby capacity retention. [•] Fluorine substitution triggers the formation of layered–layered–spinel, which stabilized the electrode structures. [•] Formation of layered-layered-spinel counters voltage decay upon subsequent cycling. [Copyright &y& Elsevier]

Abstract: Carbon nanotube (CNT) wired LiCo0.5Mn0.5PO4 nanocomposites were readily prepared using a facile one-pot hydrothermal approach. The prepared LiCo0.5Mn0.5PO4-CNT is composed of uniform nanoparticles of LiCo0.5Mn0.5PO4 intimately interconnected by CNT networks. The electrochemical test results show that the CNT networks play a critical role in maintaining electrical conduction and in ensuring electrode stability of LiCo0.5Mn0.5PO4-CNT upon cycling, thus leading to much enhanced electrochemical properties compared with neat LiCo0.5Mn0.5PO4. It is found that the LiCo0.5Mn0.5PO4-CNT composite exhibits a high capacity up to 151mAhg−1 and an energy density of 620mWhg−1, and maintain 92% of the initial capacity after 30 charge/discharge cycles, thereby indicating its potential for energy storage and conversion application. [Copyright &y& Elsevier]

Abstract: This study, by using the ortho, meta, and para forms of phenylenedimaleimide (o-, m-, and p-phenylenedimaleimide), presents an analysis of electrolyte-additive positional isomer effects that are significant to the formation of the solid electrolyte interface (SEI), and thus the resulting battery''s performance. The analysis is presented in terms of the SEI''s electrochemical properties, growth mechanism, free volume, ionic transfer properties, and its charge–discharge performance. This study shows that the reduction reaction mechanism for each of the positional isomers is the same; however, the isomers when used individually provide different degrees of reduction reaction and varying SEI physical infrastructures. O-phenylenedimaleimide can inhibit SEI formation because its three-dimensional barrier is greater than that of either m- or p-phenylenedimaleimide. This three-dimensional barrier gives rise to a loose SEI structure that reduces ionic motion resulting in discontinuous SEI formation and a decrease in ionic diffusion velocity. Battery performance testing showed that p-phenylenedimaleimide has the greatest discharge capacity, together with significant reversibility, because of dense and uniform structure of its SEI. Our results indicate that by selecting an appropriately functionalized isomer functional groups on SEI formation and thus improve battery performance. The maleimide-based additives provide valuable information on SEI formation mechanisms for future electrolytes. [Copyright &y& Elsevier]

In the present work, the electrochemical behaviour of LiFePO4/C electrode has been reported. Specially, the electrochemical impedance spectroscopies (EIS) have been studied in detail. The discharge capacity is more than 120 mAh/g. There are two semicircles being found in the Nyquist plot for the cycled electrode and one semicircle for the as-prepared electrode. It is found that the interface capacitance is in an order of magnitude of 10 μF/cm for the high-frequency semicircle, while for the second semicircle the interface capacitance is 5.3~45.4 × 10 μF/cm. It could be concluded that the high-frequency semicircle is to correspond to the charge transfer process. The function of the carbon layer is also briefly discussed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: A brand new method for synthesizing Mn(PO3(OH))·3H2O is attained in this paper. During this process, pure flake-like Mn(PO3(OH))·3H2O precipitate is prepared using C2H5OH as initiator. Besides that, LiMn0.5Fe0.5PO4/C is successfully synthesized from the Mn(PO3(OH))·3H2O precursor at 650 °C for the first time. Thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) are applied in the characterization of the Mn(PO3(OH))·3H2O precursor and LiMn0.5Fe0.5PO4/C. High-resolution transmission electron microscopy (HRTEM) is also used to investigate the morphology of LiMn0.5Fe0.5PO4/C. X-ray photoelectron spectroscopy (XPS) and galvanostatic charge and discharge test are employed to characterize the Mn(PO3(OH))·3H2O precursor and LiMn0.5Fe0.5PO4 material, respectively. The as-prepared LiMn0.5Fe0.5PO4/C material exhibited a reversible capacity of 131 mAh g−1 at 0.05 C. It can be confirmed that the incorporation of Fe into LiMnPO4 can significantly improve the electrochemical properties for improving the conductivity of the material and facilitating the Li+ diffusion. In addition, a capacity of 120 mAh g−1 is still delivered at 0.05 C rate with a capacity retention of about 91% after 25 cycles, and reversible capacity can reach 105 mAh g−1 at 1 C. [Copyright &y& Elsevier]

