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.     

Li4Ti5O12 hollow microspheres assembled by nanosheets as an anode material for high-rate lithium ion batteries

In this paper, Li₄Ti₅O₁₂ (LTO) hollow microspheres with the shell consisting of nanosheets have been synthesized via a hydrothermal route and following calcination. Because of the favorable transport properties of this hollow structure, it is the rate performance at high current densities which is exceptional. When the LTO hollow microspheres were used as the anode material in lithium ion battery, they exhibited superior rate performance and high capacity even at a very high rate (131 mAh g⁻¹ at 50 C).     

High capacity three-dimensional ordered macroporous CoFe2O4 as anode material for lithium ion batteries

A three-dimensional ordered macroporous (3DOM) cobalt ferrite (CoFe₂O₄) was prepared using polystyrene (PS) colloidal crystal template. The scanning electron microscopy (SEM) and the transmission electron microscopy (TEM) micrographs showed that the as-prepared CoFe₂O₄ material had a typical 3DOM structure, which was constructed with about 130 nm-sized macropores and 10-20 nm-sized walls. The obtained CoFe₂O₄ material had a specific surface area of 66.67 m² g⁻¹, and could deliver a relatively high capacity of 702 mAh g⁻¹ (about double that of graphite) at a current density of 0.2 mA cm⁻² after 30 cycles. Owing to the 3DOM nanoarchitecture, the as-prepared CoFe₂O₄ electrode exhibited a good rate performance. The results suggest a promising application of the 3DOM CoFe₂O₄ as anode material for lithium ion batteries.     

Binder-free carbon-coated TiO2@graphene electrode by using copper foam as current collector as a high-performance anode for lithium ion batteries

Anatase TiO₂ is widely used in lithium ion batteries (LIBs) due to its excellent safety and excellent structural stability. However, due to the poor ion and electron transport and low specific capacity (335 mAh g⁻¹) of TiO₂, its application in LIBs is severely limited. For the first time, we report a binder-free, carbon-coated TiO₂@graphene hybrid by using copper foam as current collector (TG-CM) to enhance the ionic and electronic conductivity and increase the discharge specific capacity of the electrode material without adding conductive carbon (such as super P, etc.) and a binder (such as polyvinylidene fluoride (PVDF), etc.). When serving as an anode material for LIBs, TG-CM displays excellent electrochemical performance in the voltage range of 0.01–3.0 V. Moreover, the TG-CM hybrid delivers a high reversible discharge capacity of 687.8 mAh g⁻¹ at 0.15 A g⁻¹. The excellent electrochemical performance of the TG-CM hybrid is attributed to the increased lithium ion diffusion rate due to the introduction of graphene and amorphous carbon layer, and the increased contact area between the active material and electrolyte, and small resistance with copper foam as the current collector without an additional binder (PVDF) and conductivity carbon (super P).     

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.     

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.     

High-performance hierarchical homologous scale-like CuCl/Cu foam anode for lithium ion battery

In situ growth of hierarchical scale-like CuCl on homologous Cu foam substrate for lithium ion battery (LIB) was achieved via facile anodization of Cu and the following rapid deposition of insoluble CuCl. The obtained hierarchical scale-like CuCl/Cu foam electrode were investigated in terms of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), galvanostatic charge/discharge, rate performance, cycle stability and AC impedance. When used as the anode in LIB, the as-synthesized electrode with multi-scaled pores delivered satisfactory electrochemical performances. Particularly, the reversible discharge capacity was still maintained at about 197.2 mA h/g even after 1000 cycles at high rate of 10 C, indicating excellent endurance and structural stability during the fast cyclic charge/discharge. It can be concluded that the developed hierarchical scale-like CuCl/Cu foam electrode can not only improve the electronic conductivity, but also buffer the structure strain during long term cyclic lithiation/delithiation and maintain the structural stability. Seemingly, hierarchical CuCl with high Li-storage activity and highly conductive three dimensional (3D) porous homologous Cu foam substrate jointly contributed to high electrochemical performances.     

