A preliminary investigation upon the electrochemical behavior of CoO and NiO anodes — comparative study

Among the variety of alternate anode materials being studied, the research on the exploration of 3d-metal oxide anodes gains paramount importance in the recent time, as it is bestowed with an easy preparation method and a less complicated decomposition mechanism. Towards this direction, an attempt to synthesize the compound CoO and to investigate the electrochemical behavior of the same both individually and in comparison with NiO compounds was made with a view to understand the extent to which the chosen candidates, viz., CoO and NiO can be exploited as high capacity anodes. Between the two oxides, CoO exhibited a specific capacity of at least 550 mAh/g, against NiO with an average capacity of ∼330 mAh/g. Also, the magnitude of irreversible capacity loss and the extent of capacity fade upon cycling corresponding to CoO anode were found to be lesser than NiO anodes. The enhanced specific capacity values and the better cycleability properties of CoO anodes are believed to be due to the inherent electrochemical characteristics of the compound. The type and the nature of SEI formed over the electrode surface and the formation of possible progressive agglomeration of the products of decomposition are expected to be the factors responsible for the difference in the electrochemical behavior of CoO and NiO anodes. In short, electrochemical characterization of the individual oxides are studied and probable reasons for the observed difference in the charge-discharge behavior of CoO and NiO anodes are discussed in this communication.     

TiN synergetic with micro-/mesoporous carbon for enhanced performance lithium–sulfur batteries

Porous carbon has high specific area and total pore volume but weak interaction with dissolved polysulfides. Conductive polar metal compound has strong chemical adsorption of polysulfides but difficult to attain high porosity to encapsulate sulfur series. Instead of efforts on the cathode, we prepared a composite made up of titanium nitride and three-dimensional micro-/mesoporous carbon by a facile and economic way. This composite was coated on the commercial Celgard separator as a polysulfide interceptor to enhance the performances of lithium–sulfur battery. The strategy exerts the synergetic merits of porosity, chemical adsorption, physical interception, and benign conductivity. The hierarchical carbon possesses a high specific surface area of 1571 m²/g and total pore volume of 1.56 cm³/g with the pore size centered at 1.27 and 5.30 nm. TiN can immobilize sulfur intermediates by strong chemical interaction. In addition, excellent electrical conductivity of TiN facilitates redox kinetics. The pure sulfur cathode with the modified separator delivers high initial capacity of 1130 mAh/g at 1 C (1 C?=?1675 mAh/g) and retains 500 mAh/g after 400 cycles, demonstrating superior cycling stability, rate capabilities. Discharge-charge profiles, electrochemical impedance spectrum, and cyclic voltammetry curves of batteries were investigated to support the prominent electrochemistry of the material. Further analysis and observation on the modified separator disassembled from the coin cells after cycling were conducted to probe the evolution and reaction mechanism of the coating.     

Effects of carbon content on the electrochemical properties of spherical pyrrhotine/carbon nanocomposites

Spherical pyrrhotine/carbon nanocomposites with different carbon contents were synthesized by a solvothermal method followed by heat treatment. The carbon content of the nanocomposites was controlled by changing the amount of the carbon precursor. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM); the influence of carbon layer thickness on the electrochemical performance was analyzed by charge/discharge cycling and X-ray photoelectron spectroscopy (XPS). Results show that the moderate carbon layer displays a positive effect in improving reversible capacity and the rate capability. The optimal carbon content in the pyrrhotine/carbon nanocomposites was about 15 wt.%, which can retain a high reversible capacity of 689.5 mAh/g even after 50 cycles at 0.1 C and an excellent rate capability of 393.4 mAh/g at 5 C. The synthesized nanocomposites show a promising potential as a novel anode material for lithium-ion batteries.     

Enhancing battery performance by nano Si addition to Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> as anode material on lithium-ion battery

The lithium-ion battery is a battery that is being developed to become a repository of energy, particularly for electric vehicles. Lithium titanate (Li₄Ti₅O₁₂) anodes are quite promising for this application because of its zero-strain properties so it can withstand the high rate. However, the capacity of LTO (Li₄Ti₅O₁₂) is still relatively low. Therefore, the LTO needs to be combined with other materials that have high capacity such as Si. Silicon has a very high capacity which is 4200 mAh/g, but it has a high volume of the expansion. Nano-size can also help increase the capacity. Therefore composite of LTO/nano Si is made to create an anode with a high capacity and also stability. Nano Si is added with a variation of 1, 5, and 10%. LTO/nano Si composite is characterized using XRD, SEM-EDX, and TEM-EDX. Then, to determine the battery performance, EIS, CV, and CD tests were conducted. From those tests, it is studied that Si improves the conductivity of the anode, but not significantly. The addition of Si results a greater battery capacity which is 262.54 mAh/g in the LTO-10% Si. Stability of composite LTO/nano Si is good, evidenced by the coulomb efficiency at the high rate of close to 100%.     