Abstract: Li-rich layered oxide Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is synthesized by combustion reaction using alcohol as both solvent and fuel. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the oxide synthesized at 800 °C exhibits perfect crystallinity and lattice ordering, and has particle sizes of 50–150 nm. The layered oxide delivers an initial discharge capacity of 290.1 mAh g−1 at a current density of 20 mA g−1 after activation, and exhibits improved rate capability with high discharge capacities of 238.6 and 165.0 mAh g−1 at current densities of 200 and 2000 mA g−1 in the voltage range of 2.0–4.8 V, respectively. Low Li-ion diffusion coefficient of 1.07 × 10−14−1.01 × 10−16 cm2 s−1 is calculated by galvanostatic intermittent titration technique (GITT) during the initial discharge process, indicating that the improved rate capability is mainly attributed to the small particle sizes of the Li-rich oxide. [Copyright &y& Elsevier]

Abstract: Polyindole nanofiber is prepared using electrospinning technique for the first time and evaluated as cathode active material for application in lithium ion battery. Surface morphology of the cathode is studied using scanning electron microscope. It shows porous structure constructed by nanofibers with diameter ranged from 347 nm to 180 nm. Electrochemical evaluation of the Li/polyindole nanofiber battery shows good cycling properties as well as fast charge and discharge properties. The battery achieves about 3.0 V electromotive force with discharge capacity of 83 mAh g−1 which is about 99% of theoretical value. There is slow capacity fading during cycling and the discharge capacity drops to 72% of theoretical capacity after 500 cycles at discharge current density of 40 mA g−1. At higher discharge current density like 200 mA g−1 and 400 mA g−1, the cell still can deliver stable discharge capacity of 79 mAh g−1 and 70 mAh g−1. Temperature performances test of the Li/polyindole nanofiber battery shows that the discharge capacity of the Li/polyindole nanofiber battery increases with temperature increasing. In summary, the test results have proved that polyindole nanofiber is a good candidate as cathode material for lithium ion battery. [Copyright &y& Elsevier]

Abstract: Enhancing the performance of TiO2 material in lithium-ion battery application is a promising objective. According to the photo-electrochemical activity of TiO2, herein we develop a novel and facile photo-deposition strategy to synthesize Co3O4/TiO2 composites by using TiO2 nanotubes as substrate material and ultraviolet light as energy source. The physical characterizations indicate that after the proposed procedures small-sized Co3O4 nanoparticles are well deposited on the surface of TiO2 nanotubes to form a Co3O4 layer that distributed all through the tubes. As anode materials for lithium storage, the as-synthesized Co3O4/TiO2 nanotube composites exhibit enhanced performance with higher capacity and rate capability at various test current densities than bare TiO2 nanotubes. The improved performance of composite products is mainly attributed to the coating of Co3O4 layer which can not only increase the conductivity of TiO2, but also could contribute to the overall reversible capacity during charge/discharge. [Copyright &y& Elsevier]

Abstract: As an anode material for lithium-ion batteries (LIBs), silicon offers among the highest theoretical storage capacity, but is known to suffer from large structural changes and capacity fading during electrochemical cycling. Nanocomposites of silicon with carbon provide a potential material platform for resolving this problem. We report a spray-pyrolysis approach for synthesizing amorphous silicon–carbon nanocomposites from organic silane precursors. Elemental mapping shows that the amorphous silicon is uniformly dispersed in the carbon matrix. When evaluated as anode materials in LIBs, the materials exhibit highly, stable performance and excellent Coulombic efficiency for more than 150 charge discharge cycles at a charging rate of 1A/g. Post-mortem analysis indicates that the structure of the Si–C composite is retained after extended electrochemical cycling, confirming the hypothesis that better mechanical buffering is obtained when amorphous Si is embedded in a carbon matrix. [Copyright &y& Elsevier]

