Cellulose-based carbon—A potential anode material for lithium-ion battery

A series of hard carbons was produced by the carbonization of microcrystalline cellulose powder in the temperature range of 950–1100 °C. The properties of the carbons were characterized using elemental analysis, X-ray diffraction and N₂ and CO₂ adsorption. The effect of heat-treatment temperature (HTT), pyrolytic carbon (PC) coating and discharging mode on the lithium insertion/deinsertion behavior of the carbons was assessed in a coin-type half-cell with metal lithium cathode. Increasing cellulose HTT modifies mostly carbon porosity, the surface area (S_DFT) decreases from about 500 to 167 m² g⁻¹. It is associated with lowering the reversible C_rev and irreversible C_irr capacities, but without improving relatively low (0.72) 1st cycle coulombic efficiency. Applying constant current (CC)+constant voltage (CV) discharging mode instead of conventional CC enhances the reversible capacity by 15–18%. PC coating is effective in reducing C_irr by ∼20% with a little change of C_rev. The best capacity parameters, C_rev of 458 mA h g⁻¹ and C_irr of 139 mA h g⁻¹, were measured for PC coated 1000 °C carbon. The prolonged cycling of full-cell assembled with anode of the carbon and commercial cathode revealed that after initial 20 cycles the capacity decay (0.029 mA h/cycle) is comparable to that of commercial cell with graphite-based anode.     

Layered Bi2Ca3Co2O9 composite as anode material for lithium-ion battery

Polycrystalline and single crystalline composites of Bi₂Ca₃Co₂O₉ have been prepared by the conventional solid-state reaction and flux method, respectively. X-ray powder diffraction exhibits single pure phase and characterization of c-axis orientation. Plate-like grains parallel to the hot-forging direction are observed using scanning electronic microscopy. Electrochemical measurement shows that lithium ions can be intercalated/deintercalated Bi₂Ca₃Co₂O₉ with relatively large capacity, which displays its potential as a candidate of anode material for a lithium-ion battery.     

Preparation of C/Ni–NiO composite nanofibers for anode materials in lithium-ion batteries

We report here on a systematic study about the formation of laser-induced periodic surface structures (LIPSS) on biopolymers. Self-standing films of the biopolymers chitosan, starch and the blend of chitosan with the synthetic polymer poly (vinyl pyrrolidone), PVP, were irradiated in air with linearly polarized laser beams at 193, 213 and 266 nm, with pulse durations in the range of 6–17 ns. The laser-induced periodic surface structures were topographically characterized by atomic force microscopy and the chemical modifications induced by laser irradiation were inspected via Raman spectroscopy. Formation of LIPSS parallel to the laser polarization direction, with periods similar to the laser wavelength, was observed at efficiently absorbed wavelengths in the case of the amorphous biopolymer chitosan and its blend with PVP, while formation of LIPSS is prevented in the crystalline starch biopolymer.     

Novel silicon–oxygen–carbon composite with excellent cycling steady performance as anode for lithium-ion batteries

The novel anode material for lithium-ion batteries, silicon–oxygen–carbon (Si–O–C) composite, is prepared by a liquid solidification combined with following pyrolysis process, in which silicon dioxide (SiO₂) is used as an additive agent to enhance the electrochemical performance of the composite. While the structure of the composite is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectra (FT-IR), the morphology and microstructure were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. SEM and TEM observations reveal that the Si–O–C powders are about 1 μm in diameter, and there is a homogenous pyrolyzed carbon layer about 5 nm thick on the surface of the particle. The Si–O–C sample as anode material can deliver a high initial charge capacity of 753.4 mAh g^?1, and the capacity keeps above 500.0 mAh g^?1 after 40 cycles at 100.0 mA g^?1. The electrochemical impedance spectroscopy results show that the composite exhibits lower charge transfer resistance and higher lithium-ion diffusion rate compared with the Si–C anode, which indicates that the composite Si–O–C could be used as a promising anode material for lithium-ion batteries.

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Graphical Abstract SEM images of the Si-C (a) and Si-O-C (b) samples and the TEM (c) and HRTEM (d) image of the Si-O-C sample

     

A twins-structural Sn@C core–shell composite as anode materials for lithium-ion batteries

In this paper, we report a facile method to prepare a twins-structural Sn@C core–shell composite that is used as anode materials for lithium-ion batteries. Its surface morphology and microstructures were characterized by the scanning electron microscope, X-ray diffraction, and transmission electron microscope. The electrochemical performances of Sn@C were measured by charge–discharge tests, cyclic voltammogram, and electrochemical impedance spectra. It is shown that such a composite exhibits a high initial specific capacity of 970 mA h g^?1 and a capacity retention of 400 mA h g^?1 after 50 cycles at the current density of 100 mA g^?1.     

