Nanoporous silicon flakes as anode active material for lithium-ion batteries

Nanoporous-silicon (np-Si) flakes were prepared using a combination of an electrochemical etching process and an ultra-sonication treatment and the electrochemical properties were studied as an anode active material for rechargeable lithium-ion batteries (LIBs). This fabrication method is a simple, reproducible, and cost effective way to make high-performance Si-based anode active materials in LIBs. The anode based on np-Si flakes exhibited a higher performances (lower capacity fade rate, stability and excellent rate capability at high C-rate) than the anode based on Si nanowires. The excellent performance of the np-Si flake anode was attributed to the hollowness (nanoporous structure) of the anode active material, which allowed it to accommodate a large volume change during cycling.     

Controllable synthesis of spherical silicon and its performance as an anode for lithium-ion batteries

Spherical silicon is controllably synthesized by the hydrolysis of tetraethylorthosilicate (TEOS) with the addition of different contents of ammonia to form SiO₂, then reduced by magnesium powder in argon atmosphere at 900 °C for 3 h. The experimental results show that the electrochemical performance of the as-prepared silicon anode is much affected by the morphology of silicon, and the spherical silicon with a particle size of 250–300 nm shows a reversible capacity of 1,345.8 mAh g^?1 with the capacity retention of 83.2 % after 20 cycles. The relationship between the electrochemical performance of the spherical silicon and the diameters of silicon sphere makes it possible to control the performance of the silicon anode by adjusting the hydrolysis conditions of TEOS.     

Carbon-coated silicon/crumpled graphene composite as anode material for lithium-ion batteries

Silicon is a promising anode material for high-capacity Li-ion batteries (LIBs). However, its insulating property and large volume change during the lithiation/delithiation process result in poor cycling stability and in pulverization of Si. In this work, glucose-derived carbon-coated Si nanoparticles (C–Si NPs) are in conjunction with crumpled graphene (cGr) particles by a spray-drying method to prepare a novel composite (C–Si/cGr) material. The prepared C–Si NPs are uniformly embedded in the ridges of the cGr particles. The carbon layer of C–Si can make a good contact with the graphene sheet, resulting in enhanced electrical conductivity and fast charge transfer. In addition, the unique crumpled structure of the cGr can buffer the large volume change upon cycling process and facilitate the diffusion of electrolyte into the composite material. When employed as an anode electrode of LIBs, the C–Si/cGr composites deliver enhanced electrochemical performance, including stable cycling with a discharge capacity of 790 mAh·g⁻¹ after 100 cycles and a rate capability of 654 mAh·g⁻¹ at 2C. The synergistic effect of the carbon layer coating of Si NPs and the crumpled structure of the cGr particles results in a composite with improved the electrochemical performance, which is likely related to its high electrical conductivity and good mechanical stability of composite material.     

Preparation of Si-PPy-Ag composites and their electrochemical performance as anode for lithium-ion batteries

The nanosilicon connected by polypyrrole (PPy) and silver (Ag) particles was simply synthesized by a chemical polymerization process in order to prepare Si-based anodes for Li-ion batteries. The phase structure, surface morphology, and electrochemical properties of the as-synthesized powders were analyzed by X-ray diffraction, FT-IR, scanning electron microscopy, and galvanostatic charge/discharge measurements. The cycle stability of the Si-PPy-Ag composites was greatly enhanced compared with the pure nanosilicon. A high capacity of more than 823 mA h g^?1 was maintained after 100 cycles. The improved electrochemical characteristics are attributed to the volume buffering effect as well as effective electronic conductivity of the polypyrrole and silver in the composite electrode.     