High performance binder-free quaternary composite CuO/Cu/TiO2NT/Ti anode for lithium ion battery

High performance binder-free quaternary composite CuO/Cu/TiO₂ nanotube/Ti (CuO/Cu/TiO₂NT/Ti) electrode for lithium ion battery was designed and synthesized via anodization, electrodeposition and thermal oxidation at 450 °C in the air. The as-prepared binder-free quaternary composite CuO/Cu/TiO₂NT/Ti electrode was studied in terms of XRD, XPS, SEM, EDX, galvanostatic charge/discharge, cycle stability, cyclic voltammetry (CV) and AC impedance. As expected, the binder-free quaternary composite CuO/Cu/TiO₂NT/Ti electrode displayed much higher discharge capacity, cycle stability, Li⁺ diffusion coefficient than bare TiO₂NT/Ti electrode. High Li-storage activity of CuO, high conductivity of Cu and the synergy effect among various components should be responsible for improved electrochemical performances. Additionally, binder-free combination of the various components may also contribute into the modifications due to the exclusion of negative effect of polymer binder.     

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.     

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.     

Self-assembly of Fe2O3 nanorods in carbon nanotube network as a 3D aerogel architecture for lithium ion batteries

Self-assembly of nanosized materials has been extensively studied for the assemblies usually exhibit novel properties and show potential applications in many fields. However, there are few studies about the self-assembly behavior during the formation of 3D architectures. Herein, interesting self-assembly of ultrathin α-Fe₂O₃ nanorods into micrometer-scale flakes or rods is exhibited during the formation of single walled carbon nanotube hydrogel network. The results show that this self-assembly is driven by oriented attachment mechanism with the assistance of surfactant acting as a template and 3D hydrogel structure as confined space. Benefitting from the 3D porous and interpenetrated structure, improved electron transfer network and increased active facets of Fe₂O₃, an initial charge capacity is high as 891?mAh/g and 73% could be retained after 200 cycles. While great rate capability (42% preserved at 1000?mA/g) are also demonstrating its potential for applications in lithium ion batteries.     

Electrospinning of hierarchical structure Nd10W22O81 nanowires as high performance lithium storage anode for rechargeable batteries

In this work, hierarchical structure Nd₁₀W₂₂O₈₁ nanowires are successfully prepared by a feasible electro-spinning technique followed by heat treatment. The structure, morphology and electrochemical characteristics of Nd₁₀W₂₂O₈₁ nanowires are investigated and compared with Nd₁₀W₂₂O₈₁ particles fabricated by a high temperature solid state reaction. It can be observed that Nd₁₀W₂₂O₈₁ nanowires display a “nanoparticle-in-nanowire” architecture. For comparison, solid state formed Nd₁₀W₂₂O₈₁ is composed of irregular microsized particles. This hierarchical architecture makes Nd₁₀W₂₂O₈₁ nanowires have higher Li-storage capacity and better rate performance, contributing to the larger ion channels and shorter ion transportation pathways. In addition, an in-situ X-ray diffraction investigation is also operated to study the structural evolution and reaction mechanism during the charge/discharge process. All these evidences indicate that hierarchical structure Nd₁₀W₂₂O₈₁ nanowires could be a potential high capacity anode material for rechargeable lithium-ion batteries.     

Synthesis of dandelion-like V2O3/C composite with bicontinuous 3D hierarchical structures as an anode for high performance lithium ion batteries

The dandelion-like V₂O₃/C composite was synthesized by a simple and facile template-free solvothermal method followed by a suitable thermal treatment. The dandelion-like V₂O₃/C composite is constructed by bicontinuous 3D hierarchical structures, which are formed by interconnected nanoparticles and interconnected pores, respectively. Moreover, the surface of interconnected nanoparticles is uniformly coated with an ultrathin carbon layer. Upon evaluation as an anode material for LIBs, the as-synthesized product shows superior electrochemical performance. Under the current density of 0.1?A?g^?1, the specific discharge capacity of V₂O₃/C composite is 737?mA?h?g^?1 after 100 cycles. Moreover, after 1000 cycles at a high current density of 2?A?g^?1, the sample exhibits a discharge capacity of 315?mA?h?g^?1 which is 94% of the first-cycle discharge capacity. This excellent electrochemical performance can be ascribed to its unique hierarchical structure with 3D interconnected nanopores and uniform carbon coating.     

Porous ZnO nanosheets grown on copper substrates as anodes for lithium ion batteries

Porous ZnO nanosheets are grown directly on copper substrates by a chemical bath deposition technique followed by a heat treatment. The materials are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Their electrochemical properties as anodes of lithium ion batteries are examined by cyclic voltammetry (CV) and galvanostatic discharge–charge tests. The results show that porous ZnO nanosheets exhibit higher reversible capacities and better cyclabilities than those of commercial ZnO powders. When cycled at 0.05 A g⁻¹, these nanosheets deliver initial discharge and charge capacities of 1120 and 750 mAh g⁻¹, and at 0.5 A g⁻¹, they keeps stable capacities of 400 mAh g⁻¹ up to 100 cycles, in addition, they also exhibit good rate capabilities. It is believed that the porous sheet nanostructure plays an important role in the electrochemical performance.     

