Titanium dioxide/graphene oxide composite and its application as an anode material in non-flammable electrolyte based on ionic liquid and sulfolane

A composite of aminosilane-grafted TiO₂ (TA) and graphene oxide (GO) was prepared via a hydrothermal process. The TiO₂/graphene oxide-based (TA/GO) anode was investigated in an ionic liquid electrolyte (0.7 M lithium bis(trifluoromethanesulfonyl)imide (LiNTf₂)) in ionic liquid (N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (MPPyrNTf₂)) at room temperature and in sulfolane (1 M lithium hexafluorophosphate (LiPF₆) in tetramethylene sulfolane (TMS)). Scanning and transmission electron microscopy (SEM and TEM) observations of the anode materials suggested that the electrochemical intercalation/deintercalation process in the ionic liquid electrolyte with vinylene carbonate (VC) leads to small changes on the surface of TA/GO particles. The addition of VC to the electrolyte (0.7 M LiNTf₂ in MPPyrNTf₂ + 10 wt.% VC) considerably increases the anode capacity. Electrodes were tested at different current regimes in the range 5–50 mA g^?1. The capacity of the anode, working at a low current regime of 5 mA g^?1, was ca. 245 mA g^?1, while a current of 50 mA g^?1 resulted in a capacity of 170 mA g^?1. The decrease in anode capacity with increasing current rate was interpreted as the result of kinetic limits of electrode operation. A much lower capacity was observed for the system TA/GO│1 M LiPF₆ in TMS + 10 wt.% VC│Li.     

Interlayer-expanded MoS<Subscript>2</Subscript>/graphene composites as anode materials for high-performance lithium-ion batteries

A facile strategy was developed to prepare interlayer-expanded MoS₂/graphene composites through a one-step hydrothermal reaction method. MoS₂ nanosheets with several-layer thickness were observed to uniformly grow on the surface of graphene sheets. And the interlayer spacing of MoS₂ in the composites was determined to expand to 0.95 nm by ammonium ions intercalation. The MoS₂/graphene composites show excellent lithium storage performance as anode materials for Li-ion batteries. Through gathering advantages including expanded interlayers, several-layer thickness, and composited graphene, the composites exhibit reversible capacity of 1030.6 mAh g^?1 at the current density of 100 mA g^?1 and still retain a high specific capacity of 725.7 mAh g^?1 at a higher current density of 1000 mA g^?1 after 50 cycles.     

Pyrrolic nitrogen-doped carbon sandwiched monolayer MoS<Subscript>2</Subscript> vertically anchored on graphene oxide for high-performance sodium-ion battery anodes

In this work, a novel pyrrolic nitrogen-doped carbon sandwiched monolayer MoS₂ hybrid was prepared. This sandwiched hybrid vertically anchors on graphene oxide as anode materials for sodium-ion batteries. Such electrode was fabricated by facile ionic liquid-assisted reflux and annealing methods. Owing to rational structure and enhancement from pyrrolic nitrogen dopant, this unique MoS₂/C-graphene hybrid exhibits reversible specific capacity of 486 mAh g^?1 after 1000 cycles with a low average fading capacity of 0.15 mAh g^?1 (fading cyclic rate of ca. 0.03% per cycle). A capacity of 330 mAh g^?1 is remained at the current densities of 10.0 A g^?1. The proposed strategy provides a convenient way to create new pyrrolic nitrogen-doped hybrids for energy field and other related applications.     

