Pitch carbon and LiF co-modified Si-based anode material for lithium ion batteries

To improve the electrochemical performance of silicon-based anode material, lithium fluoride (LiF) and pitch carbon were introduced to co-modify a silicon/graphite composite (SG), in which the graphite acts as a dispersion matrix. The pitch carbon helps to improve the electronic conductivity and lithium ion transport of the material. LiF is one of the main components of the solid electrolyte interphase (SEI) formed on the silicon surface, helping to tolerate the large volume changes of Si during lithiation/delithiation. The modified SG sample delivered a capacity of over 500 mA h g⁻¹, whereas unmodified SG delivered a capacity of lower than 50 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹. When performed at 4 A g⁻¹, the reversible capacity of the modified SG was 346 mAh g⁻¹, much higher than that of SG (only 37 mA h g⁻¹). The enhanced cycling and rate properties of the modified SG can be attributed to the synergetic contribution of the pitch carbon and LiF which help accommodate the volume change, reduce the side reaction, and form a stable solid electrolyte interface layer.     

Carbon-coated silicon as anode material for lithium ion batteries: advantages and limitations

Carbon coating of silicon powder was studied as a means of preparation of silicon-based anode material for lithium ion batteries. Carbon-coated silicon has been investigated at various cycling modes vs. lithium metal. Ex situ X-ray data suggest that there is irreversible reduction of crystallinity of the silicon content. Since carbon layer preserving the integrity of the particle, the reversibility of the structural changes in the amorphous state Li-Si alloy provides the reversible capacity. The progressively decreased Coulomb efficiency with cycling indicates that more and more lithium ions are trapped in some form of Li-Si alloy and become unavailable for extraction. This is the main factor for the capacity fading during cycling. Qualitative studies of the impedance spectra of the electrode material at the first cycle for the fresh anode and at the last cycle after the anode capacity faded considerably and provide further support for this model of fading mechanism.     

An urchin-like graphite-based anode material for lithium ion batteries

In situ preparation of carbon nanotubes on the surface of spherical graphite particles is made by chemical vapor deposition, resulting in an “urchin-like” hybrid material. TEM and SEM images show that carbon nanotubes are herringbone with turbulent layered structure, less than 100 nm in diameter and several micrometers in length in the average. The hybrid's use as an anode material in lithium ion batteries is examined using constant current charge-discharge tests, which prove that carbon nanotubes oriented on the surface effectively improve the reversible capacity. Cyclic voltammogram shows that there is no cathodic peak for the reaction of the Fe catalyst with Li⁺ in the charge-charge process in 0.0-1.6 V vs. Li/Li⁺ potential range.     

Electrochemical performance of nano-Pt-supported carbon anode for lithium ion batteries

A nano-Pt-supported carbon anode was prepared by supporting Pt nanoparticles onto carbon powder. Ultrafine Pt nanoparticles could be well distributed on the surface of carbon particles. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV), FTIR, and impedance spectroscopy were used to study on the electrode structure and electrochemical performance. Nano-Pt-supported carbon anode enhanced the Li discharge reaction and suppressed the solvent decomposition reaction, which are favorable for lithium batteries.     

Pyrolytic polyurea encapsulated natural graphite as anode material for lithium ion batteries

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.     

Carbon nanotube capsules encapsulating SnO2 nanoparticles as an anode material for lithium ion batteries

Carbon nanotubes capsules (CNCs) with compact, stout walls and tunable sizes were fabricated by using self-assembly of acid modified carbon nanotubes in a water-in-oil emulsion system. The effect of ultrasonic power on the formation and size of CNCs were investigated. On the basis of fabrication of CNCs, CNCs encapsulating SnO₂ nanoparticles were prepared as anode material for lithium ion batteries. The morphologies, structural characteristics and electrochemical performances of CNCs and CNCs encapsulating SnO₂ nanoparticles were systemically investigated by FE-SEM, TEM, XRD and a series of electrochemical testing techniques. The results showed that the encapsulation amount of SnO₂ in CNCs had a great influence on the reversible capacity and cycle performance of the composites. The composite with appropriate amount of SnO₂ exhibited a high reversible capacity of 383 mAh g⁻¹ and an excellent cyclability with only 0.4% capacity loss/cycle in that CNCs not only could provide high electric conductivity for composites but also effectively accommodate the volume change of SnO₂ during the cycling processes.     

