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The structural and electrochemical effects of electrospun V2O5 with selected redox-inactive dopants (namely Na+, Ba2+ and Al3+) have been studied. The electrospun materials have been characterised via a range of analytical methods including X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area measurements and scanning and transmission electron microscopy. The incorporation of dopants in V2O5 was further studied with computational modelling. Structural analysis suggested that the dopants had been incorporated into the V2O5 structure with changes in crystal orientation and particle size, and variations in the V4+ concentration. Electrochemical investigations using potentiodynamic, galvanostatic and impedance spectroscopy analysis showed that electrochemical performance might be dependent on V4+ concentration, which influenced electronic conductivity. Na+- or Ba2+-doped V2O5 offered improved conductivities and lithium ion diffusion properties, whilst Al3+ doping was shown to be detrimental to these properties. The energetics of dopant incorporation, calculated using atomistic simulations, indicated that Na+ and Ba2+ occupy interstitial positions in the interlayer space, whilst Al3+ is incorporated in V sites and replaces a vanadyl-like (VO)3+ group. Overall, the mode of incorporation of the dopants affects the concentration of oxygen vacancies and V4+ ions in the compounds, and in turn their electrochemical performance.ᅟ [ABSTRACT FROM AUTHOR]

A liquid-phase mixing method is adopted to uniformly disperse the graphene nanosheets onto LiNi 1/3 Co 1/3 Mn 1/3 O 2 cathode for high-performance Li-ion batteries (LIBs). The electrochemical performance was characterized using a full pouch cells with state-of-the-art electrode areal loading (compared to half coin cells). The addition of graphene sheets (i.e., only 1 wt%) significantly improves the high rate capability for charging and discharging operation. For example, 6 times improvement in 5  C charging was achieved providing further insights in enabling extreme fast charging for LIBs. Other benefits include longer cycleability, lower internal resistance, and higher lithium ion diffusion coefficient, demonstrated by charge-discharge cycling tests and electrochemical impedance spectroscopy. Higher capacity retention of 88.2% and decreased internal resistance of ∼0.9 Ω are observed after 400 cycles. The diffusion coefficient of Li ions is 6.49 × 10 −8  cm 2  s −1 when charged to 4.2 V, which is approximately 1.37 times higher compared to the configuration with no graphene sheet (4.74 × 10 −8  cm 2  s −1 ). The improved performance is ascribed to a robust network among the active materials formed by graphene sheets, which serves as an extended current conductor and facilitates charge transfer, ionic reversibility, and ionic transportation. [ABSTRACT FROM AUTHOR]

Electrochemical method for recovering cobalt and manganese from electrode materials of spent lithium ion batteries was studied. Electrochemical leaching of cobalt and manganese from electrode material was optimized by varying different process parameters such as time, acid concentration and current density. Both cobalt and manganese could effectively be leached out at a current density of 400 A/m 2 in 3 h using 2 M sulphuric acid. In the subsequent study, the metallic cobalt and electrolytic manganese dioxides was recovered from the leach liquor at 200 A/m 2 , pH 2–2.5 and 90 °C after removing aluminum. The commercial feasibility of the study was tested in pilot scale. Overall recovery of Co, Cu and Mn was above 96%, 97% and 99%, respectively. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide/Mn 3 O 4 (RGO/Mn 3 O 4 ) nanocomposites were synthesized via a cost-effective approach, and their microstructural and morphological features were investigated. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) results revealed that the Mn 3 O 4 nanoparticles were crystallized with particle size 50–100 nm while the size of the Mn 3 O 4 particles in RGO/Mn 3 O 4 composites decreased to 30–50 nm, suggesting that RGO promoted the dispersion of Mn 3 O 4 particles. We tested the electrochemical behavior of the RGO/Mn 3 O 4 composites for supercapacitor and Li-ion battery. And it was found that they exhibited an excellent discharge specific capacitance of about 194.8 F/g at 1.0 A/g with 90% capacity retention even after 1000 cycles in supercapacitor, and an initial discharge capacity of about 1813 mAh/g at 0.1 A/g with outstanding cycling stability in Li-ion battery. [ABSTRACT FROM AUTHOR]

