scholarly journals Phase Field Modeling of Coupled Phase Separation and Diffusion-Induced Stress in Lithium Iron Phosphate Particles Reconstructed From Synchrotron Nano X-ray Tomography

2019 ◽  
Vol 16 (4) ◽  
Author(s):  
Linmin Wu ◽  
Vincent De Andrade ◽  
Xianghui Xiao ◽  
Jing Zhang
Keyword(s):  
Phase Separation ◽  
Phase Field ◽  
Lithium Iron Phosphate ◽  
Iron Phosphate ◽  
Ion Concentration ◽  
Concentration Difference ◽  
X Ray ◽  
Aspect Ratios ◽  
Induced Stresses ◽  
And Diffusion

In this study, the phase separation phenomenon and diffusion-induced stresses in lithium iron phosphate (LiFePO4) particles under a potentiostatic discharging process have been simulated using the phase field method. The realistic particles reconstructed from synchrotron nano X-ray tomography along with idealized spherical and ellipsoid shaped particles were studied. The results show that stress and diffusion process in particles are strongly influenced by particle shapes, especially at the initial lithiation stage. Stresses in the realistic particles are higher than that in the idealized spherical ones by at least 30%. The diffusion-induced hydrostatic stress has a strong relationship with lithium ion concentration. The hydrostatic stresses and first principal stresses tend to shift from lower values to higher values as the particle takes in more lithium ions. Additionally, the diffusion-induced stresses are related to the maximum concentration difference in the particle. High concentration difference will cause high stresses. In ellipsoid particles, the stress levels increase with the aspect ratios. The model provides a design tool to optimize the performance of cathode materials with phase separation phenomena.

Enhancement of Lithium Battery Performance by Thickness Anode Film Modification

2015 ◽  
Vol 827 ◽  
pp. 156-161
Author(s):  
Rani Cahyani Fajaryatun ◽  
Therecia Wulan Sukardi ◽  
Arif Jumari ◽  
Agus Purwanto
Keyword(s):  
Polyvinylidene Fluoride ◽  
Lithium Battery ◽  
Lithium Iron Phosphate ◽  
Iron Phosphate ◽  
Electrochemical Performances ◽  
X Ray Diffraction ◽  
Battery Voltage ◽  
X Ray ◽  
Mesocarbon Microbeads ◽  
Anode Film

A lithium battery was composed of anode, cathode, and separator. The performance of lithium battery was influenced by the thickness of film, the composition of material, and the effect of surfactant and binder. This research investigated the effect of the anode film thickness to the electrochemical performances of lithium battery. Mesocarbon microbeads (MCMB) and lithium iron phosphate (LiFePO4) were used respectively as anode and cathode. Mesocarbon microbeads, carbon black (conductive agent), polyvinylidene fluoride (PVDF) as a binder and N-methyl-2-pyrrolidone (NMP) as a solvent were mixed well to produce slurry. The slurry were then coated, dried and pressed. The anode had various thickness of 50 μm, 70 μm, 100 μm, and 150 μm. The cathode film was made with certain thickness. The performance of lithium battery was examined by Eight Channel Battery Analyzer, the composition of the anode sample was examined by XRD (X-Ray Diffraction), and the crystal structure of the anode sample was analyzed by SEM (Scanning Electron Microscope). The research showed that the thickness of anode film of 100 μm gave the best performance. The battery performance decreased if the thickness was more than 100 μm. The best performance of battery voltage were between 3649 mV and 3650 mV.

Comparison between Different LiFePO4 Synthesis Routes

2007 ◽  
Vol 555 ◽  
pp. 225-230 ◽  
Author(s):  
D. Jugović ◽  
N. Cvjetićanin ◽  
M. Mitrić ◽  
S. Mentus
Keyword(s):  
Electron Microscopy ◽  
Lithium Iron Phosphate ◽  
Ultrasonic Spray Pyrolysis ◽  
Iron Phosphate ◽  
X Ray ◽  
Synthesis Conditions ◽  
Microstructural Parameters ◽  
Ultrasonic Spray ◽  
Synthesis Routes ◽  
Scanning Electron

Olivine-type lithium iron phosphate (LiFePO4) powders were synthesized applying three different methods: solid state reaction at high temperature, ultrasonic spray pyrolysis, and sonochemical treatment. The samples were characterized by X-ray powder diffraction (XRPD). Particle morphologies of the obtained powders were determined by scanning electron microscopy (SEM). It was found that structural and microstructural parameters of this material were strongly dependent on the synthesis conditions. We present here the results obtained upon optimization of each procedure for designing this cathode material.

