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Li4Ti5O12 nanosheets (LTONS) embedded in three-dimensional amorphous carbon (3DAC) are fabricated by a facile hydrothermal method. Structure and morphology analyses confirm that the Li2TiO3 impurity phase is effectively suppressed in LTONS@3DAC and that the stacking of LTONS is also significantly inhibited in the porous matrix of the 3DAC, helpfully increasing the lithium ion diffusion coefficient. Compared to LTONS, LTONS@3DAC has a greatly enhanced electrochemical performance, including superior rate capabilities of 146, 142, and 140 mAh g−1 at the current rates of 32, 48, and 64 C, respectively, and an excellent cycling stability of 140 mAh g−1 after 700 cycles at 8 C. Therefore, the LTONS@3DAC composite is promising for applications in superior-rate lithium-ion batteries.

MoO2 nanoparticle-modified Li4Ti5O12 materials were prepared via a facile solution-based method. X-ray diffraction patterns (XRD) and high resolution transmission electron microscopy (HRTEM) analyses revealed that the MoO2 nanoparticles were anchored on the surface of spinel Li4Ti5O12, and energy dispersive X-ray spectroscopy (EDX) mapping indicated the MoO2 nanoparticles distributed uniformly. Compared with the pristine Li4Ti5O12, the appropriate amount of MoO2 on the surface of the Li4Ti5O12 could not only effectively reduce the electrochemical polarization of Li4Ti5O12, but also contribute to specific capacity for lithium storage. The 3% MoO2 modified Li4Ti5O12 exhibited excellent rate capability of 116 mA h g−1 at 10 C, and superior cycling performance of 124 mA h g−1 after 450 cycles at 5 C. Since the MoO2 modification process was easy to handle and the source of Mo has affordable costs, MoO2-modified Li4Ti5O12 would be promising for industrial application.

Mechanical properties of tungsten (W) multilayer composites can be modified by the toughening layers and interfacial microstructure between W layer and toughening layer. The W/Ta multilayer composite usually shows low tensile strength and toughness because of the low strength of Ta layers and large bonding strength between W layer and Ta layer. In order to improve the strength and toughness of the W/Ta multilayer composite, Ti intermediate layers with different thickness ranging from 30 µm to 100 µm have been added between W layer and Ta layer to get a kind of W/Ti/Ta/Ti multilayer composites. It can be found that the thickness of the Ti layer has a large effect on the microstructure and mechanical properties of the W/Ta multilayer composites. The solid solution with pure β-Ti and β-Ta are formed in the Ti layer when the thickness of Ti layer is lower than 50 µm. Ti layer composed of β-Ti, β-Ta and α precipitates is developed when the thickness of Ti layer is larger than 80 µm. The comprehensive mechanical properties of the W/Ta multilayer composites increase as the thickness of Ti intermediate layer increases. The tensile strength of the W/Ti/Ta/Ti multilayer composites is up to 642 MPa, which is much higher than that of the W/Ta multilayer composites (274 MPa). The tensile strength of these multilayer composites can be evaluated by a modified mix model considering the interfacial stress concentration factor. As the fracture mechanism of the W/Ta multilayer composites is also modified by addition of the Ti layer, the toughness of the W/Ti/Ta/Ti multilayer composites is improved because of the delamination along with the W/Ti interface and plastic deformation of the Ti/Ta/Ti layer in plane stress condition.

The effect of propylene carbonate (PC)-Li + solvation structures on graphite exfoliation was investigated over a range of concentrations of PC-based electrolytes. At low concentrations of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) in PC (1.3 M and 2.1 M), the graphite anode was exfoliated. However, the graphite exfoliation could be effectively suppressed when the concentrations of dissolved LiTFSI were increased to 2.5 M and 3.3 M. The results of spectroscopic analyses and density functional theory (DFT) calculations revealed that electrochemical exfoliation of the graphite anode is closely associated with a special spatial configuration of Li + -(PC) n (1 ≤ n ≤ 4) solvation structures at various Li-salt concentrations and corresponding solid electrolyte interface (SEI) film formation mechanisms. When the concentration of LiTFSI increased from 1.3 to 3.3 M, the spatial configuration of Li + -(PC) n (1 ≤ n ≤ 4) solvation gradually changed from a tetrahedron (occupied space of 10.19 A) to planar (occupied space of 3.05 A), which reduced the structure change for co-intercalation into the graphite interlayers of Li + -(PC) n (1 ≤ n ≤ 4) solvates. Meanwhile, the affinity between Li + -(PC) n (1 ≤ n ≤ 4) solvation cations and TFSI − anions was increased, leading to the significant contribution of TFSI − anions to SEI formation on the surface of graphite. Additionally, Al corrosion was not of concern in concentrated LiTFSI electrolyte. The 3.3 M LiTFSI/PC concentrated electrolyte exhibits promising electrochemical performance in graphite||LiNi 1/3 Co 1/3 Mn 1/3 O 2 full cells.

