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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.

The application of tungsten (W) material is limited due to its intrinsic brittleness at low temperature. W-based multilayer composites are one of the solutions to improve the fracture toughness of W. In this study, a series of tungsten/tantalum (W/Ta) multilayer composites are prepared by diffusion bonding. The interfacial microstructure and fracture toughness under different deformation modes are investigated. It has been found that the flexural strength and fracture toughness loading perpendicular to the W/Ta interface are significantly higher than that loading parallel to the interface. The composites bonded at 1000 °C exhibits the highest flexural strength and fracture toughness. Both the flexural strength and fracture toughness decrease as bonding temperature increases. The decrease of flexural strength is due to recovery and recrystallization of the W layers. The decrease of fracture toughness is mainly attributed to the changes of the interfacial microstructure and fracture mechanism. For the composites bonded at 1000 °C, plastic deformation of the Ta layer and interfacial debonding are the main mechanisms for energy dissipation during crack propagation. As the bonding temperature increases, the decomposition of oxide scale and dynamic recrystallization occur at the vicinity of the W/Ta interface. A layer of fine recrystallization grains is developed at the W/Ta interface when the bonding temperature is higher than 1300 °C. As the interfacial bonding defects decreases, the interfacial bonding strength increases. Therefore, the interfacial debonding is inhibited in the composites bonded at a temperature higher than 1200 °C, instead, multiple tunnel micro-cracks appear in the W layers.

Guanylate cyclase C (GC-C) is an important receptor protein expressed by intestinal epithelial cells, and its dysregulation leads to severe intestinal diseases. Linaclotide is a 14-amino acid peptide approved by the FDA for the treatment of irritable bowel syndrome with constipation (IBS-C), which activates guanylate cyclase C to accelerate intestinal transit. Drug molecule design based on structural information plays a crucial role and the activity of linaclotide still need to improve, while the structure of linaclotide remains unknown. In this work, linaclotide and its d -enantiomer were obtained through Fmoc solid phase peptide synthesis method and co-crystalized through racemic crystallization. The crystal structure showed that linaclotide has a tight, three-beta turns structure immobilized by three pairs of disulfide bonds.

Graphene materials have recently experienced rapid developments, but large-scale production of high-quality graphene is still desired. Electrochemical exfoliation method is considered as a promising approach to meet this requirement. Here we demonstrate a non-electrified electrochemical exfoliation method to produce high-quality graphene (NEEG) sheets. By direct electrochemical reaction between graphite powders and metallic Li in 1 M LiPF6/propylene carbonate electrolyte, continuous graphite exfoliation is achieved with a high yield of excess 80% without any consumption of electric energy. The as-prepared NEEG has high quality with few defects (ID/IG = 0.45), a high C/O ratio of 27.74 and excellent electronic conductivity of 102.5 S cm−1. As conductive additives in Li4Ti5O12 electrode for lithium ion batteries, NEEG contributes to higher capacity and initial coulombic efficiency than common thermally reduced graphene oxide. Given the advantages of NEEG, the non-electrified electrochemical exfoliation method is promising for the large-scale preparation of high-quality graphene sheets.

Multilayer composites are effective to improve the toughness of Tungsten (W). To demonstrate the toughing mechanism, a series of W/Ti multilayer composites are prepared by diffusion bonding at different temperatures in a spark plasma sintering system. It shows that the mechanical properties of the composites vary with the change of bonding temperature, which is closely related with the microstructures developed at different bonding temperatures. The bending strength of the composites bonding at 1100 °C is highest, which reaches 1847 MPa. However, the composites bonding at 1200 °C has absorbed the highest fracture energy during three-point bending tests. The different microstructures developed at different bonding temperatures are mainly due to the different diffusion behaviors of W and Ti elements. The activation energy of W diffusion into Ti and Ti diffusion into W is 87.69 KJ/mol and 152.20 KJ/mol, respectively. And the diffusion coefficient of W into Ti is two orders of magnitude higher than that of Ti into W. Thus, β-Ti has formed in the Ti layer due to W diffusion into Ti. Although α-Ti is precipitated in the β-Ti, solid solution strengthening is the main strengthening mechanism in the Ti layer. The toughening mechanism of the W/Ti multilayer composites is mainly crack deflection, and the plastic deformation of the Ti layer. Meanwhile, the fracture modes of these composites are proposed.

