Nanoindentation testing of separators for lithium-ion batteries

Halalay, Ion C.; Lukitsch, M.J.; Balogh, Michael P.; Wong, Curtis A.

doi:10.1016/j.jpowsour.2013.04.036

Cited by 40 publications

(35 citation statements)

References 7 publications

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“…While all four previously mentioned materials demonstrate the validity of the Mn trapping concept for improving LIBs durability, none are suitable for practical devices, due to the inadequate mechanical properties of perfluorinated membranes 78 or the well-known drawbacks of laid-fiber membranes, 79 as well as the high cost of both perfluorinated polymers and crown ethers. We have recently shown that Mn trapping and the associated benefits for capacity retention in LMO-graphite cells upon high-temperature cycling can be obtained with several inexpensive commercially available polymeric or molecular ion-trapping materials.…”

Section: A6316mentioning

confidence: 99%

Review—Multifunctional Materials for Enhanced Li-Ion Batteries Durability: A Brief Review of Practical Options

Banerjee

Shilina

Ziv

et al. 2017

J. Electrochem. Soc.

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Transition metal (TM) ions dissolution from positive electrodes, migration to and deposition on negative electrodes, followed by Mn-catalyzed reactions of solvents and anions, with loss of Li + ions, is a major degradation (DMDCR) mechanism in Li-ion batteries (LIBs) with spinel positive electrode materials. While the details of the DMDCR mechanism are still under debate, it is clear that HF and other acid species' attack is the main cause in solutions with LiPF 6 electrolyte. We first review the work on various mitigation measures for the DMDCR mechanism, now spanning more than two decades. We then discuss recent progress on our understanding of Mn species in electrolyte solutions and the extension of a mitigation measure first proposed by Tarascon and coworkers in 1999, namely chelation of TM cations, to Mn cation trapping, HF scavenging, and alkali metal ions dispensing multi-functional materials. We focus on practicable, drop-in technical solutions, based on placing such materials in the inter-electrode space, with significant benefits for LIBs performance: increased capacity retention during operation at room and above-ambient temperatures as well as robust (both maximally ionically conducting and electronically insulating) solid-electrolyte interfaces, having reduced charge transfer and film resistances at both negative and positive electrodes. We illustrate the multifunctional materials approach with both new and previously published data. We also discuss and offer our evaluation regarding the merits and drawbacks of the various mitigation measures, with an eye for practically relevant technical solutions capable to meet both the performance requirements and cost constraints for commercial LIBs, and end with recommendations for future work. Li-ion batteries (LIBs) dominate the global market for energystorage devices nowadays and are used in a variety of applications, ranging from portable consumer electronics, to electrical grid storage, to load-levelling and electrified vehicles.1 Electrified vehicles are the most demanding among all LIBs applications in terms of both duty cycle and durability, since the batteries are subjected to a wide range of temperatures and charging/discharging rates, while customers expect a 10 years lifetime. Incessant research on various positive and negative active materials resulted in several promising electrode materials with various crystal structures and chemistries being developed over the past decades, such as layered (LiCoO 2 , LiNi 1-x-y Co x Al y O 2 , Ni 1-x-y Co x Mn y O 2 ), spinel (LiMn 2 O 4 , a.k.a. LMO; LNi 0.5 Mn 1.5 O 2 , a.k.a. LNMO), and olivine (LiFePO 4, LiVPO 4 ) for positive, as well as graphite, silicon, silicon-oxide, and lithium titanate for negative electrodes.2 New developments in electrode materials notwithstanding, LIBs for automotive transportation still need considerable improvements in terms of both performance and durability. Among transition metal (TM) oxide cathodes, LiMn 2 O 4 spinel would be most suited for automotive power cells due to i...

