Synthesis and electrochemical properties of nanostructured LiCoO2 fibers as cathode materials for lithium-ion batteries

Nanostructured LiCoO2 fibers were prepared by the sol-gel related electrospinning technique using metal acetate and citric acid as starting materials. The transformation from the xerogel fibers to the LiCoO2 fibers and the nanostructure of LiCoO2 fibers have been investigated in detail. The LiCoO2 fibers with 500 nm to 2 mum in diameter were composed of polycrystalline nanoparticles in sizes of 20-35 nm. Cyclic voltammetry and charge-discharge experiments were applied to characterize the electrochemical properties of the fibers as cathode materials for lithium-ion batteries. The cyclic voltammogram curves indicated faster diffusion and migration of Li+ cations in the nanostructured LiCoO2 fiber electrode. In the first charge-discharge process, the LiCoO2 fibers showed the initial charge and discharge capacities of 216 and 182 (mA.h)/g, respectively. After the 20th cycle, the discharge capacity decreased to 123 (mA.h)/g. The X-ray diffraction and high-resolution transmission electron microscopy analyses indicated that the large loss of capacity of fiber electrode during the charge-discharge process might mainly result from the dissolution of cobalt and lithium cations escaping from LiCoO2 to form the crystalline Li2CO3 and CoF2 impurities.     

Mechanochemical synthesis and electrochemical properties of nanostructured electrode materials for Li ion batteries

We focus on the synthesis by ball milling and on the electrochemical characterization of nanocrystalline bimetallic and composite materials to be employed as anodes in Li ion batteries. Ni₃Sn₄ and Ni₃Sn₂ based compounds were obtained by ball milling of three different Ni–Sn mixtures. The properties of the resulting anodes for Li ion batteries were evaluated as a function of composition. Moreover, a biphasic system is presented, with CoSn₂ and CoSn type structures, arising from the synthesis of the Sn₃₁Co₂₈C₄₁ composition. When cycled in a Li cell, this material showed a high reversible specific capacity, about 450 mA h g⁻¹, and a very good electrochemical and structural stability, making it of interest for application purposes. Contribution to the Fall Meeting of the European Materials Research Society, Symposium D: 9th International Symposium on Electrochemical–Chemical Reactivity of Metastable Materials, Warsaw, 17th–21st September, 2007.     

A nanoscale meshed electrode of single-crystalline SnO for lithium-ion rechargeable batteries

A high specific capacity with good cycle performance for lithium-ion rechargeable batteries was achieved by using a nanoscopically meshed electrode of single-crystalline SnO produced through Sn₆O₄(OH)₄ as the intermediate state, whereas conventional bulky electrodes of SnO readily degraded due to a large volume change during lithium-ion insertion/extraction processes. The skeletal framework of the meshed architecture would be suitable to prevent damage to the electrode through the relaxation of the mechanical strain originating from the expansion.     

Synthesis and electrochemical properties of graphene-SnS2 nanocomposites for lithium-ion batteries

Graphene-SnS₂ nanocomposites were prepared via a solvothermal method with different loading of SnS₂. The nanostructure and morphology of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD patterns revealed that hexagonal SnS₂ was obtained. SEM and TEM results indicated that SnS₂ particles distributed homogeneously on graphene sheets. The electrochemical properties of the samples as active anode materials for lithium-ion batteries were examined by constant current charge–discharge cycling. The composite with weight ratio between graphene and SnS₂ of 1:4 had the highest rate capability among all the samples and its reversible capacity after 50 cycles was 351 mAh/g, which was much higher than that of the pure SnS₂ (23 mAh/g). With graphene as conductive matrix, homogeneous distribution of SnS₂ nanoparticles can be ensured and volume changes of the nanoparticles during the charge and discharge processes can be accomodated effectively, which results in good electrochemical performance of the composites.     

