Revealing the Rate-Limiting Li-Ion Diffusion Pathway in Ultrathick Electrodes for Li-Ion Batteries

Gao, Han; Wu, Qiang; Hu, Yixin; Zheng, Jim P.; Amine, Khalil; Chen, Zonghai

doi:10.1021/acs.jpclett.8b02229

Cited by 164 publications

(116 citation statements)

References 35 publications

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“…Therefore, from the present results and those published in literature, it is reasonable to conclude that electrodes with thickness less than the ion diffusion coefficient (< 20 nm) support PC charge storage. This idea of morphology driven pseudocapacitance in thin materials structures could be drawn from the fundamental mechanism governing the charge storage in electrochemical cells [3] as well as by recently published literatures [31][32][33][34]. Fundamentally, the extend of charge diffusion in the electrode differentiates batteries and pseudocapacitors despite their similar faradaic processes.…”

Section: Resultsmentioning

confidence: 99%

Pseudocapacitive Charge Storage in Thin Nanobelts

et al. 2019

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This article reports that extremely thin nanobelts (thickness ~ 10 nm) exhibit pseudocapacitive (PC) charge storage in the asymmetric supercapacitor (ASC) configuration, while show battery-type charge storage in their single electrodes. Two types of nanobelts, viz. NiO-Co 3 O 4 hybrid and spinal-type NiCo 2 O 4 , developed by electrospinning technique are used in this work. The charge storage behaviour of the nanobelts is benchmarked against their binary metal oxide nanowires, i.e., NiO and Co 3 O 4 , as well as a hybrid of similar chemistry, CuO-Co 3 O 4. The nanobelts have thickness of ~ 10 nm and width ~ 200 nm, whereas the nanowires have diameter of ~ 100 nm. Clear differences in charge storage behaviours are observed in NiO-Co 3 O 4 hybrid nanobelts based ASCs compared to those fabricated using the other materials-the former showed capacitive behaviour whereas the others revealed battery-type discharge behaviour. Origin of pseudocapacitance in nanobelts based ASCs is shown to arise from their nanobelts morphology with thickness less than typical electron diffusion lengths (~ 20 nm). Among all the five type of devices fabricated, the NiO-Co 3 O 4 hybrid ASCs exhibited the highest specific energy, specific power and cycling stability.

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Section: Resultsmentioning

confidence: 99%

Pseudocapacitive Charge Storage in Thin Nanobelts

et al. 2019

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“…Although, increasing the electrode thickness significantly enhances the specific capacity of the electrode up to approximately 100 µm, theoretical [19,[29][30][31][32][33][34] and experimental [35][36][37][38] results clearly show that large electrode thicknesses lead to low rate capability originating from Li + diffusion limitations in the electrolyte. For example, the conductive additive content can be increased until limitations of the electron transport in the composite become negligible.…”

mentioning

confidence: 95%

“…In contrast to that, the electrode thickness and the specific capacity of the active material cannot be optimized regarding the rate performance without affecting the energy density. Although, increasing the electrode thickness significantly enhances the specific capacity of the electrode up to approximately 100 µm, theoretical [19,[29][30][31][32][33][34] and experimental [35][36][37][38] results clearly show that large electrode thicknesses lead to low rate capability originating from Li + diffusion limitations in the electrolyte. Similarly, increasing the gravimetric capacity of the active material enhances the specific capacity of the electrode, but the larger current density at a given C-rate also leads to increased Li + diffusion limitations in the electrolyte and a corresponding decline in capacity at higher rates.…”

mentioning

confidence: 99%

Diffusion‐Limited C‐Rate: A Fundamental Principle Quantifying the Intrinsic Limits of Li‐Ion Batteries