Abstract: LiNi1/3Mn1/3Co1/3O2 (NMC) as a cathode material for lithium ion batteries has been synthesized by the sol–gel method. The X-ray diffraction Rietveld refinement results indicated that single-phase NMC with hexagonal layered structure was obtained. Scanning electron microscope images revealed well crystallized NMC with uniform particle size in the range of 100–200 nm. The performance of the NMC electrodes with sodium carboxylmethyl cellulose (CMC), poly(vinylidene fluoride) (PVDF), and alginate from brown algae as binders was compared. Constant current charge–discharge test results demonstrated that the NMC electrode using CMC as binder had the highest rate capability, followed by those using alginate and PVDF binders, respectively. Electrochemical impedance spectroscopy test results showed that the electrode using CMC as the binder had lower charge transfer resistance and lower apparent activation energy than the electrodes using alginate and PVDF as the binders. The apparent activation energies of NMC electrodes using CMC, alginate, and PVDF as binders were calculated to be 27.4 kJ mol−1, 33.7 kJ mol−1, and 36 kJ mol−1, respectively. [Copyright &y& Elsevier]

Abstract: Sulfone-functionalized imidazolium ionic liquids were synthesized from direct nucleophilic substitution for the first time. Detailed NMR analysis of the products revealed the competition pathways of classic SN2 substitution and E2 elimination in the synthesis reaction. Impurities from E2 elimination can easily be overlooked during the conventional method of ionic liquid preparation via SN2 substitution. Initial electrochemical examination of the synthesized ionic liquids shows good compatibility with Li1.1(Ni1/3Co1/3Mn1/3)0.9O2 cathode material. [Copyright &y& Elsevier]

Abstract: The dynamic structural change of graphite during the electrochemical lithium intercalation at 1/3C was identified by an in situ high energy synchrotron XRD. Thanks to the fast data collecting detector and high energy X-ray beam of this characterization technique, the detailed structure change of graphite was monitored. Under a high current density, the voltage plateaus in discharge curve and superlattice peaks in XRD patterns were not observed. These results indicated that the dynamic lithium intercalation behavior was remarkably different from that described by the classical staging mechanism. Instead, a Li-riched phase as well as a series of intermediate phases for the x value in Li x C6 being larger than 0.5 were identified. This dynamic phenomenon was considered to be synergistically affected by the driving force of the intercalation reaction, van der Waals force between graphene layers and repulsive interaction between the intercalated Li specie. Basing on the experimental results, a dynamic mechanism was proposed. [Copyright &y& Elsevier]

Abstract: A new alkoxide-based sol containing lithium isopropoxide, vanadylisopropoxide, di-n-butyl-phosphate, acetic-acid and polyvinylpyrrolidone, was used for the synthesis of monoclinic α-Li3V2(PO4)3/C composites by sol-gel and electrospinning techniques. The precursor mixture was highly soluble in organic solvents and thereby suitable for different synthesis techniques like sol-gel electrospinning or conventional sol-gel synthesis, to generate α-Li3V2(PO4)3/C nanocomposites with zero- and one-dimensionality. Electrospinning resulted in well-defined nanofibers and conventional sol-gel synthesis in polydisperse, isotropic nanoparticles. Phase composition and morphology in the composite nanostructures was examined by XRD, TGA, FT-IR, Raman, SEM and HR-TEM analysis. Comparative constant-current and cyclovoltammetric measurements of α-Li3V2(PO4)3/C composite applied as conventional film electrodes (nanoparticles and nanofibers) and self-supporting nanofiber electrodes revealed the influence of electrode texturing on the electrochemical performances. The nanofibrous self-supported electrodes showed superior cycling stability giving an initial discharge capacity of 124mAhg−1 at 0.2°C with retention of 95% after 50 cycles with rate variation in a voltage range of 3–4.3V. [Copyright &y& Elsevier]

