Dissolution of Lithium Metal in Poly(ethylene oxide)

Galluzzo, Michael D.; Halat, David M.; Loo, Whitney S.; Mullin, Scott A.; Reimer, Jeffrey A.; Balsara, Nitash P.

doi:10.1021/acsenergylett.9b00459

Cited by 28 publications

(28 citation statements)

References 31 publications

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“…[34,35] Moreover, widely researched solid polymer electrolytes (SPEs) like PEO cannot stand the intensive chemical reactivity of lithium metal. [36] Lithium nuclear magnetic resonance ( 7 Li NMR) shows that lithium species can dissolve and diffuse into the bulk polymer, when a pure PEO sample is placed in contact with lithium metal at elevated temperatures. More examples are summarized in Table 1.…”

Section: Poor Chemical or Electrochemical Compatibilitymentioning

confidence: 99%

Design Principles of the Anode–Electrolyte Interface for All Solid‐State Lithium Metal Batteries

et al. 2019

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densities can reach as high as ≈2600 and ≈3500 Wh kg −1 , respectively. [3] However, lithium metal batteries based on organic liquid electrolytes (e.g., ethylene carbonate, diethyl carbonate, 1,2-dimethoxyethane) suffer from great safety hazards because of intrinsic high-reactivity and flammability of lithium metal and organic liquid electrolytes. For safety concerns, replacing high-energy LMBs using organic liquid electrolytes by building all solid-state Li metal batteries (ASSLMBs) using compatible and inflammable solid-state electrolytes (SSEs) provides a promising solution to improve the safety performances. Besides, uneven electrodeposition on metal anode, named "dendrite," is a general problem among lithium, sodium, zinc battery, etc. [4] The uncontrolled growth of dendrites leads to internal shorts, and thus, becomes a major obstacle to the commercialization of these kinds of high energy density batteries. [5,6] Solid state electrolytes were believed to be an "enabler" to efficiently prevent the proliferation of lithium dendrites because of their ultrahigh mechanical strength and nearly unit Li + transfer number. As a key component of ASSLMBs, SSEs can be divided into three categories: polymeric, inorganic, and composite materials. Polyethylene oxide (PEO), as one of the most popular solid polymeric ionic conductors, has been studied extensively since 1973 because of its low cost and better machinability within roll-toroll process. [7] However, PEO with instinct low highest occupied molecular orbitals (HOMO) cannot be compatible with highvoltage cathode materials (voltage outputs >4.0 V vs Li + /Li). Besides, the poor ionic conductivity of PEO (10 −7-10 −5 S cm −1 at room temperature) is insufficient to support high-rate charge/discharge behaviors in comparison to liquid Li metal batteries. [8] The burgeoning inorganic solid Li-ion conductors with higher ionic conductivity is a promising electrolyte system which can be used in the future ASSLMBs. [9,10] The main inorganic solid Li-ion conductors can be divided into two categories by composition, oxides and sulfides, including garnet-type, perovskite-type, sodium superionic conductor (NASICON)type, lithium superionic conductor (LISICON)-type materials, and sulfide glasses. For oxide ceramics, as a typical example, garnet-type Li 7 La 3 Zr 2 O 12 (LLZO) with a cubic phase and its related doped compounds show a high Li-ion conductivity of 10 −4-10 −3 S cm −1. [11] However, short circuits due to lithium dendrites along the grain boundaries (GBs) and large interface impedance make it a challenging task for the practical use in ASSLMBs. Sulfide-type solid electrolytes usually have higher All solid-state lithium metal batteries (ASSLMBs) provide a promising solution for next-generation rechargeable energy storage due to their high energy density and the high safety of solid-state electrolytes (SSEs). However, most SSEs lack thermodynamic intrinsic stability against Li metal and chemical reactions happen spontaneously at the interface when solid-state electrolytes...

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Section: Poor Chemical or Electrochemical Compatibilitymentioning

confidence: 99%

Design Principles of the Anode–Electrolyte Interface for All Solid‐State Lithium Metal Batteries

et al. 2019

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“…Interestingly, the conductivity increase seems to proceed in three stages: in the first 5 h conductivity is unchanged, followed by a rapid increase from 6 to 9 h, and finally a slower increase after 9 h. Such increment profile was also observed in Galluzzo et al's work. [19] One hypothesis to explain the multistage reaction profile is proposed as follows: in the beginning of the PEO/Li contact, the reaction only initiates at some well-contacted spots. Limited amounts of Li þ ions are generated at the interface, which are too far away from the electrodes to make the whole film conductive.…”

