N- and S-doped ordered mesoporous carbon tubes with efficient S confinement for high-performance Li–S batteries

The insulating properties of S/Li₂S₂/Li₂S and the soluble Li₂S₄/Li₂S₆/Li₂S₈ obstruct the practical application of Li–S batteries. In this work, highly ordered N and S co-doped mesoporous carbon tubes (NSMCTBs) with high specific surface areas and large pore volume are employed to confine and improve the utilization efficiency of S species in Li–S batteries. The strong S_nLi₂?N interaction and S–S chemical bond between thiophenic S and Li₂S_n guarantee the exceptional electrochemical performance of as-prepared NSMCTBs/S cathode. A relatively high discharge capacity of 1315.2 mAh g^?1 is achieved for the first cycle at 0.5 C and maintained at 644.1 mAh g^?1 after 500 cycles. The NSMCTBs/S with high S content of up to 80%, it also delivers a discharge capacity of 1092.1 mAh g^?1 and considerable cycling performance. More importantly, the NSMCTBs/S can effectively suppress the self-discharge behavior of Li–S batteries.     

Synthesis of Li4Ti5O12 fibers as a high-rate electrode material for lithium-ion batteries

Porous lithium titanate (Li₄Ti₅O₁₂) fibers, composed of interconnected nanoparticles, are synthesized by thermally treating electrospun precursor fibers and utilized as an energy storage material for rechargeable lithium-ion batteries. The material is characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and thermal analysis. Scanning electron microscopy results show that the Li₄Ti₅O₁₂ fibers calcined at 700?°C have an average diameter of 230?nm. Especially, the individual fiber is composed of nanoparticles with an average diameter of 47.5?nm. Electrochemical properties of the material are evaluated using cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy. The results show that as-prepared Li₄Ti₅O₁₂ exhibits good cycling capacity and rate capability. At the charge–discharge rate of 0.2, 0.5, 1, 2, 10, 20, 40, and 60?C, its discharge capacities are 172.4, 168.2, 163.3, 155.9, 138.7, 123.4, 108.8, and 90.4?mAh?g^?1, respectively. After 300 cycles at 20?C, it remained at 120.1?mAh?g^?1. The obtained results thus strongly support that the electrospun Li₄Ti₅O₁₂ fibers could be one of the most promising candidate anode materials for lithium-ion batteries in electric vehicles.     

Porous carbon nanotubes improved sulfur composite cathode for lithium-sulfur battery

Porous multi-walled carbon nanotubes (PCNTs) with multiple mesopores structure are synthesized through activation of multi-walled carbon nanotubes (MWCNTs) by potassium hydroxide. The potassium hydroxide activation process results in a significantly enhanced specific surface area with numerous small pores. The as-obtained PCNTs are employed as the conductive matrix for sulfur in the sulfur cathode. Compared with the composite sulfur cathode based on the original MWCNTs, the sulfur-PCNTs cathode shows a significantly improved cycle performance and columbic efficiency. The reversible capacity is 530 mAh?g^?1 and columbic efficiency is 90 % after 100 cycles at a current density of 100 mA?g^?1. The improvement in the electrochemical performance for S-PCNT is mainly attributed to the enlarged surface area and the porous structure of the unique mesopores carbon nanotube host, which cannot only facilitate transport of electrons and Li⁺ ions, but also trap polysulfides, retard the shuttle effect during charge/discharge process.     

Comparative investigations of LiVPO4F/C and Li3V2(PO4)3/C synthesized in similar soft chemical route

