Electrochemical performance of sulfur composite cathode materials for rechargeable lithium batteries

The structure and characteristic of carbon materials have a direct influence on the electrochemical performance of sulfur-carbon composite electrode materials for lithium-sulfur battery.In this paper,sulfur composite has been synthesized by heating a mixture of elemental sulfur and activated carbon,which is characterized as high specific surface area and microporous structure.The composite,contained 70%sulfur,as cathode in a lithium cell based on organic liquid electrolyte was tested at room temperature....     

Electrochemical performance of Yb-doped LiFePO4/C composites as cathode materials for lithium-ion batteries

LiFePO₄/C and LiYb_0.02Fe_0.98PO₄/C composite cathode materials were synthesized by simple solution technique. The samples were characterized by X-ray diffraction, scanning electron microscope, and thermogravimetric–differential thermal analysis. Their electrochemical properties were investigated by cyclic voltammetry, four-point probe conductivity measurements, and galvanostatic charge and discharge tests. The carbon-coated and Yb³⁺-doped LiFePO4 sample exhibited an enhanced electronic conductivity of 1.9 × 10^?3 Scm^?1, and a specific discharge capacity of 146 mAhg^?1 at 0.1 C. The results suggest that the improvement of the electrochemical performance can be attributed to the ytterbium doping, which facilitates the phase transformation between triphylite and heterosite during cycling, and the conductivity improvement by carbon coating.     

Facile synthesis and performance of polypyrrole-coated sulfur nanocomposite as cathode materials for lithium/sulfur batteries

In situ chemical oxidation polymerization of pyrrole on the surface of sulfur particles was carried out to synthesize a sulfur/polypyrrole （SIPPy） nanocomposite with core-shell structure. The composite was characterized by elemental analysis, X-ray diffraction, scanning/transmission electron microscopy, and electrochemical measurements. XRD and FTIR results showed that sulfur well dispersed in the core-shell structure and PPy structure was successfully obtained via in situ oxidative polymerization of pyrrole on the surface of sulfur particles. TEM observation revealed that PPy was formed and fixed to the surface of sulfur nanoparticle after polymerization, developing a well-defined core-shell structure and the thickness of PPy coating layer was in the range of 20-30 nm. In the composite, PPy worked as a conducting matrix as well as a coating agent, which confined the active materials within the electrode. Consequently, the as prepared SIPPy composite cathode exhibited good cycling and rate performances for rechargeable lithium/sulfur batteries. The resulting cell containing SIPPy composite cathode yields a discharge capacity of 1039 mAh·g^-1 at the initial cycle and retains 59% of this value over 50 cycles at 0.1 C rate. At 1 C rate, the SIPPy composite showed good cycle stability, and the discharge capacity was 475 mAh·g^-1 after 50 cycles.     

Single-source realization of Na-doped and carbon-coated LiMnPO4 nanocomposite for enhanced performance of Li-ion batteries

Journal of Solid State Electrochemistry - LiMnPO4 is of great interest as the promising cathode material in lithium-ion batteries for its low cost and good stability, but still suffers from limited...     

Electrochemical performance of all-solid lithium ion batteries with a polyaniline film cathode

We have prepared a high-density polyaniline(PANI) paste(50 mg/m L), with similar physical properties to those of paints or pigments. The synthesis of PANI is confirmed by Fourier transform infrared(FT-IR) spectroscopy. The morphologies of PANI, doped PANI, and doped PANI paste are confirmed by scanning electron microscopy(SEM). Particles of doped PANI paste are approximately 40–50 nm in diameter, with a uniform and cubic shape. The electrochemical performances of doped PANI paste using both liquid and solid polymer electrolytes have been measured by galvanostatic charge and discharge process. The cell fabricated with doped PANI paste and the solid polymer electrolyte exhibits a discharge capacity of ～87 μAh/cm2(64.0 m Ah/g) at the second cycle and～67 μAh/cm2(50.1 m Ah/g) at the 100 th cycle.     

