Multiwalled nanotube-coated mesophase carbon microbeads for use as anode material in lithium ion batteries

The recent developments in lithium ion secondary batteries (LIBs) have been achieved by using selected carbon materials as the anode. Mesophase carbon microbead (MCMB) anode materials have stable Li intercalation and de-intercalation characteristics, making them a good anode material for use in LIBs. However, batteries with pure MCMB anodes are known to have a low power density. Multiwalled carbon nanotubes (MWNTs) are one of the most promising materials for improving a range of electrochemical energy conversion and storage devices because of their unique physical properties, including high electrical conductivity and superior chemical and mechanical stability. Therefore, in this study, MWNTs were deposited on the surface of MCMB anodes to improve their electrical conductivity. The anode materials were separately functionalized using carboxylic acid and amine groups to form MWNT-COOH and MCMB-NH₂, respectively, providing them with surfaces of opposite charge. The surface morphology was assessed using scanning electron microscopy, and the electrochemical characteristics were analyzed by cyclic voltammetry and AC impedance measurements in a coin cell. The AC impedance and cyclic voltammetry measurements indicated that MCMBs with MWNTs deposited on their surfaces are promising electrode materials, providing high power density for LIBs.     

High-rate capability of carbon-coated micron-sized hexagonal TT-Nb2O5 composites for lithium-ion battery

With excellent specific capacity, superior cycle stability, safety and strong practical, Nb₂O₅ has been considered as one of the prospective anode materials for lithium-ion batteries (LIBs). However, current study suggests that Nb₂O₅ electrode materials for LIBs still face the vital issues of low electrical conductivity and poor rate performance. Therefore, carbon-coated TT-Nb₂O₅ materials are designed and synthesized through solid state method in this work, which present high specific capacity (228 mA h g^?1 at 0.2C), satisfactory rate properties (107 mA h g^?1 at 20 C). The outstanding electrochemical property can not only give the credit to the pseudocapacitance effect of TT-Nb₂O₅, but also attribute to introduction of carbon. The homogeneous carbon-coated materials enhance the electrical conductivity, increase the electron transmission speed and alleviate particle crushing. This research not only offers a new method for preparing excellent electrode materials, but also provides a kind of excellent anode material with prospective application for LIBs.     

Uniform α-Fe2O3 nanoparticles with narrow gap immobilized on CNTs through N-doped carbon as high-performance lithium-ion batteries anode

Fe₂O₃ with high theoretical capacity, low cost, and environmental friendliness has been attracted great attention in lithium-ion batteries (LIBs), which however is limited by low rate capability and fast capacity fading owing to low electronic conductivity, self-aggregation, and sever volume expansion. CNTs with excellent conductivity and unique 3D interconnected network are ideal matrices for composite electrochemical materials, but it is difficult to meet the demand of high capacity. Here, uniform α-Fe₂O₃ nanoparticles with narrow gap (~1.4 nm) were immobilized on CNTs through N-doped carbon (α-Fe₂O₃/CNTs-NC) that can address these issues. As an advanced LIBs anode, the electrode displays unprecedented specific capacity (1173 mAh/g at 0.2 A/g) and outstanding rate behavior (716.4 mAh/g at 5.0 A/g after 1200 cycles), which are even superior to the theoretical capacity (1007 mAh/g) and the performance of most reported Fe₂O₃-based anodes. Homogeneous nano-sized α-Fe₂O₃ with a narrow gap highly shortens the diffusion path for Li⁺ transport, exposes quite sufficient active sites, and prevents the volume change. Moreover, the 3D backbone of CNTs with a more homogeneously distributed electric field can enhance conductivity, and tightly contact with α-Fe₂O₃ by NC, then obtain robust structural stability, which boosts LIBs in storage capacity, rate capability, and cycling stability.     