Heubner

Schneider

Michaelis

2019

Advanced Energy Materials

124

103

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carried out to improve the energy density at the cell level, such as the development of high capacity anode [8,9] and cathode [10,11] materials, improvements of the electrode design [12,13] and composition [14][15][16] as well as optimization of the cell architecture. [17,18] Moreover, researchers analyzed the rate limiting factors of electrodes for LIBs in great detail to understand the complex charge transport and transfer reaction processes and optimize materials and cell components accordingly. [19] It has been found that the rate performance can be improved by increasing solid-state diffusivity, [20] conductive additive type and content [21] or electrode porosity, [22] by the optimization of electrolyte properties, such as concentration [23] and viscosity, [24] and by decreasing the particle size of active materials [13,25] and the electrode thickness. [26][27][28] Although these measures lead to a gradual improvement of decisive performance metrics, a tradeoff between energy and power density became obvious, forbidding arbitrary combinations of high storage capacity and fast charging capability. Understanding this tradeoff and the accompanied practical limits of LIBs is critical for their further improvement and the development of "beyond Li" battery technologies.Herein, we present a simple but powerful electrochemical principle describing the tradeoff between storage capacity and rate capability of electrodes for LIBs. Such electrodes are porous composites consisting of particles of the active storage material, binder and conductive additives coated on a metallic current collector foil. The pores are filled with a liquid electrolyte containing Li-ions as charge carriers. The specific capacity (energy density equivalent) of such an electrode is given by the specific capacity of the active material and its share in the electrode. Figure 1 illustrates the sensitivity of the specific capacity to the most decisive electrode parameters using a typical LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NCM111)-based cathode as the baseline (see Section S3 in the Supporting Information for details on the computations). Please note that here the specific capacity of the electrode also includes the masses of conductive additives, binder, current collector and the pore electrolyte, which is often ignored in the literature but has significant impact on the energy density (see Section S2 in the Supporting Information for details). It turns out that some electrode properties hardly affect the energy density, such as the porosity, the conductive additive and binder content, and the particle size (cf. Figure 1).The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/aenm.201902523.Li-ion batteries (LIBs) were continuously improved over the last decades, aiming at longer operating times of mobile electronic devices and mass implementation in high-energy applications, such as all-electric or hybrid-electric vehicles. [1][2][3][4] However, owing to safety concerns, range limitations, and inad...

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“…Patry et al evaluated the impact of electrode coating thickness on the cell cost for different cathode active materials (AMs) and found that the doubling of the electrode thickness from 50 to 100 μm for NCM 111 (Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 ) leads to a potential cost reduction of 24% per kilowatt hour ($ kW h −1 ) . Therefore, the concept of thick electrodes was recently investigated experimentally by several groups, yielding electrodes with high mass loadings, for example, coated on porous metal current collectors or produced binder‐free by Templating or Spark Plasma Sintering (SPS) and studied by modeling and simulation …”

Section: Introductionmentioning

confidence: 99%

“…During the fabrication of thick electrodes, special treatment concerning mixing, drying, and handling becomes necessary to yield mechanically stable electrodes. With regard to the electrochemical performance, thick electrodes suffer from mass transport limitations of lithium ions in the electrolyte phase and an increasing impedance for electrons in the solid phase of the electrode . Recent literature used theoretical approaches to prove that electrochemical reactions in porous electrodes under high current densities are limited by liquid‐phase transport mechanisms attributed to a concentration gradient and resulting electrolyte depletion.…”

Section: Introductionmentioning

confidence: 99%

Manufacturing Process for Improved Ultra‐Thick Cathodes in High‐Energy Lithium‐Ion Batteries

et al. 2019

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The effect of the mixing and drying process on the microstructure of ultra‐thick NCM 622 cathodes (50 mg cm−2, 8 mAh cm−2) and its implication for battery performance is investigated. It is observed that the shear force during the mixing process significantly influences the resulting microstructure with regard to binder migration during the drying process. Based on the information extracted from scanning electron microscopy–energy dispersive X‐ray spectroscopy (SEM–EDX) cross sections, the carbon binder domain (CBD) is distributed in the pore space of virtual electrodes generated by a stochastic 3D microstructure model. Simulations predict a CBD configuration that leads to optimal performance of the electrode. Furthermore, it is shown that a low drying rate has a beneficial influence toward the rate capability of the ultra‐thick cathodes. The specific energy of an ultra‐thick cathode is 18% higher compared with a cathode prepared according to the state of the art. With an improved process in a pilot scale, the advantage can be kept up to current densities of at least 3 mA cm−².

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Revealing the Rate-Limiting Li-Ion Diffusion Pathway in Ultrathick Electrodes for Li-Ion Batteries

Cited by 164 publications

References 35 publications

Pseudocapacitive Charge Storage in Thin Nanobelts

Pseudocapacitive Charge Storage in Thin Nanobelts

Diffusion‐Limited C‐Rate: A Fundamental Principle Quantifying the Intrinsic Limits of Li‐Ion Batteries

Manufacturing Process for Improved Ultra‐Thick Cathodes in High‐Energy Lithium‐Ion Batteries

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