Abstract: An electro-active LiCoO2 layer is coated onto the surface of LiNi0.8Co0.15Al0.05O2 powders via a molten salt method. The effect of calcination temperature, calcination time, flux content and coating amount on the electrochemical properties of the sample is investigated. The X-ray diffraction (XRD) analyses show that the LiCoO2 coating does not change the structure of LiNi0.8Co0.15Al0.05O2. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) measurements indicate that a uniform layer LiCoO2 particulate is coated on the surface of the LiNi0.8Co0.15Al0.05O2 particles. The electrochemical performance studies demonstrate that the 3.0wt.% LiCoO2-coated LiNi0.8Co0.15Al0.05O2 powders sintered at 800°C for 4h at weight ratio of KCl/LiNi0.8Co0.15Al0.05O2 =2 exhibit the best electrochemical properties, with an initial discharge capacity of 196.2mAhg−1 and capacity retention of 98.7% after 50cycles when cycled at a current density of 0.2C between 2.8 and 4.3V. Besides, these powders also show better rate capability and high-temperature performance than LiNi0.8Co0.15Al0.05O2. [Copyright &y& Elsevier]

Abstract: Spherical Li3V2(PO4)3/C (LVP/C) composites are successfully synthesized via two different spray-drying processes. XRD results reveal that some impurities, such as Na3V2(PO4)3, Li2NaV2(PO4)3 and Li4(P2O7), appear when sodium salt of carboxy methyl cellulose (CMC) acts as carbon source. SEM images show two different morphologies: solid spherical particles for LVP/C(A) prepared by adding CMC after pre-sintering, and hollow for LVP/C(B) prepared by adding CMC before pre-sintering. Compared to LVP/C(B), LVP(A) presents higher tap density and better electrochemical performance at any C-rate. Remarkably, another charge/discharge plateaus or anodic/cathodic peaks around 3.85V are detected for both LVP/C(A) and LVP/C(B) electrodes, which is attributed to the formation of Li3−x Na x V2(PO4)3 or some other electrochemically active composites containing Na+. CMC addition sequence has a significant influence on morphology of Li3V2(PO4)3. Furthermore, acting as carbon source and Na dopant, CMC shows a notable effect on electrochemical behavior of Li3V2(PO4)3 cathode material. [Copyright &y& Elsevier]

Abstract: A life model is developed for a lithium ion cell with a spinel-based cathode. It is assumed in the proposed model that the Mn(III) disproportionation reaction causes the degradation of the spinel cathode. The Mn(III) disproportionation reaction leads to the Mn(II) dissolving into the electrolyte and the formation of an inactive material layer which causes a resistance increase in the cathode. The proposed model is used to investigate the effects of ambient temperature and voltage range of cycling on the loss of the cell capacity and the changes in the volume fraction of the cathode active material, the radius of the cathode particle and the resistance of the cathode. [Copyright &y& Elsevier]

Abstract: Well-formed Li1.131Mn0.504Ni0.243Co0.122O2 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 cm2 s−1 and 10−15 cm2 s−1 for the initial charge platform at 3.90 V and 4.55 V, respectively, determined by galvanostatic intermittent titration technique (GITT). The Li1.131Mn0.504Ni0.243Co0.122O2 prepared by freeze drying is a promising cathode material for lithium ion batteries. [Copyright &y& Elsevier]

Abstract: Three techniques, i.e., pyrolysis of sucrose, spray of acetylene black, and propane vapor deposition, are adopted to coat carbon onto the surface of LiCoPO4 particles, and their effects are compared. The LiCoPO4/C composites are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS). The results show that the coating techniques determine the property of carbon films formed on the surface of LiCoPO4 particles, which further affect the performance of LiCoPO4. A complete and homogeneous carbon layer is the key to a high electrochemical activity and stable cycle performance. Among these LiCoPO4/C composites, the material processed via the deposition technique shows a more uniform carbon layer than that of the others, thus it exhibits a large reversible capacity of 130 mA h g−1 with favorable cyclability and rate capability in the voltage range of 3.0–5.0 V. [Copyright &y& Elsevier]