Triclinic LiVPO₄F and monoclinic Li₃V₂(PO₄)₃ are synthesized through a soft chemical process with mechanical activation assist, followed by annealing. In this process, ascorbic acid is used as reducing agent as well as carbon source. The as-prepared samples are coated with amorphous carbon. XPS analysis results show the expected valency states of ions in LiVPO₄F and Li₃V₂(PO₄)₃. The electrochemical properties of the prepared LiVPO₄F/C and Li₃V₂(PO₄)₃/C cathodes are evaluated. The as-prepared LiVPO₄F/C cathode shows an initial discharge specific capacity of 140?±?3 mAh?g^?1 at 30 mA?g^?1 in the voltage range of 3.0~4.4 V, compared with that of 138?±?3 mAh?g^?1 possessed by Li₃V₂(PO₄)₃/C. Both samples exhibit good cycle performance at different current densities. The capacity delivered by LiVPO₄F remains 95.5 and 91.7 % of its initial discharge capacity after 50 cycles at 150 and 750 mA?g^?1, respectively, while 97.4 and 90.6 % for Li₃V₂(PO₄)₃/C. But the rate capability of LiVPO₄F/C is not so good compared with as-prepared Li₃V₂(PO₄)₃/C.     

Synthesis of γ-LiV2O5 nanorods as a high-performance cathode for Li ion battery

One-dimension γ-LiV₂O₅ nanorods were synthesized using VO₂(B) nanorods as precursor in this study. The as-prepared material is characterized by X-ray diffraction, X-ray photoelectron spectrometry, Fourier-transform infrared, transmission electron microscopy (TEM), cyclic voltammetry, and charge–discharge cycling test. TEM results show that LiV₂O₅ nanorods are 90–250 nm in diameter. The nanorods deliver a maximum discharge capacity of 284.3 mAh g^?1 at 15 mA g^?1 and 270.2 mAh g^?1 is maintained at the 15th cycle. Good rate performance is also observed with the discharge capacity of 250.1 and 202.6 mAh g^?1 at 50 and 300 mA g^?1, respectively. The capacity retention at 300 mA g^?1 is 84.2% over 50 cycles. The Li⁺ diffusion coefficient of LiV₂O₅ is calculated to be 10^-10–10^?9 cm² s^?1. It is demonstrated that the nanorod morphology could greatly facilitate to shorten lithium ion diffusion pathways and increase the contact area between active material and electrolyte, resulting in high capacity and rate performance for LiV₂O₅.     

Facile simultaneous polymerization enabled in-situ confinement of size-tailored GeO2 nanocrystals in continuous S-Doped carbons for lithium storage

GeO₂ is a promising anode material for lithium ion batteries due to its high theoretical capacity (1126 mAh g^?1 for reversibly storing 4.4 Li⁺), and moderately low operating voltage (<1.5 V). Nevertheless, the fabrication of truly durable GeO₂ anode with satisfactory rate capability and cycling stability remains a big challenge because of its inherent low conductivity, and the large volume expansion upon charge-discharge that causes severe capacity fading. In this study, an innovative nanostructure with size-adjustable GeO₂ nanoparticles (16–26 nm) embedded in continuous S-doped carbon (GeO₂/S-doped carbon, GSC) has been successfully fabricated via a facile in-situ simultaneous polymerization method followed by heat treatment. The electrochemical results indicate that the as-prepared GSC composites show high reversible capacity (672.9 mAh g^?1 at 50 mA g^?1), superior rate capability (332.9 mAh g^?1 at 1000 mA g^?1), and long-term cycle life (179 mAh g^?1 after 500 cycles at 1000 mA g^?1) as anode materials for lithium ion batteries. The excellent electrochemical performance of GSC nanocomposites could be ascribed to the homogeneous and continuous S-doped carbon matrix, which provides shortened ion diffusion pathway, increased electrical conductivity, enhanced structural stability, and introduced surface/interface property.     

Activated hierarchical porous carbon@π-conjugated polymer composite as cathode for high-performance lithium storage

Organic compounds become promising candidates for cathodes of rechargeable lithium battery (RLB) due to the high theoretical capacity and improved safety. However, they exhibit low conductivity and easy dissolution in electrolyte, which leads to the low utilization of active materials and poor cycling stability of RLBs. Here, we synthesize a novel composite of activated hierarchical porous carbon supporting poly(1,5-diamino-anthraquinone) (aHPC@PDAA), using Ce(SO₄)₂ as oxidant and naphthalenesulfonic acid (NSA) as soft template for PDAA. The as-synthesized composite exhibits uniformly nanoporous structure with nano-sized PDAA particles distributed homogenously inside and outside of pores. The aHPC@PDAA cathode for RLBs achieves high electrochemical performance with a discharge capacity as much as 250 mAh g^?1 at the current density of 100 mA g^?1, which still maintains 176 mAh g^?1 after 2000 charging-discharging cycles.     

