Effect of calcination temperature on the morphology and electrochemical properties of Co3O4 for lithium-ion battery

A simple approach to synthesize Co₃O₄ in mass production by using hexamethylenetetramine (HMT, C₆H₁₂N₄) as a precipitator via hydrothermal treatment has been developed. The samples were calcinated at different temperatures ranging from 300 to 600 °C and characterized by XRD and SEM. The structure became agglomerative and collapsed with an increase in calcination temperature. Evaluation of the electrochemical performance in combination with SEM and BET analysis suggests that there is an optimum calcination temperature for Co₃O₄. It is found that the retention capacity of well crystallized Co₃O₄ hollow microspheres has a higher specific surface area at 300 °C and is almost above 94% after the 5th cycle at different current densities of 40 and 60 mA g⁻¹, which shows good long-life stability and favorable electrochemical behaviors. Using EIS analysis, we demonstrated that lithium-ion conduction inside the SEI layers and charge transfer at the electrode/electrolyte interface became hindered with an increased calcination temperature, which was in good agreement with the electrochemical behaviors of three Co₃O₄ electrodes. It is proposed that drastic capacity fading and the variation of resistive components (SEI layers and charge transfer) can be influenced by morphologies due to the calcination temperature.     

Effect of synthesis temperature on the phase structure,morphology and electrochemical performance of Ti3C2 as an anode material for Li-ion batteries

Ti₃C₂, the most widely studied MXene, was successfully synthesised by etching Al layers from Ti₃AlC₂ in HF solution. Given its distinct 2D layered structure, Ti₃C₂ is a promising anode material in Li-ion batteries because of its efficient ion transport, available large surface areas for improved ion adsorption and fast surface redox reactions. Herein, the effects of synthesis temperature on the phase structure, morphology and electrochemical performance were investigated. The materials synthesised at different temperatures were characterised by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Optimal etching occurred at 100?°C, and the synthesised Ti₃C₂ exhibited smooth surface and large layer space. The synthesised Ti₃C₂, as anode material for Li-ion batteries, can accommodate more Li⁺ than those of others, and it exhibits the most ideal electrochemical performance.     

Facile strategy to fabricate Na2Li2Ti6O14@Li0.33La0.56TiO3 composites as promising anode materials for lithium-ion battery

A robust strategy has been developed to fabricate Na₂Li₂Ti₆O₁₄@Li_0.33La_0.56TiO₃ composites as promising anode materials for lithium-ion battery. Li_0.33La_0.56TiO₃ modification does not change the basic structure of Na₂Li₂Ti₆O₁₄ but enhances the lattice parameter because few trivalent lanthanum ions enter the crystal lattice of Na₂Li₂Ti₆O₁₄. All samples show similar morphology with a narrow size distribution ranged from 100 to 500?nm. HRTEM test demonstrates that a good conductive connection between the Na₂Li₂Ti₆O₁₄ and Li_0.33La_0.56TiO₃ layer is successfully formed. The electrochemical tests show that Na₂Li₂Ti₆O₁₄@Li_0.33La_0.56TiO₃ (5?wt%) sample exhibits the lowest charge-transfer resistance, highest reversibility of lithium insertion/extraction, and the largest Li-ion diffusion coefficient among all samples, and then shows the best electrochemical activity. Hence, the Na₂Li₂Ti₆O₁₄@Li_0.33La_0.56TiO₃ (5?wt%) electrode reveals the largest lithiation and delithiation capacities at each current density. The Na₂Li₂Ti₆O₁₄@Li_0.33La_0.56TiO₃ (5?wt%) shows excellent cycling stability with a delithiation capacity of 166.8?mAh?g^?1 at 500?mA?g^?1 after 100 cycles. However, the corresponding delithiation capacity of pristine Na₂Li₂Ti₆O₁₄ is only 136.9?mAh?g^?1 after 100 cycles. Li_.33La_.56TiO₃ modification is a direct and powerful design method to enhance the delithiation and lithiation capacities and cycling stability of Na₂Li₂Ti₆O₁₄.     

