Transport of Multivalent Ions in Thermoresponsive Ionogel Electrolytes from Lyotropic Liquid Crystals
Abstract
Future electrolytes should- (1) utilize multivalent ions instead of Li+ for doubling or tripling the energy density and addressing the issue of insufficient Li resources to electrify all appliances and transportation; (2) facilitate fast charging; and (3) contain non-flammable solvents as a carrier for salt cations to ensure safety. We hypothesize that these key features may be addressed by designing heterogeneous ionogel electrolytes from lyotropic liquid crystals (LLCs) containing ionic liquids (ILs) and multivalent cations. LLCs are self-assembled amphiphiles in selective solvent(s), which have mesomorphic structures, including- lamellar, hexagonal, cubic micellar packing, and bicontinuous cubic mesophases, with a periodic domain in the 2-50 nm size range. The structure of LLC gels undergoes sharp order-order and order-disorder thermal transitions, a characteristic that can be exploited to produce electrolytes for fast-charging batteries. It should be noted that LLCs can be considered as heterogeneous electrolytes comprising ion-rich and ion-poor regions, while they transform to a homogeneous electrolyte upon order-disorder transition. However, the electrochemistry of LLC ionogels has not been fundamentally evaluated for electrolyte applications. Hence, this work aims to determine the transport of Li+, Na+, Mg2+ Ca2+, and Al3+ ions (noted as Mx+ here) in LLCs containing ILs. The model amphiphile in this work will be a nonionic surfactant- a short-chain block copolymer (BCP) of poly(ethylene oxide), PEO, and polyethylene, PE. Upon self-assembly, the IL and salt ions will selectively swell the PEO blocks, forming the conducting domains, which are nano-confined among the hydrophobic PE domains. Therefore, the interaction of PEO with IL and salt ions along with the confinement effect of the LLC structure play significant roles. We will address the following research questions in this work by employing complementary experimental and computational studies- -How do phase boundaries (order-order and order-disorder transitions) and corresponding rheological properties of surfactant + IL mixtures change in the presence of multivalent cations with different concentrations. -How do the interactions of PEO-IL, PEO-Mx+ and IL- Mx+ control the transport of IL and salt ions (i.e., transference numbers and conductivity)? What are the ion transport mechanisms in ordered and disordered surfactant + IL + multivalent cations mixtures.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 06, 2024
- Source ID
- FA95502310484
Entities
People
- Reza Foudazi
Organizations
- Air Force Office of Scientific Research
- Office of the Secretary of Defense
- University of Oklahoma