Kinetic and galvanostatic studies of a polymer electrolyte for lithium-ion batteries

Quaternary polymer electrolyte (PE) based on poly(acrylonitrile) (PAN), 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid (EMImBF₄), sulfolane (TMS) and lithium hexafluorophosphate salt (LiPF₆) (PAN-EMImBF₄-sulfolane-LIPF₆) was prepared by the casting technique. Obtained PE films of ca. 0.2–0.3 mm in thickness showed good mechanical properties. They were examined using scanning electron microscopy (SEM), thermogravimetry (TGA, DSC), the flammability test, electrochemical impedance spectroscopy (EIS) and galvanostatic charging/discharging. SEM images revealed a structure consisting of a polymer network (PAN) and space probably occupied by the liquid phase (LiPF₆ + EMImBF₄ + sulfolane). The polymer electrolyte in contact with an outer flame source did not ignite; it rather underwent decomposition without the formation of flammable products. Room temperature specific conductivity was ca. 2.5 mS cm^?1. The activation energy of the conding process was ca. 9.0 kJ mol^?1. Compatibility of the polymer electrolyte with metallic lithium and graphite anodes was tested applying the galvanostatic method. Charge transfer resistance for the C₆Li → Li⁺ + e^? anode processes, estimated from EIS curve, was ca. 48 Ω. The graphite anode capacity stabilizes at ca. 350 mAh g^?1 after the 30th cycle (20 mA g^?1).     

One-step hydrothermal synthesis of flower-like SnO2/carbon nanotubes composite and its electrochemical properties

In this work, flower-like SnO₂/carbon nanotubes (CNTs) composite was synthesized by one-step hydrothermal method for high-capacity lithium storage. The microstructures of products were characterized by XRD, FESEM and TEM. The electrochemical performance of the flower-like SnO₂/CNTs composite was measured by cyclic voltammetry and galvanostatic charge/discharge cycling. The results show that the flower-like SnO₂/CNTs composite displays superior Li-battery performance with large reversible capacity and high rate capability. The first discharge and charge capacities are 1,230 and 842 mAh g^?1, respectively. After 40 cycles, the reversible discharge capacity is still maintained at 577 mAh g^?1 at the current densities of 50, 100 and 500 mA g^?1, indicating that it’s a promising anode material for high performance lithium-ion batteries.     

A facile bubble-assisted synthesis of porous Zn ferrite hollow microsphere and their excellent performance as an anode in lithium ion battery

Pure porous hollow Zn ferrite (ZnFe₂O₄) microspheres have been successfully synthesized by a facile bubble assisted method in the presence of ammonium acetate (NH₄Ac) as an anode material in lithium ion battery. The shape, size, and morphology of Zn ferrite are investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Furthermore, the probable bubble-assisted formation mechanism of porous hollow Zn ferrite spheres based on the experimental results is proposed. With the porous hollow structure, the obtained pure Zn ferrite particle as an anode in lithium ion battery demonstrates high capacity and excellent cycle ability. The high initial discharge specific capacity is approximately 1,400 mAh g^?1 and a reversible specific capacity approaches 584 mAh g^?1 after 100 cycles at a constant current density of 100 mA g^?1. The excellent electrochemical performance of the as-prepared Zn ferrite could be attributed to the special structure with which the volume expansion and pulverization of the particles became increasingly reduced.     

Facile synthesis of CoWO<Subscript>4</Subscript>/RGO composites as superior anode materials for lithium-ion batteries

In this paper, a facile method has been developed to synthesize supported CoWO₄ on the reduced graphene oxide (RGO) as high-performance anode material for Li-ion batteries. The composites with cuboid-like CoWO₄ nanoparticles were prepared by directly adding graphene oxide into the precursor solution followed by a hydrothermal treatment. Different analytical methods like high-resolution TEM, XRD, TGA, and XPS characterizations were employed to illustrate structural information of the as-prepared CoWO₄ and CoWO₄/RGO composites. In addition, the Li-ion battery performance using the composites as anode materials was also discussed based on the detailed galvanostatic charge-discharge cycling tests. The result shows that the specific capacity of the as-prepared CoWO₄/RGO composites can reach 533.3 mAh g^?1 after 50 cycles at a current density of 100 mA g^?1. During the whole cyclic process, the coulombic efficiency was maintained higher than 90%. Therefore, CoWO₄, as an environment-friendly and cost-effective anode material, has promising potential for Li-ion batteries.     