Effect of Sn doping on the electrochemical performance of NaTi2(PO4)3/C composite

In this paper, NaTi_2-xSn_x(PO₄)₃/C (x?=?0.0, 0.2, 0.3, and 0.4) composites were fabricated via facile sol-gel method, and employed as anodes for aqueous lithium ion batteries. Effect of Sn doping with various content on electrochemical properties of NaTi₂(PO₄)₃/C was investigated systematically. Sn doping on Ti site has no obvious effect on the lattice structure and morphology of NaTi₂(PO₄)₃/C. Among all samples, NaTi_1.7Sn_0.3(PO₄)₃/C (NC-Sn-3) demonstrates the best electrochemical properties. NC-Sn-3 exhibits the outstanding rate performance, delivering a discharge capacity of 103.3, 95.2, and 87.4?mAh?g^?1 at 0.5, 7, and 20?°C, respectively, 1.7, 30.5, and 56.2?mAh?g^?1 larger than those of pristine NaTi₂(PO₄)₃/C. In addition, NC-Sn-3 shows excellent cycling performance with the capacity retention of 80.6% after 1000 cycles at 5?°C. This work reveals that Sn doped NaTi₂(PO₄)₃/C with outstanding electrochemical properties are potential anode for aqueous lithium ion batteries.     

Li6V10O28, a novel cathode material for Li-ion battery

A novel cathode material, lithium decavanadate Li₆V₁₀O₂₈ with a large tunnel within the framework structure for lithium ion battery has been prepared by hydrothermal synthesis and annealing dehydration treatment. The structure and electrochemical properties of the sample have been investigated. The novel material shows good reversibility for Li⁺ insertion/extraction and long cycle life. High discharge capacity (132 mAh/g) is obtained at 0.2 mA/cm² discharge current and potential range between 2.0 and 4.2 V versus Li⁺/Li. AC impedance of the Li/Li₆V₁₀O₂₈ cell reveals that the cathode process is controlled mainly by Li⁺ diffusion in the active material. The novel material would be a promising cathode material for Li-ion batteries.     

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.     

A simple and effective method to synthesize layered LiNi0.8Co0.1Mn0.1O2 cathode materials for lithium ion battery

Nanocrystalline materials of Ni_0.8Co_0.1Mn_0.1(OH)₂ are successfully synthesized by fast co-precipitation method. The crystalline structure and morphology of the precursors and LiNi_0.8Co_0.1Mn_0.1O₂ materials are characterized by XRD, SEM and Rietveld refinement analyses. It is found that the nanocrystalline phase and low crystallinity of Ni_0.8Co_0.1Mn_0.1(OH)₂ could help achieve its uniform mixing with lithium source, and further attribute to highly ordered layered LiNi_0.8Co_0.1Mn_0.1O₂ with low cation mixing degree. Electrochemical studies confirm that the LiNi_0.8Co_0.1Mn_0.1O₂ exhibits a good electrochemical property with initial discharge specific capacity of 192.4 mAh g^− 1 at a current density of 18 mA g^− 1, and the capacity retention after 40 cycles is 91.56%. This method is a simple and effective method to synthesize cathode material.     

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.     

Carbon-coated Bi5Nb3O15 as anode material in rechargeable batteries for enhanced lithium storage

Bismuth can alloy with lithium to generate Li₃Bi with the volumetric capacity of about 3765 mAh cm^?3 (386 mAh g^?1), rendering bismuth-based materials as attractive alloying-type electrode materials for rechargeable batteries. In this work, bismuth-based material Bi₅Nb₃O₁₅ @C is fabricated as anode material through a traditional solid-state reaction with glucose as carbon source. Bi₅Nb₃O₁₅ @C composite is well dispersed, with small particle size of 0.5–2.0?µm. The electrochemical performance of Bi₅Nb₃O₁₅ @C is reinforced by carbon-coated layer as desired. The Bi₅Nb₃O₁₅ @C exhibits a high specific capacity of 338.56 mAh g^?1 at a current density of 100?mA?g^?1. And it also presents an excellent cycling stability with a capacity of 212.06 mAh g^?1 over 100 cycles at 100?mA?g^?1. As a comparison, bulk Bi₅Nb₃O₁₅ without carbon-coating only remains 319.62 mAh g^?1 at 100?mA?g^?1, revealing poor cycle and rate performances. Furthermore, in-situ X-ray diffraction experiments investigate the alloying/dealloying behavior of Bi₅Nb₃O₁₅ @C. These insights will benefit the discovery of novel anode materials for lithium-ion batteries.     