Sol-assisted spray-drying synthesis of porous Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C microspheres as high-activity cathode materials for lithium-ion batteries

Herein, porous Li₃V₂(PO₄)₃/C microspheres made of nanoparticles are obtained by a combination of sol spray-drying and subsequent-sintering process. Beta-cyclodextrin serves as a special chelating agent and carbon source to obtain carbon-coated Li₃V₂(PO₄)₃ grains with the size of ca. 30–50?nm. The unique porous structure and continuous carbon skeleton facilitate the fast transport of lithium ion and electron. The Li₃V₂(PO₄)₃/C microspheres offer an outstanding electrochemical performance, which present a discharge capacity of 122?mAh?g^?1 at 2?C with capacity retention of 96% at the end of 1000 cycles and a high-rate capacity of 113?mAh?g^?1 at 20?C in the voltage window of 3.0–4.3?V. Moreover, the Li₃V₂(PO₄)₃/C microspheres also give considerable cycling stability and high-rate reversible capacity at a higher end-of-charge voltage of 4.8?V.

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Li+/Mg2+ Hybrid‐Ion Batteries with Long Cycle Life and High Rate Capability Employing MoS2 Nano Flowers as the Cathode Material

The demand for large‐scale and safe energy storage is increasing rapidly due to the strong push for smartphones and electric vehicles. As a result, Li⁺/Mg²⁺ hybrid‐ion batteries (LMIBs) combining a dendrite‐free deposition of Mg anode and Li⁺ intercalation cathode have attracted considerable attention. Here, a LMIB with hydrothermal‐prepared MoS₂ nano flowers as cathode material was prepared. The battery showed remarkable electrochemical properties with a large discharge capacity (243 mAh g^?1 at the 0.1 C rate), excellent rate capability (108 mAh g^?1 at the 5 C rate), and long cycle life (87.2 % capacity retention after 2300 cycles). Electrochemical analysis showed that the reactions occurring in the battery cell involved Mg stripping/plating at the anode side and Li⁺ intercalation at the cathode side with a small contribution from Mg²⁺ adsorption. The excellent electrochemical performance and extremely safe cell system show promise for its use in practical applications.     

Nanostructured Carbon/Antimony Composites as Anode Materials for Lithium‐Ion Batteries with Long Life

A series of nanostructured carbon/antimony composites have been successfully synthesized by a simple sol–gel, high‐temperature carbon thermal reduction process. In the carbon/antimony composites, antimony nanoparticles are homogeneously dispersed in the pyrolyzed nanoporous carbon matrix. As an anode material for lithium‐ion batteries, the C/Sb10 composite displays a high initial discharge capacity of 1214.6 mAh g^?1 and a reversible charge capacity of 595.5 mAh g^?1 with a corresponding coulombic efficiency of 49 % in the first cycle. In addition, it exhibits a high reversible discharge capacity of 466.2 mAh g^?1 at a current density of 100 mA g^?1 after 200 cycles and a high rate discharge capacity of 354.4 mAh g^?1 at a current density of 1000 mA g^?1. The excellent cycling stability and rate discharge performance of the C/Sb10 composite could be due to the uniform dispersion of antimony nanoparticles in the porous carbon matrix, which can buffer the volume expansion and maintain the integrity of the electrode during the charge–discharge cycles.     

Preparation of Li2SnO3 and its application in lithium‐ion batteries

Tin‐based oxide Li₂SnO₃ has been synthesized by a hydrothermal route as negative material for lithium‐ion batteries. The microstructure and electrochemical properties of the as‐synthesized materials were investigated by some characterizations means and electrochemical measurements. The as‐synthesized Li₂SnO₃ is a porous rod, which is composed of many uniform and regular nano‐flakes with a size of 50–60 nm. Li₂SnO₃ also displays an electrochemical performance with high capacity and good cycling stability (510.2 mAh g^?1 after 50 cycles at a current density of 60 mA g^?1 between 0.0 V and 2.0 V verusus Li/Li⁺). Copyright © 2013 John Wiley & Sons, Ltd.     