Tin nanoparticles embedded in ordered mesoporous carbon as high-performance anode for sodium-ion batteries

Tin (Sn) has been considered as an attractive anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity (847 mAh g^?1). Nevertheless, its low conductivity and large volume change during cycling essentially prevent the possibility of high capacity and long-term cycle for SIBs. In this work, Sn nanoparticles are well embedded into the highly ordered mesoporous carbon (CMK-3) matrix (Sn@CMK-3) using a facile sonochemical method combined with heat treatment. The resultant Sn@CMK-3 nanohybrid electrode delivers an initial charge capacity of 412 mAh g^?1 at 100 mA g^?1. A reversible capacity of 337 mAh g^?1 is obtained after 200 cycles, indicating the good cycle stability of the nanohybrid structure. The electrode also shows a potential rate capability, which maintains a capacity of 228 mAh g^?1 at 1000 mA g^?1. When the current density returns to 50 mA g^?1, the capacity goes back to 381 mAh g^?1, with a capacity retention of 86.9%. The enhanced sodium storage performance of Sn@CMK-3 nanohybrid can be related to the synergistic effect between CMK-3 and Sn.

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Graphical abstract Sn@CMK-3 nanohybrid with Sn nanoparticles uniformly distributed into the highly ordered mesoporous carbon matrix exhibited good cycling performance and rate capability.

     

Hierarchical porous CoMn<Subscript>2</Subscript>O<Subscript>4</Subscript> microspheres with sub-nanoparticles as advanced anode for high<Emphasis Type="Bold">-</Emphasis>performance lithium<Emphasis Type="Bold">-</Emphasis>ion batteries

To deal with the large volume change for lithium-ion batteries (LIBs), we illustrate the synthesis of CoMn₂O₄ microspheres with sub-nanoparticles by a hydrothermal method followed by thermal treatment. The size of microsphere is approximately 2.2 μm, and the sub-nanoparticle is about 17 nm. There is sufficient void space between CoMn₂O₄ microspheres with sub-nanoparticles for ensuring the well structural integrity. As advanced anode for LIBs, CoMn₂O₄ microspheres display stable specific capacity retention of 772 mAh g^?1 over 500 cycles at a current density of 100 mA g^?1. Such a kind of structure is beneficial for enhanced rate and cycling capabilities in LIBs applications, which could increase contact area between electrolyte and active materials, short path for lithium ions and electrons and accommodate the volume change with additional void space during cycling. It has a great application prospect for use as electrochemical energy storage because of the enhanced performance.     

Metal-free boron-doped carbon microspheres as excellent cathode catalyst for rechargeable Li–O<Subscript>2</Subscript> battery

Rechargeable Li–O₂ batteries are attracting more and more interest due to their high energy density. Meanwhile, the replacement of high-cost and scarce precious-metal catalysts has attracted more and more attention. Currently, many academic researchers have paid attention to find highly efficient metal-free catalysts as air cathode material. Herein, the boron-doped carbon microspheres (B-CMs) were prepared through a novel and facile static calcination method and showed high electrocatalytic activity as a cathode material. The battery with a B-CM cathode delivered a high initial discharge capacity of 13,757.2 mAh g^?1 and outstanding coulombic efficiency of 90.1 % at 100 mA g^?1. In addition, stable cyclability (151 cycles with stable discharge voltage of ~2.60 V with a cutoff capacity of 1000 mAh g^?1 at 200 mA g^?1) has been exhibited. These performances are due to three main points: boron carbide compound changed the surface area of the CMs and formed the mesopore architectures as well as the large surface area of 683.738 m² g^?1; the reduce of boron atom can slow down the oxidation of the CMs during the cyclings; and finally, the electron-deficient boron atom introduction greatly facilitated Li⁺ diffusion and electrolyte immersion and enhanced the oxygen reduction and evolution reaction kinetics.     

