Ionic Conductivities of Broad Dispersity Lithium Salt-Doped Polystyrene/Poly(ethylene oxide) Triblock Polymers

Abstract

We describe the impact of center polyether segment dispersity (Đ = M w/M n ∼ 1.45) on the ionic conductivities of lithium salt-doped polystyrene-block-poly­(oligo­(ethylene oxide) carbonate)-block-polystyrene (bSOS) electrolytes with narrow dispersity end blocks. Three bSOS samples with M n,total = 11.7–23.9 kg/mol were doped with lithium bis­(trifluoromethanesulfonyl)­imide (LiTFSI) with r = [Li+]/[EO units] = 0.09. Small-angle X-ray scattering (SAXS) analyses reveal that these samples with f O/salt = 0.55–0.60 self-assemble into lamellar morphologies, with ionic conductivities as high as σ = 0.19 mS/cm at 90 °C measured by electrochemical impedance spectroscopy (EIS). The ionic conductivities of LiTFSI-doped bSOS are comparable to those of salt-doped, narrow dispersity nSOS triblocks with M n ≳ 20 kg/mol, and they are 2–3 times greater than those of the narrow dispersity nSO diblock control samples. These findings are rationalized in terms of decreases in the lamellar grain sizes induced by molecular architecture and segment dispersity, which enhance intergrain connectivity and ion transport.

Synthesis and Characterization of Quadrupolar-Hydrogen-Bonded Polymeric Ionic Liquids for Potential Self-Healing Electrolytes

“…To elucidate the potential of the polymers to be applied as electrolytes the DC conductivity was investigated by broadband dielectric spectroscopy (BDS). As shown in Figure 3 a the low-molecular-weight POIL-2 showed a higher conductivity compared to the high-molecular-weight POIL-3 , matching the conclusions that—in line with expectations—low-molecular-weight POILs generally offer higher conductivity [ 25 , 26 , 27 , 28 ]. When 4% UPy moieties were introduced into the polymer backbone ( CPILU-5 ), the conductivity was barely influenced by the non-conductive UPy moieties as compared to the homopolymer POIL-2 (see red squares for POIL-2 and blue triangles for CPILU-5 in Figure 3 a).…”

“…While many POILs have been reported predominantly with polyimidazolium ions [ 17 , 21 ] or other POILs [ 18 , 22 , 23 ] as self-healing electrolytes, poly-pyrrolidinium-based self-healing electrolytes have been scarcely reported, despite the fact that pyrrolidinium-based ionic liquids generally have a higher electrochemical stability [ 24 ]. Moreover, in many publications POILs were synthesized via free radical polymerization, which offers no control over the molecular weight of POILs, thus yielding polymers with a broad polydispersity and a poor reproducibility, which significantly influences the final conductivity of the obtained polymer electrolytes [ 25 , 26 , 27 , 28 ]. While UPy was widely exploited in polymers synthesized via RAFT polymerization [ 29 , 30 , 31 ], only a few [ 32 ] RAFT kinetics studies regarding an acrylate-based UPy monomer were reported, let alone studies involving its copolymerization with ionic monomers.…”

Solid-State, Single-Ion Conducting, Polymer Blend Electrolytes with Enhanced Li+ Conduction, Electrochemical Stability, and Limiting Current Density

“…However, the high crystallinity of PEO below the melting temperature ( T m,PEO ≈ 62 °C for 10–20 kg/mol) leads to a significant reduction in conductivity near room temperature . There have been numerous studies focused on disrupting crystallinity in PEO using PEO-grafted polymethacrylates , and PEO-based copolymers. − For instance, poly­( oligo -oxyethylene methyl ether methacrylate) (POEM), with its ether-oxygen side chains, is promising in terms of significantly improved room-temperature conductivity vs analogous salt-doped PEO systems when the appropriate side-chain lengths are employed. , Other approaches also have been developed to decrease the crystallinity of PEO, including nanoparticle addition, − polymer blending, , and cross-linking. − Additionally, small-molecule plasticization − and low- T g segment introduction − have been shown to accelerate segmental relaxation, and polymer architecture modification can effectively alter the Li + -polymer coordination ,− and/or the Li + solvation-site connectivity. ,− Although improved overall conductivities have been achieved, the significant anion motion in these PEO-based electrolytes results in low t Li+ s (≈0.2) , and therefore relatively modest Li + conductivities (∼10 –4 S/cm at 60–100 °C).…”