锂离子电池正极材料LiNi_0.5Mn_1.5O_4表面包覆CuO的研究

本文首先通过共沉淀法和固相球磨法制备了纳米级的LiNi0.5Mn1.5O4高电压正极材料,然后通过溶胶-凝胶法制备了表面包覆CuO的CuO-LiNi0.5Mn1.5O4复合材料.通过对CuO包覆量为1%,3%和5%的复合材料的电化学性能对比,发现当包覆量为1%时,材料的性能最佳.在1 C下,材料的放电比容量高达126.1 mA h g?1,循环100次后容量保持率在99.5%.CuO包覆在纳米LiNi0.5Mn1.5O4材料表面,阻止电解液与活性颗粒的直接接触,削弱了电解液与LiNi0.5Mn1.5O4的相互作用,进而在一定程度上减缓了电解液的分解;CuO的包覆同时还缓解了电解液中HF对材料的攻击,阻止了锰的溶解和由此带来的结构改变,进而提高了材料的循环稳定性.     

Combustion synthesized LiMnSnO4 cathode for lithium batteries

Novel category LiMnSnO₄ compound was synthesized via. Urea assisted combustion (UAC) method at 800 °C and examined for possible use as cathode material in lithium-ion batteries. The XRD (X-ray diffraction) results of LiMnSnO₄ sample authenticate the orthorhombic crystal structure with high degree of crystallinity. Presence of uniformly distributed nanometric grains (scanning electron microscopy) with preferred local cation environment is evident from FT IR (Fourier transform infra red spectroscopic) and ⁷Li NMR (nuclear magnetic resonance spectroscopy) studies. The charge–discharge behavior of Li/LiMnSnO₄ cells demonstrated a specific capacity of 113 mA h/g, with an excellent capacity retention (95%) and Ah efficiency (>99%). Besides, the internal resistance of the Li/LiMnSnO₄ cell after 30 cycles is negligibly small, thus demonstrating good electronic conductivity and cycling stability, required for any lithium intercalating cathode material.     

One-step hydrothermal synthesis of LiMn2O4 cathode materials for rechargeable lithium batteries

LiMn₂O₄ cathode materials with high discharge capacity and good cyclic stability were prepared by a simple one-step hydrothermal treatment of KMnO₄, aniline and LiOH solutions at 120–180 °C for 24 h. The aniline/KMnO₄ molar ratio (R) and hydrothermal temperature exhibited an obvious influence on the component and phase structures of the resulting product. The precursor KMnO₄ was firstly reduced to birnessite when R was less than 0.2:1 at 120–150 °C. Pure-phased LiMn₂O₄ was formed when R was 0.2:1, and the LiMn₂O₄ was further reduced to Mn₃O₄ when R was kept in the range of 0.2–0.3 at 120–150 °C. Moreover, LiMn₂O₄ was fabricated when R was 0.15:1 at 180 °C. Octahedron-like LiMn₂O₄ about 300 nm was prepared at 120 °C, and particle size decreased with an increase in hydrothermal temperature. Especially, LiMn₂O₄ synthesized at 150 °C exhibited the best electrochemical performance with the highest initial discharge capacity of 127.4 mAh g⁻¹ and cycling capacity of 106.1 mAh g⁻¹ after 100 cycles. The high discharge capacity and cycling stability of the as-prepared LiMn₂O₄ cathode for rechargeable lithium batteries were ascribed to the appropriate particle size and larger cell volume.     

Effect of carbon sources on the electrochemical performance of Li2FeSiO4 cathode materials for lithium ion batteries

Li₂FeSiO₄ cathode materials have been prepared by sol-gel method. The effects of carbon sources on the structural, morphological and electrochemical behaviors of Li₂FeSiO₄ were investigated. The scanning electronic microscope (SEM) and X-ray diffraction powder analysis (XRD) indicate that the obtained samples using different carbon sources possess some difference in the morphology and in the particle size. The sample using the mixture of citric acid and oxalic acid as carbon source has a maximum discharge capacity of 118 mA h g^?1 at 0.1 C between 1.8 and 4.5 V. The resulting cyclic voltammograms and electrochemical impedance spectra suggest that the sample using mixed acid as carbon source has smaller polarization and smaller charge transfer impedance.     

