Vanadium nitride as a novel thin film anode material for rechargeable lithium batteries

Vanadium mononitride (VN) thin films have been successfully fabricated by magnetron sputtering. Its electrochemical behaviour with lithium was examined by galvanostatic cell cycling and cyclic voltammetry. The capacity of VN was found to be stable above 800 mAh g⁻¹ after 50 cycles. By using ex situ X-ray diffraction, high-resolution transmission electron microscopy and selected area electron diffraction as well as in situ spectroelectrochemical measurements, the electrochemical reaction mechanism of VN with lithium was investigated. The reversible conversion reaction of VN into metal V and Li₃N was revealed. The high reversible capacity and good stable cycle of VN thin film electrode made it a new promising lithium-ion storage material for future rechargeable lithium batteries.     

Fabrication of NiO-ZnO/RGO composite as an anode material for lithium-ion batteries

NiO-ZnO/RGO composite was obtained by the annealing of an Ni (OH)₂-Zn (OH)₂/RGO precursor, which has been fabricated by in situ ultrasonic agitation. Moreover, the NiO-ZnO nanoflakes are evenly distributed on the RGO sheets based on the scanning electron microscope (SEM) and transmission electron microscope (TEM) characterization results. When the NiO-ZnO/RGO composite was used as an anode material in lithium-ion batteries (LIBs), the electrodes exhibited a high reversible capacity of 1017 mA h/g at a current density of 100 mA/g after 200 cycles and a specific capacity of 458 mA h/g at 500 mA/g even after 400 cycles. The electrode even reached a capacity of 185 mA h/g at a current density of 2000 mA/g. The excellent electrochemical properties of the NiO-ZnO/RGO composite might be attributable to the NiO-ZnO nanoflakes offering rich electrochemical reaction sites and shortening the diffusion length for lithium ion (Li⁺), as well as the RGO sheets improving the transfer rates of Li⁺ and electron during the charge-discharge process.     

Carbon-coated Bi5Nb3O15 as anode material in rechargeable batteries for enhanced lithium storage

Bismuth can alloy with lithium to generate Li₃Bi with the volumetric capacity of about 3765 mAh cm^?3 (386 mAh g^?1), rendering bismuth-based materials as attractive alloying-type electrode materials for rechargeable batteries. In this work, bismuth-based material Bi₅Nb₃O₁₅ @C is fabricated as anode material through a traditional solid-state reaction with glucose as carbon source. Bi₅Nb₃O₁₅ @C composite is well dispersed, with small particle size of 0.5–2.0?µm. The electrochemical performance of Bi₅Nb₃O₁₅ @C is reinforced by carbon-coated layer as desired. The Bi₅Nb₃O₁₅ @C exhibits a high specific capacity of 338.56 mAh g^?1 at a current density of 100?mA?g^?1. And it also presents an excellent cycling stability with a capacity of 212.06 mAh g^?1 over 100 cycles at 100?mA?g^?1. As a comparison, bulk Bi₅Nb₃O₁₅ without carbon-coating only remains 319.62 mAh g^?1 at 100?mA?g^?1, revealing poor cycle and rate performances. Furthermore, in-situ X-ray diffraction experiments investigate the alloying/dealloying behavior of Bi₅Nb₃O₁₅ @C. These insights will benefit the discovery of novel anode materials for lithium-ion batteries.     

Bismuth sulfide and its carbon nanocomposite for rechargeable lithium-ion batteries

Bi₂S₃ and Bi₂S₃/C nanocomposites prepared by high-energy mechanical milling were evaluated as electrode materials in lithium secondary batteries. For a Bi₂S₃/C nanocomposite, Bi₂S₃ nanocrystallites were well distributed in an amorphous carbon matrix. The reaction mechanism of the Bi₂S₃/C electrode was also examined during the first cycle. The Bi₂S₃/C nanocomposite anode showed superior electrochemical performance (ca. 500 mAh g⁻¹ and 85% of the capacity retention over 100 cycles).     

