One-Pot Green Synthesis of a PEO/TCPP/LiClO₄ Solid Polymer Electrolyte with Improvement of Ion Transport

Abstract

All-solid-state Li-ion batteries (ASSBs) composed of safe and reliable solid electrolyte materials have become increasingly important in energy storage systems. Poly(ethylene oxide) (PEO)-based electrolytes have been rapidly developed for ASSBs over recent years due to their nonflammability, shape flexibility, good interface contact with electrodes, and better electrochemical stability. Nevertheless, their low ionic conductivity remains a serious issue to be addressed urgently. Herein, we report a solid composite polymer electrolyte film with homogeneous network structures, which is composed of a LiClO 4 -added PEObased polymer matrix plasticized with an additive meso-tetra (carboxyphenyl) porphyrin (TCPP), a kind of porphyrin covalent organic framework (COF) material, and obtained by a green and easy-to-scale solution-casting technique to improve the ionic conductivity and simplify the synthesis process. To the best of our knowledge, this is the first report on introducing TCPP into the PEO electrolyte. It demonstrates that the blending of PEO with TCPP can effectively suppress the PEO crystallinity and enhance the ion conductivity of the solid polymer electrolytes. As the content of TCPP reaches 8 wt %, it exhibits maximum ionic conductivities of 2.34 × 10 −5 and 2.21 × 10 −4 S cm −1 at 25 and 65 °C, respectively, which is about five times higher than that of the polymer reference electrolyte. It additionally brings an improved t Li + value of 0.23 at room temperature with an electrochemical stability window of up to 5 V vs Li + /Li. In addition, when compared to the pure PEO film, a significant improvement in thermal stability is observed. This work may provide a new concept for building a new type of homogeneous COF-PEO-based composite polymer electrolyte film (CPE) that can be utilized as a desirable material in solid electrolytes for lithium-ion battery applications.

Hexagonal Boron Nitride Modulates Crystallinity and Charge Mobility in Poly(ethylene oxide)–NaNO3 Electrolytes

“…Polymer crystallinity is analyzed based on the two primary peaks at 19 and 23° exhibited by pure PEO. The peak at 19° is indexed to the [120] crystal plane, and that at 23° is attributed to the [032] crystal plane. − Changes in peak intensity, peak position, and peak width are direct manifestations of changes in PEO crystallinity caused by the PEO–salt interaction and/or PEO–h-BN interactions.…”

A flexible solid-state electrolyte based on comb-like PEG-functionalized covalent organic frameworks for lithium metal batteries

“…Some researchers dope the PEO/ PEG electrolyte into the channels of COFs to utilize the potential synergy of PEG-based and COF-based solid electrolytes. 19,20 For instance, Cheng et al 21 developed a novel solid electrolyte (TPBD-LiPF 6 @PEO) with a high ionic conductivity of 0.543 mS cm −1 at 25 °C and demonstrated that the strong interaction between TPBD of a -CvO peak and Li + promotes LiPF 6 dissociation. Wang et al 22 proposed a strategy to incorporate lowmolecular-weight polyethylene glycol (PEG) into COFs with anionic, neutral, or cationic skeletons to accelerate Li + conduction and the ion conductivity of PEG including a cationic COF can reach 1.78 × 10 −3 S cm −1 at 120 °C.…”

Solid Polymer Electrolyte Based on an Ionically Conducting Unique Organic Polymer Framework for All-Solid-State Lithium Batteries

“…Further, different covalent organic polymers with ionic functionality or capable of hydrogen bonding with the PEO chains were also dispersed as fillers into the PEO matrix where the improved electrochemical performances were ascribed to the suppressed crystallization of the PEO domains. 33,34 Based on the above considerations, herein, a unique organic polymer framework (OPF) was synthesized by the Suzuki− Miyaura coupling reaction between 2,5-dibromo-3-(2-(2-(2ethoxyethoxy)ethoxy)ethyl)thiophene and triazine-phenyl boronic acid. Such organic covalent frameworks without long side chains on their backbone are generally crystalline in nature.…”

“…Most of these reports are focused on anchoring PEG groups to the organic frameworks and evaluating their performance as solid electrolytes as such at high temperatures. Further, different covalent organic polymers with ionic functionality or capable of hydrogen bonding with the PEO chains were also dispersed as fillers into the PEO matrix where the improved electrochemical performances were ascribed to the suppressed crystallization of the PEO domains. , …”