Facile synthesis of N-doped carbon-coated Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> anode for application in high-rate lithium ion batteries

A facile sol-gel approach for the synthesis of lithium titanate composite decorated with N-doped carbon material (LTO/NC) is proposed. Urea is used as a nitrogen source in the proposed approach. The LTO/NC exhibits superior electrochemical performances as an electrode material for lithium-ion batteries, delivering a discharge capacity of as high as 103 mAh g^?1 at a high rate of 20 C and retaining a stable reversible capacity of 90 mAh g^?1 after 1000 cycles, corresponding to 100% capacity retention. These excellent electrochemical performances are proved by the nanoscale structure and N-doped carbon coating. NC layers were uniformly dispersed on the surface of LTO, thus preventing agglomeration, favoring the rapid migration of the inserted Li ion, and increasing the Li⁺ diffusion coefficient and electronic conductivity. LTO with the appropriate amount of NC coating is a promising anode material with applications in the development of high-powered and durable lithium-ion batteries.     

Red phosphorus encapsulated in porous carbon derived from cigarette filter solid waste as a promising anode material for lithium-ion batteries

Red phosphorus (RP) is considered to be one of the promising anode materials for lithium-ion batteries (LIBs) on account of its high theoretical capacity (2596 mAh g^?1), abundant resources, and environmental friendliness. However, the intrinsic insulating nature and large volume change during lithium insertion/extraction process lead to drastic capacity loss upon cycling. Recently, great attention has been devoted to constructing P-based composites via mixing with carbon materials. Here, a novel P/C composite, in which red P nanoparticles were homogeneously distributed in cigarette filter-derived porous carbon (CPC), was fabricated by vaporization-condensation method. Due to the unique characteristics of porous carbon, including high specific area, good conductivity, and rich internal porous structure, CPC obtained by means of heat treatment that serves as conductive matrix to load red P could be of great benefits, which can not only improve the overall electrical conductivity but also mitigate the volume expansion issues. As a result, the RP/CPC composite as an anode material for LIBs delivers a good cycling stability (500 mAh g^?1 at 100 mA g^?1 with a high Coulombic efficiency above 99% after 50 cycles) and rate capability (355 mAh g^?1 even at 1000 mA g^?1).     

Synthesis of hierarchical nanospheres Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/graphene composite and its application in lithium-ion battery as a high-performance anode material

A hierarchically nanospherical α-Fe₂O₃/graphene composite with a homogeneous mono-pore size of 4 nm has been prepared using a hydrothermal method. The composite showed an extremely high rate performance and good cycling stability when applied as an anode material for lithium-ion batteries owing to its unique three dimensional architecture. A specific capacity of 110 mAh/g was obtained at an extremely high current rate of 40 A/g and recover to 830 mAh/g at 0.5 A/g after 60 cycles. After 250 cycles at 2 A/g, the composite electrode exhibited a capacity of 630 mAh/g with a columbic efficiency of 99.5 %.     

Template‐Free Fabrication of Hollow NiO–Carbon Hybrid Nanoparticle Aggregates with Improved Lithium Storage

Hollow NiO–carbon hybrid nanoparticle aggregates are fabricated through an environmental template‐free solvothermal alcoholysis route. Controlled hollow structure is achieved by adjusting the ratio of ethylene glycol to water and reaction time of solvothermal alcoholysis. Amorphous carbon can be loaded on the NiO nanoparticles uniformly in the solvothermal alcoholysis process, and the subsequent calcination results in the formation of hollow NiO–C hybrid nanoparticle aggregates. As anode materials for lithium‐ion batteries, it exhibits a stable reversible capacity of 622 mAh g^?1, and capacity retention keeps over 90.7% after 100 cycles at constant current density of 200 mA g^?1. The NiO–C electrode also exhibits good rate capabilities. The unique hollow structures can shorten the length of Li‐ion diffusion and offer a sufficient void space, which sufficiently alleviates the mechanical stress caused by volume change. The hybrid carbon in the particles renders the electrode having a good electronic conductivity. Here, the hollow NiO‐C hybrid electrode exhibits excellent electrochemical performance.     