3D-structured carbon-coated MnO/graphene nanocomposites with exceptional electrochemical performance for Li-ion battery anodes

MnO has a high theoretical capacity, moderate discharge plateau, and low polarization when it is used as the anode material in lithium battery. However, the issues that limit its application are its poor conductivity and large volume changes, which can easily result in the collapse of electrode structure during long-term cycling. In the present work, a carbon-coated MnO/graphene 3D-network anode material is synthesized by an electrostatic adsorption of dispersed precipitates precipitation method. The MnO nanoparticles coated by carbon are uniformly distributed on the surface of graphene nanosheets and form a 3D sandwich-like nanostructure. A carbon layer is coated on the surface of MnO nanoparticles, which slows down the volume expansion in the process of lithium intercalation. The graphene nanosheets are cross-linked through carbons in this 3D nanostructure, which provides mechanical support and effective electron conduction pathways during the charge-discharge. The electrochemical tests indicate that the prepared 3D carbon-coated MnO/graphene electrode exhibits an excellent rate capacity of 1247.3 and 713.2 mAh g^?1 at 100 and 1000 mA g^?1, respectively. The capacity is 792.2 mAh g^?1 after long cycle at a current density of 1000 mA g^?1. The specific capacity is higher than that of MnO-based composite lithium anode materials currently reported. The superior rate and cycling performances are attributed to the unique 3D-network structure, which provides an effectively conductive network, buffers volume expansion, and prevents falling and aggregation of MnO in the charge and discharge process of the electrode materials. The 3D-structured carbon-coated MnO/graphene anode material will have an excellent application prospect.

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Graphical abstract Cyclic performance at 1 A g^?1 and SEM images (inset) of the 3D-structured carbon-coated MnO/graphene nanocomposite.

     

Polyaniline encapsulated silicon nanocomposite as high-performance anode materials for lithium ion batteries

Polyaniline encapsulated silicon (Si/PANI) nanocomposite as anode materials for high-capacity lithium ion batteries has been prepared by an in situ chemical polymerization of aniline monomer in the suspension of Si nanoparticles. The obtained Si/PANI nanocomposite demonstrates a reversible specific capacity of 840 mAh g^?1 after 100 cycles at a rate of 100 mA g^?1 and excellent cycling stability. The enhanced electrochemical performance can be due to that the polyaniline (PANI) matrix offers a continuous electrically conductive network as well as enhances the compatibility of electrode materials and electrolyte as a result of suppressing volume stress of Si during cycles and preventing the agglomeration of Si nanoparticles.     

NiO/CNTs derived from metal-organic frameworks as superior anode material for lithium-ion batteries

In this work, porous NiO microspheres interconnected by carbon nanotubes (NiO/CNTs) were successfully fabricated by the pyrolysis of nickel metal-organic framework precursors with CNTs and evaluated as anode materials for lithium-ion batteries (LIBs). The structures, morphologies, and electrochemical performances of the samples were characterized by X-ray diffraction, N₂ adsorption-desorption, field emission scanning electron microscopy, cyclic voltammetry, galvanostatic charge/discharge tests, and electrochemical impedance spectroscopy, respectively. The results show that the introduction of CNTs can improve the lithium-ion storage performance of NiO/CNT composites. Especially, NiO/CNTs-10 exhibits the highest reversible capacity of 812 mAh g^?1 at 100 mA g^?1 after 100 cycles. Even cycled at 2 A g^?1, it still maintains a stable capacity of 502 mAh g^?1 after 300 cycles. The excellent electrochemical performance of NiO/CNT composites should be attributed to the formation of 3D conductive network structure with porous NiO microspheres linked by CNTs, which benefits the electron transfer ability and the buffering of the volume expansion during the cycling process.     