NiFe-NiFe2O4/rGO composites: Controlled preparation and superior lithium storage properties

Binary transition-metal oxides with spinel structure have great potential as advanced anode materials for lithium-ion batteries (LIBs). Herein, NiFe-NiFe₂O₄/ reduced graphene oxide (rGO) composites are obtained via a facile cyanometallic framework precursor strategy to improve the lithium storage performance of NiFe₂O₄. In the composites, NiFe-NiFe₂O₄ nanoparticles with adjustable mass ratios of NiFe₂O₄ to NiFe alloy are homogeneously deposited on rGO sheets. As anode material for LIBs, the optimized NiFe-NiFe₂O₄/rGO composite displays remarkably enhanced lithium storage performance with an initial specific capacity as high as 1362 mAh g⁻¹ at 0.1 A g⁻¹ and a decent capacity retention of ca. 80% after 130 cycles. Besides, the composite delivers a reversible capacity of 550 mAh g⁻¹ at 1 A g⁻¹ after 300 cycles. During the charge–discharge cycles, the aggregation of the NiFe-NiFe₂O₄ nanoparticles and the structural collapse of the electrode can be well alleviated by rGO sheets. Moreover, the conductivity of the electrode can be significantly improved by the well-conductive NiFe alloy and rGO sheets. All these contribute to the improved lithium storage performance of NiFe-NiFe₂O₄/rGO composites.     

Carbon-coated porous Si/C composite anode materials via two-step etching/coating processes for lithium-ion batteries

A highly stable Si/SiO_x/C composite was synthesized in this study through NaOH etching and carbon-coating approaches for use as an anode material in Li-ion batteries (LIBs). The two-step process not only enhanced the electronic conductivity of the as-synthesized Si/SiO_x/C composite by using the two-step etching/coating processes to enhance the columbic efficiency of Si during cycling processes but also architecturally provided an amorphous Si/SiO_x composite to buffer volume expansion. The Raman spectroscopy and X-ray diffraction results demonstrate that the etching process involves a transition from crystalline Si to amorphous SiO_x. The Fourier transform infrared spectroscopy results further confirm that the vibration mode of Si–O bonding changes from symmetric to asymmetric. The Brunauer–Emmett–Teller analysis reveals that we can control specific surface area and pore-size distribution of NaOH-modified Si by tuning the parameters pertaining to the solid content of Si in NaOH solution. After optimizing the etching and carbon-coating processes, the modified Si/C composite delivered ~780 mAh g⁻¹ for more than 200 cycles at 0.5C, which was better than un-modified one of 315 mAh g⁻¹ after 200 cycles. The results clearly indicate that we could improve cycle stability of Si anode drastically through the NaOH etching process and carbon coating modification. The proposed methodology may provide a potential approach to promoting the synthesis of Si-based anodes for use in the commercial applications of LIBs.     

A review study on the recent advances in developing the heteroatom-doped graphene and porous graphene as superior anode materials for Li-ion batteries

Graphene materials, with their distinctively fascinating physicochemical properties, have been receiving great attention as favorable anode materials for use in Li-ion batteries (LIBs). However, the high affinity of graphene nanosheets to restack and agglomerate during electrode assembly reduces the deliverable specific capacity due to the limited available surface area and active sites for Li-ion storage. Furthermore, the high aspect ratio of graphene nanosheets could result in long transport pathways for Li-ions and consequently limiting the rate performance. These drawbacks can be significantly improved via the functionalization of graphene by various heteroatoms and also the formation of porous graphene, adding unique beneficial properties to the inherent characteristics of graphene. Here, a comprehensive review of porous and/or heteroatom doped graphene anode materials for LIBs is presented, which summarizes in detail the main recent literature from their procedure, optimum synthesis parameters, relevant mechanisms, and the obtained morphology/structure to their electrochemical performance as the LIBs anode. Finally, the research gaps are proposed. This review will promote the basic understanding and further development of porous and/or doped graphene materials as anodes for LIBs.     