DTT-doped MWCNT coating for checking shuttle effect of lithium-sulfur battery

In order to improve the rate and reversible capacity of lithium-sulfur (Li-S) battery, a reagent of dithiothreitol (DTT) was utilized to check the dissolution and shuttle of long-chain lithium polysulfides (LiPSs) by cutting the disulfide bond (–S–S– bonds) in them. The slurry of DTT-doped multi-walled carbon nanotubes (MWCNTs) was coated on the surface of sulfur cathode as a shield to slice the long-chain LiPSs to short-chain ones for checking the dissolution and migration of LiPSs to lithium anode. The morphology and structure of the electrodes were observed by scanning electron microscopy (SEM). The electrochemical performance was tested by galvanostatic charge-discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The initial discharge capacity of S-DTT- carbon nanotube paper (CNTP) electrode reached 1670 and 949 mAh/g at 0.05 and 2 C respectively with a coulombic efficiency of over 99%. The electrode maintained a reversible specific capacity of 949 mAh/g after 45 cycles at 2 C. This suggested that the DTT-doped MWCNT coating can restrain shuttle effect and improve the rate and capacity of Li-S battery. The S-DTT-CNTP electrode not only accommodates the volume expansion but also provides stable electronics and ions channels.     

Internal reforming in intermediate temperature solid oxide fuel cells running on natural gas

Methane steam reforming has been studied over a range of nickel/ceria-gadolinia cermet anodes, over the temperature range 500–700 °C appropriate for intermediate temperature ceriagadolinia based SOFCs. The influence of operating temperature and methane/steam ratio on the reforming characteristics, methane conversion and product selectivity, and the carbon deposition on the anode during reforming, has been determined for each anode. Nickel/ceria powders made from gas atomised intermetallic precursors have been studied as potential anode materials for intermediate temperature ceria-gadolinia based SOFCs running on natural gas. The powders have been characterised structurally and evaluated for their methane reforming characteristics and their resistance to carbon deposition during internal reforming, especially at low steam/methane ratios, over the relevant operating temperature ranges of ceriagadolinia based SOFCs. Their performance has been compared to conventionally prepared anodes and anodes generated from cast alloys, with very favourable results. Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002.     

Carbon@SnS<Subscript>2</Subscript> core-shell microspheres for lithium-ion battery anode materials

A novel unique C@SnS₂ core-shell structure composites consisting of well-dispersity carbon microspheres and ultrathin tin disulfide nanosheets were successfully synthesized for the first time through a simple solvothermal method. The thin SnS₂ nanosheets grew onto the carbon microspheres surfaces perpendicularly and formed the close-knit porous structure. When it was used as anode materials for lithium-ion batteries, the hybrid C@SnS₂ core-shell structure composites showed a remarkable electrochemical property than pure SnS₂ nanosheets. Typically, the hybrid composites with SnS₂ nanosheet shells and carbon microsphere’s core exhibited an excellent initial discharge capacity of 1611.6 mAh/g. Moreover, the hybrid composites exhibited capacities of 474.8–691.6 mAh/g at 100 mA/g over 50 battery cycles, while the pure SnS₂ could deliver capacities of 243–517.6 mAh/g in the tests. The results indicated that the improvement of lithium storage performance of the core-shell structure C@SnS₂ anode materials in terms of rate capability and cycling reversibility owing to the introduction of the smooth carbon microspheres and special designing of core-shell structure.     

One-pot synthesis and electrochemical property of MnO/C hybrid microspheres

In this paper, we reported a one-pot method to synthesize MnO/C hybrid microspheres via solvothermal approach for the first time. Only peaks of MnO could be observed from X-ray diffractometry patterns, indicating that the carbon in the composite was amorphous. Scanning electron microscope and transmission electron microscopy images showed that the surfaces of these as-prepared spheres were relatively smooth and of about 2.2 μm in diameter. Electrochemical property demonstrated that the annealed MnO/C hybrid microspheres possessed higher reversible capacity and cycling stability than that of MnO nanoparticles. The annealed MnO/C hybrid microspheres exhibited a large initial charge capacity of 856 mAh?g^?1, and the stabilized capacity was as high as 601 mAh?g^?1 after 30 cycles. These improvements can be ascribed to the amorphous carbon, which can enhance the conductivity of MnO, suppress the aggregation of active particles, and increase their structural stability during cycling.     