Revisiting and enhancing electrochemical properties of SnO2 as anode for sodium-ion batteries

Journal of Solid State Electrochemistry - The tin oxide (SnO2) thin films have been prepared by the pulsed laser deposition (PLD) at deposition temperatures (Td) ranging from 300 to...     

SnO2 sheet/graphite composite as anode material with improved electrochemical performance for lithium-ion batteries

The SnO₂ sheet/graphite composite was synthesized by a hydrothermal method for high-capacity lithium storage. The microstructures of products were characterized by XRD and FE-SEM. The electrochemical performance of SnO₂ sheet/graphite composite was measured by galvanostatic charge/discharge cycling and EIS. The first discharge and charge capacities are 1,072 and 735 mAh g^?1 with coulombic efficiency of 68.6 %. After 40 cycles, the reversible discharge capacity is still maintained at 477 mAh g^?1. The results show that the SnO₂ sheet/graphite composite displays superior Li-battery performance with large reversible capacity and good cyclic performance.     

Hierarchically ordered porous nickel oxide array film with enhanced electrochemical properties for lithium ion batteries

Hierarchically ordered porous nickel oxide array film was prepared by electrodeposition through monolayer polystyrene spheres template. The as-prepared film had a highly porous structure of interconnected macrobowls array possessing nanopores. As anode material for lithium ion batteries, the porous array NiO film exhibited weaker polarization, higher coulombic efficiency and better cycling performance in comparison with the dense NiO film. After 50 cycles, the discharge capacity of porous array NiO film was 518 mAh g^? 1 at 1 C rate, higher than that of the dense NiO film (287 mAh g^? 1). The enhancement of the electrochemical properties was due to the unique hierarchical porous architecture, which provided fast ion/electron transfer and alleviated the structure degradation during the cycling process.     

Negative and positive electrode materials for lithium-ion batteries

MnV₂O_{6 + δ}5 (0.5 < δ < 1) amorphous oxides reversibly insert large amounts of Li (e.g. Li₁₂MnV₂O_6.96) at low voltage (≈ 1 V). During the first Li insertion, Mn⁴⁺ is first reduced to Mn²⁺ and V⁵⁺ is reduced to V³⁺. Upon further cycling, the V oxidation state varies reversibly between +3 and +5, whereas the average Mn oxidation state varies reversibly between +2 and ~+2.6. Reversible lithium deintercalation of LiCr_yMn_{2 − y}O₄ (0 < y < 1) occurs in two steps at ≈ 4.9 V and 4 V. The cyclability is excellent for y≤ 0.5. It becomes very poor for y ≥ 0.75 due to a migration of transition metal cations from 16d to 8a and I6c sites, where they accumulate upon cycling.     

Improved electrochemical performance of NaAlO2-coated LiCoO2 for lithium-ion batteries

Journal of Solid State Electrochemistry - NaAlO2-coated LiCoO2 materials have been synthesized as cathode materials for lithium-ion batteries. The NaAlO2 layer is coated on the LiCoO2 particles...     

A broad pore size distribution mesoporous SnO2 as anode for lithium-ion batteries

Journal of Solid State Electrochemistry - We demonstrate here that mesoporous tin dioxide (abbreviated M-SnO2) with a broad pore size distribution can be a prospective anode in lithium-ion...     

Flower-like SnO2 nanoparticles grown on graphene as anode materials for lithium-ion batteries

Tin oxide (SnO₂)/graphene composite was synthesized from SnCl₂?·?2H₂O and graphene oxide (GO) by a wet chemical-hydrothermal route. The GO was reduced to graphene nanosheet (GNS) and flower-like SnO₂ nano-crystals with size about 40 nm were homogeneously distributed on the surface of GNS. The SnO₂/graphene composites delivered a superior first discharge capacity of 1941.9 mAhg^?1 with a reversible capacity of 901.7 mAhg^?1 at the current density of 100 mAg^?1. Moreover, even at higher densities of 200 and 500 mAg^?1, the SnO₂/graphene composite still maintained enhanced cycling stability. After 40 cycles, the discharge capacity was still maintained at 691.1 mAhg^?1 at the current density of 100 mAg^?1. The SnO₂/graphene composite displayed an outstanding Li-battery performance with large reversible capacity and enhanced rate performance, which can be attributed to the highly uniform distribution of SnO₂ nanoparticles and high reduction degree of graphene. This result strongly indicates that the SnO₂/graphene composite was a promising anode material in high-performance lithium-ion batteries.     