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Section: A6316mentioning

confidence: 99%

Review—Multifunctional Materials for Enhanced Li-Ion Batteries Durability: A Brief Review of Practical Options

Banerjee

Shilina

Ziv

et al. 2017

J. Electrochem. Soc.

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“…These modulus values are much higher than those reported for typical PEG-based ion conducting materials, 70,74 and on par with some of the highest reported to date. 37,53 These values also show favorable comparison to commercial separators made of polytetrafluoroethylene or a composite of silica, alumina and poly(ethylene terephthalate) that each showed a Young's modulus of approximately 60 MPa by nanoindentation 75. …”

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confidence: 91%

Wide Bicontinuous Compositional Windows from Co-Networks Made with Telechelic Macromonomers

et al. 2014

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Phase-separated and self-assembled co-network materials offer a simple route to bicontinuous morphologies, which are expected to be highly beneficial for applications such as ion, charge, and oxygen transport. Despite these potential advantages, the programmed creation of co-network structures has not been achieved, largely due to the lack of well-controlled chemistries for their preparation. Here, a thiol-ene end-linking platform enables the systematic investigation of phase-separated poly(ethylene glycol) (PEG) and polystyrene (PS) networks in terms of the molecular weight and relative volume fractions of precursor polymers. The ion conductivity and storage modulus of these materials serve as probes to demonstrate that both phases percolate over a wide range of compositions, spanning PEG volume fractions from ∼0.3-0.65. Small angle X-ray scattering (SAXS) shows that microphase separation of these co-networks yields disordered structures with d-spacings that follow d∼Mn0.5, for 4.8 kg/mol

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“…21 To date, reports in the literature of compressive properties have been limited to studies on the properties of entire pouch cells [22][23][24][25] and a study of the local mechanical properties of a separator using nanoindentation techniques. 26 This work presents a procedure for characterizing the mechanical properties of a separator under compression. The compressive properties of a microporous polypropylene separator are then characterized under different strain rates and solvent environments.…”

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Mechanical Properties of a Battery Separator under Compression and Tension

Cannarella

Liu

Leng

et al. 2014

J. Electrochem. Soc.

204

143

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Knowledge of the compressive mechanical properties of battery separator membranes is important for understanding their long term performance in battery cells where they are placed under compression. This paper presents a straightforward procedure for measuring the compressive mechanical properties of battery separator membranes using a universal compression testing machine. The compressive mechanical properties of a microporous polypropylene separator are characterized over a range of strain rates and in different fluid environments. These measurements are then compared to measurements of the rate and fluid-dependent mechanical properties of the separator under tension. High strain rate dependence due to viscoelasticity is observed in both tension and compression. An additional rate dependence due to poroelastic effects is observed in compression at high strain rates. A reduction in mechanical properties is observed in DMC solvent environments for both tension and compression, but is found to be less pronounced in compression. The difference in mechanical properties between compression and tension highlight the anisotropic nature of battery separators and the importance of measuring compressive properties in addition to tensile properties. The battery separator is a porous polymer membrane used to create a physical barrier between electrodes in a battery cell. The separator must be mechanically robust to ensure safe operation over the cell's service life: mechanical failure leading to electrode contact can result in catastrophic failure of the cell.1-3 Such failure often follows from puncture or thermal shrinkage of the membrane.4-6 Non-catastrophic battery failure through the form of accelerated degradation can also result from separator deformation. [7][8][9] The importance of the mechanical properties of the separator with respect to battery safety and durability has consequently motivated much research on the mechanical properties of battery separators.Previous works on the mechanical properties of separator have mainly investigated the mechanical properties under tension. [10][11][12][13][14] While knowledge of the tensile properties of the separator are important from a manufacturing standpoint, where the separator is placed under tension during cell assembly, the tensile properties are less relevant for general battery operation. This is because the separator is placed under compression during typical battery operating conditions, where it is compressed in the direction normal to the plane of the large separator face by the anode and cathode. This compressive stress is cyclic owing to reversible electrode strains and gradually increases during operation as a result of irreversible volumetric increases occurring on the electrodes. 9,15 These stack stresses during operation have been observed to be on the order of 1MPa in previous work, 9,15,16 although the presence of geometric non-uniformities (e.g. particles and curved faces) can result in local stresses that are significantly higher. 17-19The mechanical...

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Nanoindentation testing of separators for lithium-ion batteries

Cited by 40 publications

References 7 publications

Review—Multifunctional Materials for Enhanced Li-Ion Batteries Durability: A Brief Review of Practical Options

Review—Multifunctional Materials for Enhanced Li-Ion Batteries Durability: A Brief Review of Practical Options

Wide Bicontinuous Compositional Windows from Co-Networks Made with Telechelic Macromonomers

Mechanical Properties of a Battery Separator under Compression and Tension

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