Characterization of a hybrid Li-ion anode system from pulsed laser deposited silicon on CVD-grown multilayer graphene

A hybrid anode system for lithium (Li) ion battery applications based on pulsed laser deposited silicon films on chemical vapor deposited multilayer graphene (MLG) layers on a nickel foam substrate was electrochemically characterized. The as-grown material was directly fabricated into an anode without a binder, and tested in a half-cell configuration. There is evidence of the participation of both the multilayer graphene and the Si in the transport of Li ions. Even when cycled under stressful voltage limits that accelerate degradation, the MLG–Si films displayed higher stability than Si-only anodes, especially at higher cycling rates. Unlike the Si cells that display capacity fade even within the first few cycles, the MLG–Si cells show a very narrow spread in capacity, indicative of the role of the graphene layers in improving adhesion of the Si and acting as a compliant buffer for its volume expansion. Stable average specific capacities of ~1,200 mAh/g per total weight of MLG + Si, over 80 cycles at C/5 rate, were obtained for the MLG–Si anode. Pre- and post-cycling characterization of the anode materials revealed the differences between the two systems.     

Porous NiO hollow quasi-nanospheres derived from a new metal-organic framework template as high-performance anode materials for lithium ion batteries

Porous hollow metal oxides derived from nanoscaled metal-organic framework (MOF) have drawn tremendous attention due to their high electrochemical performance in advanced Li-ion batteries (LIBs). In this work, porous NiO hollow quasi-nanospheres were fabricated by an ordinary refluxing reaction combination of a thermal decomposition of new nanostructured Ni-MOF, i.e., {Ni₃(HCOO)₆·DMF}_n. When evaluated as an anode material for lithium ion batteries, the MOF derived NiO electrode exhibits high capacity, good cycling stability and rate performance (760 mAh g^?1 at 200 mA g^?1 after 100 cycles, 392 mAh g^?1 at 3200 mA g^?1). This superior lithium storage performance is mainly attributed to the unique hollow and porous nanostructure of the as-synthesized NiO, which offer enough space to accommodate the dramstic volume change and alleviate the pulverization problem during the repeated lithiation/delithiation processes, and provide more electro-active sites for fast electrochemical reactions as well as promote lithium ions and electrons transfer at the electrolyte/electrode interface.     

Advanced LiTi<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C anode by incorporation of carbon nanotubes for aqueous lithium-ion batteries

Inferior rate capability is a big challenge for LiTi₂(PO₄)₃ anode for aqueous lithium-ion batteries. Herein, to address such issue, we synthesized a high-performance LiTi₂(PO₄)₃/carbon/carbon nanotube (LTP/C/CNT) composite by virtue of high-quality carbon coating and incorporation of good conductive network. The as-prepared LTP/C/CNT composite exhibits excellent rate performance with discharge capacity of 80.1 and 59.1 mAh g^?1 at 10 C and 20 C (based on the mass of anode, 1 C = 150 mA g^?1), much larger than that of the LTP/C composite (53.4 mAh g^?1 at 10 C, and 31.7 mAh g^?1 at 20 C). LTP/C/CNT also demonstrates outstanding cycling stability with capacity retention of 83.3 % after 1000 cycles at 5 C, superior to LTP/C without incorporation of CNTs (60.1 %). As verified, the excellent electrochemical performance of the LTP/C/CNT composite is attributed to the enhanced electrical conductivity, rapid charge transfer, and Li-ion diffusion because of the incorporation of CNTs.     

Effect of carbon coating on the electrochemical performance of LiFePO<Subscript>4</Subscript>/C as cathode materials for aqueous electrolyte lithium-ion battery

Organic electrolyte is widely used for lithium-ion rechargeable batteries but might cause flammable fumes or fire due to improper use such as overcharge or short circuit. That weakness encourages the development of tools and materials which are cheap and environmental friendly for rechargeable lithium-ion batteries with aqueous electrolyte. Lithium iron phosphate (LiFePO₄) with olivine structure is a potential candidate to be used as the cathode in aqueous electrolyte lithium-ion battery. However, LiFePO₄ has a low electronic conductivity compared to other cathodes. Conductive coating of LiFePO₄ was applied to improve the conductivity using sucrose as carbon source by heating to 600 °C for 3 h on an Argon atmosphere. The carbon-coated LiFePO₄ (LiFePO₄/C) was successfully prepared with three variations of the weight percentage of carbon. From the cyclic voltammetry, the addition of carbon coatings could improve the stability of cell battery in aqueous electrolyte. The result of galvanostatic charge/discharge shows that 9 % carbon exhibits the best result with the first specific discharge capacity of 13.3 mAh g^?1 and capacity fading by 2.2 % after 100 cycles. Although carbon coating enhances the conductivity of LiFePO₄, excessive addition of carbon could degrade the capacity of LiFePO₄.     