Nanoscale SnS with and without carbon-coatings as an anode material for lithium ion batteries

SnS nanoparticles were mechnochemical synthesized and then co-heated with polyvinyl alcohol (PVA) at various temperatures to obtain carbon coating. All amorphous carbon-coated SnS particles had average particle size of about 20-30 nm, revealed by transmission electron microscopy (TEM). During discharge-charge, ex situ XRD results indicated that SnS firstly decomposed to Sn, then lithium ions intercalated into Sn. The reaction of Li⁺ and Sn was responsible for the reversible capacity in cycling process. The lithium ion insertion and extraction mechanism of SnS anode was similar to that of Sn-based oxide. Electrochemical capacity retention of carbon-coated SnS obtained at 700 °C was superior to that of other prepared SnS anodes and especially the rate capability was obviously enhanced due to good electric conductivity and buffering matrix effects of carbon coating.     

Effects of heteroatoms on electrochemical performance of electrode materials for lithium ion batteries

Recent studies of lithium ion batteries focus on improving electrochemical performance of electrode materials and/or lowering cost. Doping of active materials with heteroatoms is one promising method. This paper reviews the effects of heteroatoms on anode materials such as carbon- and tin-based materials, and cathode materials such as LiCoO₂, LiNiO₂, LiMn₂O₄ and V₂O₅. There are favorable and unfavorable effects, which depend on the species and physicochemical states of heteroatoms and the parent electrode materials. In the application of lithium ion batteries advantageous factors should be exploited, unwelcome side effects should be avoided as far as possible. Considerable gains towards improved electrochemical performance of the electrode materials have been achieved. Nevertheless, there are still problems needing further investigation including theoretical aspects, which will in the meanwhile stimulate the investigation for better electrode materials.     

Hydrazine hydrate-induced hydrothermal synthesis of MnFe2O4 nanoparticles dispersed on graphene as high-performance anode material for lithium ion batteries

Herein, a MnFe₂O₄/graphene (MnFe₂O₄/G) nanocomposite has been synthesized via a facile N₂H₄·H₂O-induced hydrothermal method. During the synthesis, N₂H₄·H₂O is employed to not only reduce graphene oxide to graphene, but also prevent the oxidation of Mn²⁺ in alkaline aqueous solution, thus ensuring the formation of MnFe₂O₄/G. Moreover, MnFe₂O₄ nanoparticles (5–20 nm) are uniformly anchored on graphene. MnFe₂O₄/G electrode delivers a large reversible capacity of 768 mA h g⁻¹ at 1 A g⁻¹ after 200 cycles and high rate capability of 517 mA h g⁻¹ at 5 A g⁻¹. MnFe₂O₄/G holds great promise as anode material in practical applications due to the outstanding electrochemical performance combined with the facile synthesis strategy.     

Three-dimensional reticular tin-manganese oxide composite anode materials for lithium ion batteries

Tin-manganese oxide film with three-dimensional (3D) reticular structure has been prepared by electrostatic spray deposition (ESD). X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicate that the film is amorphous. X-ray-photoemission spectroscopy (XPS) demonstrates that the 3D grid is composed of tin-manganese oxide. As an anode electrode for the lithium ion battery, the tin-manganese oxide film has 1188.3 mAh g⁻¹ of initial discharge capacity and very good capacity retention of 656.2 mAh g⁻¹ up to the 30th cycle. Such a composite film can be used as an anode for lithium ion batteries with higher energy densities.     