Li3.9Cr0.3Ti4.8O12 nanofibers with one-dimensional (1D) morphology and excellent electrical conductivity are prepared via a facile electrospinning technique. The as-prepared Li3.9Cr0.3Ti4.8O12 nanofibers exhibit excellent lithium storage performance with superior rate capability and low-temperature performance: 140 mAh g−1 at 10 C and 91 mAh g−1 at 50 C rates at room temperature, 100 mAh g−1 at 1 C rate at −20 °C. The superior electrochemical performance of Li3.9Cr0.3Ti4.8O12 nanofibers is attributed to the 1D nano-architectures composed of nanocrystals and the reduced grain size in Li3.9Cr0.3Ti4.8O12, both of which facilitate the Li+ ion transport. The Li3.9Cr0.3Ti4.8O12 nanofibers also have a high Ti3+ concentration and an in-situ surface coating layer of Li2CrO4, which could enhance intraparticle and interparticle electronic conductivities of Li3.9Cr0.3Ti4.8O12 grains, respectively.

Tungsten (W) laminate materials are very promising to improve the fracture toughness of tungsten. In this study, four kinds of tungsten laminated composites with different interlayers, including Ta, Ti, Ti/Ta/Ti, and W layers, are fabricated by spark plasma sintering (SPS). Compared with the W/W, W/Ti and W/Ta multilayer composites, the W/Ti/Ta composites exhibit the highest tensile strength (581 MPa) and elongation (7.9%). It shows that a gradual decrease of strength and a gradual increase of ductility from the W layer to the Ta layer can be obtained in the W/Ti/Ta multilayer composites. The tensile strength of these multilayer composites can be approximately predicted by the modified rule of mix. The toughening mechanism can be attributed to the energy dissipation caused by interfacial debonding, plastic deformation of interlayers, and crack bridging of the intermediate layer. The results show that the mechanical properties of the different tungsten-based multilayers are closely related to the toughening interlayers, which is beneficial to design tungsten laminates with high strength and toughness.

The effect of tungsten content on deformation texture and microstructure of Ta-W alloy is studied. It is found that the increase of tungsten content results in the strengthening of α-fiber and the weakening of γ-fiber in Ta-W alloys. The volume fraction of γ-fiber developed in Ta-10W alloy is lower than that in Ta-2.5W alloys. Meanwhile, a more significant through-thickness texture gradient is formed in Ta-10W alloy. The addition of tungsten has an important effect on the ability cross-slip of dislocations. Therefore, more dislocation loops and activated slip systems can be seen in Ta-2.5W alloy. The size of the dislocation cells in Ta-2.5W alloy is larger than that in Ta-10W alloy. As shear bands tends to appear in γ-fiber, the density of shear bands in the Ta-2.5W alloy is much higher than that of Ta-10W alloy at the same reduction strain. Meanwhile, the wavelength of the wavy shear bands in Ta-10W alloy is smaller than that in Ta-2.5W alloy. In Ta-10W alloy, new grains with Goss orientation can be seen in periodic shear bands developed in {111} orientations, which is different from that in Ta-2.5W alloy.

Lithium-rich layered oxide cathode is a promising high-capacity cathode material for high-energy lithium-ion batteries. However, to achieve its high capacity, the development of high-voltage electrolytes is essential. In this work, trimethyl phosphite (TMP) is investigated as an electrolyte additive for high-voltage lithium-ion batteries using Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 cathode. When 1% TMP is introduced into the electrolyte, cycling performance and rate capability of the Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 cathode are improved significantly. The Li/Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 cell with the TMP-containing electrolyte exhibits high capacity retention of 81.3% after 100 cycles and good rate capability of 150 mA h g −1 at 5 C and 90 mA h g −1 at 10 C, while the capacity of the cell without TMP is 48 mA h g −1 at 5 C. Based on the measurements on impedance spectra and thermal stability, it is concluded that TMP can effectively deactivate the catalyzing effect of some transition metal ions on the surface of the Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 cathode.