We unravel the role of flake dimensionality on the lithiation/de-lithiation processes and electrochemical performance of anodes based on few-(FLG) and multi-layer graphene (MLG) flakes prepared by liquid phase exfoliation (LPE) of pristine graphite. The flakes are sorted by lateral size (from 380 to 75 nm) and thickness from 20 (MLG) to 2 nm (FLG) exploiting a sedimentation-based separation in centrifugal field and, finally, deposited onto Cu disks for the realization of four binder-free anodes. The electrochemical results show that decreasing lateral size and thickness leads to an increase of the initial specific capacity from ≈590 to ≈1270mAhg −1 . However, an increasing irreversible capacity is also associated to the reduction of flakes’ size. We find, in addition, that the preferential Li ions storage by adsorption rather than intercalation in small lateral size (<100 nm) FLG flakes has a detrimental effect on the average de-lithiation voltage, resulting on low voltage efficiency of these anodes. We believe that the results reported in this work, provide the guidelines for the practical exploitation of graphene-based electrodes. [ABSTRACT FROM AUTHOR]

MoO 2 has gained renewed attention as a safe oxide anode host material for lithium ion insertion because of its high gravimetric/volumetric capacity and highly stable cycling behavior. However, these recent results are completely contrary to previous reports. To confirm that MoO 2 is an appropriate anode material as well as further understand lithium ion reactions when inserted into MoO 2 , we combine electrochemical characterization of MoO 2 electrodes and ex situ X-ray diffraction analysis with first principle calculations. Theoretical capacity of the MoO 2 electrode (∼209 mAh g −1 ) and stable capacity retention up to 100 cycles are simultaneously attained using a proper particle size and type of binder. Ex situ XRD analysis with first principle calculations of the phase transformation of MoO 2 electrodes shows that MoO 2 undergoes reversible structural changes upon lithiation and subsequent delithiation, clearly demonstrating that nanostructured MoO 2 can be used as an anode material for highly reliable lithium ion batteries. [ABSTRACT FROM AUTHOR]

A series of anatase TiO 2 nanowires (TiO 2 -NWs) and Ag-modified TiO 2 nanowires (TiO 2 @Ag-NWs) film electrodes with hierarchical 3D nano-network structure are successfully synthesized via a facile hydrothermal process followed by the traditional silver mirror reaction. Successful modification of silver nanoparticles onto the TiO 2 -NWs surface is confirmed by X-ray diffraction, scanning electron microscope, transmission electron microscopy with energy-dispersive X-ray analysis, and inductively coupled plasma technique. The electrochemical performances of the TiO 2 -NWs and TiO 2 @Ag-NWs film electrodes are also investigated in this work. Compared with the pristine TiO 2 -NWs, the TiO 2 @Ag-NWs nanomaterial exhibits a higher rate capability and better reversibility. At charge/discharge rates of 50, 100, 200, 400, 800, 1600 and 3350 mA/g, the discharge capacities of the TiO 2 @Ag-NWs electrodes are 237, 219, 198, 179, 159, 139 and 120 mAh/g, respectively. After 120 cycles at 200 mA/g, its capacity retention was as high as 99.1% with little capacity fading. [ABSTRACT FROM AUTHOR]

α-MoO nanobelts were synthesized by simple hydrothermal method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Cyclic voltammogram (CV) and galvanostatic charge/discharge testing techniques were employed to evaluate electrochemical behaviors of α-MoO materials. Results showed that α-MoO nanobelts with about 80 nm in diameter and 5-12 μm in length were grown in the orthorhombic system. Electrochemical characterisation confirmed that in lithium ion insertion/extraction process, the first intercalation of lithium ion in α-MoO at about 2.8 V was irreversible, corresponding to LiMoO (0 < x ≤ 0.25) and the parent MoO materials coexisting, the second lithium ion inter-calation was reversible at the potential range of 2.2-2.4 V followed by LiMoO (0.25 < x ≤ 0.5), and below 1.0 V the mechanism of lithium ion storage changed from lithium ion intercalation reaction into lithium alloying reaction. The α-MoO nanobelts showed better electrochemical performance, 319 mA h g initial discharge capacity, around 52% capacity retention after 20 cycles than that of α-MoO bulk. [ABSTRACT FROM AUTHOR]