Hierarchical SnO2 with double carbon coating composites as anode materials for lithium ion batteries

Hierarchical SnO₂ with double carbon coating (polypyrrole-derived carbon and reduced graphene oxide in order) composites have been successfully synthesized as anode materials for lithium ion batteries. The composites were characterized and examined by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, cyclic voltammetry, and galvanostatic discharge/charge tests. Such a novel nanostructure can not only provide a high conductivity but also prevent aggregation of SnO₂ nanoparticles, leading to the improvement of the cycling performance. Comparing with pure hierarchical SnO₂ and polypyrrole-derived carbon-coated hierarchical SnO₂, hierarchical SnO₂ with double carbon coating composite exhibits higher lithium storage capacities and better cycling performance, 554.8 mAh g^?1 after 50 cycles at a current density of 250 mA g^?1. In addition, the rate performance of hierarchical SnO₂ with double carbon coating composite is also very well. For all the improved performances, this double carbon coating architecture may provide some references for other electrode materials of lithium ion batteries.     

Layered LiNi<Subscript>0.80</Subscript>Co<Subscript>0.15</Subscript>Al<Subscript>0.05</Subscript>O<Subscript>2</Subscript> as cathode material for hybrid Li<Superscript>+</Superscript>/Na<Superscript>+</Superscript> batteries

LiNi_0.80Co_0.15Al_0.05O₂ (NCA) is explored to be applied in a hybrid Li⁺/Na⁺ battery for the first time. The cell is constructed with NCA as the positive electrode, sodium metal as the negative electrode, and 1 M NaClO₄ solution as the electrolyte. It is found that during electrochemical cycling both Na⁺ and Li⁺ ions are reversibly intercalated into/de-intercalated from NCA crystal lattice. The detailed electrochemical process is systematically investigated by inductively coupled plasma-optical emission spectrometry, ex situ X-ray diffraction, scanning electron microscopy, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy. The NCA cathode can deliver initially a high capacity up to 174 mAh g^?1 and 95% coulombic efficiency under 0.1 C (1 C?=?120 mA g^?1) current rate between 1.5–4.1 V. It also shows excellent rate capability that reaches 92 mAh g^?1 at 10 C. Furthermore, this hybrid battery displays superior long-term cycle life with a capacity retention of 81% after 300 cycles in the voltage range from 2.0 to 4.0 V, offering a promising application in energy storage.     

Electrochemical property of α-PbO prepared from the spent negative powders of lead acid batteries

To make full and economic use of the spent lead acid batteries (LABs), we have invented a novel route to separate their negative electrode material from positive one, which are respectively used to fabricate α-PbO for new LABs. This paper reports preparation and electrochemical property of α-PbO from the spent negative material which is compose of PbSO₄ (the major phase) and Pb (the minor phase). To make things simpler, pure PbSO₄ is firstly used as the model compound and desulfated with (NH₄)₂CO₃ to obtain PbCO₃, which is then calcined in air at different temperatures to produce PbO. At 450 °C, the calcination produces pure α-PbO that discharges a capacity of 98.6 mAh g^?1 at the current density of 120 mA g^?1 after 50 charging and discharging cycles of 100 % DOD. By using the same procedures, the real spent negative powder is also treated to produce pure α-PbO, which discharges a similar capacity of 100 mAh g^?1 at 120 mA g^?1. This is 25 % higher than that of industrial leady oxide. These results show that the small amount of metallic lead has little effect on the treatment.     

Tin oxide-titanium oxide/graphene composited as anode materials for lithium-ion batteries

A tin oxide-titanium oxide/graphene (SnO₂-TiO₂/G) ternary nanocomposite as high-performance anode for Li-ion batteries was prepared via a simple reflux method. The graphite oxide (GO) was reduced to graphene nanosheet, and the SnO₂-TiO₂ nanocomposites were evenly distributed on the graphene matrix in the SnO₂-TiO₂/G nanocomposite. The as-prepared SnO₂-TiO₂/G nanocomposites were employed as anode materials for lithium-ion batteries, showing an outstanding performance with high reversible capacity and long cycle life. The composite delivered a superior initial discharge capacity of 1,594.6 mAh g^?1 and a reversible specific capacity of 1,500.3 mAh g^?1 at a current density of 100 mA g^?1. After 100 cycles, the reversible discharge capacity was still maintained at 1,177.4 mAh g^?1 at a current density of 100 mA g^?1 with a high retained rate of reversible capacity of 73.8 %. The addition of small amount of TiO₂ nanoparticles improved the cycling stability and specific capacity of SnO₂-TiO₂/G nanocomposite, obviously. The results demonstrate that the SnO₂-TiO₂/G nanocomposite is a promising alternative anode material for practical Li-ion batteries.     