Electrochemical stability of silicon/carbon composite anode for lithium ion batteries

Silicon/carbon composite anode materials were prepared by pyrolyzing the phenol-formaldehyde resin (PFR) mixed with silicon and graphite powders. Scanning electron microscopic (SEM) observation showed that the morphology stability of the composite electrodes can be retained during cycling. A structure evolution mechanism is proposed to illuminate the enhancement of cycleability of the composite electrode. The composite used as anode material for lithium ion batteries possesses a reversible capacity of over 700 mAh/g.     

Electrochemical reaction of the SiMn/C composite for anode in lithium ion batteries

The SiMn-graphite composite powder was prepared by mechanical ball milling and its electrochemical performances were evaluated as the candidate anode materials for lithium ion batteries. It is found that the cyclic performance of the composite materials is improved significantly compared to SiMn alloy and pure silicon. The heat treatment of the electrodes is beneficial for enhancing the cyclic stabilities. The SiMn-20 wt.% graphite composite electrode after annealing at 200 °C has an initial reversible capacity of 463 mAh g⁻¹ and a charge-discharge efficiency of 70%. Moreover, the reversible capacity maintains 426 mAh g⁻¹ after 30 cycles with a coulomb efficiency of over 97%. The phase structure and morphology of the composite were analyzed by X-ray diffraction (XRD) and scanning electron microscopy. The lithiation/delithiation behavior was investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The composite materials appear to be promising candidates as negative electrodes for lithium rechargeable batteries.     

Composite silicon film with connected silicon nanowires for lithium ion batteries

Composite silicon film, which is composed of silicon nanowires, Si-Au eutectic and Si particles as the melding spots, was prepared as anode for lithium ion batteries by a special secondary deposition process with vapor-liquid-solid (VLS) mechanism. Au-Si eutectic particles act as the melding spots between silicon nanowires. An attractive electrochemical performance with 88% of the coulombic efficiency in the first cycle was obtained in the charge-discharge tests. The connection among silicon nanowires by dispersed Si-Au particles is the key factor for the enhancement of its electrochemical reversibility.     

Morphological and crystallite size impact on electrochemical performance of electrospun rutile and rutile/multiwall carbon nanotube nanofibers for lithium ion batteries

A sol–gel based route was used to produce TiO₂ based nanocomposites. Sols were electrospun into continuous nanofibers and calcined to get rutile phase. Fibers with diameter around 100 nm and crystallites size between 10 and 50 nm were obtained. The morphological impact and crystallites size dependence of the electrochemical performance for as-synthesized materials are reported. Enhancements using inert calcination atmosphere and incorporation of multi-wall carbon nanotubes (MWCNT) into the system are also presented.     

A hierarchical porous carbon material for high power, lithium ion batteries

We synthesize a carbon anode material with unique nanostructure for high power lithium ion batteries. The carbon material is composed of numerous clusters of carbon nanobeads, and shows a macro-meso-micro hierarchical porous structure. This unique nanostructure appears to facilitate the rapid transfer of lithium ions and a very large ion adsorption. It exhibits a reversible capacity of 407.4 mAh g⁻¹ and its rate performance is drastically improved in comparison with that of the commercial graphite. The unique structure enables the anode to combine the advantages of both lithium ion batteries and electrochemical double layer capacitors, resulting in the good electrochemical performance.     

An easy and scalable approach to synthesize three-dimensional sandwich-like Si/Polyaniline/Graphene nanoarchitecture anode for lithium ion batteries

A new three-dimensional (3D) sandwich-like Si/Polyaniline/Graphene nanoarchitecture anode for lithium ion batteries (LIBs) is successfully fabricated through an easy approach. In this nanoarchitecture, the in-situ polymerized electronic conductive polyaniline (PAni) hydrogel, acting as “glue”, agglutinates tightly to both the silicon nanoparticles (SiNPs) and graphene sheets, forming efficient conductive networks with high elastic modulus and high tensile strength. This mechanically robust nanoarchitecture can endure the great volume change of silicon and retain structural stability during Li-ion insertion/extraction. The electrodes consisting of this 3D sandwich-like Si/Polyaniline/Graphene nanoarchitecture reveal excellent electrochemical performance. The progress made in this work provides an easy and scalable route for preparing Si-based anode materials with high performance for advanced LIBs.     

