S.H. Ng

Flame spray-pyrolyzed vanadium oxide nanoparticles for lithium battery cathodes

Vanadium pentoxide (V2O5) nanoparticles (30-60 nm) were made by a one-step and scalable flame spray pyrolysis (FSP) process. Optimization of the FSP processing conditions (precursor concentration and injection rate) enhanced the electrochemical performance of these nanoparticles. Increasing the cut-off potential for discharging from 1.5 to 2.5 V vs. Li/Li+ improved the cycle life of these V2O5 nanoparticles. Particles with the lowest specific surface area (approximately 32 m2 g(-1)) and highest phase purity (up to 98 wt%) showed excellent cyclability between 2.5 and 4.0 V vs. Li/Li+, retaining a specific charge of 110 mAh g(-1) beyond 100 cycles at a specific current of 100 mA g(-1), and also superior specific charge of 100 mAh g(-1) at specific current up to 20C rate (or 2000 mA g(-1)).

Electrochemistry of LiV3O8 Nanoparticles Made by Flame Spray Pyrolysis

LiV 3 O 8 nanoparticles (primary particles with ca. 50 nm diameter) have been synthesized by flame spray pyrolysis (FSP). The powder was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and galvanostatic cycling. The initial discharge capacity of the LiV 3 O 8 nanoparticles is 271 mAh g -1 when discharged from its open-circuit potential to 2.0 V vs Li/Li + at a specific current of 100 mA g -1 under ambient conditions. The nanoparticles retained a specific discharge capacity of 180 mAh g -1 beyond 50 cycles. This paper describes the synthesis route as well as the characterizations of the FSP-produced LiV 3 O 8 nanoparticles.

Spray Pyrolyzed PbO-Carbon Nanocomposites as Anode for Lithium-Ion Batteries

A new approach has been used to prepare nanostructured lead oxide-carbon (PbO-C) composites via the spray pyrolysis technique. In this study, the electrochemical performance of the PbO-carbon nanocomposites as anode materials for lithium-ion rechargeable batteries was investigated. The prepared powders consist of fine nanocrystalline PbO homogeneously distributed within an amorphous carbon matrix with highly developed surface area. The estimated average crystal sizes of these nanocomposites from X-ray diffraction (XRD) patterns are in the range of 26-102 nm. The combination of spray technology and carbon addition increased the specific surface area (above 6 m 2 g -1 ) and the conductivity of PbO, improved the specific capacity, and maintained cycle life with a reversible capacity above 100 mAh g -1 beyond 50 cycles. The increase in capacity retention for PbO-carbon compared to that of pure PbO was due to the presence of a conductive and highly developed carbon matrix that can absorb large volume changes during the alloying/dealloying of lead with lithium over the 1.50 to 0.01 V potential range, which yields Li x Pb alloys (0 < x < 4.5).

A Feasibility Study on the Use of Li4V3O8 as a High Capacity Cathode Material for Lithium‐Ion Batteries

Li(4)V(3)O(8) materials have been prepared by chemical lithiation by Li(2)S of spherical Li(1.1)V(3)O(8) precursor materials obtained by a spray-drying technique. The over-lithiated vanadates were characterised physically by using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and electrochemically using galvanostatic charge-discharge and cyclic voltammetry measurements in both the half-cell (vs. Li metal) and full-cell (vs. graphite) systems. The Li(4)V(3)O(8) materials are stable in air for up to 5 h, with almost no capacity drop for the samples stored under air. However, prolonged exposure to air will severely change the composition of the Li(4)V(3)O(8) materials, resulting in both Li(1.1)V(3)O(8) and Li(2)CO(3). The electrochemical performance of these over-lithiated vanadates was found to be very sensitive to the conductive additive (carbon black) content in the cathode. When sufficient carbon black is added, the Li(4)V(3)O(8) cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li(1.1)V(3)O(8) precursor material, that is, retaining an average charge capacity of 205 mAh g(-1) at 2800 mA g(-1) (8C rate; 1C rate means full charge or discharge of a battery in one hour), when cycled in the potential range of 2.0-4.0 V versus Li metal. When applied in a non-optimised full cell system (vs. graphite), the Li(4)V(3)O(8) cathode showed promising cycling behaviour, retaining a charge capacity (Li(+) extraction) above 130 mAh g(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mA g(-1) (C/3 rate).

Hexagonal-shaped tin glycolate particles: a preliminary study of their suitability as li-ion insertion electrodes.