Electrochemical studies of few-layered graphene as an anode material for Li ion batteries

Few-layered graphene (FLG) with specific surface area of only ~8.2 m² g^?1 was synthesized from graphene oxide (GO) using microwave-assisted exfoliation. GO was prepared using modified Hummers method. Few-layered nature of the exfoliated material was confirmed by electron microscopy, X-ray and electron diffraction, and Raman spectroscopy. Coin cells were fabricated using FLG as an anode and lithium metal as a counter electrode. The cells were tested using cyclic voltammetry and galvanostatic cycling techniques. FLG showed reversible capacity values of ~400 and ~250 mAh g^?1 at current rates of 0.1 and 1 C, respectively. Columbic efficiency was more than 98 % while cycle to cycle capacity fading was less than 2 %. Maximum discharge or charging capacity was below 0.3 V, a preferable characteristic for achieving ideal anodic behavior.     

Highly porous disk-like shape of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> as an anode material for lithium ion batteries

A novel disk-like shape of Co₃O₄ with high porosity was synthesized by a facile hydrothermal approach followed by calcination at 485 °C for 2 h. In order to further confirm the crystal structure, morphology, particle size, surface area, and porosity of the sample, a series of corresponding characterization techniques were used. The disk-like shape of Co₃O₄ as an anode delivered excellent rate capability such as 510.5 mAh g^?1 at 4.0 C, which is much higher than the theoretical capacity of commercial graphite anode (372 mAh g^?1). However, the electrode could not recover the high capacity during the long-term cycling at various higher current rates due to the deformation of the structure as confirmed by the ex situ studies. It is believed that the obtained remarkable structural feature with numerous void pores within the structure may be helpful for short-term cycling due to the large contact areas between the electrode and the electrolyte and a shorter diffusion length for lithium ion insertion but unable to act as a buffer to relax the volume expansion/contraction and alleviate the structural damage of the electrode during long-term cycling.     

Electrospun Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript>/Li<Subscript>2</Subscript>TiO<Subscript>3</Subscript> composite nanofibers for enhanced high-rate lithium ion batteries

Li₄Ti₅O₁₂/Li₂TiO₃ composite nanofibers with the mean diameter of ca. 60 nm have been synthesized via facile electrospinning. When the molar ratio of Li to Ti is 4.8:5, the Li₄Ti₅O₁₂/Li₂TiO₃ composite nanofibers exhibit initial discharge capacity of 216.07 mAh g^?1 at 0.1 C, rate capability of 151 mAh g^?1 after being cycled at 20 C, and cycling stability of 122.93 mAh g^?1 after 1000 cycles at 20 C. Compared with pure Li₄Ti₅O₁₂ nanofibers and Li₂TiO₃ nanofibers, Li₄Ti₅O₁₂/Li₂TiO₃ composite nanofibers show better performance when used as anode materials for lithium ion batteries. The enhanced electrochemical performances are explained by the incorporation of appropriate Li₂TiO₃ which could strengthen the structure stability of the hosted materials and has fast Li⁺-conductor characteristics, and the nanostructure of nanofibers which could offer high specific area between the active materials and electrolyte and shorten diffusion paths for ionic transport and electronic conduction. Our new findings provide an effective synthetic way to produce high-performance Li₄Ti₅O₁₂ anodes for lithium rechargeable batteries.