Graphene nanosheet and carbon layer co-decorated Li4Ti5O12 as high-performance anode material for rechargeable lithium-ion batteries

In this study, we report a facile strategy for anchoring Li₄Ti₅O₁₂ (LTO) particles wrapped within carbon shells onto graphene nanosheet (GNS) using the freeze-drying assisted microwave irradiation method. In this designed structure, a conductive three-dimensional network can be formed by connecting the GNS and carbon layer which is benefit for the transport of electron and Li⁺-ion. When used as anode material for lithium-ion batteries, this hybrid composite exhibits an excellent high-rate performance with specific capacities of 171.5, 168.2, 160.1, 151.7 and 136.4 mAh g⁻¹ at various current rates of 1, 2, 5, 10 and 20 C, respectively. Furthermore, the specific capacity of the obtained anode still retains 99.6% of the initial value after 20 cycles at 20 C. The enhanced battery performance can be attributed to the improved electronic conductivity of each LTO grain via uniform carbon coating and GNS wrapping. As a consequence, this novel strategy developed in this study may open a new way to fabricate other electrodes for advanced renewable energy conversion and storage applications.     

Hematite nanoflakes as anode electrode materials for rechargeable lithium-ion batteries

Hematite (α-Fe₂O₃) nanoflakes and nanocubes were synthesized by liquid-solid-solution method and their properties as anode electrode materials for rechargeable Li⁺-ion batteries were measured. When changing the water to ethanol volume ratio in the synthesis system, the nanocrystals can be changed from α-Fe₂O₃ to α-FeOOH, with shapes being tuned from nanoflakes to nanocubes, non-uniform particles and nanowires. When assembled as the anode electrode materials in rechargeable Li⁺-ion batteries, the hematite nanoflakes showed one more plateau in the first discharge progress of the voltage-composition curves than hematite nanocrystals with other shapes in the literature. X-ray diffraction, high-resolution transmission electron microscope and electrochemical data showed that this extra plateau came from the formation of Li₂Fe₃O₄ nanoclusters and amorphous Li₂O. This experiment showed that like sizes, shapes of nanocrystals may also affect the detailed electrochemical progress.     

One-step synthesis of Li-doped NiO as high-performance anode material for lithium ion batteries

The poor electronic conductivity and huge volume expansion of NiO are the vital barriers when used as anode for lithium ion batteries. In order to solve above issues, Li-doped NiO are prepared by a facile one-step ultrasonic spray pyrolysis method. The effects of Li doping on the morphology, structure and chemical composition of the Li-doped NiO powders are extensively studied. When used as lithium ion batteries anode, it is demonstrated that the doping of Li has significant positive effect on improving the electrochemical performance. After 100 cycles at 400 mA g⁻¹, The Li-doped NiO samples deliver a discharge capacity of 907 mAh g⁻¹, much more than that of un-doped sample (736 mAh g⁻¹). The improved electrochemical performances can be ascribed to the improved p-type conductivity and lower impedance, which are confirmed by Rietveld refinement, X-ray photoelectron spectroscopy and electron impedance spectroscopy.     

Sn-Co-artificial graphite composite as anode material for rechargeable lithium batteries

Nanosized Sn-Co prepared by ultrasonic-assisted chemical reduction is milled with artificial graphite (AG) to form Sn-Co-AG composite. The as-prepared materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectrometry and Brunauer-Emmett-Telle (BET) surface area measurement. XRD patterns show that Sn-Co particles are poorly crystallized and artificial graphite has a typical hexagonal graphite structure phase. The diffraction peaks of Sn-Co particles remain the same but some of AG obviously change after milling Sn-Co with AG. BET areas of AG, Sn-Co and Sn-Co-AG are 1.569, 13.187 and 6.754 m² g⁻¹, respectively. SEM images display the as-prepared Sn-Co particles have a size distribution ranging from 20 to 70 nm in diameter. After milling Sn-Co with AG, Sn-Co particles keep similar morphology but there is a perceptible change in AG. Electrochemical tests show that Sn-Co-AG composite possesses much improved electrochemical performance than the state-of-the-art graphite. This composite has great potential as an alternative material for improving the energy density of a lithium ion secondary battery.     