Highly ordered three-dimensional macroporous FePO4 as cathode materials for lithium–ion batteries

Highly ordered three-dimensional macroporous 3DOM FePO₄ cathode material was prepared by using a colloidal crystal template. The effects of the annealing temperature on the morphology changes and the electrochemical properties of the composite were investigated. The 3DOM FePO₄ prepared at 400 °C shows the excellent cycling stability and good rate capability as a cathode for lithium–ion batteries.     

Electrochemical characterization of non-stoichiometric Cu2S x cathode for lithium batteries

Journal of Solid State Electrochemistry - Electrochemical performances of non-stoichiometric Cu2S x (1.25 ≤ x ≤ 0.625) cathodes prepared by spray...     

Bismuth chloride@mesocellular carbon foam nanocomposite cathode materials for rechargeable chloride ion batteries

Chloride ion batteries(CIB) are considered to be one of the most promising energy storage devices. As cathode materials for CIBs, metal chlorides have many advantages, such as high theoretical energy density, abundant elemental resources and ideal discharge voltage plateau. However, the dissolution and huge volume change of metal chlorides during cycling lead to considerable short lifespan, which limits their potential application for CIBs. Herein, the bismuth chloride nanocrystal is confined in...     

Crosslinked polyacrylonitrile precursor for S@pPAN composite cathode materials for rechargeable lithium batteries

S@pPAN has become promising cathode materials in rechargeable batteries due to its high compressed density,low E/S ratio,no polysulfide dissolution,no self-discharge,and stable cycling.However,it is a big challenge to enhance its sulfur content which determines its practical specific capacity.Herein,we prepare crosslinked PAN as precursor,leading to effective enhancement of sulfur content up to 55 wt%and a reversible specific capacity of 838 mAh g _composites^-1 at 0.2C.Because of the microporous structure and high specific area,crosslinked PAN provides more space to accommodate sulfur molecule and improve the interfacial reaction of S@pPAN as well.This work provides a promising direction to design S@pPAN for lithium sulfur batteries with high energy density.     

Morphology-controllable synthesis of LiMn2O4 particles as cathode materials of lithium batteries

We reported a new method for the preparation of morphology-controllable LiMn₂O₄ particles. In this method, dimension-different MnO₂ nanowires synthesized hydrothermally by adjusting the reaction temperature were used as the precursor. The morphology and structure of the resulting products were characterized with scanning electron microscope and X-ray diffraction, and the performances of the prepared LiMn₂O₄ samples as cathode material of lithium batteries were investigated by cyclic voltammetry and galvanostatic charge/discharge test. The results indicate that the morphology of LiMn₂O₄ transforms from tridimensional particle (TP) to unidimensional rod (UR) through quadrate lamina (QL) with increasing the diameter and length of MnO₂ nanowires. Although the cyclic stabilities of LiMn₂O₄-TP, LiMn₂O₄-QL, and LiMn₂O₄-UR are very close (the 0.1 C capacity after 50 cycles is 101, 93, and 99 mAh g^?1 at 25 °C, and 84, 78, and 82 mAh g^?1 at 50 °C, respectively), LiMn₂O₄-QL delivers much higher rate capacity (about 70 mAh g^?1 at 5 C and 30 mAh g^?1 at 10 C) than LiMn₂O₄-TP and LiMn₂O₄-UR (about 20 mAh g^?1 at 5 C, 3 mAh g^?1 at 10 C, 25 mAh g^?1 at 5 C, and 3 mAh g^?1 at 10 C).     

Si/C nanocomposite anode materials by freeze-drying with enhanced electrochemical performance in lithium-ion batteries

The nanostructured Si/graphite composites embedded with the pyrolyzed polyethylene glycol was synthesized from coarse silicon and natural graphite by a facile and cost-effective approach. The Si/C nanocomposite showed the fluffy carbon-coated structure, which was confirmed by the SEM and TEM measurements. The as-obtained Si/C nanocomposite, employed as anode material in lithium-ion batteries, exhibited significantly enhanced rate capability and cycling stability. The improved electrochemical stability of the composite was evaluated by EIS and galvanostatically charge/discharge test. A reversible capacities as high as 85% and 91% of the initial charge capacities, could be maintained for the Si/C nanocomposite electrode after 40 cycles under the high current densities of 500 and 1,000?mA?g^?1, respectively. The relatively low cost and excellent electrochemical capability of the Si/C nanocomposite would well meet the challenge in rapid charge and discharge for large-size lithium-ion rechargeable batteries.     