Spinel LiMnO and multidoped spinel LiMnCoCrNiFeO were synthesized by the glycine-nitrate method and coated with lithium borosilicate (LBS) in order to enhance the electrochemical performance at room temperature. The structure and electrochemical performance of all samples were characterized by inductively coupled plasma-mass spectrometer (ICP-MS), X-ray diffraction (XRD), differential thermal analysis/thermogravimetry (DTA/TG), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and galvanostatic charge-discharge measurements. The XRD analysis shows that the samples exhibit a pure spinel phase. The SEM results indicated that LBS particles had encapsulated the surface of the undoped and multidoped LiMnO without causing any structural change. The charge-discharge tests showed that LiMnCoCrNiFeO displays better cycling performance than the pristine LiMnO at room temperature. However, in the same conditions, LBS-coated LiMnCoCrNiFeO and LiMn O have better cycling performance than uncoated samples. The results suggest that multidoped and LBS-coated LiMnO could develop into a promising cathode material for lithium ion batteries. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive model coupling the effects of hydrostatic stress, surface/interface stress, phase transformation and the structure of electrodes. First, the governing equation of moving phase interface with hydrostatic stress is established. Under the effect of hydrostatic stress, phase transformation process is much faster, which means phase transformation time is overestimated in previous publications. Then, a cross-scale analysis is presented to investigate the size effect owing to hydrostatic stress, surface stress and interface stress separately, which concludes that the effect of hydrostatic stress is significant for the stress field in microelectrode particles, whereas that of surface/interface stress is highlighted in nano-ones. Finally, an electrochemical variable 'efficiency' (ratio of effective capacity over total capacity) is defined. The advantages of hollow structure electrodes on stress and efficiency are analysed. The present model is helpful for the material and structure design of electrodes of lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: The structure and electrochemical properties of epitaxial thin film LiNi0.5Mn1.5O4 electrodes are investigated for lithium ion secondary batteries applications. The orientation and thickness of the LiNi0.5Mn1.5O4 films are controlled by changing the substrate orientation and the pulse laser deposition time, respectively. The lattice parameters of the films increase with film thickness and the manganese valence decreases without any change in the nickel valence. Regardless of their orientation, all the films exhibit reversible capacities of 80–130 mAh g−1. The dependence of the discharge capacity on film thickness indicates a nanosize effect. The electrochemical properties of the high voltage spinel system are significantly dependent on their electronic properties, lattice orientations, and film thicknesses of the electrodes. [Copyright &y& Elsevier]

Highlights: [•] Equilibrium potential curves for lithium intercalation electrode. [•] Activity correction and phase transition treatment for intercalation electrode. [•] Single particle model with effective diffusivity for lithium intercalation process. [•] Accurate simulation of discharge/charge prediction. [Copyright &y& Elsevier]

Abstract: An electrochemical model is developed to investigate capacity recovery methods for cycled lithium ion batteries. Different capacity recovery methods are evaluated and compared. The center recovery method for commercial batteries is found to be impractical because it causes severe solid surface concentration gradients which may harm the batteries. On the contrary, the center recovery method for novel batteries with porous current collector sheets is better than the bottom recovery method because smaller solid surface concentration gradients are detected and less relaxation time is required during capacity recovery. Capacity recovery methods which discharge negative electrodes is superior to those which discharge positive electrodes of cycled batteries as smaller solid surface concentration gradients is generated and less relaxation time is required at the same discharging current. [Copyright &y& Elsevier]