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.     

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.     

Electrochemical performance and local cationic distribution in layered LiNi1/2Mn1/2O2 electrodes for lithium ion batteries

LiNi_1/2Mn_1/2O₂ electrodes with layered structure were synthesized by solid-state reaction between lithium hydroxide and mixed Ni,Mn oxides obtained from co-precipitated Ni,Mn carbonates and hydroxides and freeze-dried Ni,Mn citrates. The temperature of the solid-state reaction was varied between 800 and 950 °C. This method of synthesis allows obtaining oxides characterized with well-crystallized nanometric primary particles bounded in micrometric aggregates. The extent of particle agglomeration is lower for oxides obtained from freeze-dried Ni,Mn citrates. The local Mn⁴⁺ surrounding in the transition metal layers was determined by X-band electron paramagnetic resonance (EPR) spectroscopy. It has been found that local cationic distribution is consistent with α,β-type cationic order with some extent of disordering that depends mainly on the precursors used. The electrochemical extraction and insertion of lithium was tested in lithium cells using Step Potential Electrochemical Spectroscopy. The electrochemical performance of LiNi_1/2Mn_1/2O₂ oxides depends on the precursors used, the synthesis temperature and the potential range. The best electrochemical response was established for LiNi_1/2Mn_1/2O₂ prepared from the carbonate precursor at 900 °C. The changes in local environment of Mn⁴⁺ ions during electrochemical reaction in both limited and extended potential ranges were discussed on the basis of ex situ EPR experiments.     

Preparation and characterization of three dimensionally ordered macroporous Li4Ti5O12 anode for lithium batteries

Three dimensionally ordered macroporous (3DOM) Li₄Ti₅O₁₂ membrane (80 μm thick) was prepared by a colloidal crystal templating process. Colloidal crystal consisting of monodisperse polystyrene particles (1 μm diameter) was used as the template for the preparation of macroporous Li₄Ti₅O₁₂. A precursor sol consisting of titanium isopropoxide and lithium acetate was impregnated into the void space of template, and it was calcined at various temperatures. A macroporous membrane of Li₄Ti₅O₁₂ with inverse-opal structure was successfully prepared at 800 °C. The interconnected pores with uniform size (0.8 μm) were clearly observed on the entire part of membrane. The electrochemical properties of the three dimensionally ordered Li₄Ti₅O₁₂ were characterized with cyclic voltammetry and galvanostatic charge and discharge in an organic electrolyte containing a lithium salt. The 3DOM Li₄Ti₅O₁₂ exhibited a discharge capacity of 160 mA h g⁻¹ at the electrode potential of 1.55 V versus Li/Li⁺ due to the solid state redox of Ti^3+/4+ accompanying with Li⁺ ion insertion and extraction. The discharge capacity was close to the theoretical capacity (167 mA h g⁻¹), which suggested that the Li⁺ ion insertion and extraction took place at the entire part of 3DOM Li₄Ti₅O₁₂ membrane. The 3DOM Li₄Ti₅O₁₂ electrode showed good cycle stability.     

Ultrafine SnO2 dispersed carbon matrix composites derived by a sol-gel method as anode materials for lithium ion batteries

Ultrafine crystalline SnO₂ particles (2-3 nm) dispersed carbon matrix composites are prepared by a sol-gel method. Citric acid and hydrous SnCl₄ are used as the starting constituents. The effect of the calcination temperatures on the structure and electrochemical properties of the composites has been studied. Structure analyses show that ultrafine SnO₂ particles form and disperse in the disordered carbon matrix in the calcination temperature range of 500-800 °C, forming SnO₂/C composites, and the carbon content shows only a slight increase from 35.8 wt.% to 39.1 wt.% with the temperature. Nano-Sn particles form when the calcination temperature is increased to 900 °C, forming a SnO₂/Sn/C composite, and the carbon content is increased to 49.3 wt.%. Electrochemical testing shows that the composite anodes provide high reversible cycle stability after several initial cycles, maintaining capacities of 380-400 mAh g⁻¹ beyond 70 cycles for the calcination temperature of 600-800 °C. The effect of the structure feature of the ultrafine size of SnO₂ and the disordered carbon matrix on the lithium insertion and extraction process, especially on the reversible behavior of the lithium ion reaction during cycling, is discussed.     

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.