Tin glycolate particles were prepared by a simple, one-step, polyol-mediated synthesis in air in which tin oxalate precursor was added to ethylene glycol and heated at reflux. Hexagonal-shaped, micron-sized tin glycolate particles were formed when the solution had cooled. A series of tin oxides was produced by calcination of the synthesized tin glycolate at 600-800 degrees C. It was revealed that the micron-sized, hexagonal-shaped tin glycolate now consisted of nanosized tin-based particles (80-120 nm), encapsulated within a tin glycolate shell. XRD, TGA, and FT-IR measurements were conducted to account for the three-dimensional growth of the tin glycolate particles. When applied as an anode material for Li-ion batteries, the synthesized tin glycolate particles showed good electrochemical reactivity in Li-ion insertion/deinsertion, retaining a specific capacity of 416 mAh g(-1) beyond 50 cycles. This performance was significantly better than those of all the other tin oxides nanoparticles (<160 mAh g(-1)) obtained after heat treatment in air. We strongly believe that the buffering of the volume expansion by the glycolate upon Li-Sn alloying is the main factor for the improved cycling of the electrode.

Foam-like, microstructural SnO2–carbon composite thin films synthesized via a polyol-assisted thermal decomposition method

Foam-like, microstructural SnO2-carbon composite thin films were synthesized by refluxing SnCl2.2H2O in ethylene glycol (EG) at 195 degrees C for 4 h under vigorous stirring in air followed by thermal decomposition of the as-synthesized precursor solution, whereby the products were deposited onto stainless steel (SS) substrates. Subsequently, the decomposed product, which now consists only of the microstructural SnO2-carbon composite thin film, without the addition of any binder and carbon black conductive agent, was directly applied as an anode material for use in a Li-ion rechargeable battery. Physical and electrochemical characterizations of the as-synthesized thin films were carried out. The foam-like, microstructural SnO2-carbon composite thin films that undergo thermal decomposition in air at 300 degrees C demonstrated the best cyclability, delivering a specific discharge capacity of approximately 496 mAh g(-1) beyond 100 cycles. We believe that the presence of a uniform, SnO2-carbon network throughout the foam-like thin film, acts not only as an improved conducting network but also buffered the volume expansion upon Li-Sn alloying, resulting in a much improved cycling of the composite thin film electrode.

A feasibility study on the use of Li(4)V(3)O(8) as a high capacity cathode material for lithium-ion batteries.

Li(4)V(3)O(8) materials have been prepared by chemical lithiation by Li(2)S of spherical Li(1.1)V(3)O(8) precursor materials obtained by a spray-drying technique. The over-lithiated vanadates were characterised physically by using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and electrochemically using galvanostatic charge-discharge and cyclic voltammetry measurements in both the half-cell (vs. Li metal) and full-cell (vs. graphite) systems. The Li(4)V(3)O(8) materials are stable in air for up to 5 h, with almost no capacity drop for the samples stored under air. However, prolonged exposure to air will severely change the composition of the Li(4)V(3)O(8) materials, resulting in both Li(1.1)V(3)O(8) and Li(2)CO(3). The electrochemical performance of these over-lithiated vanadates was found to be very sensitive to the conductive additive (carbon black) content in the cathode. When sufficient carbon black is added, the Li(4)V(3)O(8) cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li(1.1)V(3)O(8) precursor material, that is, retaining an average charge capacity of 205 mAh g(-1) at 2800 mA g(-1) (8C rate; 1C rate means full charge or discharge of a battery in one hour), when cycled in the potential range of 2.0-4.0 V versus Li metal. When applied in a non-optimised full cell system (vs. graphite), the Li(4)V(3)O(8) cathode showed promising cycling behaviour, retaining a charge capacity (Li(+) extraction) above 130 mAh g(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mA g(-1) (C/3 rate).

A Feasibility Study on the Use of Li4V3O8as a High Capacity Cathode Material for Lithium-Ion Batteries

Li(4)V(3)O(8) materials have been prepared by chemical lithiation by Li(2)S of spherical Li(1.1)V(3)O(8) precursor materials obtained by a spray-drying technique. The over-lithiated vanadates were characterised physically by using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and electrochemically using galvanostatic charge-discharge and cyclic voltammetry measurements in both the half-cell (vs. Li metal) and full-cell (vs. graphite) systems. The Li(4)V(3)O(8) materials are stable in air for up to 5 h, with almost no capacity drop for the samples stored under air. However, prolonged exposure to air will severely change the composition of the Li(4)V(3)O(8) materials, resulting in both Li(1.1)V(3)O(8) and Li(2)CO(3). The electrochemical performance of these over-lithiated vanadates was found to be very sensitive to the conductive additive (carbon black) content in the cathode. When sufficient carbon black is added, the Li(4)V(3)O(8) cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li(1.1)V(3)O(8) precursor material, that is, retaining an average charge capacity of 205 mAh g(-1) at 2800 mA g(-1) (8C rate; 1C rate means full charge or discharge of a battery in one hour), when cycled in the potential range of 2.0-4.0 V versus Li metal. When applied in a non-optimised full cell system (vs. graphite), the Li(4)V(3)O(8) cathode showed promising cycling behaviour, retaining a charge capacity (Li(+) extraction) above 130 mAh g(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mA g(-1) (C/3 rate).