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.

Elongated lamellar bands parallel to rolling plane are usually formed in γ-fiber of Ta W alloys at high strains. However, in this study, a type of lamellar bands oriented with α-fiber is formed in Ta 10 W alloy cold-rolled to 5%. Meanwhile, island equiaxed grains with special orientations can be seen in the lamellar bands. Furthermore, the lamellar bands are not homogenously distributed in the whole samples and concentrated in some elongated-grain bands. Although the lamellar bands are composed of extending planar dislocation boundaries with one or two dislocation cells across, they cannot result from incremental rotation of microbands or microshear bands, since no shear bands appear in these lamellar bands at such low strain. Therefore, the lamellar bands can be initiated by the retained elongated lamellar boundaries after annealing. They show a persistent microstructural feature as the ratio of reduction increases. As the hardness and dislocation density of the persistent lamellar bands is quite different from that of other deformed microstructures, these bands are bad for plastic deformation process. Meanwhile, protrusions at high-angle lamellar boundaries migrating to the recovered lamellar bands are observed during annealing because of the inhomogeneous dislocation microstructure. The lamellar bands can be fully eliminated when the annealing temperature reaches 1500 °C.

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.

The cubic Ca/Ta-substituted Li6.55(La2.95Ca0.05)(Zr1.5Ta0.5)O12 (LLCZTO) electrolytes were synthesized at 800 °C with Li3BO3 as additives. The optimal amount of Li3BO3 and its influences on the microstructure, crystal structures, Li+ conductivity and the stability of the Li6.55(La2.95Ca0.05)(Zr1.5Ta0.5)O12 were studied by SEM, XRD and EIS. Among all the samples, when the molar ratio of Li3BO3 to the Li6.55(La2.95Ca0.05)(Zr1.5Ta0.5)O12 is 4:5, the highest Li+ conductivity of 1.33 × 10−4 S cm−1 at 30 °C is obtained. When the LLCZTO samples are exposed in air, the Li+ conductivity is deteriorated possibly owing to the side reactions between the LLCZTO and the H2O or CO2 in the air. The Li3BO3 addition can alleviate such deterioration of the Li+ conductivity.

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.

In order to show the formation mechanism of {001}〈210〉 orientation, a Ta-2.5W alloy was cold rolled to a large strain when many microbands are aligned with rolling direction. The {001}〈210〉 orientation is usually developed in a deformation band with normal direction//〈001〉 next to {111}〈110〉 orientation. The {001}〈210〉 and {111}〈110〉 orientations share a common rotation axis of 〈111〉 and a highly stressed slip system of {110}〈111〉. The orientation relationship between {001}〈210〉 and {111}〈110〉 orientations could be a twin relationship (60°/〈111〉). The {001}〈210〉 orientation is probably developed by the rotation of intra-grain deformation bands, which is related with the shear banding and rigid body rotation. When the strain reaches 90%, deformation bands are crossed by shear bands and the orientations are changed. However, the {001}〈210〉 orientation can still be seen. The {001}〈210〉 oriented grains grow larger during subsequent annealing at 1223 K to 1323 K attribute to the coincident site lattice interfaces.

The work presents a detailed investigation of the microstructure characteristics of the γ-fiber (normal direction// ) in electron beam melted Ta-2.5W alloy subjected to cold rolling. With increasing strain, the average space of microbands decreases towards a saturation value which is about 0.5 μm. The typical microstructure in γ fiber is microbands and shear bands in different appearance. The microbands are relatively straight and aligned close with slip planes when the strain is lower than 60%. The non-crystallographic irregular microbands and shear bands prevail in γ fiber when the strain is larger than 70%. When the strain reaches 90%, a group of parallel macroshear bands are formed. The orientation of γ fiber can spread up to 60°. Both {111} and {001} new orientations are developed in {111} orientation. Many new developed high angle boundaries of these new grains are coincident site lattice boundaries (Σ3 and Σ9). Meanwhile, these new grains and matrix always share a common or with matrix.