Crystal structure and electrochemical performance of Li3V2(PO4)3 synthesized by optimized microwave solid-state synthesis route

To investigate the crystal structure and electrochemical performance of samples synthesized under different microwave solid-state synthesis condition, a series of Li₃V₂(PO₄)₃ samples has been synthesized at five different temperatures for 3-5 min and at 750 °C for various time. The as-synthesized Li₃V₂(PO₄)₃ samples are characterized and studied by ICP-AES analysis, X-ray diffraction (XRD), Rietveld analysis, scanning and transmission electron microcopy (SEM and TEM). At relatively lower temperature (650 °C) and very short reaction time (3 min), pure phase of Li₃V₂(PO₄)₃ could be synthesized in microwave irradiation field. The crystal structure and Li atomic fractional coordinate present a significant deviation upon the change of microwave irradiation temperature and time. Relatively, the diffusion ability of lithium cations and the electrochemical performance are affected. Under the proper reaction temperature and time, the carbon-free samples MW750C5m and MW850C3m show the best specific discharge capacity 126.4 and 132 mAh g⁻¹ at the voltage range of 3.0-4.3 V, near the reversible cycling of two lithium ions per Li₃V₂(PO₄)₃ formula unit (133 mAh g⁻¹). At the voltage range of 3-4.8 V, the sample MW750C5m presents the best initial specific charge capacity of 197 mAh g⁻¹, equivalent to the reversible cycling of three lithium ions per Li₃V₂(PO₄)₃ formula unit (197 mAh g⁻¹). The initial discharge capacity, the samples MW750C5m and MW850C3m present high specific discharge capacity 183.4 and 175.7 mAh g⁻¹, respectively. The relationship among microwave irradiation condition, crystal structure, lithium atomic fractional coordinates and the electrochemical performance have been discussed in detail.     

Synthesis and electrochemical studies of a layered spheric TiO2 through low temperature solvothermal method

This paper demonstrates a low temperature solvothermal method for the synthesis of a layered spheric TiO₂. The crystal structure and morphology of the material were characterized by using X-ray diffraction (XRD) and scanning electron miscopy (SEM). Electrochemical performances of the TiO₂ when used as anode material in lithium ion batteries were investigated by galvanostatic charge/discharge and cyclic voltammetry experiments. A discharge capacity of 179 mAh g⁻¹ was obtained in the potential range between 3.0 and 1.5 V. No significant capacity decay was observed in the successive 30 cycles showing satisfactory cycling performance of the electrode.     

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.     

Effects of fluorine doping on the electrochemical properties of LiV3O8 cathode material

A series of fluorine-doped lithium trivanadates LiV₃O_8−yF_z (z = 0, 0.03, 0.05, 0.1, 0.15, 0.2 and 0.5) were synthesized by the solid-state reaction. X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscope (SEM) tests show that a proper amount of fluorine substituting for oxygen in LiV₃O₈ can modify its structure and surface morphology. Charge-discharge tests show that the doped samples with a proper amount of fluorine display good cycling stability, high coulombic efficiency and good rate capability, compared with undoped sample. The cyclic voltammetry (CV), area-specific impedance (ASI) and electrochemical impedance spectroscopy (EIS) tests indicate that the doped samples with a low fluorine content can stabilize the interface between the surface layer of the active particles and the electrolyte after cycling, while a high fluorine content form an unstable interface. The fluorine substitution is a convenient and effective method for improving the electrochemical performances of LiV₃O₈.     

Facile synthesis and electrochemical performance of nitrogen-doped porous hollow coaxial carbon fiber/Co3O4 composite

Economy and efficiency are two important indexes of lithium-ion batteries (LIBs) materials. In this work, nitrogen doped hollow porous coaxial carbon fiber/Co₃O₄ composite (N-PHCCF/Co₃O₄) is fabricated using the fibers of waste bamboo leaves as the template and carbon resource by soaking and thermal treatment, respectively. The N-PHCCF/Co₃O₄ exhibits an outstanding electrochemical performance as anode material for lithium ion batteries, due to the nitrogen doping, coaxial configuration and porous structure. Specifically, it delivers a high discharge reversible specific capacity of 887 mA h g^?1 after 100 cycles at the current density of 100 mA g^?1. Furthermore a high capability of 415 mA h g^?1 even at 1 A g^?1 is exhibited. Most impressively, the whole process is facile and scalable,exhibiting recycling of resource and turning waste into treasure in an eco-friendly way.     