Abstract: Electrochemical impedance spectroscopy for lithium ion batteries has recently gained increasing attention due to its ability of non-invasive evaluation of important electrochemical parameters. Commonly used three-electrode test cells, however, proved unreliable due to asymmetric current line distributions, causing severe distortions of impedance spectra. Finite element method (FEM) simulations can visualize these current lines at different frequencies and simulate impedance spectra at given geometries. By applying FEM simulations to a recently developed coaxial impedance test cell, limiting conditions for reliable impedance measurements could be identified. Using a reference electrode in coaxial position yields sufficiently reliable results as long as the electrode misalignment is small compared to the electrolyte thickness and edge effects are prevented. [Copyright &y& Elsevier]

Abstract: The complex nature of lithium ion batteries makes the tracking of individual physical processes difficult. However, having a good knowledge thereof is indispensable for a continuous improvement of cell performance and lifetime. In this study, the impedance response of a commercial 18650 cell was investigated within a wide frequency range (100 kHz–2 μHz) by combining electrochemical impedance spectroscopy and time domain measurements. In parallel, the original 18650 cell was opened. Thus, the electrode materials could be tested in an experimental test set-up using a reference electrode, which allowed the separation of anode and cathode processes. The different kinds of impedance data sets were de-convoluted in the space of relaxation times, enabling a refined separation of physical processes like charge transfer or solid state diffusion. This multistep approach, which is not tied to a particular electrochemistry, allowed the identification of the dominating physical processes being hidden in the impedance spectrum of the original 18650 cell. [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: 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: 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: 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]

Abstract: It is well-known that some surface modifiers or additives can effectively improve the electrode properties of Li-storage materials. But, some of them may be harmful to the finished battery. The coupling and the interaction between the cathode, separator, electrolyte and anode should be considered when selecting the additives. One example was presented in this work. The electrochemistry of LiFe0.4Mn0.6PO4/C+Ag composite lithium ion battery cathode has been investigated. It was found from the results that the Ag additive can effectively improve the high-rate discharge-ability of LiFe0.4Mn0.6PO4/C composite cathodes and increase the reversibility. But the further intensive investigation has revealed that Ag is not suitable to use as the additive in cathode materials if the operation voltage of cathode electrode is more than 3.7V vs. Li/Li+. [Copyright &y& Elsevier]

Abstract: Micrometric LiMn2O4 particles are mechano-chemically modified by ball-milling to obtain a mixture of nano- and micro-scale particles. This mixture is tested as a potential active cathode material for rapid-charge Li ion batteries, and also as a model system for studying the detailed kinetics of Li intercalation/de-intercalation in such electrodes. Ragone plots recorded using galvanostatic measurements indicate enhanced power delivery characteristics of the ball-milled LiMn2O4 compared to its unprocessed counterpart. The processed material also exhibits improved resistance against electrolyte reactions and surface film formation. Due to these advantageous electrochemical attributes, the ball-milled LiMn2O4 serves as an adequately suited system for exploring certain fundamental aspects of Li intercalation in this material. Scan rate dependent slow scan cyclic voltammetry helps to identify the kinetic and diffusion controlled features of Li transport in mechano-chemically processed LiMn2O4. Electrochemical impedance spectroscopy substantiates these findings further and provides detailed kinetic parameters, including voltage dependent charge transfer resistance and diffusion coefficient of Li transport. [Copyright &y& Elsevier]

Abstract: In the search of high-performance materials for lithium ion batteries, Li2CoPO4F offers many advantages like high theoretical capacity and high operating potential. The synthesis of Li2CoPO4F has been reinvestigated considering a conventional solid state reaction and an unconventional way. Due to the long heat-treatments required by the conventional approach, a beginning of grains coalescence is observed. Limiting particles growth has been allowed by a shorter reaction done by SPS (Spark Plasma Sintering). By this method, the synthesis of Li2CoPO4F was greatly shortened (from 10h to 9min), which favours the getting of submicrometric particles. The comparison of the electrochemical properties of the Li2CoPO4F obtained by the different ways confirms the advantages of SPS synthesis in performance enhancement. [ABSTRACT FROM AUTHOR]

