Composite cathode structure/property relationships

Babinec, Susan J.; Tang, Haoyu; Talik, Andrew; Hughes, Stephanie; Meyers, Gregory F.

doi:10.1016/j.jpowsour.2007.06.071

Cited by 46 publications

(36 citation statements)

References 4 publications

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“…Figure 3a shows an average elastic modulus for swollen binder films of ∼200 MPa in agreement with the literature. 26 The swollen binder exhibited a similar dependence on carbon black weight fraction as the dry films. The elastic moduli for binder films swollen in a 3:7 mixture of ethylene carbonate:ethyl methyl carbonate are also shown for comparison.…”

Section: Mechanical Properties Of Polyvinylidene Fluoride-carbon Blacmentioning

confidence: 86%

“…Propylene carbonate has a relatively low evaporation rate and with a single component the composition was consistent throughout the experiment. Babinec et al 26 found only small differences between the measured Young's modulus and strain to failure of binder films saturated with pure propylene carbonate and a mixture of ethylene carbonate with diethyl carbonate. Our own measurements comparing propylene carbonate to other solvent mixtures also found only small differences in the measured Young's modulus and solvent uptake as will be reported in the next section.…”

Section: Methodsmentioning

confidence: 98%

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Conductivity Degradation of Polyvinylidene Fluoride Composite Binder during Cycling: Measurements and Simulations for Lithium-Ion Batteries

Grillet

Humplik

Stirrup

et al. 2016

J. Electrochem. Soc.

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The polymer-composite binder used in lithium-ion battery electrodes must both hold the electrodes together and augment their electrical conductivity while subjected to mechanical stresses caused by active material volume changes due to lithiation and delithiation. We have discovered that cyclic mechanical stresses cause significant degradation in the binder electrical conductivity. After just 160 mechanical cycles, the conductivity of polyvinylidene fluoride (PVDF):carbon black binder dropped between 45-75%. This degradation in binder conductivity has been shown to be quite general, occurring over a range of carbon black concentrations, with and without absorbed electrolyte solvent and for different polymer manufacturers. Mechanical cycling of lithium cobalt oxide (LiCoO 2 ) cathodes caused a similar degradation, reducing the effective electrical conductivity by 30-40%. Mesoscale simulations on a reconstructed experimental cathode geometry predicted the binder conductivity degradation will have a proportional impact on cathode electrical conductivity, in qualitative agreement with the experimental measurements. Finally, ohmic resistance measurements were made on complete batteries. Direct comparisons between electrochemical cycling and mechanical cycling show consistent trends in the conductivity decline. This evidence supports a new mechanism for performance decline of rechargeable lithium-ion batteries during operation -electrochemically-induced mechanical stresses that degrade binder conductivity, increasing the internal resistance of the battery with cycling. Lithium-ion batteries (LIB) are an enabling energy storage technology for portable consumer electronics, electric vehicles and renewable power generation in part due to their high energy densities. The energy density is driven by not only the relatively large potential of lithium-ion chemistries, but also the ability of active materials to store large amounts of lithium.1 The most common graphitic carbon anode can absorb up to one lithium for every carbon atom. Recent research on higher capacity anodes such as silicon has highlighted an increased need for understanding the mechanics of lithium-ion batteries. As the lithium is shuttled between the anode and cathode, the active materials expand and contract to accommodate the lithium. The resulting volume changes are accentuated for high capacity materials such as silicon which can increase in volume by up to 400% during lithiation. 2Because most LIB electrodes are porous multicomponent composites, understanding the generation and impact of mechanical stresses on batteries can be difficult. The electrode is generally 50-75 vol% solid fraction with active material consisting of micron-sized particles held together by an active binder, which is itself a composite of conductive carbon particles and polymer. The performance of the battery is highly dependent on this complex structure which must allow efficient ion and electron transport through the electrode. The void space in the porous structure allows lith...

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Section: Mechanical Properties Of Polyvinylidene Fluoride-carbon Blacmentioning

confidence: 86%

Section: Methodsmentioning

confidence: 98%

Conductivity Degradation of Polyvinylidene Fluoride Composite Binder during Cycling: Measurements and Simulations for Lithium-Ion Batteries

Grillet

Humplik

Stirrup

et al. 2016

J. Electrochem. Soc.

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“…But PEO is usually not utilized in composite electrodes for LiB because this polymer electrochemical stability window is limited to 4 V vs. Li/ Li + , which is not suitable for high voltage positive electrodes such as LiCoO 2 . As a result, polymers with higher electrochemical stability such as poly(tetrafluoro ethylene), PTFE, or PVdF have been most widely adopted as the binder for composite electrodes in LiB [7][8][9][10]. A copolymer of vinylidene fluoride with hexafluoropropylene, PVdF-HFP, is used in both polymeric electrolyte and composite electrode of the plastic LiB technology [11].…”

Section: The Usual and New Binder Combinationsmentioning

confidence: 99%

Functions of polymers in composite electrodes of lithium ion batteries

Lestriez¹

2010

Comptes Rendus. Chimie

150

100

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“…Nevertheless, it is important to note that polarization is a global variant representing the average behavior of the electrodes in the cell. There are localized effects that can contribute to capacity variations within the constituents of the electrode matrix due to inhomogeneity in current density, grain size distribution, additive composition, conductive path, pore distribution, due to the composite nature of the electrode design and the variations in cell processing related to slurry mixing and tape casting [22][23][24][25].…”

Section: The As-received Ocv Values (Reported Inmentioning

confidence: 99%

Origins and accommodation of cell variations in Li-ion battery pack modeling

Dubarry¹,

Vuillaume²,

Liaw³

2009

Int. J. Energy Res.

181

117

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SUMMARYRechargeable battery industry will see significant growth in the use of battery systems for portable devices and power electronics, renewable energy storage, power systems for transportation, and telecom backup power applications. Despite such promising market sentiment, the battery system management remains as a challenging issue to be resolved in order to provide a safe and reliable power and energy storage system. Here we report advancement in the battery management approach by providing a solution to analyze battery performance variations in a lot of batteries produced from the same manufacturing process. A lot of 100 Li-ion cells were analyzed in order to quantify the inherent cell variations associated with cell manufacturing process and test protocol. Both statistical and electrochemical analyses were used to characterize and quantify the capacity variations among the cells along with other parameters that can be readily derived from the test results. Information extracted from a minimal testing of the cells in the lot and more intensive characterizations on a few cells including one as the nominal sample cell allows the establishment of a single cell model (SCM), based on a generic equivalent circuit, with high accuracy in predicting cell performance. The analyses also permit a carefully crafted logic development of how to separate the origins that cause the cell variations in performance. Such separation of the attributes enable a proper tuning of the cell parameters in the model, which allows the accommodation of cell variations in a battery pack model to handle most of the imbalance issues. A careful validation of the SCM to predict performance of any arbitrary cell in the lot with high accuracy was demonstrated.

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Composite cathode structure/property relationships

Cited by 46 publications

References 4 publications

Conductivity Degradation of Polyvinylidene Fluoride Composite Binder during Cycling: Measurements and Simulations for Lithium-Ion Batteries

Conductivity Degradation of Polyvinylidene Fluoride Composite Binder during Cycling: Measurements and Simulations for Lithium-Ion Batteries

Functions of polymers in composite electrodes of lithium ion batteries

Origins and accommodation of cell variations in Li-ion battery pack modeling

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