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.

In this study, a series of the W/Ta multilayer composites are prepared by spark plasma sintering (SPS) at different temperature. The relationship between the sintering temperature and tensile properties are investigated in detail. Large equiaxed recrystallization grains appear in the W layers when the sintering temperature reaches 1200 °C. The W/Ta multilayer composites have a better comprehensive performance when the sintering temperature is 1100 °C. The fracture mechanisms of the W/Ta multilayer composites can be divided into two types based on the bonding strength of the interface. When the sintering temperature is lower than 1200 °C, delamination cracks can be seen. Meanwhile, necks and shear cracks appear in the Ta layers. When the sintering temperature reaches 1200 °C, delamination cracks disappear. Meanwhile, a lot of shear bands can be observed in the Ta layers. As the sintering temperature increases, the fracture mode of the W layers changes from transgranular cleavage fracture to intergranular fracture. And the fracture mode of the Ta layers is always ductility fracture. However, the ductility of the Ta layers decreases since the stress state changes from plane stress state to plane strain state. The tensile strength of the W/Ta multilayer composites can be calculated by the proposed model considering the stress concentration factor in the interface.

The NY-ESO-1 (A39-A68) peptide hydrazide was prepared through 9-fluorenyl-methoxycarbonyl solid-phase peptide synthesis (Fmoc SPPS) from a new 9-fluorenyl-methoxycarbonyl hydrazine 2-chlorotrityl chloride (Fmoc-hydrazine 2CTC) resin. The new resin was ideal for long-term storage and usage in Fmoc SPPS. Besides, the title peptide hydrazide could be transformed nearly quantitatively into the corresponding peptide thioester, which was both isolable and usable directly in native chemical ligation (NCL).

Cyclic peptide trypsin inhibitor SFTI-1 was synthesized via intramolecular ligation of a linear peptide hydrazide with high yield. This cyclization strategy did not cause epimerization at the C-terminal Arg residue. CD spectrum and NMR spectroscopy analysis demonstrated that well-folded SFTI-1 could be obtained via standard oxidative folding process. Thus, we present a simple and cost-efficient strategy for the synthesis of SFTI-1.

A novel and simple in-situ solid-state reaction route is developed to synthesize a three-dimensional (3D) porous carbon fiber film-supported Li 3 V 2 (PO 4 ) 3 membrane electrode. The carbon film is obtained via the carbonization of a bioproduct rice paper (RP). The carbon film can function as both a current collector and a 3D electronic conduction network for the loaded Li 3 V 2 (PO 4 ) 3 particles. The structure and electrochemical properties of the Li 3 V 2 (PO 4 ) 3 membrane electrode are characterized. As a free-standing membrane electrode, it exhibits good rate performance at room temperature with a specific capacity of 108 and 142 mAh g −1 at 10 C rate in the voltage range of 3.0–4.3 V and 3.0–4.8 V, respectively. It also shows good cycling performance with a specific capacity of 123 mAh g −1 after 500 cycles at 1 C rate in the voltage range of 3.0–4.8 V.

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 effects of Al substitution for Ni or (and) Mn in LiNi 0.5 Mn 1.5 O 4 spinel on the structures and electrochemical properties are investigated. Powders of LiNi 0.5 Mn 1.5 O 4 , Li 0.95 Ni 0.45 Mn 1.5 Al 0.05 O 4 , LiNi 0.475 Mn 1.475 Al 0.05 O 4 and Li 1.05 Ni 0.5 Mn 1.45 Al 0.05 O 4 are synthesized by a thermopolymerization method. Their structures and electrochemical properties are studied by X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, cyclic voltammetry and galvanostatic charge–discharge testing. The introduction of Al in these LiNi 0.5 Mn 1.5 O 4 samples has resulted in structure variation, and greatly improved their cyclic performance and rate capability. The effects of Al substitutions for Ni and Mn in the LiNi 0.5 Mn 1.5 O 4 are different. Compared with LiNi 0.5 Mn 1.5 O 4 , Li 0.95 Ni 0.45 Mn 1.5 Al 0.05 O 4 demonstrates higher specific capacity at room temperature but faster capacity fading at elevated temperatures. Li 1.05 Ni 0.5 Mn 1.45 Al 0.05 O 4 displays a lower discharge capacity but better capacity retention at 55 °C. Moreover, the cyclic performance and rate capability of the Ni-substituted Li 0.95 Ni 0.45 Mn 1.5 Al 0.05 O 4 , Ni/Mn co-substituted LiNi 0.475 Mn 1.475 Al 0.05 O 4 and Mn-substituted Li 1.05 Ni 0.5 Mn 1.45 Al 0.05 O 4 at room temperature are similar, and have improved substantially compared with the Al-free LiNi 0.5 Mn 1.5 O 4 sample.