Preparation and electrochemical performance of bramble-like ZnO array as anode materials for lithium-ion batteries

A bramble-like ZnO array with a special three-dimensional (3D) nanostructure was successfully fabricated on Zn foil through a facile two-step hydrothermal process. A possible growth mechanism of the bramble-like ZnO array was proposed. In the first step of hydrothermal process, the crystal nucleus of Zn(OH) ₄ ^2? generated by the zinc atoms and OH^? ions fold together preferentially along the positive polar (0001) to form the needle-like ZnO array. In the second step of hydrothermal process, the crystal nuclei of Zn(OH) ₄ ^2? adjust their posture to keep their c-axes vertical to the perching sites due to the sufficient environmental force and further grow preferentially along the (0001) direction so as to form bramble-like ZnO array. The electrochemical properties of the needle- and bramble-like ZnO arrays as anode materials for lithium-ion batteries were investigated and compared. The results show that the bramble-like ZnO material exhibits much better lithium storage properties than the needle-like ZnO sample. Reasons for the enhanced electrochemical performance of the bramble-like ZnO material were investigated.     

Sn-Sb and Sn-Bi alloys as anode materials for lithium-ion batteries

Sn/SnSb, Sn/Bi, and Sn/SnSb/Bi multi-phase materials were synthesised via reduction of cationic precursors with NaBH₄ and with Zn, and were tested for their suitability as anode materials for Li-ion batteries by galvanostatic cycling. The rapid reduction with NaBH₄ yielded the finer materials with the better cycling stabilities, whereas the reduction with Zn yielded the purer materials with the lower irreversible capacities in the first cycle. Reversible capacities of ∼ 600 mAh g⁻¹, ∼ 350 – 400 mAh g⁻¹, and ∼ 500 mAh g⁻¹ were obtained for Sn/SnSb, Sn/Bi, and Sn/SnSb/Bi, respectively. The cycling stability of the materials decreased in the order Sn/SnSb>Sn/SnSb/Bi>Sn/Bi, which is in part attributed to the presence / absence of intermetallic phases which undergo phase-separation during lithiation. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

Facile preparation of SGC composite as anode for lithium-ion batteries

The silicon/graphite/carbon (SGC) composite was successfully prepared by ball-milling combined with pyrolysis technology using nanosilicon, graphite, and phenolic resin as raw materials. The structure and morphology of the as-prepared materials are characterized by X–ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). Meanwhile, the electrochemical performance is tested by constant current charge–discharge technique, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements. The electrodes exhibit not only high initial specific capacity at a current density of 100 mA g^?1, but also good capacity retention in the following 50 cycles. The EIS results indicate that the electrodes show low charge transfer impedance R_sf?+?R_ct. The results promote the as-prepared SGC material as a promising anode for commercial use.     

Nanostructured WO3 thin film as a new anode material for lithium-ion batteries

Nanostructured WO₃ thin film has been successfully fabricated by radio-frequency magnetron sputtering method and its electrochemistry with lithium was investigated for the first time. The reversible discharge capacity of WO₃/Li cells cycled between 0.01 V and 4.0 V was found above 626 mAh/g during the first 60 cycles at the current density 0.02 mA/cm². By using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and selected-area electron diffraction measurements, the reversible conversion of WO₃ into nanosized metal W and Li₂O was revealed. The high reversible capacity and good recyclability of WO₃ electrode made it become a promising cathode material for future rechargeable lithium batteries.     

A review of research on hematite as anode material for lithium-ion batteries

Hematite (α-Fe₂O₃) nanomaterials have been investigated intensively as a promising anode material for Li-ion batteries due to their advantages such as high theoretical capacity, low cost, environmental friendliness, high resistance to corrosion, etc. However, their practical application is hampered by poor capacity retention, low Coulombic efficiency, and poor high-rate capacity. To overcome these drawbacks, many effective works have been proposed. This review focuses first on the present status of α-Fe₂O₃ nanomaterials in the field of Li-ion batteries including their features, synthesized methods, modification, application and then on their near future development.     

Silicon/carbon nanocomposites used as anode materials for lithium-ion batteries

Silicon/carbon nanocomposites are prepared by dispersing nano-sized silicon in mesophase pitch and a subsequent pyrolysis process. In the nanocomposites, silicon nanoparticles are homogeneously distributed in the carbon networks derived from the mesophase pitch. The silicon/carbon nanocomposite delivers a high reversible capacity of 841 mAh g^?1 at the current density of 100 mA g^?1 at the first cycle, high capacity retention of 98 % over 30 cycles, and good rate performance. The superior electrochemical performance of nanocomposite is attributed to the carbon networks with turbostratic structure, which enhance the conductivity and alleviate the volume change of silicon.     