Electrochemical performance of La<Subscript>0.75</Subscript>Sr<Subscript>0.25</Subscript>Cr<Subscript>0.9</Subscript>M<Subscript>0.1</Subscript>O<Subscript>3</Subscript> perovskites as SOFC anodes in CO/CO<Subscript>2</Subscript> mixtures

The performance of La_0.75Sr_0.25Cr_0.9M_0.1O₃ (M = Mn, Fe, Co, and Ni) perovskitic materials as anodes was studied for a CO-fueled solid oxide fuel cell. The electrocatalytic performance and the tolerance to carbon deposition were investigated, while electrochemical characterization was carried out via AC impedance spectroscopy and cyclic voltammetry. The La_0.75Sr_0.25Cr_0.9Fe_0.1O₃ perovskite showed the best anode performance at temperatures above 900 °C; while at temperatures below 900 °C, the best performance was achieved with the La_0.75Sr_0.25Cr_0.9Co_0.1O₃ material. AC impedance spectroscopy was used for a semi-quantitative analysis of the LSC-M_0.1 anodes performance in view of total cell and charge transfer resistance. All anode materials exhibit high electronic conductivity and presumably do not substantially contribute to the overall cell resistance and concomitant ohmic losses.     

Electrochemical performance of Ni1−xFex–Ce0.8Gd0.2O1.9 cermet anodes for solid oxide fuel cells using hydrocarbon fuel

Ni_1?xFe_x bimetallic-based cermet anodes were investigated for hydrocarbon-fueled solid oxide fuel cells. Ni_1?xFe_x–Ce_0.8Gd_0.2O_1.9 cermet anodes were synthesized using a glycine nitrate process, and their electrical conductivity and the amount of carbon deposits were found to decrease with increasing Fe content. The anode polarization resistance for the CH₄ fuel was significantly reduced by Fe alloying, which was strongly related to the carbon deposition behavior. The maximum power density of the single cell with Ni_0.85Fe_0.15–Ce_0.8Gd_0.2O_1.9 in CH₄ at 800 °C was 0.27 W/cm². Fe alloying significantly improved the electrochemical performance of solid oxide fuel cells in CH₄ fuel by suppressing carbon deposition.     

NiCo2O4 nanosheets and nanocones as additive-free anodes for high-performance Li-ion batteries

Development of novel electrode materials with high energy and power densities for lithium-ion batteries (LIBs) is the key to meet the demands of electric vehicles. Transition metal oxides that can react with large amounts of Li⁺ for electrochemical energy storage are considered promising anode materials for LIBs. In this work, NiCo₂O₄ nanosheets and nanocones on Ni foam have been synthesized via general hydrothermal growth and low-temperature annealing treatment. They exhibit high rate capacities and good cyclic performance as LIB anodes owing to their architecture design, which reduces ion and electron transport distance, expands the electrode–electrolyte contact, increases the structural stability, and buffers volume change during cycles. Notably, NiCo₂O₄ nanosheets deliver an initial capacity of 2239 mAh g⁻¹ and a rate capacity of 964 mAh g⁻¹ at current densities of 100 and 5000 mA g⁻¹, respectively. The corresponding values of nanocones are 1912 and 714 mAh g⁻¹. Hence, the as-synthesized NiCo₂O₄ nanosheets and nanocones, which are carbon-free and binder-free with higher energy densities and stronger connections between active materials and current collectors for better stability, are promising for use in advanced anodes for high-performance LIBs.     

Hollow Co2SiO4 microcube with amorphous structure as anode material for construction of high performance lithium ion battery