Effect of Niobium Doping on Electrochemical Properties of Microwave Synthesized Carbon Coated Nanolithium Iron Phosphate for High Rate Underwater Applications

2018 ◽  
Vol 16 (2) ◽  
Author(s):  
A. Srinivas Kumar ◽  
T. V. S. L. Satyavani ◽  
M. Senthilkumar ◽  
P. S. V. Subba Rao
Keyword(s):  
Solid Solution ◽  
Lithium Iron Phosphate ◽  
Electrochemical Impedance ◽  
Rate Capability ◽  
Lithium Ion ◽  
Iron Phosphate ◽  
High Rate ◽  
X Ray ◽  
Niobium Doping ◽  
Carbon Coated

Lithium iron phosphate (LiFePO4) for lithium-ion batteries is considered as perfect cathode material for various military applications, especially underwater combat vehicles. For deployment at high rate applications, the low conductivity of LiFePO4 needs to be improved. Cationic substitution of niobium in the native carbon coated LiFePO4 is one of the methods to enhance the conductivity. In the present work, how the niobium doped solid solution could be formed is studied. Nanopowders of LiFePO4/C and Li1−xNbxFePO4/C (x = 0.05, 0.1, 0.15, 0.16) are synthesized from precursors using microwave synthesis. The solid solution formation up to (x = 0.15) Li1−xNbxFePO4/C without impurity phases is confirmed by X-ray diffraction (XRD) pattern and Fourier transform infrared spectroscopic (FTIR) results. Particle distribution is obtained by scanning electron microscope from the synthesized powders. Energy dispersive X-ray spectrometer (EDS) results qualitatively confirmed the presence of niobium. Also, direct current (dc) conductivities are measured using sintered pellets and activation energies are calculated using Arrhenius equation. The dependence of conductivity and activation energy of LiFePO4/C on variation of niobium doping is investigated in this study. CR2032 type coin cells are fabricated with the synthesized materials and subjected to cyclic voltammetry studies, rate capability and cycle life studies. Diffusion coefficients are obtained from electrochemical impedance spectroscopy studies. It is observed that room temperature dc conductivity improved by niobium doping when compared to LiFePO4/C (0.379 × 10−2 S/cm) and is maximum for Li0.9Nb0.1FePO4/C (40.58 × 10−2 S/cm). It is also observed that diffusion coefficient of Li+ in Li0.9Nb0.1FePO4/C (13.306 × 10−9 cm2 s−1) improved by two orders of magnitude in comparison with the pure LiFePO4 (10 − 12 cm2 s−1) and carbon-coated nano LiFePO4/C (0.632 × 10−11 cm2 s−1). Cells with Li0.9Nb0.1FePO4/C are able to deliver useful capacity of around 104 mAh/g at 10 C rate. More than 500 cycles are achieved with Li0.9Nb0.1FePO4/C at 20 C rate.

Synthesis and Characterization of LiFePO4 / PPy Composite Powders

2008 ◽  
Vol 58 ◽  
pp. 205-210 ◽  
Author(s):  
Xiang Zhong Ren ◽  
Xi Li ◽  
Pei Xin Zhang ◽  
Jian Hong Liu ◽  
Qian Ling Zhang ◽  
...  
Keyword(s):  
Lithium Iron Phosphate ◽  
Heat Stability ◽  
Iron Phosphate ◽  
Chemical Oxidation ◽  
X Ray Diffraction ◽  
Composite Powders ◽  
Doping Agent ◽  
X Ray ◽  
Oxidation Agent

A series of lithium iron phosphate /polypyrrole (LiFePO4/PPy) composite powders were synthesized by chemical oxidation method with different doping agent and oxidation agent. The composite powders were characterized by scanning electron microscopy (SEM), Fourier Transform Infrared Spectrum (FTIR), and X-ray diffraction (XRD). The results showed that the composite powders composed of PPy and LiFePO4. And the doping of polypyrrole in LiFePO4 could weaken the XRD intensity of LiFePO4 , but could not destroy its crystallization. With the increase of pyrrole in LiFePO4/ PPy composite powders, the polypyrrole on the surface of LiFePO4 increased and dispersed more homogeneously. Thermogravimetric analysis (TGA) data indicated the heat-stability of LiFePO4/PPy was very good that the composite powders would not oxidate till 300°C in the air flow.

scholarly journals Cahn-Hilliard Reaction Model for Isotropic Li-ion Battery Particles

2013 ◽  
Vol 1542 ◽  
Author(s):  
Yi Zeng ◽  
Martin Z. Bazant
Keyword(s):  
Phase Separation ◽  
Lithium Iron Phosphate ◽  
Chemical Potential ◽  
Iron Phosphate ◽  
Reaction Model ◽  
Li Ion Battery ◽  
Two Phase ◽  
Basic Physics ◽  
Shrinking Core ◽  
Li Ion

ABSTRACTUsing the recently developed Cahn-Hilliard reaction (CHR) theory, we present a simple mathematical model of the transition from solid-solution radial diffusion to two-phase shrinking-core dynamics during ion intercalation in a spherical solid particle. This general approach extends previous Li-ion battery models, which either neglect phase separation or postulate a spherical shrinking-core phase boundary under all conditions, by predicting phase separation only under appropriate circumstances. The effect of the applied current is captured by generalized Butler-Volmer kinetics, formulated in terms of the diffusional chemical potential in the CHR theory. We also consider the effect of surface wetting or de-wetting by intercalated ions, which can lead to shrinking core phenomena with three distinct phase regions. The basic physics are illustrated by different cases, including a simple model of lithium iron phosphate (neglecting crystal anisotropy and coherency strain).

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