Nanowires embedded porous TiO2@C nanocomposite anodes for enhanced stable lithium and sodium ion battery performance

A porous carbon nanocomposite with embedded TiO₂ nanowires (NWs) was synthesized using a two-step synthetic method in which carbon matrix was obtained by carbonizing a vacuum dried gel. This unique structure in which TiO₂ nanowires uniformly distributed in and tightly bonded to the carbon matrix shortened the electron transport path and reduced the transmission resistance. Nanoporous structure ensured continuous transfer of Li⁺/Na⁺ and supplied a large specific surface area of 280.82 m² g⁻¹ to provide more active sites. Different from other existing works on TiO₂@C anode materials with TiO₂ loading higher than 60 wt%, the obtained very small amount of TiO₂ (~12 wt%) improved the electrochemical and long-cycle performance of carbon substrate with TiO₂ NWs embedded significantly, due to uniformly distributed TiO₂ NWs throughout the carbon matrix. These TiO₂@C composite anodes could deliver a specific capacity of 286 mA h g⁻¹ at 0.3 C, 197 mA h g⁻¹ at 0.15 C for lithium and sodium ion batteries, respectively. It maintained remarkably stable reversible capacities of 128 and 125 mA h g⁻¹ for lithium and sodium ion batteries at 3 C during 2500 cycles, respectively. Smaller fluctuations and smoother curves demonstrated that sodium ion storage was more stable than lithium ion storage for the TiO₂@C composite anode. In addition, the capacitive contributions of TiO₂@C in both systems are quantified by kinetics analysis.     

One-dimensional Ti2Nb10O29 nanowire for enhanced lithium storage

Among a variety of host materials for lithium storage, titanium-niobium oxides exhibit great potential in application. Herein, Ti₂Nb₁₀O₂₉ nanowire is synthesized via an electrospinning method. Compared with bulk Ti₂Nb₁₀O₂₉ prepared by solid-state approach, the electrochemical properties of Ti₂Nb₁₀O₂₉ nanowire is better. According to the galvanostatic charging-discharging test, the initial capacity of 232.8 mAh g^?1 for Ti₂Nb₁₀O₂₉ nanowire is displayed. Besides, it exhibits superior rate performance. With the current density set as 0.5, 1, 2, 3, 4 and 5 C, the Ti₂Nb₁₀O₂₉ nanowire can deliver the specific capacity of 251.3, 240.3, 221.8, 205.3, 188.1 and 174.5 mAh g^?1, respectively. Furthermore, its cycling performance is superior. The capacity retention of Ti₂Nb₁₀O₂₉ nanowire is 85.90% after 900 cycles at 12 C, which is obviously superior than that of bulk Ti₂Nb₁₀O₂₉ (25.16%). Finally, a Ti₂Nb₁₀O₂₉/LiCoO₂ full cell is fabricated, which exhibits excellent electrochemical performance, demonstrating its potential for practical application.     

Compositing SrLi2Ti6O14 with chemical deposited silver for enhancing lithium ion storage

One of the main issues for titanium-based anode materials is their poor electronic conductivity and this issue can affect their rate performance. For conquering this drawback, many approaches have been proposed. In this report, SrLi₂Ti₆O₁₄ as one of the titanium-based anode materials is prepared via a facile sol–gel method and subsequently it has been composited with silver to elevate its electronic conductivity. Upon the analysis of electrochemical results, the SrLi₂Ti₆O₁₄/Ag composite with 6?wt% Ag can deliver an initial capacity of 164.9?mAh?g^?1. After 50 cycles, the sample can still retain 154.6?mAh?g^?1 with 93.8% retention of the first cycle. Meanwhile, the SrLi₂Ti₆O₁₄/Ag composite with 6?wt% Ag can also exhibit good rate capacities, even at 300?mA?g^?1, its capacity can be firmly kept at 140.0?mAh?g^?1. In addition, in situ X-ray diffraction characterization shows the structural reversibility of the SrLi₂Ti₆O₁₄/Ag composite with 6?wt% Ag during cycling. All the electrochemical results indicate that the SrLi₂Ti₆O₁₄/Ag composite with 6?wt% Ag can be a promising anode material for lithium ion batteries.     