To solve the problem of large volume expansion of cobalt silicate electrode during cyclic process and low electric conductivity, Co₂SiO₄ with amorphous, porous and hollow structure is firstly designed to act as high performance lithium ion battery (LIB) anode. Compared with crystalline materials, the amorphous Co₂SiO₄ microcube could facilitate Li⁺ diffusion to enhance their performance of LIBs because of isotropic characteristics. Here, the amorphous Co₂SiO₄ hollow microcube (named as a-Co₂SiO₄ HC) was prepared by mild hydrothermal method with use of MnCO₃ microcube as hard-template. Benefitting from the advantages of such structure, Li⁺ diffusion rate was greatly accelerated and the volume expansion can be alleviated. The as-prepared amorphous Co₂SiO₄ hollow microcube as anode material of LIBs exhibited significantly improved electrochemical performance of 610 mAh g⁻¹ even after 380 cycles at 500 mAh g⁻¹ than their crystalline counterpart (only 280 mAh g⁻¹ retained after 380 cycles). This work is a good try to employ amorphous metal silicate in LIBs and simultaneously motivate the exploration of other amorphous materials for high performance LIBs, SIBs, catalysts, etc.     

In situ growth of LaSr(Fe,Mo)O4 ceramic anodes with exsolved Fe–Ni nanoparticles for SOFCs: Electrochemical performance and stability in H2, CO,and syngas

Fe–Ni nanoparticle–decorated LaSr(Fe,Mo)O₄ Ruddlesden–Popper (R–P) perovskite anodes, named R–LSFMNx, were prepared in situ by reducing perovskites La_0.5Sr_0.5Fe_0.9Mo_0.1–xNi_xO_3–δ (LSFMNx; x = 0.03–0.07) under SOFC anode operating conditions. Electrolyte–supported single cells with a configuration of R–LSFMNx|La_0.9Sr_0.1Ga_0.8Mg_0.2O_3–δ (LSGM)|Ba_0.5Sr_0.5Co_0.9Nb_0.1O_3–δ were used to evaluate the electrochemical performances and redox/long–term stability of the R–LSFMNx anodes fuelled by H₂, CO, and simulated syngases (x% H₂/CO; x = 50–10). EIS analyses indicated that the increased Ni level in the exsolved Fe–Ni nanocatalysts significantly promotes fuel diffusion/adsorption/dissociation, which plays a rate–limiting role in the anode fuel oxidation. Furthermore, the incremental Ni in Fe–Ni alloy also enhances the anode redox/long–term stability and carbon resistance/tolerance, and the R–LSFMN0.07 anode, i.e., Ni level in Fe–Ni alloy attaining ～14 mol.%, displays the optimal stability and carbon resistance/tolerance. Finally, the potential of the R–LSFMN0.07 anode for direct utilization of syngas was demonstrated by the characterization of the electrochemical performance and stability based on the R–LSFMN0.07 anode cell.     

Synthesis and characterization of GaNb11O29@C for high-performance lithium-ion battery

The GaNb₁₁O₂₉ shows an open Wadsley-Roth shear structure, which is of great benefit to store ions in rechargeable batteries. In this work, we successfully synthesize GaNb₁₁O₂₉@C via a simple solid-state reaction method combined with carbon-coating modification. As anode for LIBs, the as-synthesized GaNb₁₁O₂₉@C sample exhibits wonderful electrochemical behaviors. It exhibits high reversible capacity (227.3 mA h g⁻¹), outstanding rate capability (58.91% retention at 700 mA g⁻¹) and excellent long cycle performance (0.036% capacity decay per cycle). The enhancement of diffusion kinetics and rate performance assigns to the increased surface reaction activity and electrical conductivity. The open and stable crystal framework structure guarantees rapid lithium-ion migration, excellent rate performance and long cycle performance. These results tell that GaNb₁₁O₂₉@C is promising anode material for the application in advanced LIBs.     

A Lignin-Based Carbon Anode with Long-Cycle Stability for Li-Ion Batteries

Due to its wide source and low cost, biomass-based hard carbon is considered a valuable anode for lithium-ion batteries (LIBs). Lignins, as the second most abundant source in nature, are being intensively studied as candidate anode materials for next generation LIBs. However, direct carbonization of pure lignin usually leads to low specific surface area and porosity. In this paper, we design a porous carbon material from natural lignin assisted by sacrificing a metal–organic framework (MOF) as the template. The MOF nanoparticles can disperse the lignin particles uniformly and form abundant mesopores in the composites to offer fast transfer channels for Li⁺. The as-prepared carbon anode shows a high specific capacity of 420 mAh g⁻¹ with the capacity retention of 99% after 300 cycles at 0.2 A g⁻¹. Additionally, it keeps the capacity retention of 85% after long cycle of 1000 cycles, indicating the good application value of the designed anode in LIBs. The work provides a renewable and low-cost candidate anode and a feasible design strategy of the anode materials for LIBs.     

