Cyclopropenium Cationic-Based Covalent Organic Polymer-Enhanced Poly(ethylene oxide) Composite Polymer Electrolyte for All-Solid-State Li–S Battery

Abstract

Cyclopropenium cationic-based covalent organic polymer (iCP@TFSI) was successfully prepared through the SN2 reaction and ion replacement process, which can be incorporated into the PEO/LiTFSI matrix as a filler. The obtained solid-state polymer electrolytes were utilized for an all-solid-state lithium–sulfur (Li–S) battery. Padding iCP@TFSI into the PEO matrix not only has a positive influence on both the ionic conductivity and the mechanical capacity of solid-state polymer electrolytes but also increases the stability of the lithium metal anode, which essentially improves the overall cycling ability of all-solid-state Li–S batteries. Among the membranes attained, the PEO-10%iCP@TFSI electrolyte displays the best ionic conductivity up to 1.2 × 10–3 S·cm–1 at 80 °C. The symmetrical lithium battery exhibits higher cycle stability (600 h) due to the higher mechanical properties related to more stable lithium metal interfaces. The Li–S battery based on the PEO-10%iCP@TFSI electrolyte exhibits excellent electrochemical performance with better Coulombic efficiency and outstanding cycling stability. Its capacity is maintained at 490 mAh·g–1 after 500 cycles at 1 C with a 0.032% decay rate each cycle, and the Coulombic efficiency is close to 100% during the whole cycling.

Recent Progress in Quasi/All-Solid-State Electrolytes for Lithium–Sulfur Batteries

“…As shown in Figure 3D, the ultimate tensile strength of PEO-10%iCP@TFSI electrolyte can reach 1.9 MPa, and the elongation at break augments to 3,557.15%. Additionally, LSBs with PEO-10%iCP@TFSI electrolyte have the high Coulombic efficiency, excellent cycling stability, and low capacity fade of 0.032% per cycle after 500 cycles at 1 °C (Wang et al, 2021). As shown in Figure 3E, the PEO/iCP@TFSI electrolyte shows high thermal stability at above 300 °C, and it meets the basic requirements of energy storage.…”

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. , …”

Nano-Confinement of Insulating Sulfur in the Cathode Composite of All-Solid-State Li–S Batteries Using Flexible Carbon Materials with Large Pore Volumes

“…The holy grail of practical application for the given secondary batteries is to employ inexpensive active materials that can be used at as much loading as possible while providing highly durable discharge/charge cycles with the full utilization of energy stored. The use of lithium metal as an anode material of secondary batteries is an attractive means to achieve a high density storage of energy because of its high gravimetric theoretical capacity (3861 mA h g –1 ) and low electrochemical potential of −3.0 V versus a normal hydrogen electrode. − On the contrary, various compounds, such as LiCoO 2 , − LiFePO 4 , − Mo 2 S, Si, , and S, − have been investigated as the active materials of the counterpart cathodic reactions. Among them, Li–S systems with sulfur as a cathode material are promising because sulfur is inexpensive, abundant, and readily available.…”