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.

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.

Carbon encapsulated graphite was prepared by coating polyurea on the surface of natural graphite particles via interfacial polymerization followed by a pre-oxidation at 250 °C in air and a heat treatment at 850 °C in nitrogen. FT-IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to investigate the structure of the graphite before and after the surface modification. Galvanostatic cycling, dc impedance spectroscopy, and cyclic voltammetry were used to investigate the electrochemical properties of the modified graphite as the anode material of lithium cells. The modified graphite shows a large improvement in electrochemical performance such as higher reversible capacity and better cycleability compared with the natural graphite. It can work stably in a PC-based electrolyte with the PC content up to 25 vol.% because the encapsulated carbon can depress the co-intercalation of solvated lithium ion. The initial coulombic efficiency of C-NG and NG in non-PC electrolyte is 74.9 and 88.5%, respectively.

A new type of Li 3 PO 4 -based composite electrolyte films was fabricated with an approach similar to Bellcore technology. The films are composed of Li 3 PO 4 fine powder, SiO 2 nanoparticles, dibutyl( o -)phthalate (DBP) and a polymer matrix poly(vinyldiene fluoride). X-ray diffraction, scanning electron microscopy and photo scattering techniques were employed to analyze the Li 3 PO 4 powder synthesized by a chemical precipitation method. AC impedance spectroscopy was used to measure the electrical properties of the composite electrolyte films. The effect of the addition of different concentration nanoparticles SiO 2 and DBP on the conductivities of the Li 3 PO 4 -based composite electrolyte was analyzed. It is found that the optimized starting composition with a mass ratio Li 3 PO 4 :SiO 2 :DBP:Kynar 2801 (PVDF–12% HFP):acetone equal to 30:5:30:35:100 gives rise to the highest ionic conductivity of 2.4 × 10 −8 S/cm at 30 °C and 1.7 × 10 −7 S/cm at 100 °C with an activation energy of 0.32 eV. It is comparable with that of Li 3 PO 4 thin films obtained from sputtering or electrostatic spray deposition (ESD) techniques. The presence of the plasticizer DBP and nanoparticles SiO 2 plays an important role to minimize the resistance for lithium-ion conduction between Li 3 PO 4 particles. In addition, for the graphite/composite/graphite measurement cell, the apparent conductivity for the charge-transfer process between the electrolyte film and the graphite electrode is about one order of magnitude lower than that of the composite electrolyte with an activation energy of 0.56 eV. The development of such composite films opens opportunities to thermally stable electrolytes for rechargeable lithium batteries.

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. In this work, for the first time the change of ac susceptibility of cells was in situ monitored during charge–discharge process. A strong permanent magnetic material, NdFeB alloy, was investigated as an anode material for rechargeable lithium batteries. Both original and partially oxidized NdFeB powders were made into electrodes. Structural characterization was performed on the NdFeB electrodes by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. An alloy (core)–oxide (shell) structure was found for those partially oxidized samples. The electrochemical cycling of cells made of the NdFeB electrodes against lithium was measured. The first lithium intercalation capacity of a treated NdFeB can be up to about 831 mAh/g, while a rather reversible capacity of up to 352 mAh/g can be obtained. With a specially designed cell, we were able to monitor in situ the change of relative ac susceptibility during charge and/or discharge steps. A clearly monotonous relationship is found between the ac susceptibility of a cell and its depth-of-discharge (DOD). A mechanism based on skin effect and eddy current change is proposed to explain this susceptibility versus DOD relationship.

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.