Abstract: The Li x Ni0.23Co0.12Mn0.65O2 electrode system with various compositions (x =1.19, 1.33, 1.46, 1.58) was synthesized from a metal oxide precursor synthesized by co-precipitation method. The XRD patterns of the prepared powders revealed a hexagonal α-NaFeO2 structure (space group: R-3m, 166) and the existence of a Li2MnO3 phase in the composite structure. In particular, the low Li content sample shows a three integrated structure (spinel, Li2MnO3, LiMO2) for a Li/Metal(Ni/Co/Mn) mol ratio of 1.2. Scanning electron microscopy showed that all the synthesized samples contained spherical agglomerates with a size of 8–10μm. Among the samples tested, Li1.46Ni0.23Co0.12Mn0.65O2 shows relatively high charge and discharge capacity for the first cycle is 287, 192.9mAhg−1, respectively. Also, charge transfer resistance was also significantly improved compare with other samples. [Copyright &y& Elsevier]

Abstract: Oxides and phosphates of transition metals are now predominant cathode materials of lithium-ion batteries. Organic redox active materials, conducting polymers in particular, could be a more environmentally friendly alternative. But their electrochemical characteristics were of insufficient level as to the charge capacity, rate capability and cyclability. Here, electrochemical performance of lithium salt doped polyaniline samples prepared by mechanochemical and chemical methods is comparatively analyzed as an active component of cathode masses of lithium batteries. It is shown that mechanochemically prepared polyaniline possesses specific capacity close to the theoretical limit as well as high rate capability and cyclability during prolonged charge–discharge. [Copyright &y& Elsevier]

Abstract: There is increasing interest in flexible, safe, high-power thin-film lithium-ion batteries which can be applied to various modern devices. Although TiO2 in rutile phase is highly attractive as an anode material of lithium-ion batteries for its high thermal stability and theoretical capacity of 336mAhg−1 and low price, its inflexibility and sluggish lithium intercalation kinetics of bulk phase strongly limit its practical application for particular in thin-film electrode. Here we show a simple way to prepare highly flexible self-standing thin-film electrodes composed of mesoporous rutile TiO2/C nanofibers with low carbon content (<15wt.%) by electrospinning technique with outstanding electrochemical performance, which can be applied directly as electrodes of lithium-ion batteries without the further use of any additive and binder. The atmosphere during calcination plays a critical role in determining the flexible nature of thin film and particle size of TiO2 in as-fabricated nanofibers. Big size (10cm×4cm), flexible thin film is obtained after heat treatment under 10%H2–Ar at 900°C for 3h. After optimization, the diameter of fibers can reach as small as ∼110nm, and the as-prepared rutile TiO2 films show high initial electrochemical activity with the first discharge capacity as high as 388mAhg−1. What is more, very stable reversible capacities of ∼122, 92, and 70mAhg−1 are achieved respectively at 1, 5 and 10C rates with negligible decay rate within 100 cycling times. [Copyright &y& Elsevier]

Abstract: The carbon-coated monoclinic Li3V2(PO4)3/C composite was prepared via rheological phase method with EDTA (ethylene diamine tetraacetic acid), a new type of carbon source. XRD patterns demonstrate the pure monoclinic structure of the sample. The images of SEM show the uniform and optimized particles size, which greatly improves the electrochemical performance. The TEM test shows the amorphous carbon around the surface of the particles. In the potential range of 3.0–4.3V, the initial discharge capacity is 129.1mAh/g at 0.1C which is almost near the theoretical capacity, and it keeps so fairly stable that a discharge capacity of more than 125mAh/g can still be held after 50 galvanostatical cycles. It also exhibits an excellent rate capability with high discharge capacities of more than 108mAh/g at 2C after 100cycles. [Copyright &y& Elsevier]