Facile synthesis of CuO mesocrystal/MWCNT composites as anode materials for high areal capacity lithium ion batteries

CuO mesocrystal entangled with multi-wall carbon nanotube (MWCNT) composites are synthesized through a facile scalable precipitation and a followed oriented aggregation process. When evaluated as anode materials for lithium ion batteries, the CuO-MWCNT composites exhibit high areal capacity and good cycling stability (1.11 mA h cm⁻² after 400 cycles at the current density of 0.39 mA cm⁻²). The excellent electrochemical performance can be ascribed to the synergy effect of the unique structure of defect-rich CuO mesocrystals and the flexible conductive MWCNTs. The assembled architecture of CuO mesocrystals can favor the Li-ion transport and accommodate the volume change effectively, as well as possess the structural and chemical stability of bulk materials, while the entangled MWCNTs can maintain the structural and electrical integrity of the electrode during the cycles.     

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.     

Facile synthesis of porous hollow Co3O4 microfibers derived-from metal-organic frameworks as an advanced anode for lithium ion batteries

Co₃O₄, as a promising anode material for the next generation lithium ion batteries to replace graphite, displays high theoretical capacity (890 mAh g⁻¹) and excellent electrochemical properties. However, the drawbacks of its poor cycle performance caused by large volume changes during charge-discharge process and low initial coulombic efficiency due to large irreversible reaction impede its practical application. Herein, we have developed a porous hollow Co₃O₄ microfiber with 500 nm diameter and 60 nm wall thickness synthesized via a facile chemical precipitation method with subsequent thermal decomposition. As an advanced anode for lithium ion batteries, the porous hollow Co₃O₄ microfibers deliver an obviously enhanced electrochemical property in terms of lithium storage capacity (1177.4 mA h g⁻¹ at 100 mA g⁻¹), initial coulombic efficiency (82.9%) and cycle performance (76.6% capacity retention at 200th cycle). This enhancement could be attributed to the well-designed microstructure of porous hollow Co₃O₄ microfibers, which could increase the contact surface area between electrolyte and active materials and accommodate the volume variations via additional void space during cycling.     

Synthesis of porous hollow six-branched star-like MnO and its enhanced electrochemical properties as a lithium ion anode material

Novel structured porous hollow six-branched star-like MnO was synthesized via a facile, surfactant-free hydrothermal decomposition, which was followed by high-temperature heat treatment. Compared with the nonporous hollow six-branched star-like MnO₂, the porous hollow six-branched star-like MnO realized substantially higher electrochemical performance (844.8 mAh g⁻¹ at 0.5 A g⁻¹ after 200 cycles and 769.7, 741.7, 728.9, 713.2, and 704.4 mAh g⁻¹ at 0.1, 0.3, 0.5, 1, and 1.5 A g⁻¹, respectively, for porous star-like MnO, compared with 338.4 mAh g⁻¹ and 476.7, 392.4, 357, 303.4, and 269.9, respectively, under the same testing conditions for nonporous star-like MnO₂). The superior performance of the porous hollow six-branched star-like MnO is attributed to its enhanced electrode kinetics, which are due to an enlarged active contact area and shortened electron and Li⁺ conduction paths.     

Effects of TiO2 starting materials on the synthesis of Li2ZnTi3O8 for lithium ion battery anode

Lithium zinc titanate (Li₂ZnTi₃O₈) anode materials have been successfully synthesized using rutile-TiO₂ with different particle sizes as titanium sources via a molten-salt method. Various physical and electrochemical methods are applied to characterize the effects of TiO₂ particle sizes on the structures and physicochemical properties of the Li₂ZnTi₃O₈ materials. When the particle size of TiO₂ is too small (10 nm), it is difficult to homogeneously mix TiO₂ with the other raw materials. Thus, the final product Li₂ZnTi₃O₈ has poor crystallinity, large particle size, small specific surface area, pore volume and average pore diameter, which are disadvantageous to its electrochemical performance. Using TiO₂ with the proper particle size of 100 nm as the titanium source, the Li₂ZnTi₃O₈ (R-100-LZTO) with excellent electrochemical performance can be obtained. At 1 A g⁻¹, 175.8 and 163.6 mA h g⁻¹ are delivered at the 1st and the 200th cycles, respectively. The largest capacities of 163, 133.3 and 122.5 mA h g⁻¹ are delivered at 2.5, 5 and 6 A g⁻¹, respectively. The good high-rate performance of the R-100-LZTO originates from the good crystallinity, small particle size, large specific surface area and average pore diameter, low charge-transfer resistance and high Li⁺ diffusion coefficient.     