The effect of TiO<Subscript>2</Subscript> coating on the electrochemical performance of ZnO nanorod as the anode material for lithium-ion battery

ZnO nanorods were coated with TiO₂ thin film using the atomic layer deposition (ALD) process. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the crystal structure and surface morphology of the coated composites. Results of galvanostatic charge and discharge tests and cyclic voltammograms suggest that lithium ions can reversibly intercalate into and deintercalate from TiO₂-coated ZnO nanorods, and that stable cycling behavior in an ethylene carbonate-based electrolyte can be achieved. The TiO₂ coating is believed to reduce the degree of reaction electrodes have with the electrolyte during the charge–discharge process since the inactive coating layer prevents the electrode from having direct contact with the electrolyte. Furthermore, the one-dimensional nanorods provide a relatively higher surface area than those of their bulk form or thin film, which allows a much greater portion of atoms on the surface to undergo the electrochemical reaction. The electrochemical study indicates that the TiO₂-coated ZnO nanorod arrays might be a candidate for the anode material in Li-ion batteries.     

A carbon–LiFePO<Subscript>4</Subscript> nanocomposite as high-performance cathode material for lithium-ion batteries

A cathode material of an electrically conducting carbon–LiFePO₄ nanocomposite is synthesized by wet ball milling and spray drying of precursor powders prior to a solid-state reaction. The structural characterization shows that the composite is composed of LiFePO₄ crystals and 4.8 wt.% amorphous carbon. Galvanostatic charge/discharge measurements indicate that the composite exhibits a superior high energy and high cycling stability. This composite delivers a discharge capacity of 159.1 mAh g⁻¹ at 0.1 C, 150.8 mAh g⁻¹ at 1 C, and 140.1 mAh g⁻¹ at 2 C rate. The capacity retention of 99% is achieved after 200 cycles at 2 C. The 18,650 cylindrical batteries are assembled using the composite as cathode materials and demonstrate the capacity of 1,400 mAh and the capacity retention of 97% after 100 cycles at 1 C. These results reveal that the as-prepared LiFePO₄–carbon composite is one of the promising cathode materials for high-performance, advanced lithium-ion batteries directed to the hybrid electric vehicle and pure electric vehicle markets.     

Self-assembly of metal–organic frameworks and graphene oxide as precursors for lithium-ion battery applications

We fabricated composites of Fe₂O₃/reduced graphene oxide as lithium-ion batteries anode material with controlled structures by employing self-assembly of metal–organic frameworks (MOFs) and polymer-functionalized graphene oxide as precursors. By electrostatic interaction, the negatively charged MOFs, Prussian Blue (PB), are assembled on poly(diallyldimethylammonium chloride) (PDDA)-functionalized graphene oxide (positive charge). Then the PB cubes become FeOOH nanosheets when treated with sodium hydroxide. Upon further annealing, the FeOOH nanosheets transform to Fe₂O₃ nanoparticles while the graphene oxide become reduced graphene oxide simultaneously. It was found that the composites have good performance as anode of lithium-ion battery. This work shows a new way for self-assembling MOFs and 2D materials.     

Molybdenum carbide nano-sheet as a high capacity anode material for monovalent alkali metal-ion batteries—Theoretical investigation

This contribution presents a theoretical investigation of monovalent metal-ion adsorption and diffusion on two-dimensional (2D) buckled nanostructure of molybdenum carbide (MoC) by using the first principle method. We find that buckled MoC nanostructure exhibits great stability, semiconducting electronic property, and high performance as electrode material. Interestingly, Crystal Orbital Hamilton population (COHP) method results show that buckled MoC is chemically stable in a wide range of temperatures, and various Li, Na, ions adsorbed configurations, which is beneficial for anode materials. Especially, single-layer MoC exhibits a superior theoretical capacity of 993.16 mA h g⁻¹ for Li-ions and 496.58 mA h g⁻¹ for Na/K-ions. The storage capacity of 1200 mA h g⁻¹ is found for the adsorption of ions on multilayer bulk MoC. Moreover, migration energy barriers are predicted as 0.38 eV for Li, 0.32 eV for Na, and 0.24 eV for K; these remarkable results determine the applicability of buckled MoC as ideal anode material for metal-ion battery applications.     