Facile high yield synthesis of MgCo2O4 and investigation of its role as anode material for lithium ion batteries

In this article, we have reported a one-step scalable synthesis of MgCo₂O₄ nanostructures as efficient anode material for Li-ion batteries and investigated the role of post-synthesis calcination temperature (400, 600 and 800 °C) on its physiochemical properties and electrochemical performances. The XRD pattern of the calcinated sample at 400 °C (MC 400) indicates a pure phase of MgCo₂O₄. However, on increasing the calcination temperature to 600 °C (MC 600), an additional phase corresponding to MgO was detected and the corresponding XRD peak intensity further increased on increasing the calcination temperature to 800 °C (MC 800 °C). This was accompanied by a morphological transformation from flake and rod-like nanostructures, to an agglomerated dense flake-like morphology. Electrochemical studies revealed that the calcination temperature plays an important role in determining the electrochemical performance of the MgCo₂O₄ as anode material. In a half cell, the MC 600 showed the best electrochemical performance with high discharge capacity of 980 mA h g⁻¹ (2nd discharge at 60 mA g⁻¹) and a reversible discharge capacity of 886 mA h g⁻¹ at the end of 50 cycles with high coulombic efficiency of 98%. Long term stability was carried out at 0.5C which showed a capacity retention of 358 mA h g⁻¹ at the end of 500 cycles. The superior electrochemical performance of the MC600 can be attributed to the presence of the small amount of MgO, which is believed to provide the anode materials better structural stability during cycling. The claim was further supported by ex-situ TEM analysis of the anode material of a cycled cell (50 cycles).     

Core/shell-structured nickel cobaltite/onion-like carbon nanocapsules as improved anode material for lithium-ion batteries

Core/shell-structured nanocapsules consisting of a nickel cobaltite (NiCo₂O₄) nanoparticle core encapsulated in an onion-like carbon (C) shell are synthesized by arc-discharge and air-annealing methods. Void spaces between NiCo₂O₄ core and the carbon shell are observed in the NiCo₂O₄/C nanocapsules. Lithium-ion batteries fabricated using the nanocapsules as the anode material exhibit enhanced initial coulombic efficiency of 82.3% and specific capacity of 1197.2 mA h/g after 300 cycles at 0.2 A g⁻¹ current density. Varying the rate of charge/discharge current from 0.2 to 4 A/g does not show negative effects on the recycling stability of the nanocapsules and a recoverable specific capacity as high as 1270.4 mA h/g is obtained. The introduction of the onion-like C shell and the presence of the void spaces are found to increase the contact areas between the electrolyte and the nanocapsules for improved electrolyte diffusion, to enhance the electronic conductivity and ionic mobility of the NiCo₂O₄ nanoparticle cores, and to accommodate the change in volume during the lithium-ion insertion/extraction process.     

High reversible capacity of SnO2/graphene nanocomposite as an anode material for lithium-ion batteries

A gas–liquid interfacial synthesis approach has been developed to prepare SnO₂/graphene nanocomposite. The as-prepared nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller measurements. Field emission scanning electron microscopy and transmission electron microscopy observation revealed the homogeneous distribution of SnO₂ nanoparticles (2–6 nm in size) on graphene matrix. The electrochemical performances were evaluated by using coin-type cells versus metallic lithium. The SnO₂/graphene nanocomposite prepared by the gas–liquid interface reaction exhibits a high reversible specific capacity of 1304 mAh g⁻¹ at a current density of 100 mA g⁻¹ and excellent rate capability, even at a high current density of 1000 mA g⁻¹, the reversible capacity was still as high as 748 mAh g⁻¹. The electrochemical test results show that the SnO₂/graphene nanocomposite prepared by the gas–liquid interfacial synthesis approach is a promising anode material for lithium-ion batteries.     