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.     

Improvement of cycle performance of lithium ion cell LiMn2O4/LixV2O5 with aqueous solution electrolyte by polypyrrole coating on anode

The reasons of capacity fading during cycling process of LiMn₂O₄/Li_xV₂O₅ lithium ion cell with 5 M LiNO₃ aqueous solution as electrolyte were investigated. XRD and ICP results showed that the properties of the anode have more impact on the cycle life of the cell. In an attempt to improve the cycle performance of the as-assembled cell, coating with an ionic conductive polypyrrole (PPy) on the surface of the anode was proposed via in situ polymerization method. Cycling tests revealed that the stability of the lithium ion cell with surface coated anode has been greatly improved. Moreover, the capability of the cell with coated anode was also enhanced compared with the cell with bare anode.     

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.     

In-situ grown hierarchical ZnCo2O4 nanosheets on nickel foam as binder-free anode for lithium ion batteries

Nickle foam-supported hierarchical ZnCo₂O₄ nanosheets was prepared via a facile solution-based method. Porous ZnCo₂O₄ nanosheets were in-situ grown on current collector, forming a binder-free electrode. When evaluated as anode for Lithium ion batteries (LIB_S), the binder-free electrode showed an attractive electrochemical performance. A reversible capacity of 773?mAh?g^?1 could be stably delivered after a 500-cycle test at a current density of 0.25?A?g^?1, with a high capacity retention of 87%. The electrode could maintain a high reversible capacity of 245?mA?h?g^?1 even at an elevated current density of 8.0?A?g^?1. Integrated structure and rich porosity of the binder-free electrode were believed to contribute to the superior performance. Thus, the Nickle foam-supported ZnCo₂O₄ electrode is a promising anode for high performance LIBs in the coming future.     

Improving electrochemical performance of graphitic carbon in PC-based electrolyte by nano-TiO2 coating

Graphitic carbon was coated with nano-TiO₂ by a simple mechanical process. X-ray diffraction and scanning electron microscopy were used to measure the crystal structure and surface morphology of the coated composite. Tests of galvanostatic discharge and charge and cyclic voltammograms suggest that the decomposition of propylene carbonate and the exfoliation of graphite are greatly suppressed. Lithium ions can reversibly intercalate into and deintercalate from the TiO₂-coated graphite, and quite stable cycling behavior in propylene carbonate-based electrolyte is achieved.     

Preparation and electrochemical properties of LiCoO2-LiNi0.5Mn0.5O2-Li2MnO3 solid solutions with high Mn contents

The solid solutions LiCoO₂-LiNi_1/2Mn_1/2O₂-Li₂MnO₃ with higher Mn content have been prepared by a spray drying method between 750 and 950 °C and their electrochemical performances have also been characterized. The effects of the Li content on the structure and electrochemical performance of the samples have been studied. It was found that their lattice parameters a, c and V increase with the increase in Ni content and the decrease in Co content. The solid solutions xLiCoO₂-yLiNi_1/2Mn_1/2O₂-(1−x−y)Li₂MnO₃ with x = 0.18, 0.27 and y = 0.2 have the largest discharge capacity, which is more than 200 mAh/g in the voltages of 3.0-4.6 V. It is believed that the optimum Co content x in xLiCoO₂-yLiNi_1/2Mn_1/2O₂-(1−x−y)Li₂MnO₃ is between 0.2 and 0.3 in the charge-discharge voltage range of 3.0-4.6 V. The solid solutions xLiCoO₂-yLiNi_1/2Mn_1/2O₂-(1−x−y)Li₂MnO₃ with x = 0.18-0.36 and y = 0.2 have the excellent cycling performance and the capacity retention attains to almost 100% after 50 cycles. Moreover, it is found that the discharge capacity gradually increases with the increment of cycle number especially in the initial 10 cycles. XRD showed that the layered structure has been kept all the time in 20 cycles, which is perhaps the reason why the sample has the excellent cycling performance.