Molecular‐level Designed Polymer Electrolyte for High‐Voltage Lithium–Metal Solid‐State Batteries

Abstract

In solid polymer electrolytes (SPEs) based Li-metal batteries, the inhomogeneous migration of dual-ion in the cell results in large concentration polarization and reduces interfacial stability during cycling. A special molecular-level designed polymer electrolyte (MDPE) is proposed by embedding a special functional group (4-vinylbenzotrifluoride) in the polycarbonate base. In MDPE, the polymer matrix obtained by copolymerization of vinylidene carbonate and 4-vinylbenzotrifluoride is coupled with the anion of lithium-salt by hydrogen bonding and the "σ-hole" effect of the CF bond. This intermolecular interaction limits the migration of the anion and increases the ionic transfer number of MDPE (t Li + = 0.76). The mechanisms of the enhanced t Li + of MDPE are profoundly understood by conducting first-principles density functional theory calculation. Furthermore, MDPE has an electrochemical stability window (4.9 V) and excellent electrochemical stability with Li-metal due to the CO group and trifluoromethylbenzene (ph-CF 3 ) of the polymer matrix. Benefited from these merits, LiNi 0.8 Co 0.1 Mn 0.1 O 2 -based solid-state cells with the MDPE as both the electrolyte host and electrode binder exhibit good rate and cycling performance. This study demonstrates that polymer electrolytes designed at the molecular level can provide a broader platform for the high-performance design needs of lithium batteries.

A Review of Polymer‐based Solid‐State Electrolytes for Lithium‐Metal Batteries: Structure, Kinetic, Interface Stability, and Application

“…Types of lithium salts and polymer matrix with different main chains and functional groups also affect the electrochemical window of solid electrolytes [142] . Lithium bis(oxalate)borate (LiDFOB) is a good lithium salt that promotes oxidation‐resistant and low‐resistance electrode/electrolyte interface layer.…”

“…[141] Types of lithium salts and polymer matrix with different main chains and functional groups also affect the electrochemical window of solid electrolytes. [142] Lithium bis(oxalate)borate (LiDFOB) is a good lithium salt that promotes oxidation-resistant and low-resistance electrode/electrolyte interface layer. The relationship between poly (ethylene-glycol) diacrylate (PEGDA) as a matrix and an electrochemical window in solid electrolytes is shown in Figure 10(b).…”

Quasi-Solid Polymer Electrolyte with Multiple Lithium-Ion Transport Pathways by In Situ Thermal-Initiating Polymerization

“…The lower dissociation energy of ligand ions and the lower ion migration activation energy are also important factors in facilitating the rapid and homogeneous transport flux of Li + across space . In contrast, high dielectric constant polymers such as polycarbonate or polyacrylate may be more suitable choices for electrolyte matrix than PEO, which has a lower intrinsic dielectric constant. − The ionic conductivity of SS|In situ PDEGDA/PVDF FMs|SS cell at different operating temperatures from 25 to 100 °C was examined by the EIS (Figure f). Attributed to the optimization of the Li + transport pathway, the ionic conductivity of QSPEs can reach 1.41 × 10 –4 S cm –1 at room temperature.…”

A Stable Polymer‐based Solid‐State Lithium Metal Battery and its Interfacial Characteristics Revealed by Cryogenic Transmission Electron Microscopy

“…[ 29–32 ] Therefore, to construct compatible electrode/electrolyte interphase, the synergic effects of polymer matrices, Li salts, and additives in PVDF‐HFP‐based electrolyte should be considered. [ 33–38 ]…”

“…[29][30][31][32] Therefore, to construct compatible electrode/electrolyte interphase, the synergic effects of polymer matrices, Li salts, and additives in PVDF-HFP-based electrolyte should be considered. [33][34][35][36][37][38] Herein, a novel PVDF-HFP-based polymer electrolyte (PPE) using LiBF 4 and propylene carbonate (PC) plasticizer is developed to build stable SSLMBs. The PPE has high ionic conductivity up to 1.15 × 10 −3 S cm −1 at room temperature (RT) and a wide electrochemical stability window (5.0 V versus Li + /Li).…”