The electronic structure and electrochemical parameters of ternary NiSn0.5Ti0.5 phase are investigated by plane-wave pseudopotential method of the first-principle. The interstitial sites are firstly filled with lithium atoms, and then the substitution for Ni sites occurs. The results show that the Fermi level of lithium-intercalated phase goes up with the increasing lithium concentration. These interactions of M-M covalent bonds (M=Ni, Sn, Ti) become weak, while Li-M bonds are found to increase. NiSn0.5Ti0.5 phase is characterized with high theoretical capacity and low voltage of lithium-intercalation. The obvious volume effect from 77.15% to 189.94% would lead to the failure of the electrode material, and therefore the NiSn0.5Ti0.5 compound should be limited as low as possible in multi-element Sn-based alloy. [ABSTRACT FROM AUTHOR]

Abstract: Some polyanionic compounds, e.g. TiP2O7 and LiTi2(PO4)3 with 3D framework structure were proposed to be used as anodes of lithium ion battery with aqueous electrolyte. The cyclic voltammetry properties TiP2O7 and LiTi2(PO4)3 suggested that Li-ion de/intercalation reaction can occur without serious hydrogen evolution in 5M LiNO3 aqueous solution. The TiP2O7 and LiTi2(PO4)3 give capacities of about 80mAh/g between potentials of −0.50V and 0V (versus SHE) and 90mAh/g between −0.65V and −0.10V (versus SHE), respectively. A test cell consisting of TiP2O7/5M LiNO3/LiMn2O4 delivers approximately 42mAh/g (weight of cathode and anode) at average voltage of 1.40V, and LiTi2(PO4)3/5M LiNO3/LiMn2O4 delivers approximately 45mAh/g at average voltage of 1.50V. Both as-assembled cells suffered from short cycle life. The capacity fading may be related to deterioration of anode material. [Copyright &y& Elsevier]

Abstract: Nanosized silver particles were uniformly distributed on the surface of silicon particles by electroless deposition (ED) and high-energy mechanical milling (HEMM) methods, respectively. The HEMM-prepared Si/Ag composite with 10 wt.% silver exhibited a high first coulombic efficiency of 83.4% and a large capacity of ca. 800 mA h g−1 over 30 cycles as a result of conductivity enhancement. It was suggested that electric contact between silicon particles played a significant role in improving the cyclability of silicon electrode. [Copyright &y& Elsevier]

We report a novel computational simulation study of the performance of Lithium Ion Battery (LIB) NMC electrodes for different compositions. The novelty of this work relies on the explicit consideration with three-dimensional resolution of the Active Material (AM) and the Carbon-Binder Domains (CBD) resulting from simulations of the electrode manufacturing processes and considered as spatially separated phases. A multi-phase volumetric mesh is generated and imported into COMSOL Multiphysics using the INNOV meshing algorithm recently published by us. A 4D-resolved electrochemical model is then applied to simulate the electrochemical behavior of the electrode mesostructure upon LIB cell discharge. Several mesostructural parameters are extracted and the differences in the electrochemical response due to the variations of these parameters are investigated. Furthermore, the 4D-resolved electrochemical model allows assessing the impact of CBD spatial location and its transport properties towards Li+ on the overall electrochemical response, as well as identifying spatial operation heterogeneities inside the electrode. The model assesses then phenomena which are very difficult to investigate based only on experimental approaches, and it aims to become a useful complementary tool of them. • 4D-resolved lithium ion battery cell model with detailed cathode description. • Explicit consideration of active material and carbon/binder spatial location. • Cathode electrode mesostructure calculated by manufacturing process simulation. • Analysis of the impact of carbon/binder location and properties on cell discharge. • Application to NMC electrodes and evaluation of operation spatial heterogeneities. [ABSTRACT FROM AUTHOR]