Enhanced electrochemical performance of carbon nanospheres–LiFePO4 composite by PEG based sol–gel synthesis

Xie

et al. 2011

Ionics

LiFePO 4 -positive electrode material was successfully synthesized by a solid-state method, and the effect of storage temperatures on kinetics of lithium-ion insertion for LiFePO 4 -positive electrode material was investigated by electrochemical impedance spectroscopy. The chargetransfer resistance of LiFePO 4 electrode decreases with increasing the storage temperatures. This suggests that it has a high electrochemical activity at high temperature. The diffusion coefficient of lithium ion is greatly increased with increasing the storage temperatures, indicating that the kinetics of Li + and electron transfer into the electrodes were much fast at high storage temperature.

Section: Introductionmentioning

confidence: 98%

Kinetic study on LiFePO4-positive electrode material of lithium-ion battery

Xie

et al. 2011

Ionics

“…Carbon prevents the growth of particles during the sintering process and enhances electronic conductivity through improved contacts between particles. Various carbon sources have been reported for the LiFePO 4 /C composite, such as sucrose [18][19][20], glucose [21], polyethylene glycol (PEG) [22,17], polyvinyl alcohol (PVA) [23,18,24], and citric acid [25]. Polyvinyl alcohol is a common carbon resource and widely used for improving the performance of LiFePO 4 .…”

Section: Introductionmentioning

confidence: 99%

Preparation and characterization LiFePO4/C nanowires and their improved performance for lithium-ion batteries

Bai

Chen

et al. 2015

Ionics

LiFePO 4 /C nanowires were successfully synthesized via evaporated self-assembly assisted by polyvinyl alcohol at room temperature. The structure, morphology, and composition of the as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). The experimental results show that LiFePO 4 /C nanowires are uniform about 50-100 nm in diameter and 1 μm in length. LiFePO 4 /C nanowires exhibit excellent electrochemical performance and attain the discharge-specific capacity of 155 mAhg −1 at 1C rate and 118 mAhg −1 at 20C rate. The capacity retention is 98 % after 100 cycles at 20C rate.

“…Charge/discharge curves for In-LFP-600 and In-LFP-700 samples at 1 C are depicted in Figure 5. Typical two-phase nature of the lithium extraction and insertion reactions between LiFePO4 and FePO4 is implied by the flat nature of the charge-discharge potential curves around ~3.4 V [33]. The steep rise and fall in the profiles at the large specific capacity values refer to the charge transfer activation and concentration polarizations with contribution from limited miscibility between the LiFePO4 and FePO4.…”

Section: Electrochemical Measurementsmentioning

confidence: 99%

Optimization of Electrochemical Performance of LiFePO4/C by Indium Doping and High Temperature Annealing

et al. 2017

Abstract:We have prepared nano-structured In-doped (1 mol %) LiFePO 4 /C samples by sol-gel method followed by a selective high temperature (600 and 700 • C) annealing in a reducing environment of flowing Ar/H 2 atmosphere. The crystal structure, particle size, morphology, and magnetic properties of nano-composites were characterized by X-ray diffraction (XRD), scanning electron microsopy (SEM), transmission electron microscopy (TEM), and 57 Fe Mössbauer spectroscopy. The Rietveld refinement of XRD patterns of the nano-composites were indexed to the olivine crystal structure of LiFePO 4 with space group Pnma, showing minor impurities of Fe 2 P and Li 3 PO 4 due to decomposition of LiFePO 4 . We found that the doping of In in LiFePO 4 /C nanocomposites affects the amount of decomposed products, when compared to the un-doped ones treated under similar conditions. An optimum amount of Fe 2 P present in the In-doped samples enhances the electronic conductivity to achieve a much improved electrochemical performance. The galvanostatic charge/discharge curves show a significant improvement in the electrochemical performance of 700 • C annealed In-doped-LiFePO 4 /C sample with a discharge capacity of 142 mAh·g −1 at 1 C rate, better rate capability (~128 mAh·g −1 at 10 C rate,~75% of the theoretical capacity) and excellent cyclic stability (96% retention after 250 cycles) compared to other samples. This enhancement in electrochemical performance is consistent with the results of our electrochemical impedance spectroscopy measurements showing decreased charge-transfer resistance and high exchange current density.