Achieving Low-Energy-Barrier Ion Hopping in Adhesive Composite Polymer Electrolytes by Nanoabsorption

Abstract

Adhesive polymer electrolytes are of great interest for next-generation high-energy-density solid-state batteries but their practical applications have been blocked by extremely low ionic conductivity that is fundamentally caused by a coupling transport mechanism. Here, to boost the ionic conductivity, we propose a decoupled low-energy-barrier ion-hopping mechanism that is realized by surface absorption from nanoparticles. To test this model, Al 2 O 3 nanoparticles are composited with a fully amorphous and adhesive ultrahigh-molecular-weight poly(ethylene oxide) (UHMWPEO)−Li + complex. It is found that the ion conductivity can be improved to 9.94 ± 1.57 × 10 −5 S cm −1 at 20 °C, ca. about 20 times of the pure complex electrolyte. Meanwhile, the ion-hopping energy barrier is reduced by 67%, yielding a low activation energy of 0.25 eV. This phenomenon is further explained by the nanoabsorption effects on shrinking the free volume (the hopping distance) and stabilizing the hopping sites. Further, the strong nanoabsorption effects also notably improve the mechanical properties as well as the electrochemical stability of the resultant nanocomposite electrolyte. When the adhesive composite electrolyte is coated onto a commercial separator, it effectively improves the stability of Li metal and the cycling performance lasts for 2000 h before its failure, demonstrating the potential applications in Li−metal batteries.

Design of High‐Entropy Tape Electrolytes for Compression‐Free Solid‐State Batteries

“…However, when the HE‐skin is too thin (e.g., 2 µm), the interfacial toughness sharply decreases to only 59.5 ± 7.6 J m −2 . This phenomenon may be caused by the reduced electrostatic or van der Waals interactions at the interface, [ 27 ] when the skin layer is too thin to form stable contact. On the other hand, HE‐PEO exhibits poor mechanical strength (Figure 2h), and the mechanical properties of HETE primarily depend on the skeleton layer.…”

Hydrogen Bonding Induced Confinement Effect between Ultrafine Nanowires and Polymer Chains for Low-Energy-Barrier Ion Transport in Composite Electrolytes

“…In PEO-LiTFSI electrolyte (PL) system, the high-energy barrier caused by a large amount of free volume blockage inhibits lithium ion transport between different chain segments in the polymer matrix (Figure S1). In order to achieve low-energy barrier lithium ion conduction, boehmite (γ-AlOOH), a precursor of Al 2 O 3 with nonionized −OH on its surface, was added in electrolytes as an inert filler. Although the introduction of the BNPs could enable the dissolution of lithium salts to release the Li + and absorb the anions, the dispersed particles hardly form a continuous path for lithium ion conduction (Figure S1).…”

A Supertough and Highly‐Conductive Nano‐Dipole Doped Composite Polymer Electrolyte with Hybrid Li+‐Solvation Microenvironment for Lithium Metal Batteries

“…A smaller free volume is also beneficial to shorten the ion hopping distance and to reduce the energy barrier. [ 52 ] Additionally, Raman analysis was performed to detect the uncoordinated TFSI − and the TFSI − coordinated with Li + . [ 53 ] The Raman spectra in Figure 4d show that the d‐HNT doping greatly helps dissociate the LiTFSI salt.…”