A facile synthesis of heteroatom-doped carbon framework anchored with TiO<Subscript>2</Subscript> nanoparticles for high performance lithium ion battery anodes

Titanium dioxide (TiO₂)-based materials have been well studied because of the high safety and excellent cycling performance when employed as anode materials for lithium ion batteries (LIBs), whereas, the relatively low theoretical capacity (only 335 mAh g^?1) and serious kinetic problems such as poor electrical conductivity (~?10^?13S cm^?1) and low lithium diffusion coefficient (~?10^?9 to 10^?13 cm² s^?1) hinder the development of the TiO₂-based anode materials. To overcome these drawbacks, we present a facile strategy to synthesize N/S dual-doping carbon framework anchored with TiO₂ nanoparticles (NSC@TiO₂) as LIBs anode. Typically, TiO₂ nanoparticles are anchored into the porous graphene-based sheets with N, S dual doping feature, which is produced by carbonization and KOH activation process. The as-obtained NSC@TiO₂ electrode exhibits a high specific capacity of 250 mAh g^?1 with a coulombic efficiency of 99% after 500 cycles at 200 mA g^?1 and excellent rate performance, indicating its promising as anode material for LIBs.     

Fabrication of urchin-like NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> microspheres assembled by using SDS as soft template for anode materials of Lithium-ion batteries

In this paper, the urchin-like NiCo₂O₄ microspheres assembled by using sodium dodecyl sulfate (SDS) as soft template are successfully fabricated by a facile procedure including microemulsion-solvothermal reaction and subsequent calcination at 400 °C for 4 h. The structure and morphology of synthesized NiCo₂O₄ particles are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It has been clearly revealed that the prepared three-dimensional urchin-like NiCo₂O₄ microspheres are constituted by one-dimension nanowires. As it is applied to anode for lithium-ion batteries (LIBs), the initial coulombic efficiency is up to 75.7%, and the specific reversible capacity retains up to 1034.2 mAh/g even after 40 cycles at a current density of 100 mA/g. Furthermore, as the current density gradually increases to 800 mA/g, it still delivers the reversible capacity of 895.4 mAh/g. The high reversible specific capacity, perfect cyclability, and rate performance are attributed to the unique urchin-like NiCo₂O₄ microspheres, which can alleviate the volume expansion and shorten the diffusion path of ions and electrons during lithiation/delithiation process. The self-standing urchin-like NiCo₂O₄ microspheres may be a very promising candidate in place of the commercial graphite-based anode materials for high-performance LIBs.     

Mesoporous carbon-titania nanocomposites for high-power Li-ion battery anode material

We have investigated the Li-ion battery anode properties of several kinds of mesoporous composites of carbon and titanium dioxides (titania, TiO₂) prepared by tri-constituent co-assembly method. The maximum reversible capacity (197 mAh/g) at current density of 50 mA/g was obtained for the composite of TiO₂:carbon=7:3 calcined at 600 °C. It was also found that the composite maintained the high reversible capacity as large as 109 mAh/g even at the high current density of 1000 mA/g.     

Nanocaging Silicon Nanoparticles into a Porous Carbon Framework toward Enhanced Lithium-Ion Storage

Silicon (Si) shows overwhelming promise as the high-capacity anode material of Li-ion batteries with high energy density. However, Si-based anodes are subjected to a limited electrochemical cycling lifetime due to their large volume change. Herein, a honeycomb-like biomass-derived carbon nanosheet framework is reported to encapsulate Si nanoparticles via a facile molten salt templating method. The carbon framework provides sufficient void space for effectively accommodating the large volume expansion of Si upon Li⁺ insertion. Moreover, the interconnected carbon skeletons afford fast electron/ion transport pathways for improving the reaction kinetics. Consequently, the porous Si/carbon composite could exhibit a high and stable Li storage capacity of 1022 mAh g⁻¹ at 0.2 A g⁻¹ over 100 cycles along with superior rate capability (555 mAh g⁻¹ at 5 A g⁻¹). This study demonstrates an effective structural design strategy for Si-based anodes toward stable lithium energy storage.