Solid polymer electrolytes based on Li+/ionic liquid for lithium secondary batteries

Insight into the use of ionic liquid-based polymer electrolyte for super capacitor application (RAFM-2022)

In this study, we are presenting the recent progress toward PEO-based polymer electrolytes doped with low viscosity ionic liquids with a strong emphasis on ionic liquid doped-in polymer electrolytes for energy storage applications, particularly towards electric double layer capacitors. The reliable transmission mechanism suggested by previous researchers to address the increasing trend in transport properties is ascertained with a sharp sense of the presence of different concentrations of interaction, i.e. polymer ionic liquid was also presented in detail.

Influence of polyethylene glycol plasticizer on the structural and electronic properties of PEO-NaI complex: a density functional study

Ab initio study has been carried out to investigate the influence of low molecular weight polyethylene glycol (PEG) plasticizer on structural and electronic properties of the polyethylene oxide-sodium iodide (PEO-NaI) polymer-metal complex. DOS and PDOS analysis provided a quantitative explanation of the electronic bandgap of the PEO-NaI and PEO-PEG-NaI system. Hirshfeld population charge analysis (HPA) explains better dissociation of NaI in presence of polyethylene glycol, based on the Hard Soft Acid Base Principle. Also, an increase in amorphic content of polymer system is observed with the addition of PEG, evident from the increment in the strength of anti-bonding orbitals in COOP plot. Bond strength of the polymeric system is also found to be affected with the addition of plasticizer. The findings provide an avenue that the present polymer system [PEO-PEG-NaI] is a potential candidate to be used as an electrolyte for next-generation energy storage technology.

Building Better Batteries in the Solid State: A Review

Most of the current commercialized lithium batteries employ liquid electrolytes, despite their vulnerability to battery fire hazards, because they avoid the formation of dendrites on the anode side, which is commonly encountered in solid-state batteries. In a review two years ago, we focused on the challenges and issues facing lithium metal for solid-state rechargeable batteries, pointed to the progress made in addressing this drawback, and concluded that a situation could be envisioned where solid-state batteries would again win over liquid batteries for different applications in the near future. However, an additional drawback of solid-state batteries is the lower ionic conductivity of the electrolyte. Therefore, extensive research efforts have been invested in the last few years to overcome this problem, the reward of which has been significant progress. It is the purpose of this review to report these recent works and the state of the art on solid electrolytes. In addition to solid electrolytes stricto sensu, there are other electrolytes that are mainly solids, but with some added liquid. In some cases, the amount of liquid added is only on the microliter scale; the addition of liquid is aimed at only improving the contact between a solid-state electrolyte and an electrode, for instance. In some other cases, the amount of liquid is larger, as in the case of gel polymers. It is also an acceptable solution if the amount of liquid is small enough to maintain the safety of the cell; such cases are also considered in this review. Different chemistries are examined, including not only Li-air, Li-O2, and Li-S, but also sodium-ion batteries, which are also subject to intensive research. The challenges toward commercialization are also considered.

Conductivity-Relaxation Relations in Nanocomposite Polymer Electrolytes Containing Ionic Liquid

In this study, we have used nanocomposite polymer electrolytes, consisting of poly(ethylene oxide) (PEO), δ-Al₂O₃ nanoparticles, and lithium bis(trifluoromethanesolfonyl)imide (LiTFSI) salt (with 4 wt % δ-Al₂O₃ and PEO:Li ratios of 16:1 and 8:1), and added different amounts of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesolfonyl)imide (BMITFSI). The aim was to elucidate whether the ionic liquid is able to dissociate the Li-ions from the ether oxygens and thereby decouple the ionic conductivity from the segmental polymer dynamics. The results from DSC and dielectric spectroscopy show that the ionic liquid speeds up both the segmental polymer dynamics and the motion of the Li⁺ ions. However, a close comparison between the structural (α) relaxation process, given by the segmental polymer dynamics, and the ionic conductivity shows that the motion of the Li⁺ ions decouples from the segmental polymer dynamics at higher concentrations of the ionic liquid (≥20 wt %) and instead becomes more related to the viscosity of the ionic liquid. This decoupling increases with decreasing temperature. In addition to the structural α-relaxation, two more local relaxation processes, denoted β and γ, are observed. The β-relaxation becomes slightly faster at the highest concentration of the ionic liquid (at least for the lower salt concentration), whereas the γ-relaxation is unaffected by the ionic liquid, over the whole concentration range 0-40 wt %.