Flexible free-standing graphene-silicon composite film for lithium-ion batteries

Flexible, free-standing, paper-like, graphene-silicon composite materials have been synthesized by a simple, one-step, in-situ filtration method. The Si nanoparticles are highly encapsulated in a graphene nanosheet matrix. The electrochemical results show that graphene-Si composite film has much higher discharge capacity beyond 100 cycles (708 mAh g^? 1) than that of the cell with pure graphene (304 mAh g^? 1). The graphene functions as a flexible mechanical support for strain release, offering an efficient electrically conducting channel, while the nanosized silicon provides the high capacity.     

Synthesis of a silicon-graphite composite for the hybrid electrode of lithium-ion batteries

Comprehensive analysis was made of the cycling parameters (reversible specific capacity, Coulomb efficiency of cycles, accumulated irreversible capacity, and retention of reversible capacity) of a hybrid electrode based on a mixture of MAG synthetic graphite and silicon-graphite composite produced by mechanical grinding.     

New electrode materials for lithium-ion batteries (Review)

The main principles of operation of modern lithium-ion batteries and the modern trends in development of new-generation batteries are described.     

Heterogeneous nanostructured electrode materials for electrochemical energy storage

In order to fulfil the future requirements of electrochemical energy storage, such as high energy density at high power demands, heterogeneous nanostructured materials are currently studied as promising electrode materials due to their synergic properties, which arise from integrating multi-nanocomponents, each tailored to address a different demand (e.g., high energy density, high conductivity, and excellent mechanical stability). In this article, we discuss these heterogeneous nanomaterials based on their structural complexity: zero-dimensional (0-D) (e.g. core-shell nanoparticles), one-dimensional (1-D) (e.g. coaxial nanowires), two-dimensional (2-D) (e.g. graphene based composites), three-dimensional (3-D) (e.g. mesoporous carbon based composites) and the even more complex hierarchical 3-D nanostructured networks. This review tends to focus more on ordered arrays of 1-D heterogeneous nanomaterials due to their unique merits. Examples of different types of structures are listed and their advantages and disadvantages are compared. Finally a future 3-D heterogeneous nanostructure is proposed, which may set a goal toward developing ideal nano-architectured electrodes for future electrochemical energy storage devices.     

Cellular porous polyvinylidene fluoride composite membranes for lithium-ion batteries

Macroporous polyvinylidene fluoride (PVdF) membranes were prepared by a phase inversion method and evaluated as battery separators. Two totally different morphologies (cellular and finger-like) were obtained by coagulating PVdF solutions with two different solvents. The cellular membranes were formed immediately by precipitating the PVdF solution with a latent solvent (acetone) in water, while the finger-like membranes were precipitated from the PVdF solution with a true solvent (N-methyl-2-pyrrolidone). The incorporation of a silica filler decreased the ionic resistance of the PVdF membranes of both morphologies. However, the cellular membranes showed better mechanical properties and enabled higher ionic conductivities than the finger-like ones, especially when the silica loading was low. Compared with a conventional untreated polyolefin separator, the porous PVdF membranes showed good wettability by a liquid electrolyte. After being activated with a commercial LiPF₆–ethylene carbonate–dimethyl carbonate electrolyte, the PVdF membranes were tested for their applications in lithium-ion batteries. Coin cells with these PVdF membranes exhibited stable cycling performance and good rate capability at room temperature. However, the cellular membranes are preferred over the finger-like ones because they offer higher mechanical performance, and can be processed into flat membranes more easily.