Lithium-ion batteries with high charge rate capacity: Influence of the porous separator

Djian, Damien; Alloin, Fannie; Martinet, Sébastien; Lignier, Hélène; Sanchez, Jean‐Yves

doi:10.1016/j.jpowsour.2007.07.018

Cited by 195 publications

(133 citation statements)

References 13 publications

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“…2,14,22 In many publications, impedance based techniques are used to measure the effective conductivity. Unfortunately, the value of the MacMullin numbers vary quite significantly for the same separator material which, e.g., can be illustrated for the reported MacMullin numbers for Celgard 2500 separator of 8.5 (Patel et al…”

mentioning

confidence: 99%

Tortuosity Determination of Battery Electrodes and Separators by Impedance Spectroscopy

Landesfeind

Hattendorff

Ehrl

et al. 2016

J. Electrochem. Soc.

511

596

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Lithium ion battery performance at high charge/discharge rates is largely determined by the ionic resistivity of an electrode and separator which are filled with electrolyte. Key to understand and to model ohmic losses in porous battery components is porosity as well as tortuosity. In the first part, we use impedance spectroscopy measurements in a new experimental setup to obtain the tortuosities and MacMullin numbers of some commonly used separators, demonstrating experimental errors of <8%. In the second part, we present impedance measurements of electrodes in symmetric cells using a blocking electrode configuration, which is obtained by using a non-intercalating electrolyte. The effective ionic resistivity of the electrode can be fit with a transmission-line model, allowing us to quantify the porosity dependent MacMullin numbers and tortuosities of electrodes with different active materials and different conductive carbon content. Best agreement between the transmission-line model and the impedance data is found when constant-phase elements rather than simple capacitors are used. Motivation.-Advanced battery models are a valuable tool for evaluating the performance, safety, and life-time of lithium ion batteries, since they can provide insight into the kinetics and the transport characteristics of batteries, which are not or only partially accessible by experiments. To obtain quantitative and meaningful numerical results, the choice of appropriate physical models and boundary conditions with the corresponding, accurately determined, kinetic and transport parameters are key issues. For numerical simulations of battery systems, the ion-transport model for concentrated electrolyte solutions introduced by Newman et al.1 is frequently used. Since the microscopic geometry of actually used porous electrodes and separators are largely unknown, a homogenization approach is applied for the macroscopic description of porous media. In this case, the influence of the microstructure on the macroscopic behavior is modeled by additional geometric parameters such as the porosity ε and the tortuosity τ. The porosity ε is a well-defined property of a porous medium, which can be determined easily. In contrast, the effective tortuosity of separators and particularly of electrodes are more difficult to quantify, and, to further complicate the matter, many different definitions for the tortuosity τ are used in the literature. Thus, the different tortuosity definitions will be presented prior to reviewing the literature concerned with determining the tortuosity or the effective ionic conductivity of porous battery separators and electrodes.

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mentioning

confidence: 99%

Tortuosity Determination of Battery Electrodes and Separators by Impedance Spectroscopy

Landesfeind

Hattendorff

Ehrl

et al. 2016

J. Electrochem. Soc.

511

596

View full text Add to dashboard Cite

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“…The resulting graph revealed a high degree of correlation following the equation Eq. (21). This equation reveals, that the simulation based tortuosity factor (and as such, tortuosity) is always higher than the geometric based value of the same sample in cases, where either value is > 1.…”

Section: Mesh Based Calculation Methodsmentioning

confidence: 91%

Tortuosity in electrochemical devices: a review of calculation approaches

Tjaden

Brett

Shearing

2016

International Materials Reviews

211

188

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The tortuosity of a structure plays a vital role in the transport of mass and charge in electrochemical devices. Concentration polarisation losses at high current densities are caused by mass transport limitations and are thus a function of microstructural characteristics. As tortuosity is notoriously difficult to ascertain, a wide and diverse range of methods has been developed to extract the tortuosity of a structure. These methods differ significantly in terms of calculation approach and data preparation techniques. Here, we review tortuosity calculation procedures applied in the field of electrochemical devices to better understand the resulting values presented in the literature. Visible differences between calculation methods are observed, especially when using porosity-tortuosity relationships and when comparing geometric and flux based tortuosity calculation approaches.

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“…Even B100, the most resistive, yielded a MacMullin number lower than that of Celgard2400. 43,44 For shutdown temperature, i.e. where the EPS starts to soften and close pores, log Z re (at 1 kHz) was plotted vs. temperature (Figure 8).…”

Section: Resultsmentioning

confidence: 99%

Polyvinylidene Difluoride–Polyethyleneoxide Blends for Electrospun Separators in Li-Ion Batteries

Monaca

Giorgio

Focarete

et al. 2017

J. Electrochem. Soc.

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Polyvinylidenedifluoride (PVdF) and polyethyleneoxide (PEO) are blended and electrospun in order to obtain membranes suitable as Li-ion battery separators. The separators are characterized, and their properties investigated and compared with those of PVdF and commercial separators. The PVdF-PEO based separators ensure increased conductivities, greater electrolyte uptake and higher porosities than commercial polyolefines, all factors that improve cell performance. Li-ion batteries are one of the most mature and most wide spread energy storage systems on the market. They supply almost every laptop, smartphone and tablet and are among the most widely used storage systems in hybrid and electric vehicles. Today Li-ion technology is approaching its limits of energy density (200-250 Wh/kg) 1,2 thanks to new and advanced high-voltage and high-capacity electrode materials. Hence, most electrochemical research seeks to improve cycle life and safety.2-9 However, in order to meet the new conditions required by high voltage electrodes and to enhance the other aforementioned features, the development of so-called inactive materials is mandatory. A key inactive material is the separator. It prevents physical and electrical contact between electrodes while allowing ions to flow through it. It must have a high chemical and electrochemical stability vis-á-vis the electrode and electrolyte materials and should be mechanically strong enough to withstand the high stress during battery assembly. The separator must also be sufficiently porous to absorb a large quantity of liquid electrolyte, thus assuring high ionic conductivity. On the other hand, the separator inevitably increases the electrical resistance of the cell, thereby significantly worsening the battery performance. Indeed, it must be very thin and porous in order to achieve high energy and power densities while ensuring sufficient mechanical robustness. 10-13The perfect separator has yet to be invented, its development depending on trade-offs among the aforementioned properties in order to obtain the specific features for the desired application. Safety too is an important concern. A necessary feature of separators is the shutdown function, i.e. the ability to shut the battery down when overheating occurs due, for example, to a short circuit, overcharging or exposure to external heat sources, in order to prevent thermal runaway.14,15 Nearly all separators today used in liquid electrolyte batteries are based on microporous polyolefin membranes given their good mechanical properties, thinness and low cost. Much research effort of late has been devoted to the development of innovative, highly porous separators based on non-woven mats. One well known method of mat preparation is electrospinning technology. 13,16,17 Electrospinning is a low cost technology with respect to other techniques used to manufacture nanofibers, e.g. extrusion, drawing, phase separation. It is also commonly used to fabricate highly porous nanostructures or nanofibrous non-woven membranes characterized b...

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Lithium-ion batteries with high charge rate capacity: Influence of the porous separator

Cited by 195 publications

References 13 publications

Tortuosity Determination of Battery Electrodes and Separators by Impedance Spectroscopy

Tortuosity Determination of Battery Electrodes and Separators by Impedance Spectroscopy

Tortuosity in electrochemical devices: a review of calculation approaches

Polyvinylidene Difluoride–Polyethyleneoxide Blends for Electrospun Separators in Li-Ion Batteries

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