LiNi0.5Mn1.5O4 and LiNi0.45M0.10Mn1.45O4 (M = Fe, Co, Cr) powders are prepared and systematically investigated as 5 V cathode materials for lithium-ion batteries. X-ray diffraction, Raman spectroscopy and scanning electron microscopy are employed to study their structures. The electrochemical cyclic performance and rate capability at room temperature and 55 °C are characterized and compared. The results indicate that the introductions of Fe, Co or Cr ions favor the crystal structure of the spinel in a F d 3 ¯ m symmetry compared with a symmetry of P4332 for the un-doped LiNi0.5Mn1.5O4. Excellent cycle life is measured for these 5 V Co- and Fe-doped electrodes. When cycled at 1C rate, about 95.9%, 93.1% and 81.7% of their initial capacities can be retained after 500 cycles for LiNi0.45Co0.10Mn1.45O4, LiNi0.45Fe0.10Mn1.45O4 and LiNi0.45Cr0.10Mn1.45O4, respectively. Their electrochemical performances at 55 °C are also much better than the un-doped sample. Three possible capacity fading mechanisms including structural transformation, the dissolution of the spinel into the electrolyte, and the oxidation of the electrolyte are discussed. The decomposition of the electrolyte is regarded as the most important mechanism.

The γ-Li 2 CuZrO 4 with a double rock-salt structure, as a lithium-ion compound, has never been reported on their physical and physicochemical properties. The γ-Li 2 CuZrO 4 was prepared by a solid-state reaction process. X-ray diffraction was used to analyze the structure of the products. Its electrical properties were characterized by both DC and AC measurements in the temperature range from 133 to 1273 K. Cyclic voltammetry and galvanostatic cell cycling were also employed to evaluate its electrochemical performance. It is found to be a pure electronic semiconductor with a fairly high conductivity (10 −5 S/cm at 133 K, 10 −2 S/cm at 300 K and 10 −1 S/cm at 1173 K). The average activation temperature is 14.4 kJ/mol. When increasing the temperature above 1073 K, a phase transition from γ to β takes place. When reacting with lithium in an electrochemical cell, γ-Li 2 CuZrO 4 decomposes into three phases during the initial discharge process, and possesses a reversible capacity of about 70 mAh/g.

Layered LiCo1/3Ni1/3Mn1/3O2 as a lithium insertion positive-electrode material was prepared by a radiated polymer gel method. The synthesis conditions and microstructure, morphology and electrochemical properties of the products were investigated by XRD, SEM and electrochemical cell cycling. It was found that the positive-electrode material annealed at 950 °C showed the best electrochemical property with the first specific discharge capacity of 178 mAh/g at C/6 and stable cycling ability between 2.8 and 4.5 V versus Li/Li+. The optimized LiCo1/3Ni1/3Mn1/3O2 exhibited rather good rate capability with the specific capacity of 173 mAh/g at 0.2C and 116 mAh/g at 4C under a fast charge and discharge mode in rate performance test.

Nanosized α-Fe2O3 (ca. 50 nm) and Li–Fe composite oxides (ca. 29 nm) powders were synthesized via gel polymer route. The gels were obtained with thermal polymerization of acrylic acid solutions of iron and lithium nitrates. The calcination of these gels at temperatures from 300 °C to 500 °C results in α-Fe2O3 from Fe(NO3)3 precursor and Li–Fe composite oxides Li2O–Fe3O4–LiFeO2 from a mixed precursors of Fe(NO3)3 and LiNO3. Thermal gravimetric analysis, X-ray diffraction and transmission electron microscopy were used to investigate the precursors and products. The electrochemical performance of the Fe-based oxides was also evaluated. After 200 cycles, their capacity can be as high as 1300 mAh/g for α-Fe2O3 and 1400 mAh/g for Li–Fe oxide while the initial capacity loss is as low as 21.8%. The Li–Fe oxide electrodes exhibit better capacity retention than the α-Fe2O3 electrodes. They are interesting negative electrodes for high energy density lithium-ion batteries.