The impact of carbon shell on a Sn–C composite anode for lithium-ion batteries

Spherical Sn–carbon core-shell powders (CSCM/Sn) were synthesized through a resorcinol–formaldehyde microemulsion polymerization performed in the presence of SnO₂ powders, followed by carbonization in an inert atmosphere. Scanning electron microscope and X-ray diffractometry analyses showed that the Sn powders were thoroughly encapsulated within the carbon microspheres. The CSCM/Sn presented much better cyclability than the conventional Sn–carbon microsphere composite. In core-shell-structured composite, most of the Sn particles were encased inside carbon microspheres and not easy to aggregate or fall off from the microspheres. The carbon shell suppressed the aggregation of tin particles and alleviated the volume change of tin, and the conductive carbon shell effectively decreased the polarization during cycling, giving rise to better high rate performance and excellent capacity retention ability. It is shown that surface structure plays an important role in alloy/C composite anode materials for lithium-ion battery.     

Electrochemical characteristics of Li4 − x Cu x Ti5O12 used as anode material for lithium-ion batteries

Cu-doped Li₄Ti₅O₁₂ (Li_4???x Cu _x Ti₅O₁₂) materials were synthesized by solid-state method. Cu-doping does not change the crystal structure of Li₄Ti₅O₁₂ material but increases its lattice constant. The particle size of Li_4???x Cu _x Ti₅O₁₂ powders decreases with increasing Cu-doping level. Cu-doping does not change the specific capacity at low current density, but can improve the cycling stability and the rate capability of Li₄Ti₅O₁₂ significantly. This is mainly attributed to the enhanced electronic and ionic conductivity and the decreased charge transfer resistance, caused by the increased specific surface area of active Li_4???x Cu _x Ti₅O₁₂ powders. The Li_3.8Cu_0.2Ti₅O₁₂ anode material exhibits the best cycling stability and rate capability.     

Two-dimensional PC_3 as a promising anode material for potassium-ion batteries: First–principles calculations

With the diversified development of the battery industry, potassium-ion batteries(PIBs) have aroused widespread interest due to their safety and high potassium reserves on earth. However, the lack of suitable anode materials limits their development and application to a certain extent. Based on first-principles calculations, we investigate the possibility of using PC_3 monolayer as the anode material for PIBs. PC_3 sheet has excellent electrical properties and meets the prerequisite of anode materials. The storage capacity of potassium is as high as 1200 m Ah·g~(-1), which is better than many other reported potassium-ion anode materials. In addition, the outstanding advantages of PC_3 sheet, such as low diffusion barrier and moderate open-circuit voltage, make it a potential anode candidate for PIBs.     

Electrochemical and microstructural investigations on an as-cast and solution-annealed Al–Mg–Sn–Ga alloy as anode material in sodium chloride solution

In this research, the electrochemical properties of a stir cast Al-0.65Mg-0.15Sn-0.05Ga (wt.%) alloy as an anode material in 3 wt.% NaCl solution was examined by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion behavior of the material was also evaluated using self-corrosion rate, hydrogen evolution, open circuit and closed circuit potentials, and anode efficiency measurements. In addition, the microstructure of the material was studied using scanning electron microscopy (SEM) and the intermetallic particles were analyzed by energy dispersive spectrometer (EDS). The results showed that tin inclusions were formed within the grains and along the grain boundaries and the dissolution of aluminum substrate was occurred preferentially around these particles leading to form round pits. The dissolution of alloy was accompanied by hydrogen gas evolution from cathodic tin particles. Polarization measurements showed active behavior with considerably negative corrosion potential value without any passive region. The obtained impedance results showed an increase in the impedance values due to the coverage of anode surface by reaction products during immersion. A sample of the alloy which was subjected to homogenizing annealing at 570 °C showed more active behavior by providing more negative open and closed circuit potential values and improved anode efficiencies at higher impressed currents, but evolved higher amounts of hydrogen compared to the as-cast anode.

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Graphical abstract This paper aims at evaluating the electrochemical and microstructural characteristics of an as-cast and solution-annealed Al-0.65Mg-0.15Sn-0.05Ga alloy anode which was fabricated by stir casting. The polarization and EIS results indicate negative corrosion potential and OCP values without passive region. The activity and anodic efficiency of the solution-annealed anode was higher in high impressed current densities but evolves more hydrogen

     

Nanoporous carbon microspheres as matrix of sulfur to prepare sulfur/carbon cathode material for lithium–sulfur battery

A high specific surface area (2798.8 m² g^?1) of nanoporous carbon microsphere (NPCM) is prepared by activated carbon microsphere in hot CO₂ atmosphere, which is used as matrix material of sulfur to prepare NPCM/sulfur composite cathode material by a melt-diffusion method. The NPCM/sulfur composite cathode material with the sulfur content of 53.5% shows high discharge capacity; the initial discharge capacity is 1274 mAh g^?1 which maintains as high as 776.4 mAh g^?1 after 50 cycles at 0.1 C current. At high current density of 1 C, the NPCM/sulfur cathode material still shows initial discharge capacity of 830.3 mAh g^?1, and the reversible capacity retention is 78% after 50 cycles. To study the influence of different sulfur content of NPCM/sulfur cathode material to the performance of Li–S battery, the different sulfur content of NPCM/sulfur composite cathode materials is prepared by changing the thermal diffusion time and the ratio of sulfur powder to NPCM. The performance of NPCM/sulfur cathode material with different sulfur content is studied at a current of 0.1 C, which will be very important to the preparation of high-performance sulfur/carbon cathode material with appropriate sulfur content.     