Chemically shortened multi-walled carbon nanotubes used as anode materials for lithium-ion batteries

An easy chemically cutting process, modified Hummers' method, was proposed to treat multi-walled carbon nanotubes, successfully cutting pristine long, entangled carbon nanotubes into hydrosoluble pieces, mostly less than 200 nm. This short, chemically oxidized carbon nanotube was then applied as an anode material for lithium-ion batteries. The as-prepared material possessed higher reversible capacity and coulombic efficiency. The intrinsic factors were explored by X-ray photoelectron spectroscopy and cyclic voltammetry.     

Tin oxide nano-flower-anchored graphene composites as high-performance anode materials for lithium-ion batteries

The SnO₂ nano-flower/graphene (SnO₂-NF/GN) composites were synthesized by using graphene (GN) and SnO₂ nano-flower (SnO₂-NF). Among them, the SnO₂-NFs were prefabricated by using sodium hydroxide and stannic chloride pentahydrate (SnCl₄·5H₂O) as raw materials. The results of SEM show that the SnO₂-NFs are uniformly dispersed on the surface of GN. Furthermore, compared with the pure SnO₂, the as-prepared SnO₂-NF/GN composites displayed superior cycle performace and high rate capability. The SnO₂-NF/GN composite delivers a specific capacity of 650 mAh g^?1 after 60 cycles and an excellent rate capability of 480 mAh g^?1 at 2000 mA g^?1.     

Sn and SnO2-graphene composites as anode materials for lithium-ion batteries

Sn and SnO₂-graphene composites were synthesized using hydrothermal process, followed by annealing in Ar/H₂ atmosphere, and characterized using x-ray diffraction, scanning electron microscopy, and transition electron microscopy. The results indicated that the polycrystalline metallic Sn forms nanospheres with a diameter of 100?～?300 nm, while the SnO₂ nanoparticles are much smaller with a size below 15 nm, which adsorb tightly on the surface of graphene sheets. The Sn and SnO₂-gaphene composites showed good electrochemical performance. After 55 charging/discharging cycles, the capacity remains above 440 mAh/g at a cycling rate of 400 mA/g and the coulombic efficiency is 99.1 %. The good electrochemical properties of the composites are partially contributed to the graphene component with good mechanical flexibility and electrical conductivity, which is an excellent carbon matrix for dispersing the Sn and SnO₂ nanostructures and provides the electron transport pathways as well.     

Double-walled core-shell structured Si@SiO2@C nanocomposite as anode for lithium-ion batteries

Double-walled core-shell structured Si@SiO₂@C nanocomposite has been prepared by calcination of silicon nanoparticles in air and subsequent carbon coating. The obtained Si@SiO₂@C nanocomposite demonstrates a reversible specific capacity of about 786 mAh g^?1 after 100 cycles at a current density of 100 mA g^?1 with a capacity fading of 0.13 % per cycle. The enhanced electrochemical performance can be due to that the double walls of carbon and SiO₂ improve the electronic conductivity and enhance the compatibility of electrode materials and electrolyte as a result of accommodating the significant volumetric change during cycles. The interlayer SiO₂ may release the mechanical strain and enhance the interfacial adhesion between carbon shell and silicon core.     

Theoretical prediction of borophene monolayer as anode materials for high-performance lithium-ion batteries

Three morphologies of two-dimension Boron with metallicity have been successfully synthetized by experiments. To access the potential of β₁₂ borophene (□) and χ₃ borophene monolayer (◇) as anode materials for lithium ion batteries, first-principles calculations based on density functional theory (DFT) are performed. Lithium atom is preferentially absorbed over the center of the hexagonal B atom hollow of β₁₂ and χ₃ borophene monolayer. The fully lithium storage phase of β₁₂ and χ₃ borophene monolayer corresponds to Li₈B₁₀ and Li₈B₁₆ with a theoretical specific capacity of 1983 and 1240 mA h g^?1, respectively, much larger than other two-dimension materials. Interestingly, lithium ion diffusion on β₁₂ borophene (□) monolayer is extremely fast with a low-energy barrier of 41 meV. Meanwhile, lithiated-borophene monolayer shows enhanced metallic conductivity during the whole lithiation process. Compared to the buckled borophene (△), the extremely enhanced lithium adsorption energy of β₁₂ and χ₃ phase with vacancies weakens lithium ion diffusion. Therefore, it is important to control the generation of vacancy in the buckled borophene (△) anode for lithium ion batteries. Borophene is a promising candidate with high capacity and high rate capability for anode material in lithium ion batteries.     

