In Situ Polymerized Electrolytes with Fully Cross-Linked Networks Boosting High Ionic Conductivity and Capacity Retention for Lithium Ion Batteries

Abstract

In this report, quasi-solid polymer electrolytes (QPEs) based on dicationic imidazolium-based poly(ionic liquid) (PIL) cross-linker end capped with polyethylene glycol (PEG) segments have been UV cured directly onto lithium anode via an in situ solventless strategy, creating a direct, effective, and versatile method for electrolyte production. Depending on the composition, room temperature ionic conductivities are found to vary between 0.7 and 1.1 mS cm −1 , while compressive elastic moduli reveal the values between 0.072 and 0.349 MPa observed at a 5% strain. These results, together with FT-IR analysis, indicate that fully cross-linked networks can be formed in the QPE-1:1.6 sample, which is conducive to generating well-connected ion channels and affords the assembled lithium ion batteries (LIBs) with a wide electrochemical window and a remarkable discharge capacity retention (153 mAh g −1 at 0.2 C and 133 mAh g −1 at 1 C) at 25 °C. Also, the adopted in situ polymerization can contribute to an enhanced electrolyte/electrode interfacial compatibility and conformal attachment, suppressing the growth of lithium dendrites and extending the cycle life of the assembled battery. Both the outstanding electrochemical properties of QPE-1:1.6 and the facile fabrication process potentially make it one of the promising electrolyte candidates for future LIBs developments.

Enhanced Energy Storage in Lithium-Metal Batteries via Polymer Electrolyte Polysulfide–Polyoxide Conetworks

“…Nevertheless, the resulting Li–S bonds are still attached to the conetwork in the form of side branches since the S–S bonds are initially parts of the polysulfide chains before the S–S bond scission by Li cations. Although the Li ions undergoing complexation with the end-capped sulfur of the side branches cannot travel over large distances, these Li ions are still capable of forming polarization, reminiscent of EDLC character, against the electrons at the interface of the NMC cathode containing conductive carbon (Super-P), which was used as part of a PVDF binder to afford electron conduction through a current collector to an outer circuit. − Hence, the suggested pseudocapacitor-like character of the CV curves of the PEM in Figure d is plausible. A reverse process can also be anticipated, i.e., S–S can be recombined with continued cycling by releasing Li ions from the Li + –S – bonds since the S–S bond scission by Li ions is known to be reversible.…”

Organosulfur Materials for Rechargeable Batteries: Structure, Mechanism, and Application

“…The ionic conductivity can reach 1.07 × 10 −3 S cm −1 at room temperature. 277 The lithium-ion transference number (LTN) is one of the important parameters for electrolyte. A high LTN could enable low concentration polarization and suppress the lithium dendrite growth.…”

“…Pentaerythritol tetrakis (3-mercaptopropionate) (PETMP) with a star structure is the most frequently used cross-linker for the highly cross-linked copolymers obtained through the thiol–ene click reactions with ene monomers. − Suk et al reported a semi-interpenetrating organosulfur-based solid polymer electrolyte through the reaction of PETMP and the star-shaped hexakis­(allyloxy)­cyclo-triphosphazene (PAL) cross-linker, with poly­(ethylene glycol) dimethyl ether (PEGDME) as a plasticizer . The obtained polymer electrolyte shows a high ionic conductivity of 7.4 × 10 –4 S cm –1 at 30 °C with an electrochemical window of 5.66 V. The Li/LiFePO 4 cell with the electrolyte shows an initial discharge capacity of 147 mAh g –1 at a 0.5 C rate and the capacity retention is 97% after 100 cycles.…”

“…A poly­(ionic liquid)-based organosulfur copolymer electrolyte was developed by Tseng et al It possesses the advantages of low flammability, negligible vapor pressure, and high solubility. The ionic conductivity can reach 1.07 × 10 –3 S cm –1 at room temperature …”