Effect of Ni/Mn ratio on the performance of LiNi x Mn2 − x O4 cathode material for lithium-ion battery

Lithium nickel manganate is recognized as a type of promising cathode material for lithium-ion battery, due to its advantages such as high voltage, high power density, and relative lower cost. In this paper, a series of LiNi _x Mn_2???x O₄ cathode materials with various molar ratio of Ni/Mn have been prepared with a co-precipitation method, followed by a solid state reaction, and the effect of the molar ratio of Ni/Mn on the structure and properties of materials are intensively investigated by means of X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), and performance measurements, etc. It is revealed that all the samples with x from 0 to 0.5 have well-defined spinel structure and fit well to Fd-3 m space group. With the increase of the molar ratio of Ni/Mn, the diffraction peaks shift to higher angle slightly and the lattice parameter decreases gradually by the XRD results. Furthermore, it is found that the capacity at the 4.0 V plateau decreases while the capacity at 4.7 V plateau increases with the increase of the ratio of Ni/Mn, and the total discharge capacity shows growth trend with the increase of Ni content. It is important that all the samples with various molar ratio of Ni/Mn exhibit good cyclic stability. Based on the experimental results, we suggest that the Ni may incorporate into the lattice of LiMn₂O₄ substituting of Mn. The plateau at 4.7 V is related to the Ni ions and the plateau at 4.0 V is related to the Mn ions in the materials.     

Young's modulus as a function of composition for an n-type lead–antimony–silver–telluride (LAST) thermoelectric material

For 17 cast lead–antimony–silver–telluride (LAST) thermoelectric specimens (representing 14 different chemical compositions), a combination of Vickers and Knoop microindentation techniques were used to determine the composition-dependent Young's modulus, E, which ranged from 24 to 68?GPa. Following microindentation, independent nanoindentation measurements were also performed on 10 of the 17 specimens. In the literature, for pseudobinary joins in ternary or quaternary compounds (with the compositions A _x B_{1– x} C or A _x B_{1– x} CD, respectively), changes in the Young's modulus have been expressed as quadratic functions of the compositional parameter x. In this study, we extend the quadratic functional form to a paraboloid in four composition variables to describe composition-dependent changes in E for the LAST compounds. Also, the composition-dependent changes in LAST are compared to the trends observed in the literature for E and bulk modulus for systems described by a single compositional variable.     

Single-crystalline α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanohexahedron as outstanding anode material for lithium-ion batteries

In this paper, single-crystalline hexahedron hematite is successfully obtained by a simple hydrothermal approach with assistance of PVP as surfactant. SEM and XRD results show that the as-obtained α-Fe₂O₃ has a nanohexahedron shape with high uniformity and high crystallinity. The effects of a few factors influencing the morphology of α-Fe₂O₃, such as PVP amount, reaction temperature, etc., are investigated carefully. More importantly, time-dependent experiments are carried out to have in-depth insight into the formation of the single-crystalline α-Fe₂O₃ nanohexahedron. Based on the full characterization of as-obtained α-Fe₂O₃, it is concluded that PVP as surfactant plays an important role in the formation of the hexahedron shape of α-Fe₂O₃. Besides, the proposed formation mechanism of α-Fe₂O₃ nanohexahedron is that the shape of α-Fe₂O₃ evolves from the nuclei, needle-like shapes, and urchin-like aggregates to the hexahedron shape, driven by minimization of surface energy and Ostwald ripening. When used as an anode material for lithium-ion batteries, nanohexahedron α-Fe₂O₃ shows a high rate capability. Moreover, after 150 cycles, the storage capacity of α-Fe₂O₃ is still up to 680 mAh g^?1 and almost remains unchanged, suggesting high cyclability.

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Graphical Abstract ?

     

Suitable Solutions for the Navier–Stokes Problem with an Homogeneous Initial Value

This paper is devoted to the study of strong or weak solutions of the Navier–Stokes equations in the case of an homogeneous initial data. The case of small initial data is discussed. For large initial data, an approximation is developed, in the spirit of a paper of Vishik and Fursikov. Qualitative convergence is obtained by use of the theory of Muckenhoupt weights.