Abstract: SnO2 nanoparticles uniformly decorated polypyrrole (PPy) nanowires are synthesized by a facile two-step electrochemical reaction method: electropolymerization and electrodeposition. The nanostructured SnO2–PPy hybrids show porous reticular morphology and homogenous distributions. The reticular SnO2–PPy nanowires can increase the electrode/electrolyte interface and accommodate the volume variation of SnO2. When applied as anode materials for lithium ion batteries, the unique nanostructured hybrids deliver meaningfully improved Li+ storage performance with the first reversible capacity of 690 mAh g−1. This facile synthesis procedure can also be simply grafted to other inorganic–organic hybrid composites. [Copyright &y& Elsevier]

Abstract: CaF2-coated LiMn1/3Ni1/3Co1/3O2 cathode material is prepared via a wet chemical process followed by a solid state reaction. High-resolution transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) show that the well coated CaF2 layer has a thickness of 4–8nm, and no interaction of chemical bonding is observed. The CaF2-coated LiMn1/3Ni1/3Co1/3O2 exhibits discharge capacity retention of 98.1% at 0.1C after 50 cycles and high initial discharge capacity of 146.3mAhg−1 at 5C. Furthermore, even at an elevated charge–discharge rate of 5C, capacity retention maintains above 85%. Electrochemical impedance spectroscopy (EIS) shows that the CaF2 coating can stabilize the surface structure and reduce the charge transfer resistance. The CaF2 modification has a promising application in improving the performance of layered oxide cathode materials for Li-ion batteries. [Copyright &y& Elsevier]

Abstract: The cycle performance of spinel LiMn2O4 at 25 and 55°C is improved by LaF3 modification via a chemical deposition method. The physical and electrochemical performances of pristine and LaF3-coated LiMn2O4 cathode materials are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical measurements. The coated LiMn2O4 with 2.92wt% LaF3 (LaF3-3-LMO) displays capacity retentions of 90.1% and 84.2% at 25 and 55°C, respectively, after 100 cycles, much higher than those of pristine LiMn2O4, 72.7% and 54.8%. The concentration of manganese dissolved from LaF3-3-LMO in electrolyte is much lower than that from pristine LiMn2O4. The analysis of AC impedance indicates that the charge transfer resistance (R ct) and the increase of R ct for LaF3-3-LMO during cycling are much lower than those for pristine LiMn2O4. The significantly improved electrochemical performance of the LaF3-coated LiMn2O4 can be attributed to the reduction of manganese dissolution in electrolyte and charge transfer resistance with the help of LaF3 coating. [Copyright &y& Elsevier]

LiFePO (LFP) nanobars, microplates and nanorods have been selectively synthesized via a solvothermal method in a water-ethylene glycol (EG) binary solvent with HPO, LiOH·HO, and FeSO·7HO as starting materials. The morphology and size of the as-obtained LFP products can be deliberately controlled by varying the volume ratio of EG to water. The formation mechanism and electrochemical properties of different LFP morphologies have been investigated. With carbon coating, the Li-ion diffusion coefficients of LFP nanorods, nanobars and micro-plates are 2.58×10, 2.91×10, and 7.22×10 cm s, respectively. For the carbon-coated nanorods, excellent rate capability and cyclability were attained. At 5 C, the capacity was 141 mAh g for the first cycle and maintained 120 mAh g after 100 cycles; at 10 C, the capacity was still as high as 132 mAh g. [ABSTRACT FROM AUTHOR]

Abstract: Ac impedance spectra of electrochemical systems are analyzed by considering adequate equivalent circuits, while the differentiation of responses for each elemental step is sometimes difficult. In this study, enlarged impedances were measured by lowering the temperature of a lithium ion battery (LIB) to make the separation of confusing responses easier. The impedance spectra obtained at the temperatures between −20 °C and 20 °C showed drastic change in sizes with shifting of the characteristic frequency. The analysis of impedance spectra using an equivalent circuit revealed changes in resistance of each component and shifting of the time constant for each elemental step. The frequency domain of impedance response of solid electrolyte interphase (SEI) was found to overlap with that of the inductive component of the outer electric lead at 20 °C in our study. The impedance measurement at the low temperatures is considered to be useful for the detection of the SEI and the accurate evaluation of LIB. [Copyright &y& Elsevier]