Microwave-assisted one-pot synthesis of SnC2O4/graphene composite anode material for lithium-ion batteries

Currently, SnC₂O₄ is considered as one of the most promising anode materials for high-energy lithium-ion batteries (LIBs) because its charge capacity is higher than that of metal oxides. Herein, a facile microwave-assisted solvothermal method was employed to obtain SnC₂O₄/GO composites within only 30?min, which is time-efficient. The amount of SnC₂O₄ was increased to 95.3?wt% to improve the capacity of the composite. Pure SnC₂O₄ with a high specific surface area of 19.6?m² g^?1 without any other tin compound was used for fabrication. The SnC₂O₄/GO composite exhibited excellent electrochemical performance, with reversible discharge/charge capacity of 657/659?mA?h?g^?1 after 100 cycles at 0.2?A?g^?1. Furthermore, at high current densities of 1.0 and 2.0?A?g^?1, the SnC₂O₄/GO composite anode exhibited high reversible discharge/charge capacities of 553/552 and 418/414?mA?h?g^?1, respectively, after 200 cycles at room temperature. These improvements were likely obtained because SnC₂O₄ was well composited with graphene, which not only offered rapid electron transfer but also released the tension produced by the volumetric effect during repeated lithiation/delithiation. Cyclic voltammetry (CV) was also performed to further study the electrochemical reactions of SnC₂O₄/GO. The facile microwave-assisted solvothermal method used herein is considered as a highly efficient method to fabricate metal oxalate/graphene composites for use as anode materials in LIBs.     

Si/C composite lithium-ion battery anodes synthesized from coarse silicon and citric acid through combined ball milling and thermal pyrolysis

Silicon and related materials have recently received considerable attention as potential anodes in Li-ion batteries for their high theoretical specific capacities. To overcome the problem of volume variations during the Li insertion/extraction process, in this work, Si/C composites with low carbon content were synthesized from cheap coarse silicon and citric acid by simple ball milling and subsequent thermal treatment. The effects of ball milling time and calcination temperature on the structure, composition and morphology of the composites were systematically investigated by the determination of specific surface area (BET) and particle-size distribution, X-ray diffraction (XRD), O₂-TPO, and scanning electron microscopy (SEM). The capacity and cycling stability of the composites were systematically evaluated by electrochemical charge/discharge tests. It was found that both the initial capacity and the cycling stability of the composites were dependent on the milling and calcination conditions, and attractive overall electrochemical performance could be obtained by optimizing the synthesis process.     

In-situ synthesis of reduced graphene oxide wrapped Mn3O4 nanocomposite as anode materials for high-performance lithium-ion batteries

We report a novel in-situ symbiosis method to prepare reduced graphene oxide wrapped Mn₃O₄ nanoparticles (rGO/Mn₃O₄) with uniform size about 50 nm as anodes for lithium-ion batteries (LIBs), which can simplify the preparation process and effectively reduce pollution. The rGO/Mn₃O₄ nanocomposite exhibited a reversible specific capacity of 795.5 mAh g^?1 at 100 mA g^?1 after 200 cycles (capacity retention: 87.4%), which benefits from the unique structural advantages and the synergistic effect of rGO and Mn₃O₄. The Mn₃O₄ nanoparticles encapsulated among the rGO nanosheets exhibited good electrochemical activity, and the multilayer wrinkled rGO sheets provided a stable 3D conduction channel for Li⁺/e^? transport. The rGO/Mn₃O₄ nanocomposite is a promising anode candidate for advanced LIBs with excellent cycling performance and rate performance. Furthermore, this new preparation method can be extended to green and economical synthesis of advanced graphene/manganese-based nanocomposites.     

