Investigation of charge transfer kinetics of Li-Intercalation in LiFePO 4

Heubner, Christian; Schneider, Michael; Michaelis, Alexander

doi:10.1016/j.jpowsour.2015.04.103

Cited by 72 publications

(48 citation statements)

References 31 publications

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“…The equivalent circuit model used to fit the EIS data is shown as an inset in Figure 3b. 42 The Nyquist spectra show the expected features which were fit using 6 circuit elements as follows: A high frequency intercept on the real impedance axis which represents the ohmic transport losses in the electrolyte and bulk-Si is modeled by the resistance, R ohmic . Since highly conductive Si wafers were used, R ohmic comprises mostly the electrolyte resistance.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Charge Transfer Reaction Kinetics at the Silicon-Liquid Electrolyte Interface

Swamy¹,

Chiang²

2015

J. Electrochem. Soc.

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Since the gravimetric lithiation capacity of silicon is roughly ten times that of graphite, while their mass densities are comparable, for the same particle size the current density required to cycle a silicon electrode at a given C-rate is about ten times greater than that of graphite. Depending on the magnitude of the corresponding Butler-Volmer exchange current density, jo, such high current densities may cause the charge transfer kinetics at the silicon-electrolyte interface to become rate limiting. Previously reported values of jo for Si differ by about 10 orders of magnitude. Here we report jo measurements using electrochemical impedance spectroscopy (EIS) for single crystal electronically conductive silicon wafers with well-defined (100) and (111) orientations and active surface areas. The electrochemical cycling regime was designed to avoid artifacts due to stress-induced surface cracking of Si upon lithiation. The exchange current density of the silicon-electrolyte interface is found to be 0.1 ± 0.01 mA/cm2 when using electrolyte consisting of 1 M LiPF6 in EC/DMC (1/1 by wt) + FEC (10 wt%) + VC (2 wt%). These results are then used to illustrate the dependence of kinetic overpotential on particle size and C-rate for silicon compared to lower volumetric capacity compounds such as graphite.

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Section: Resultsmentioning

confidence: 99%

Electrochemical Charge Transfer Reaction Kinetics at the Silicon-Liquid Electrolyte Interface

Swamy¹,

Chiang²

2015

J. Electrochem. Soc.

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“…In the particular case of batteries, EIS provides information about the kinetic and mass transport properties of the cells and allows the relation of these electrical measurements to the physical processes. One of the advantages of EIS is that the measured effects can be easily translated into equivalent electrical circuits, which are commonly based on combinations of resistive, capacitive, and inductive elements along with constant phase elements (CPEs) [20][21][22][23][24]. In the literature, it is common to find the evolution of the resistive parts with state-of-charge (SoC) [9,18,22,25,26] but less information is available about the evolution of capacitance or characteristic frequency [20,26].…”

Section: Introductionmentioning

confidence: 99%

Impedance Characterization of an LCO-NMC/Graphite Cell: Ohmic Conduction, SEI Transport and Charge-Transfer Phenomenon

Ovejas

Cuadras

2018

Batteries

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Currently, Li-ion cells are the preferred candidates as energy sources for existing portable applications and for those being developed. Thus, a proper characterization of Li-ion cells is required to optimize their use and their manufacturing process. In this study, the transport phenomena and electrochemical processes taking place in LiCoO2-Li(NiMnCo)O2/graphite (LCO-NMC/graphite) cells are identified from half-cell measurements by means of impedance spectroscopy. The results are calculated from current densities, instead of absolute values, for the future comparison of this data with other cells. In particular, impedance spectra are fitted to simple electrical models composed of an inductive part, serial resistance, and various RQ networks—the parallel combination of a resistor and a constant phase element—depending on the cell. Thus, the evolution of resistances, capacitances, and the characteristic frequencies of the various effects are tracked with the state-of-charge (SoC) at two aging levels. Concretely, two effects are identified at the impedance spectrum; one is clearly caused by the charge transfer at the positive electrode, whereas the other one is presumably caused by the transport of lithium ions across the solid electrolyte interphase (SEI) layer. Moreover, as the cells age, the characteristic frequency of the charge transfer is drastically reduced by a factor of around 70%.

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“…This indicates increasing limitations of the lithium insertion reaction, e. g. due to ohmic and charge transfer resistance or mass transport limitations. Thereby, LCO is clearly more rate limited in comparison with LFP, which can be caused by larger charge transfer limitations and more sluggish diffusion kinetics [11] as well as ionic and electronic charge transport limitations in the composite. [12,13] The differences in the rate performance of LFP and LCO also become obvious in the results of the CV analysis plotted in Figure 4.…”

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confidence: 51%

Deconvolution of Cyclic Voltammograms for Blended Lithium Insertion Compounds by using a Model‐Like Blend Electrode

et al. 2017

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The blending of different lithium insertion compounds is a promising attempt to tailor the electrochemical performance of electrodes for lithium‐ion batteries. Remarkable improvements regarding power density and safety issues have been made. However, the understanding of basic interactions between the constituents of the blend is still ongoing. Herein, we separate the current responses from the individual constituents during cyclic voltammetric measurements by using a special experimental setup and a model‐like blended insertion electrode. This approach enables the deconvolution of the cyclic voltammogram of the blend, assignment of redox peaks, identification of kinetic limitations, and observation of internal dynamics, gaining fundamental insights towards the properties of blended insertion electrodes.

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Investigation of charge transfer kinetics of Li-Intercalation in LiFePO 4

Cited by 72 publications

References 31 publications

Electrochemical Charge Transfer Reaction Kinetics at the Silicon-Liquid Electrolyte Interface

Electrochemical Charge Transfer Reaction Kinetics at the Silicon-Liquid Electrolyte Interface

Impedance Characterization of an LCO-NMC/Graphite Cell: Ohmic Conduction, SEI Transport and Charge-Transfer Phenomenon

Deconvolution of Cyclic Voltammograms for Blended Lithium Insertion Compounds by using a Model‐Like Blend Electrode

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