Control of Lithium Salt Partitioning, Coordination, and Solvation in Vitrimer Electrolytes
Seongon Jang,
Erick I. Hernandez Alvarez,
Chen Chen
et al.
Abstract:Vitrimers are an important class of materials offering advantages over conventional thermosets due to their self-healing properties and reprocessability. Vitrimers are ideal candidate materials for solid polymer electrolytes because their viscoelasticity and conductivity can be independently tuned by salt addition in distinct ways from linear polymer electrolytes while further providing resistance to lithium dendrite propagation. In this work, the chemical and physical properties of vinylogous urethane (VU) vi… Show more
“…The use of dynamic covalent cross-links, rather than irreversible chemical cross-links, would render APCN-based polymer electrolytes processable and recyclable without compromising their network characteristics. Although there are several examples in the literature on self-healable polymer network electrolytes, − there are only a small number of examples also including their recycling, with these examples concerning only networks based on simple building blocks and not APCNs. − Thus, the recycling and re-evaluation of APCN-based electrolytes bearing dynamic covalent cross-links are yet to be explored, something undertaken within the present study.…”
We present the development of a platform of welldefined, dynamic covalent amphiphilic polymer conetworks (APCN) based on an α,ω-dibenzaldehyde end-functionalized linear amphiphilic poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEG-b-PPG-b-PEG, Pluronic) copolymer end-linked with a triacylhydrazide oligo(ethylene glycol) triarmed star cross-linker. The developed APCNs were characterized in terms of their rheological (increase in the storage modulus by a factor of 2 with increase in temperature from 10 to 50 °C), self-healing, self-assembling, and mechanical properties and evaluated as a matrix for gel polymer electrolytes (GPEs) in both the stretched and unstretched states. Our results show that water-loaded APCNs almost completely self-mend, self-organize at room temperature into a body-centered cubic structure with long-range order exhibiting an aggregation number of around 80, and display an exceptional room temperature stretchability of ∼2400%. Furthermore, ionic liquid-loaded APCNs could serve as gel polymer electrolytes (GPEs), displaying a substantial ion conductivity in the unstretched state, which was gradually reduced upon elongation up to a strain of 4, above which it gradually increased. Finally, it was found that recycled (dissolved and re-formed) ionic liquid-loaded APCNs could be reused as GPEs preserving 50−70% of their original ion conductivity.
“…The use of dynamic covalent cross-links, rather than irreversible chemical cross-links, would render APCN-based polymer electrolytes processable and recyclable without compromising their network characteristics. Although there are several examples in the literature on self-healable polymer network electrolytes, − there are only a small number of examples also including their recycling, with these examples concerning only networks based on simple building blocks and not APCNs. − Thus, the recycling and re-evaluation of APCN-based electrolytes bearing dynamic covalent cross-links are yet to be explored, something undertaken within the present study.…”
We present the development of a platform of welldefined, dynamic covalent amphiphilic polymer conetworks (APCN) based on an α,ω-dibenzaldehyde end-functionalized linear amphiphilic poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEG-b-PPG-b-PEG, Pluronic) copolymer end-linked with a triacylhydrazide oligo(ethylene glycol) triarmed star cross-linker. The developed APCNs were characterized in terms of their rheological (increase in the storage modulus by a factor of 2 with increase in temperature from 10 to 50 °C), self-healing, self-assembling, and mechanical properties and evaluated as a matrix for gel polymer electrolytes (GPEs) in both the stretched and unstretched states. Our results show that water-loaded APCNs almost completely self-mend, self-organize at room temperature into a body-centered cubic structure with long-range order exhibiting an aggregation number of around 80, and display an exceptional room temperature stretchability of ∼2400%. Furthermore, ionic liquid-loaded APCNs could serve as gel polymer electrolytes (GPEs), displaying a substantial ion conductivity in the unstretched state, which was gradually reduced upon elongation up to a strain of 4, above which it gradually increased. Finally, it was found that recycled (dissolved and re-formed) ionic liquid-loaded APCNs could be reused as GPEs preserving 50−70% of their original ion conductivity.
Improving the total ionic conductivity
(σ) of solid polymer
electrolytes (SPEs) is critical to the development of solid-state
sodium (Na) batteries. In this work, we investigate the effect of
two-dimensional (2D), dual-Lewis hexagonal boron nitride (h-BN) filler
on polymer structure and ion transport properties of P(EO)24:Na+ and P(EO)4:Na+ mixtures of
poly(ethylene oxide) (PEO)-bis (fluorosulfonylimide) (NaFSI). Below
the critical percolation concentration threshold for the h-BN flakes,
X-ray diffraction and differential scanning calorimetry studies show
that an increase in h-BN concentration initially induces an increase
in PEO crystallinity followed by a decrease due to competing effects
between heterogeneous nucleation of PEO lamellae and its spherulitic
confinement, respectively. Raman spectroscopy reveals that h-BN improves
NaFSI dissociation in the semi-dilute SPEs which is supported by density
functional theory calculations. Our calculations suggest that PEO
can almost fully dissociate a NaFSI molecule with a coordination number
of 6. We propose an h-BN-“assisted” mechanism to explain
this observation, wherein h-BN aids PEO in better matching the dissociation
energy of the NaFSI salt by virtue of its dual-Lewis surface chemistry.
A corresponding 4× increase in σ is observed for the P(EO)24:Na+ SPEs using electrochemical impedance spectroscopy.
The P(EO)4:Na+ SPEs do not show this increase,
which is likely due to a significantly different local solvation environment
wherein contact ion pairs and aggregates (AGGs) dominate. Our findings
highlight the role of filler chemistry in the design and development
of composite solid polymer electrolytes for Na batteries.
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