Section: Resultsmentioning

confidence: 99%

“…Galluzzo et al reported conductivity increases in a salt-free, PEO-based Li|Li symmetric cells after holding at 120 C for 10 days. [19] They proposed that Li metal can be dissolved by PEO in the form of Li þ ions and free electrons. This is partially supported by 1) Fourier transform infrared spectroscopy (FTIR) data of PEO showing that the PEO backbone remains intact in the bulk of the polymer and 2) electrochemical experiments showing there is no Li þ concentration gradient in the electrolyte, though it is unlikely that the postulated "free" electrons remain unreacted.…”

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confidence: 99%

Increasing Ionic Conductivity of Poly(ethylene oxide) by Reaction with Metallic Li

Liu

Counihan

Zhu

et al. 2021

Adv Energy and Sustain Res

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One of the most important technological advances in sustainable energy harvesting and storage is the development of the Liion battery technology. In recent years, increasing demand for energy has revived development of sustainable storage technologies with Li metal as the anode due to the high theoretical specific capacity of Li metal (3860 mA h g À1 ). [1][2][3][4] As a result, the focus of much research in the field of Li energy storage is centered on development of solid electrolyte materials that can replace flammable organic solvents and enable the use of Li metal anodes, required for high energy density batteries. [5,6] To fully implement solid-solid Li-ion technology, many challenges need to be resolved, namely the stability of electrode materials and electrolytes and selectivity of electrochemical interfaces. [7] Addressing these will minimize undesired side reactions at electrode surfaces and suppress Li dendrite formation on the anode to improve battery performance and lifetime.Polyethylene oxide (PEO), in particular, has attracted great interest as a polymer electrolyte for use in solid state Li batteries due to its low glass transition temperature (%À60 C), mechanical properties, low material cost, and good interfacial contact with the anode. [8][9][10] However, the ionic conductivity of pure PEO at room temperature is %10 À9 -10 À8 S cm À1 , five orders of magnitude lower than the practical threshold (10 À3 S cm À1 ) needed to achieve realistic charge-discharge rates. [11] This necessitates further doping with salts, e.g., LiTFSI. Even then, the best room temperature conductivity of simple LiTFSI-doped PEO is around 10 À5 S cm À1 , so high temperatures (≥60 C) are required to achieve sufficient ionic conductivity.When mixed with lithium salts, ether oxygens in the PEO backbone coordinate to Li þ , leading to salt dissociation and mobile charge carriers in the mixture. [12] The introduction of salt also suppresses polymer crystallization, leading to more amorphous content within PEO, which also improves conductivity. [9] However, the anion greatly contributes to the increased ionic conductivity of doped PEO. Strong coordination between ether oxygens and Li þ cations leads to low lithium transference

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“…The mapping results for these isles in a battery cycled with no external pressure shows that the formation of isles depends on the reactions that take place in these regions and not on the applied pressure on the battery, as suggested by Hovington et al 1 . Galluzzo et al 26 has shown that lithium metal dissolves and diffuses in the polyether bulk as Li + and a free electron. Lithium metal may then reduce the salt in the polymer.…”

Section: Resultsmentioning

confidence: 99%

In situ observation of solid electrolyte interphase evolution in a lithium metal battery

et al. 2019

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Lithium metal is a favorable anode material in all-solid Li-polymer batteries because of its high energy density. However, dendrite formation on lithium metal causes safety concerns. Here we obtain images of the Li-metal anode surface during cycling using in situ scanning electron microscopy. Constructing videos from the images enables us to monitor the failure mechanism of the battery. Our results show the formation of dendrites on the edge of the anode and isles of decomposed lithium bis(trifluoromethanesulfonyl)imide on the grain boundaries. Cycling at high rates results in the opening of the grain boundaries and depletion of lithium in the vicinity of the isles. We also observe changes in the surface morphology of the polymer close to the anode edge. Extrusion of lithium from these regions could be evidence of polymer reduction due to a local increase in temperature and thermal runaway assisting in dendrite formation.

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Dissolution of Lithium Metal in Poly(ethylene oxide)

Cited by 28 publications

References 31 publications

Design Principles of the Anode–Electrolyte Interface for All Solid‐State Lithium Metal Batteries

Design Principles of the Anode–Electrolyte Interface for All Solid‐State Lithium Metal Batteries

Increasing Ionic Conductivity of Poly(ethylene oxide) by Reaction with Metallic Li

In situ observation of solid electrolyte interphase evolution in a lithium metal battery

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