Three‐Dimensional MoS2 Hierarchical Nanoarchitectures Anchored into a Carbon Layer as Graphene Analogues with Improved Lithium Ion Storage Performance

Much attention has recently been focused on the synthesis and application of graphene analogues of layered nanomaterials owing to their better electrochemical performance than the bulk counterparts. We synthesized graphene analogue of 3D MoS₂ hierarchical nanoarchitectures through a facile hydrothermal route. The graphene‐like MoS₂ nanosheets are uniformly dispersed in an amorphous carbon matrix produced in situ by hydrothermal carbonization. The interlaminar distance between the MoS₂ nanosheets is about 1.38 nm, which is far larger than that of bulk MoS₂ (0.62 nm). Such a layered architecture is especially beneficial for the intercalation and deintercalation of Li⁺. When tested as a lithium‐storage anode material, the graphene‐like MoS₂ hierarchical nanoarchitectures exhibit high specific capacity, superior rate capability, and enhanced cycling performance. This material shows a high reversible capacity of 813.5 mAh g^?1 at a current density of 1000 mA g^?1 after 100 cycles and a specific capacity as high as 600 mAh g^?1 could be retained even at a current density of 4000 mA g^?1. The results further demonstrate that constructing 3D graphene‐like hierarchical nanoarchitectures can effectively improve the electrochemical performance of electrode materials.     

Synthesis of Li3Ni x V2−x (PO4)3/C cathode materials and their electrochemical performance for lithium ion batteries

Li₃Ni _x V_2?x (PO₄)₃/C (x?=?0, 0.02, 0.04 and 0.06) samples have been synthesized via an improved sol–gel method. X-ray diffraction patterns indicate that the structure of the prepared samples retains monoclinic, and the single phase has not been changed with Ni doping. From the analysis of electrochemical performance, the Li₃Ni_0.04?V_1.96(PO₄)₃/C sample exhibits the best electrochemical property. It delivers a discharge capacity of 112.1 mAh?g^?1 with capacity retention of 95.2 % over 300 cycles at 10 C rate in the range of 3.0–4.8 V; cyclic voltammetry and electrochemical impedance spectra testing further prove that the electrochemical reversibility and lithium ion diffusion behavior of Li₃V₂(PO₄)₃ have also been effectively improved through Ni doping.     

Study of carbon surface-modified Li[Li0.2Mn0.54Ni0.13Co0.13]O2 for high-capacity lithium ion battery cathode

Carbon surface-modified Li-excess layered oxide solid solution Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ cathode is fabricated through a liquid phase route using polyvinylpyrrolidone as carbon source. X-ray diffraction and X-ray photoelectron spectroscopy indicate that the crystal structure and the chemical states of elements for Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ are kept after carbon surface treatment. The high-resolution transmission electron microscopy demonstrated the existence of very little carbon on the surface and the clear boundary after carbon treatment. The carbon surface-modified sample delivers a discharge capacity of 293.2 mAh?g^?1 at C/10 rate (suppose 1 C rate?=?250 mA?g^?1) and 191.6 mAh?g^?1 at 1 C rate between 2.0 and 4.8 V; the capacity retention rate is ～86 % after 70 cycles at 1 C rate. Superior electrochemical properties can be contributed to the carbon surface modification in these aspects including minimizing nanoparticle aggregation and cell polarization, increasing the electronic conductivity, suppressing the elimination of oxide ion vacancies, as well as suppressing the formation of the thick solid electrolyte interfacial layer. Moreover, the annealing process of carbon surface modification might be able to consume Li₂CO₃ impurity partly and cause the recrystallization of the surface disordered layer.     