Electrochemical properties of PABTH as cathode materials for rechargeable lithium battery

The electrochemical properties of polyanthra [1′,9′,8′-b,c,d,e] [4′,10′,5′-b′,c′,d′,e′]bis-[1,6,6a(6a-S^IV)trithia]pentalene (PABTH) were studied. It is found that PABTH exhibits a good cyclability and high capacity of 290 mAh/g in 1 M LiTFSI/DXL–DME (2:1 by weight) electrolyte. Detailed electrochemical characterization reveals that the capacity fading of PABTH within the first several cycles is due to the loss of ABTH monomer or its oligomer that is contained in PABTH in the form of soluble discharging products. It also needs to be noted that PABTH and ABTH has much higher charge–discharge efficiency (up to 95%) than that of sulfur (below 85%) because the S–S bond is fixed to the backbone.     

Electrochemical properties of LiFePO4-multiwalled carbon nanotubes composite cathode materials for lithium polymer battery

LiFePO₄-multiwalled carbon nanotubes (MWCNTs) composites were prepared by a hydrothermal method followed by ball-milling and heat treating. Cyclic voltammetry, ac impedance and galvanostatic charge/discharge testing results indicate that LiFePO₄-MWCNTs composite exhibits higher discharge capacity and rate capability than pure LiFePO₄ at high-rate at room temperature. It is demonstrated that the added MWCNTs not only increase the electronic conductivity and lithium-ion diffusion coefficient but also decrease crystallite size and charge transfer resistance of LiFePO₄-MWCNTs composite.     

Soft mechanochemical synthesis: Preparation of cathode materials for rechargeable lithium batteries

To prepare intercalation lithium — transition metal oxide cathode materials for rechargeable lithium batteries, the reactions in the mixtures of the correspondent hydroxides in highly energetic planetary activators, so called ‘soft mechanochemical synthesis’ were studied. The method can be used for direct preparation of final products in a high dispersed and disordered state, as well as for obtaining high reactive precursors yielding final products by the subsequent brief heating at considerably lower temperatures as compared to conventional ceramic method. The as prepared products were analyzed using X-ray diffraction, TG, IRS, XPS, ⁷Li NMR, EPR, diffuse reflectance spectroscopy, electron microscopy, BET, and electrochemical measurements. The peculiarities of crystal structure, electronic state of transition metal ions and cycling behaviour of materials are discussed. The method as proposed is concluded to be economically effective and ecologically clean.     

Effect of vanadium doping on electrochemical performance of LiMnPO4 for lithium-ion batteries

A series of LiMn_1-x V _x PO₄ samples have been synthesized successfully via a conventional solid-state reaction method. The active materials are characterized by x-ray diffraction, x-ray photoelectron spectroscopy, and scanning electron microscopy. The electrochemical performances of the samples are tested using cyclic voltammetry, electrochemical impedance spectroscopy, and charge/discharge measurement techniques. It is confirmed that the samples are in single phase when the content of vanadium (x) is lower than 0.05. If that content is higher than 0.1, the samples are shown to contain an additional conductive phase of Li₃V₂(PO₄)₃. The vanadium doping significantly enhances the electrochemical properties of LiMnPO₄. It is underlined that the optimal ratio for a low-vanadium doping with the best electrochemical performance is 0.1 and this material exhibits a corresponding initial charge and discharge capacity of 98.9 and 98.1 mAh g^?1 at 0.1 C under 50 °C. The capacity retention is higher than 99 % after 30 cycles. The dramatic electrochemical improvement of the LiMnPO₄ samples is ascribed to the strengthened ability of lithium-ion diffusion and enhanced electronic conductivity for the V-doped samples.