Tin dioxide/carbon nanotube composites with high uniform SnO2 loading as anode materials for lithium ion batteries

SnO₂/multi-walled carbon nanotube (MWCNT) composites were prepared by the solvothermal method and subsequent heat treatment at 360 °C. The samples were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Results on the higher SnO₂ content composite sample indicate that a uniform layer of SnO₂ nanocrystals with crystal size around 5 nm was deposited on the surface of the carbon nanotubes. The composite demonstrates a reversible lithium storage capacity of 709.9 mAh g⁻¹ at the first cycle and excellent cyclic retention up to 100 cycles as anode for lithium ion batteries.     

In-situ grown hierarchical ZnCo2O4 nanosheets on nickel foam as binder-free anode for lithium ion batteries

Nickle foam-supported hierarchical ZnCo₂O₄ nanosheets was prepared via a facile solution-based method. Porous ZnCo₂O₄ nanosheets were in-situ grown on current collector, forming a binder-free electrode. When evaluated as anode for Lithium ion batteries (LIB_S), the binder-free electrode showed an attractive electrochemical performance. A reversible capacity of 773?mAh?g^?1 could be stably delivered after a 500-cycle test at a current density of 0.25?A?g^?1, with a high capacity retention of 87%. The electrode could maintain a high reversible capacity of 245?mA?h?g^?1 even at an elevated current density of 8.0?A?g^?1. Integrated structure and rich porosity of the binder-free electrode were believed to contribute to the superior performance. Thus, the Nickle foam-supported ZnCo₂O₄ electrode is a promising anode for high performance LIBs in the coming future.     

Binder-free multilayered SnO2/graphene on Ni foam as a high-performance lithium ion batteries anode

The reasonable structure construction of electrode materials with superior performance is desired for the new generation lithium ion batteries (LIBs). Herein, binder-free multilayered SnO₂/graphene (GN) on Ni foam was fabricated via a dip coating method. SnO₂ nanoparticles and GN were alternatively coated on Ni foam to form a sandwich-like structure. The wrapping of GN can raise the conductivity and keep the structural integrality of the binder-free material, preventing structure collapse arised from the volume expansion of SnO₂. Benefiting from the porous Ni foam framework and sandwich-like structure, the SnO₂/GN composite exhibited good rate performance and excellent cycle stability. High capacities of 708 and 609?mAh?g^?1 were achieved at rates of 1 and 2?A?g^?1. Besides, the SnO₂/GN electrode delivered a high capacity of 757?mAh?g^?1 after 500 cycles at 1?A?g^?1.     

A comparison of electrochemical performance of natural graphite sulfurized by ball-milling and heat-treating as an anode for lithium ion batteries

Natural graphite (NG) was sulfurized by heat-treating or by high energy ball-milling the blend of NG with sulfur powder. The effect of the surface functional groups, containing sulfur, on the performance of the NG anode for a lithium ion battery was then investigated. X-ray photoelectron spectroscopy revealed that the sulfur was introduced onto the surface of NG in both of these methods. The results of scanning electron microscopy and Raman spectroscopy showed that the surface disorder of NG increased after sulfurization. Charge/discharge tests showed that the reversible capacity of the first cycle was increased after surface sulfurization and that the coulombic efficiency of the first cycle increased for the heat-treated sample but decreased for the ball-milled one. The change in the electrochemical performance was due to a number of factors including an increase in new active sites for lithium storage and an increase in surface area and increased disorder of the sulfurized NG samples.