Multistep sintering preparation and electrochemical performances of LiFe0.7 V0.2PO4/C cathode material for lithium-ion batteries

Cathode material LiFe_0.7?V_0.2PO₄/C is successfully synthesized by multistep sintering through carbon thermal reaction including 650 °C for 10 h and 750 °C for 6 h. The crystal structure and surface morphology of the synthesized materials are characterized by X-ray diffractometer and scanning electron microscope, respectively. Cycle voltammetry, electrochemical impedance spectroscopy, and charge–discharge test are used to investigate the electrochemical performances of these samples. The results revealed that the synthesized LiFe_0.7?V_0.2PO₄/C material simultaneously contains olivine structure LiFePO₄ and monoclinic structure Li₃V₂(PO₄)₃. It shows improved conductivity, Li-ion diffusion coefficient, excellent charge/discharge performance, and reversibility due to both the incorporation of Li₃V₂(PO₄)₃ fast ion conductor and the employed multistep sintering. The initial discharge specific capacities of LiFe_0.7?V_0.2PO₄/C by multistep sintering are 167.8, 154.7, and 140.8 mAh g^?1 at 0.5, 1, and 2 C, respectively. After a total of 230 cycles at different rates, the sample still shows good performances. After 100 cycles at 2 C, the capacity retention is 99.1 %, and the capacity is 139.6 mAh g^?1. The LiFe_0.7?V_0.2PO₄/C material synthesized by this method can be used as a cathode material for advanced lithium-ion batteries.     

Nanostructured lithium-free oxyanion cathode, Li x Co2(MoO4)3 [0≤ x <3] for 3 V class lithium batteries

A new nanostructured framework-type polyanion material, Li _x Co₂(MoO₄)₃ [0≤?x?<3], was studied as a positive electrode for use in 3-Volt class lithium-ion cells for the first time. The new material was synthesized in a lithium-free composition and examined its structure, morphology, and electrochemical characteristics. Co₂(MoO₄)₃ was found to crystallize in a monoclinic structure with lattice parameters: a?=?14.280(9) ?, b?=?3.382(8) ?, c?=?10.557(1) ?, and β?=?117.9728° (space group P2/m). The redox behavior of this new material was demonstrated in lithium-containing test cells. The material offered a discharge capacity of approximately 110 mAh g^?1 between 3.5 and 1.5 V during the first cycle and retained 50% capacity at the end of the 20th cycle. The poor capacity retention is obviously attributed to the poor electronic conductivity of Co₂(MoO₄)₃ owing to its open framework structure. To overcome the intrinsic low electronic conductivity of polyanion materials, we have adapted a nanocomposite approach by way of adding nanoporous carbon matrix (particle size approximately 10 nm) together with the conventional conductive additive (acetylene black) and demonstrated that the overall electronic conductivity could be improved significantly, yielding an initial discharge capacity of 121 mAh g^?1 using nanocomposite electrode in the potential range 3.5 V down to 2.0 V.     

Surfactant assisted solvothermal synthesis of LiFePO_4 nanorods for lithium-ion batteries

Well-shaped and uniformly dispersed LiFePO_4 nanorods with a length of 400–500 nm and a diameter of about 100 nm, are obtained with participation of a proper amount of anion surfactant sodium dodecyl sulfonate(SDS) without any further heating as a post-treatment. The surfactant acts as a self-assembling supermolecular template, which stimulated the crystallization of LiFePO_4 and directed the nanoparticles growing into nanorods between bilayers of surfactant(BOS). LiFePO_4 nanorods with the reducing crystal size along the b axis shorten the diffusion distance of Li~+ extraction/insertion, and thus improve the electrochemical properties of LiFePO_4 nanorods. Such prepared LiFePO_4 nanorods exhibited excellent specific capacity and high rate capability with discharge capacity of 151 mAh/g, 122 mAh/g and 95 mAh/g at 0.1C, 1 C and 5 C, respectively. Such excellent performance of LiFePO_4 nanorods is supposed to be ascribed to the fast Li~+ diffusion velocity from reduced crystal size along the b axis and the well electrochemical conductivity. The structure, morphology and electrochemical performance of the samples were characterized by XRD, FE-SEM, HRTEM, charge/discharge tests, and EIS(electrochemical impedance spectra).     