Synthesis and electrochemical analysis of Sn2Fe-TiOx-C composite as a high-performance anode material for Li-ion batteries

Tin-based intermetallic compounds are regarded as a promising alternative for Li secondary battery anodes due to their high specific and volumetric capacity, as well as their low operating potential. However, the materials’ cycling performance still cannot meet the required standards for commercialization. In this study, we designed and synthesized a Sn₂Fe-TiO_x-C composite as a high-capacity anode material via high-energy mechanical milling and hydrogen treatment. The synthesized material was characterized by several analytical tools. The reaction mechanism of the composite electrode with Li was investigated with ex situ X-ray diffraction analysis, and the conversion of Sn₂Fe to Li–Sn alloy and Fe during Li insertion and its reversibility were confirmed. The results of an electrochemical test showed that a reversible capacity of 651 mAh g^?1 was retained after 100 cycles. This cycling stability could be attributed to the microstructure in which Sn₂Fe was uniformly distributed in the TiO_x and carbon matrix. Additionally, there was an improvement in rate performance after hydrogen treatment because titanium oxide produced during mechanical milling was partially reduced, which was helpful for enhancing the electrical conductivity of the composite electrode.     

Ti2Nb10O29@C hollow submicron ribbons for superior lithium storage

Titanium niobate prepared by traditional techniques has the shortcomings of low ion diffusion coefficient as well as poor electrical conductivity, which drastically reduce its applicability. In this work, we prepare carbon coated Ti₂Nb₁₀O₂₉ hollow submicron ribbons (Ti₂Nb₁₀O₂₉@C HSR) using a simple electrospinning procedure. As anode material for lithium-ion batteries (LIBs), it delivers a high charge capacity of 259.7 mAh g^?1 at 1 C with low capacity loss of 0.013% in long-term cycles. Increased the current density to 5 C, Ti₂Nb₁₀O₂₉@C HSR can maintain a reversible capacity of 189.9 mAh g^?1, indicating its good rate performance. Additionally, this work uses in-situ X-ray diffraction (XRD) to provide an explanation for the lithium storage process in Ti₂Nb₁₀O₂₉@C HSR, demonstrating the high reversibility during charge/discharge cycles. Therefore, Ti₂Nb₁₀O₂₉@C HSR has outstanding cycle adaptability and structural reversibility to be a promising anode for LIBs.     

Carbon-Coated SnO2 Nanorod Array for Lithium-Ion Battery Anode Material

Carbon-coated SnO₂ nanorod array directly grown on the substrate has been prepared by a two-step hydrothermal method for anode material of lithium-ion batteries (LIBs). The structural, morphological and electrochemical properties were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical measurement. When used as anodes for LIBs with high current density, as-obtained array reveals excellent cycling stability and rate capability. This straightforward approach can be extended to the synthesis of other carbon-coated metal oxides for application of LIBs.     

Decorating ZnO nanoflakes on carbon cloth: Free-standing,highly stable lithium-ion battery anodes

A facile chemical bath deposition method to grow 10-nm-thick ZnO nanoflakes (NFs) on carbon cloth (CC) was developed; further, free-standing, flexible lithium-ion -battery (LIB) anodes with good electrical contact between current collector and the active substance were prepared. The as-prepared ZnO NFs/CC-based LIB anodes showed a high specific capacity of 1754 mAh g⁻¹ at a current density of 0.1 A g⁻¹, a capacity retention of almost 52.9% at a current density of 2 A g⁻¹, as well as high rate capability. Moreover, the anodes demonstrated a high capacity with reversiblity of approximately 1650 mAh g⁻¹ and only 6% capacity fading at a current density of 0.1 A g⁻¹, even after 100 cycles. These results imply that the synthesized, unique ZnO NFs/CC nanostructures can be employed as high-efficiency anode materials for flexible LIBs.