A hierarchical porous carbon material for high power, lithium ion batteries

We synthesize a carbon anode material with unique nanostructure for high power lithium ion batteries. The carbon material is composed of numerous clusters of carbon nanobeads, and shows a macro-meso-micro hierarchical porous structure. This unique nanostructure appears to facilitate the rapid transfer of lithium ions and a very large ion adsorption. It exhibits a reversible capacity of 407.4 mAh g⁻¹ and its rate performance is drastically improved in comparison with that of the commercial graphite. The unique structure enables the anode to combine the advantages of both lithium ion batteries and electrochemical double layer capacitors, resulting in the good electrochemical performance.     

Simple solution-combustion synthesis of Fe2TiO5 nanomaterials with enhanced lithium storage properties

The porous Fe₂TiO₅ particles are successfully synthesized through a facile one step solution combustion method. The Fe₂TiO₅ negative materials exhibit remarkable electrochemical performance with discharge capacities of 371.4?mAh g^?1 at the 100 th cycle, and display promising rate stability with discharge capacities 76.6?mAh·g^?1 at a high current density of 3.2?A?g^?1. In addition, the mechanism of electrochemistry reaction is illustrated by the CV, raman and EIS measurements, the irreversible capacity mainly causes from the irreversible lithium insertion at 1.8?V. The results indicate that the one step solution combustion synthesis of porous Fe₂TiO₅ is a promising strategy for developing low-cost and high-performance Ti-based negative materials.     

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.     

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

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

Lithium storage behaviors of PbNb2O6 in rechargeable batteries

Herein, we propose a new anode material, PbNb₂O₆, for use in lithium-ion batteries. PbNb₂O₆ can be synthesized via a simple and traditional solid-state method. The as-prepared powder exhibits an average size distribution of about 0.5 μm. When tested in a lithium-ion cell, the PbNb₂O₆ electrode can exhibit a charge capacity of 245.2 mAh g⁻¹ at 200 mA g⁻¹, and after 80 cycles, the capacity can retain a charge capacity of 181.4 mAh g⁻¹, showing 0.32% capacity fading per cycle. Furthermore, the capacity of the PbNb₂O₆ electrode is 223.1 mAh g⁻¹, even when cycled at 1000 mA g⁻¹, and a capacity of 150.7 mAh g⁻¹ is maintained up to 500 cycles. In addition, the lithiation mechanism of PbNb₂O₆ is investigated via various techniques. Interestingly, PbNb₂O₆ exhibits high capacity without the contribution of two redox couples of niobium after the initial cycles. Finally, all Results suggest that PbNb₂O₆ has potential for use as an electrode in lithium-ion batteries.     

Bi-component MnO/ZnO hollow microspheres embedded in reduced graphene oxide as electrode materials for enhanced lithium storage

Novel composite of bi-component MnO/ZnO (denoted as MZO) hollow microspheres embedded in reduced graphene oxide (RGO) as a high performance electrode material for Lithium ion batteries (LIBs) is prepared via one-pot hydrothermal method and subsequent annealing. The structures and morphologies of as-prepared hybrid materials are characterized by X-ray diffraction, scanning electron microscopy, Raman spectra, FTIR and transmission electron microscopy. The results reveal that the MZO hollow microspheres with nanometer-sized building blocks are well dispersed in the RGO support. The electrochemical tests show that the hybrid material has a reversible capacity of 660 mAh/g at a current density of 100 mA/g with a coulombic efficiency of 98% after 100 cycles. Besides, a specific capacity of about 207 mAh/g is retained even at a current density as high as 1600 mA/g, exhibiting high reversibility and good capacity retention. Our results suggest that the composite of bi-component MZO hollow microspheres embedded in RGO will be promising electrode materials for low-cost, environmentally friendly and high-performance LIBs.     