Template-free synthesis of hierarchical NiO microtubes as high performance anode materials for Li-ion batteries

Hierarchical nanostructured NiO (h-NiO) microtubes were prepared by a simple wet-chemical synthesis without the use of template or surfactant, followed by the calcination of α-Ni(OH)₂ precursor. The structural characterization of the h-NiO microtubes were performed by scanning microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), the results of which indicated that the obtained h-NiO microtubes are covered by the nanosheet grown perpendicularly on the tube surface. The unique hierarchical nanostructure of h-NiO microtubes with high surface area and many voids facilitates the electrochemical reaction as well as the short ion and electron transport pathway. Therefore, as anode electrode of Li-ion batteries, the h-NiO microtubes deliver largely enhanced cycle capacity of 770 mAh·g⁻¹ at a current density of 0.5 C after 200 cycles with high columbic efficiency, compared to the NiO rods. These results suggest that the h-NiO microtubes can be a promising anode material for Li-ion batteries.     

Synthesis and performance of Li2NiTi3O8 as a new anode material for lithium-ion batteries

The titanate spinel Li₂NiTi₃O₈ is proposed for the first time as a new anode for lithium-ion batteries and successfully synthesized via a facile ball-milling assisted solid-state reaction method. The sample is characterized by X-ray diffraction patterns (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), galvanostatic charge–discharge tests, cyclic voltammetry (CV) tests, and electrochemical impedance spectroscopy (EIS). The results reveal that the Li₂NiTi₃O₈ nanoparticles have well-distributed morphology, and the particle size ranges between 100 and 300 nm. Although the initial coulombic efficiency is only 56.3 %, the Li₂NiTi₃O₈ electrode still exhibits a high rate capability and excellent cycling stability. The Li₂NiTi₃O₈ anode provides a large capacity of 212.3 mAh g^?1 at 0.1 A g^?1 after 10 cycle, which is close to its theoretical capacity (223.6 mAh g^?1). Even after 100 cycles, it still delivers a quite high capacity of 203.98 mAh g^?1, with no significant capacity fading. This indicates that the as-synthesized Li₂NiTi₃O₈ material is a promising anode material for lithium-ion batteries.     

Facile and surfactant-free synthesis of SnO<Subscript>2</Subscript>-graphene hybrids as high performance anode for lithium-ion batteries

A facile microwave-assisted ethylene glycol method is developed to synthesize the SnO₂ nanoparticles dispersed on or encapsulated in reduced graphene oxide (SnO₂-rGO) hybrids. The morphology, structure, and composition of SnO₂-rGO are investigated by scanning electron microscopy, transmission electron microscope, thermo-gravimetric analyzer, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electrochemical performance of SnO₂-rGO as anode materials for lithium-ion batteries was tested by cyclic voltammetry, galvanostatic charge–discharge cycling, and rate capability test. It is found that the SnO₂ nanoparticles with a uniform distribution have p-type doping effect with rGO nanosheets. The as-prepared SnO₂-rGO hybrids exhibit remarkable lithium storage capacity and cycling stability, and the possible mechanism involved is also discussed. Their capacity is 1222 mAhg^?1 in the first cycle and maintains at 700 mAhg^?1 after 100 cycles. This good performance can be mainly attributed to the unique nanostructure, good structure stability, more space for volume expansion of SnO₂, and mass transfer of Li⁺ during cycling.     

A novel LiSnVO4 anode material for lithium-ion batteries

Ionics - In this work, a new material LiSnVO4 has been prepared via sol-gel method utilizing ammonium metavanadate, acetates of tin and lithium as starting materials, and nitric acid and oxalic...