A biomass-derived biochar-supported NiS/C anode material for lithium-ion batteries

Nickel sulfides are perfect anode materials for high-capacity and low-cost lithium-ion batteries (LIBs); however, with the shortcoming of polysulfide intermediate dissolution, volume expansion exceeding the limit during cycling also restricts their development. Herein, NiS/C composite materials are successfully anchored on chestnut shell fluff (CSF)-derived biochar by a glucose-auxiliary hydrothermal method along with an annealing treatment. The CSF biochar acts as an effective electron transmission channel for the rapid lithiation/delithiation of NiS and as a fixed sulfur carrier for inhibiting the dissolution of polysulfide. Glucose restrains the accumulation of NiS particles and then transforms into uniform amorphous carbon during annealing, which is more effective in buffering for rapid volume variation. Moreover, the CSF-NiS/C electrode exhibits a remarkable specific capacity of 1522.8 mAh g^-1 (0.1 A g^-1) and distinguished rate performance with 295 mAh g^-1 capacity (3 A g^-1), which are better than those of the pure NiS/C anode material displays. Researchers may be inspired by both of these reasonable design and synthesis strategies that are beneficial for the development of high-performance nickel-based sulfide anode materials for LIBs.     

Nano-porous Si/C composites for anode material of lithium-ion batteries

Nano-porous silicon composite incorporated with graphite and pyrolyzed carbon was synthesized and investigated as a promising anode material for lithium-ion batteries. The nano-porous Si/graphite composite was prepared via two-step ball-milling followed by etching process. Then carbon was incorporated by using different approaches. The nano-porous Si/graphite/C composite exhibits a reversible capacity of about 700 mAh/g with no capacity loss up to the 120th cycle at a constant current density of 0.2 mA/cm². The superior electrochemical characteristics are attributed to the nanosized pores in Si particles, which suppress the volume effect, and buffering action as well as excellent electronic and ionic conductivity of carbon materials.     

A novel composite containing nanosized silicon and tin as anode material for lithium ion batteries

A novel composite consisting of nanosized Sn and Si as well as some lithium containing phases was synthesized by a mechanochemical reaction between SiO/SnO and Li using high energy mechanical milling (HEMM) with graphite as a dispersant, followed by a thermal treatment. The electrochemically active nanoclusters of Si and Sn derived by the mechanochemical reduction were uniformly distributed in the elastic matrix of lithium-containing phases and graphite. The difference in the reactive potential of Sn and Si with lithium was favorable for reducing the mechanical stress of the active hosts. Furthermore, the dispersion of Sn among the elastic matrix may contribute to an improved electrical connection among the Si based hosts and the current collectors. As a result, the composite presented a rechargeable capacity of 574.1 mAh g⁻¹ after 200 cycles. The capacity fading rate was thus calculated to be less than 0.2% per cycle. The cyclability of the composite was much superior to those of the SnO and SiO electrodes.     

Synthesis and electrochemical properties of Li2ZnTi3O8 fibers as an anode material for lithium-ion batteries

Li₂ZnTi₃O₈ fibers are synthesized by thermally treating electrospun Zn(CH₃COO)₂/LiOAc/TBT/PVP fibers and utilized as an energy storage material for rechargeable lithium-ion batteries. The material is characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermal analysis. Scanning electron microscopy results show that the Li₂ZnTi₃O₈ fibers have an average diameter of 200 nm. Electrochemical properties of the material are evaluated using cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy. The results show that as-prepared Li₂ZnTi₃O₈ has a high specific discharge capacity of 227.6 mAh g⁻¹ at the 2nd cycle. Its electrochemical performance at subsequent cycles shows good cycling capacity and rate capability. The obtained results thus strongly support that the electrospinning method is an effective method to prepare Li₂ZnTi₃O₈ anode material with higher capacity and rate capability.     

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.     