Preparation of NiO/multiwalled carbon nanotube nanocomposite for use as the oxygen cathode catalyst in rechargeable Li–O2 batteries

NiO/multiwalled carbon nanotube (NiO/MWCNT) nanocomposites have been prepared and used for a Li–O₂ battery cathode catalyst. Electrochemical measurements demonstrate that the batteries with NiO/MWCNT catalyst have a discharge capacity of 2,500 mAh g^?1, a charge capacity of 2,100 mAh g^?1, and a rechargeable ability performing better than Ketjenblack (KB) and MWCNTs. KB has the largest discharge capacity (2,700 mAh g^?1) due to the highest surface area and pore volume but the worst charging behavior due to poor mass transport in the small-width pore (2.48 nm). MWCNTs have a much better charging performance owing to a larger pore width (8.93 nm) than carbon black. NiO/MWCNTs have the largest charge capacity because of the facilitated mass transport in the comparatively large pores (7.68 nm) and the increased catalytic ability produced by the NiO nanoparticles. These improvements are also responsible for the best cycle and rate performances of the nanocomposites among the three catalysts.     

Preparation and Electrochemical Performance of Li[Ni1/3Co1/3Mn1/3]O2 Synthesized Using Li2CO3 as Template

Porous structure Li[Ni_1/3Co_1/3Mn_1/3]O₂ has been synthesized via a facile carbonate co‐precipitation method using Li₂CO₃ as template and lithium‐source. The physical and electrochemical properties of the materials were examined by many characterizations including TGA, XRD, SEM, EDS, TEM, BET, CV, EIS and galvanostatic charge‐discharge cycling. The results indicate that the as‐synthesized materials by this novel method own a well‐ordered layered structure α‐NaFeO₂ [space group: R‐3m(166)], porous morphology, and an average primary particle size of about 150 nm. The porous material exhibits larger specific surface area and delivers a high initial capacity of 169.9 mAh·g^?1 at 0.1 C (1 C=180 mA·g^?1) between 2.7 and 4.3 V, and 126.4, 115.7 mAh·g^?1 are still respectively reached at high rate of 10 C and 20 C. After 100 charge‐discharge cycles at 1 C, the capacity retention is 93.3%, indicating the excellent cycling stability.     

Physical and electrochemical properties of La-doped LiFePO4/C composites as cathode materials for lithium-ion batteries

Olivine-type LiFePO₄ is one of the most promising cathode materials for lithium-ion batteries, but its poor conductivity and low lithium-ion diffusion limit its practical application. The electronic conductivity of LiFePO₄ can be improved by carbon coating and metal doping. A small amount of La-ion was added via ball milling by a solid-state reaction method. The samples were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM)/mapping, differential scanning calorimetry (DSC), transmission electron microscopy (TEM)/energy dispersive X-ray spectroscopy (EDS), and total organic carbon (TOC). Their electrochemical properties were investigated by cyclic voltammetry, four-point probe conductivity measurements, and galvanostatic charge and discharge tests. The results indicate that these La-ion dopants do not affect the structure of the material but considerably improve its rate capacity performance and cyclic stability. Among the materials, the LiFe_0.99La_0.01PO₄/C composite presents the best electrochemical behavior, with a discharge capacity of 156 mAh g^?1 between 2.8 and 4.0 V at a 0.2 C-rate compared to 104 mAh g^?1 for undoped LiFePO₄. Its capacity retention is 80% after 497 cycles for LiFe_0.99La_0.01PO₄/C samples. Such a significant improvement in electrochemical performance should be partly related to the enhanced electronic conductivities (from 5.88?×?10^?6 to 2.82?×?10^?3 S cm^?1) and probably the mobility of Li⁺ ion in the doped samples. The LiFe_0.99La_0.01PO₄/C composite developed here could be used as a cathode material for lithium-ion batteries.