Abstract: Promising capacity retention (more than 92% of initial capacity after 100cycles), was exhibited in cells (graphite/xLi2MnO3·yLiMO2) with 2wt.% LiDFOB as additive. The outstanding cell performance was associated with the formation of stable solid electrolyte interface (SEI) film on the surface of electrodes derived from LiDFOB. Compared to the effect of the LiBOB additive, the main reason responsible for the greatly improved durability in LiDFOB added cells might be attributed to the more stable SEI film with lower interfacial resistance on the surface of anode. [Copyright &y& Elsevier]

The high capacity cathode materials with charge voltage above 4.5 V are widely being developed. To reduce surface reactivity at high voltage, Al2O3 and pullulan are used for coating on the Li(Li0.08Ni0.34Co0.08Mn0.5)O2 surface and are characterized by electrochemical analysis. Charge/discharge and electrochemical results reveal that the organic coating sustains in high voltage cycles. Ionic conductivity of surface coating plays a key role in the battery performance. [ABSTRACT FROM AUTHOR]

In this study, Li3V2(1-x)Fe3x(PO4)3 (0 ≤ x ≤ 0.09) powders are prepared via a solution method and heattreated at 700 °C for 8 hours. The chemical composition, morphology, crystalline structure, and valence of iron in the prepared samples were investigated with ICP, SEM, XRD, and EXAFS. The effects of Fe-substitution for vanadium sites on the electrochemical properties as cathode materials for lithium ion batteries are studied with capacity retention study and incremental capacity analysis. In addition to the monoclinic Li3V2(PO4)3 phase, olivine LiFePO4 is also observed when x ≥ 0.03. The valence of iron in the prepared powders is predominately 3+ at low substitution level (x ≤ 0.05), while the ratio of the Fe2+ to Fe3+ increases abruptly when the substitution level is higher than x = 0.07. Among the prepared samples, Li3V1.86Fe0.21(PO4)3 shows the best cycling performance at rates higher than 1C. It demonstrates discharge capacities of 141.2 mAh/g for second cycle and 126 mAh/g after 30 cycles at 5C rate. [ABSTRACT FROM AUTHOR]

Summary: High energy lithium ion batteries are in demand for consumer electronics, electric-drive vehicles and grid-scale stationary energy storage. Si is of great interest since it has 10 times higher specific capacity than traditional carbon anodes. However, the poor cyclability due to the large volume change of Si upon insertion and extraction of lithium has been an impediment to its deployment. This review outlines three fundamental materials challenges associated with large volume change, and then shows how nanostructured materials design can successfully address these challenges. There have been three generations of nanostructure design, encompassing solid nanostructures such as nanowires, hollow nanostructures, and clamped hollow structures. The nanoscale design principles developed for Si can also be extended to other battery materials that undergo large volume changes. [ABSTRACT FROM AUTHOR]

Abstract: Li3V2(PO4)3/C cathode material was synthesized by using a freeze-drying method followed by carbon-thermal reduction. This as-prepared material has a uniform particle size distribution and a well carbon coating on the surface of Li3V2(PO4)3 particles. The Li3V2(PO4)3/C exhibits good electrochemical performance and cycling stability. Between 3.0 and 4.3V, the composite delivered a reversible capacity of 125.2mAhg−1 at a charge–discharge rate of 1.48C (1C=133mAg−1) and without obviously capacity fading after 100 cycles. Even at 14.8C and 29.6C rates, it can still deliver discharge capacities of 105.6mAhg−1 and 93.3mAhg−1, and the discharge capacities of 84.5 and 60.5mAhg−1 are sustained after 500 cycles, respectively. [Copyright &y& Elsevier]