A new class of LiCo 1− x Zr x /2 Mg x /2 O 2 ( x = 0, 0.02, 0.06, 0.10, 0.20) materials has been synthesized using a solution–combustion method with mixed acetates/nitrates as the starting materials. The structure of the synthesized oxides was analyzed using X-ray diffraction (XRD). Iodometry titration was used to measure the oxidation state of cobalt. The electrochemical performance of LiCo 1− x Zr x /2 Mg x /2 O 2 electrodes was analyzed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge cycling studies in the voltage range 2.7–4.2 V (versus Li metal). It is found that the maximum doping level ( x ) is around 0.06, above which Li 2 MgZrO 4 is formed as an impurity phase. The use of combined Zr–Mg doping has resulted in the decrease of the electrode impedance and increase of the specific capacity and the stability of 3.6 V plateau efficiency.

In order to investigate the effect of copper oxide naturally formed on copper as the common anode current collector and as an electrode additive, the electrochemical behavior of lithium insertion in three naturally surface-oxidized copper powders and one copper foil was studied. Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), particle size distribution measurement, galvanostatic cell cycling and cyclic voltammetry were employed for structural and electrochemical characterization. Although the XRD analysis can only detect the presence of pure Cu phase, the XPS analysis reveals clearly the presence of a CuO layer on the copper powders or the copper foil. The thickness of this CuO layer is estimated as thick as 147 nm. The lithiation capacity associated with this CuO layer can reach 48 mAh/g for copper powders but only 1 mAh/g for the foil. This small capacity, or 5.2 × 10 −3 mAh/cm 2 per unit area of copper foil, is fortunately negligible compared with that of a common anode material in a lithium-ion cell; while the capacity associated with this CuO layer must be taken into account when using a copper powder as an additive to improve the cycling stability.

As the cathode materials for rechargeable lithium batteries, five commercial lithium cobalt oxide powders have been investigated for a comparative study. The X-ray diffraction analysis indicates that all these powders exhibit the α-NaFeO 2 layered structure. The size distribution and morphology were analyzed by particle sedimentation method and scanning electron microscopy (SEM). Their electrochemical properties including cycleability and especially 3.6 V plateau efficiency, a recently required control parameter, are compared. Two kinds of modifications, i.e. Li 2 CO 3 coating and high-temperature treatment, have been applied to improve the electrochemical performance of one of these five powders. After the high-temperature treatment in air, cobalt oxidation-state becomes higher and Li(Li x Co 1− x )O 2 is formed. Both of the two modified means can significantly improve the 3.6 V-plateau efficiency through suppressing the cell impedance rise during cycling. A general discussion on the factors influencing the plateau efficiency is also given.

The miniaturization of rechargeable lithium-ion batteries requires high quality thin-film electrodes. Electrostatic spray deposition (ESD) technique was used to fabricate LiMn2O4 thin-film electrodes with three different morphologies: sponge-like porous, fractal-like porous, and dense structures. X-ray diffraction (XRD) and scanning electron microscopy were used to analyze the structures of the electrodes. These electrodes were made into coin cells against metallic lithium for electrochemical characterization. Galvanostatic cycling of the cells revealed different rate capability for the cells with LiMn2O4 electrodes of different morphologies. It is found that the cells with LiMn2O4 electrodes of porous, especially the sponge-like porous, morphology better rate capability than those with dense LiMn2O4 electrodes. Electrochemical impedance spectroscopy (EIS) study indicates that the large surface area of the porous electrodes should be attributed to the smaller interfacial resistance and better rate capability.

The search for a reliable indicator of state-of-charge and even the remaining energy of a lithium-ion cell is of great importance for various applications. This study was an exploratory effort to use magnetic susceptibility as the indicator. Magnetic Alnico alloy was investigated as an anode material for rechargeable lithium batteries. Both pristine and partially oxidized Alnico powders were made into electrodes. Structural characterization was performed on the Alnico electrodes by means of X-ray diffraction, scanning electron microscopy, and inductively coupled plasma analysis. The electrochemical cycling of cells made of the Alnico electrodes against lithium was measured. The first lithium intercalation capacity of a treated Alnico can be up to about 600 mAh/g, while a rather reversible capacity of up to 180 mAh/g can be obtained. The capacity increases with the extent of oxidation of Alnico. It was observed that the ac susceptibility of an electrode changes with depth-of-discharge (DOD). We have proposed an electrode model with a core-shell structure, which can explain this susceptibility vs. DOD relationship. Keywords: State-of-charge, Magnetic susceptibility, Lithium batteries, Electrode, Oxidation