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.     

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.     

Molten hydroxides synthesis of hierarchical cobalt oxide nanostructure and its application as anode material for lithium ion batteries

Hierarchical Co₃O₄ nanostructure is synthesized via a self-assembled process in molten hydroxides. The morphologies, crystal structures and the phase transformation processes are analyzed by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. As an anode material for lithium ion batteries, the hierarchical Co₃O₄ exhibit an initial capacity of 1336 mAh g⁻¹ and a stable capacity of 680 mAh g⁻¹ over 50 cycles. More importantly, high rate capability is obtained at different current densities between 140 and 1120 mA g⁻¹. The improved electrochemical performance of Co₃O₄ could be attributed to the unique hierarchical nanostructure.     

Nanoscale SnS with and without carbon-coatings as an anode material for lithium ion batteries

SnS nanoparticles were mechnochemical synthesized and then co-heated with polyvinyl alcohol (PVA) at various temperatures to obtain carbon coating. All amorphous carbon-coated SnS particles had average particle size of about 20-30 nm, revealed by transmission electron microscopy (TEM). During discharge-charge, ex situ XRD results indicated that SnS firstly decomposed to Sn, then lithium ions intercalated into Sn. The reaction of Li⁺ and Sn was responsible for the reversible capacity in cycling process. The lithium ion insertion and extraction mechanism of SnS anode was similar to that of Sn-based oxide. Electrochemical capacity retention of carbon-coated SnS obtained at 700 °C was superior to that of other prepared SnS anodes and especially the rate capability was obviously enhanced due to good electric conductivity and buffering matrix effects of carbon coating.     

NiSe2 encapsulated in N-doped TiN/carbon nanoparticles intertwined with CNTs for enhanced Na-ion storage by pseudocapacitance

Transitional metal selenides are considered as potential anode candidates for sodium-ion batteries (SIBs) because of their relatively high theoretical capacity and environmental benign. However, the large volume change derived from the conversion reaction and the sluggish kinetics due to the inherent low electrochemical conductivity hinder their practical application. Herein, composite materials of NiSe₂ encapsulated in nitrogen-doped TiN/carbon nanoparticles with carbon nanotubes (CNTs) on the surface (NiSe₂@N-TCP/CNTs) are fabricated via pyrolysis and selenization processes. In this composite, TiN inside the carbon matrix can enhance the conductivity and structural stability. CNTs that are in-situ grown on the surface not only further enhance the conductivity of the composites, but also offer sufficient space to buffer the volume expansion and alleviate serious aggregation of NiSe₂ nanoparticles. Benefit from these merits, the NiSe₂@N-TCP/CNTs showed a lower charge transfer resistance and a faster Na⁺ diffusion rate than materials without growing CNTs. When used as the anode of SIBs, the NiSe₂@N-TCP/CNTs electrode delivered a reversible capacity of 344.0 mAh g^?1 after 1000 cycles at 0.2 A g^?1, and still maintained at 272.7 mAh g^?1 even at a high current density of 2 A g^?1. The remarkable electrochemical performance is mainly attributed to the special designed hierarchical structures and pseudocapacitance sodium storage behavior.     

金属有机聚合物基负极材料的制备及其储锂性能Q

为了寻求优异电化学性能的新型金属有机聚合物基负极材料，以偏苯三甲酸作为有机配体和六水硝酸钴进行配位，通过水热法合成了一种新型的钴基金属有机聚合物（Co-MOP）。在空气气氛下，对Co-MOP分别以500 ℃、600 ℃、700 ℃高温煅烧获得相应的Co-MOP-500、Co-MOP-600、Co-MOP-700衍生材料。Co-MOP衍生材料用作锂离子电池负极材料进行了研究。电化学测试结果显示Co-MOP-600展现出了优异的电化学性能。在100 mA/g的电流密度下，Co-MOP-600电极的首圈放电比容量达到1818.5 mAh/g，循环100圈后比容量还能维持1308.5 mAh/g。