Preparation and characterization of SrLi2Ti6O14@C/Ag as lithium storage anode material for rechargeable batteries

In this work, silver and carbon co-coated SrLi₂Ti₆O₁₄ is synthesized by using a solid-state assisted solution method, with glucose as carbon source and silver nitrate as Ag source. The structural and morphological properties of as-prepared samples are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), which confirm that C/Ag composite layer is uniformly coated on the surface of SrLi₂Ti₆O₁₄. Electrochemical measurements like galvanostatic charge/discharge tests, rate performance, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis are also undertaken to evaluate and compare the lithium storage capability of SrLi₂Ti₆O₁₄ before and after coating. According to the results, SrLi₂Ti₆O₁₄@C/Ag presents enhanced electrochemical capability compared with bare material. It can be found that bare SrLi₂Ti₆O₁₄ only delivers the reversible capacity of 140.32 mA h g⁻¹ with capacity retention of 90.7% at 100 mA g⁻¹ after 200 cycles. In contrast, SrLi₂Ti₆O₁₄@C/Ag presents the reversible capacity of 151.20 mA h g⁻¹ with only 6.7% capacity loss after 200 cycles. The improvement is owing to the increase of electronic conductivity and the decrease in the redox polarization after coating. In order to further investigate the structural stability of SrLi₂Ti₆O₁₄@C/Ag, in-situ XRD was performed as well. All the results prove that the C/Ag co-coating has positive effect on the electrochemical performance of SrLi₂Ti₆O₁₄.     

Electrochemical properties of SnO2/carbon composite materials as anode material for lithium-ion batteries

SnO₂/carbon composite anode materials were synthesized from SnCl₄·5H₂O and sucrose via a hydrothermal route and a post heat-treatment. The synthesized spherical SnO₂/carbon powders show a cauliflower-like micro-sized structure. High annealing temperature results in partial reduction of SnO₂. Metallic Sn starts to emerge at 500 °C. High Sn content in SnO₂/carbon composite is favorable for the increase of initial coulombic efficiency but not for the cycling stability. The SnO₂/carbon annealed at 500 °C exhibits high specific capacity (∼400 mAh g⁻¹), stable cycling performance and good rate capability. The generation of Li₂O in the first lithiation process can prevent the aggregation of active Sn, while the carbon component can buffer the big volume change caused by lithiation/delithiation of active Sn. Both of them make contribution to the better cycle stability.     

Review on doping strategy in Li4Ti5O12 as an anode material for Lithium-ion batteries

Lithium-Ion Batteries (LIBs) as rechargeable energy storages play a key role in saving oil and decreasing exhaust emissions which are used for many applications including electric vehicles and electronic devices. Lithium titanate (LTO) as a promised anode material provides not only the Li-ion extraction and intercalation reversibility but also low volume changing during Li transmission. Nevertheless, LTO has some limitations which can be improved by some strategies such as doping. Dopants as a substation in the crystal structure of LTO could result in better performance in LIBs. In this report, doping of LTO with all kinds of dopants and with different fabrication methods is reviewed.     

Cobalt ferrite thin films as anode material for lithium ion batteries

Spinel cobalt ferrite (CoFe₂O₄) thin films have been fabricated by 355 nm reactive pulsed laser deposition on stainless steel substrates. XRD and SEM analyses showed that the CoFe₂O₄ films exhibited a polycrystalline structure and were composed of nanoparticles with an average size of 80 nm. At 1C rate, the initial irreversible capacity of polycrystalline CoFe₂O₄ film electrode cycled between 0.01 and 3.0 V reached 1280 mAh/g. After 20 cycles, the reversible discharge capacities decreased and sustained about 610 mAh/g. The diffusion coefficient of Li ion for CoFe₂O₄ films was determined by ac impedance method, and the average value was estimated to be 1.1 × 10⁻¹³ cm²/S. Based on ex situ XRD, SEM and XPS data, the electrochemical mechanism of CoFe₂O₄ film with lithium upon cycling was proposed. During the first discharge, the amorphization process of CoFe₂O₄ film electrode is accompanied with the reduction of Co²⁺ and Fe³⁺ into metal Co and Fe, respectively, and then the reversible oxidation/reduction processes of Co, Fe and Li₂O take place in the subsequent charge/discharge cycles.