Quasi-Solid-State Polymer Electrolyte Based on Highly Concentrated LiTFSI Complexing DMF for Ambient-Temperature Rechargeable Lithium Batteries

Abstract

Solid-state polymer electrolytes (SPEs) complexing a plasticizer is a valid strategy to improve the poor ionic conductivity of SPEs at ambient temperature. In this study, a quasi-SPE based on a polyurethane matrix (QSPE-PU) is constructed by regulating the contents of bis(trifluoromethanesulfonyl) imide (LiTFSI) salt and N,N-dimethylformamide (DMF) and shows high performance in ambient-temperature rechargeable lithium batteries. Highly concentrated LiTFSI is designed to anchor DMF, decreasing the free solvent molecules in the QSPE to improve the stability with lithium metal. Meanwhile, DMF can fully dissociate the highly concentrated LiTFSI, providing more carriers. The prepared QSPE-PU40 shows a high ionic conductivity of 1.12 × 10 −4 S cm −1 at ambient temperature since DMF not only provides more carriers but also enhances the movement of the polymer segments and lowers the energy barrier of lithium ion migration. Density functional theory calculations further prove that DMF facilitates the conduction of lithium ions in the QSPE system. QSPE-PU40 shows good compatibility with the lithium metal electrode by forming a stable solid electrolyte interphase during lithium plating/stripping processes. The lithium ferrophosphate (LFP)/QSPE-PU40/Li battery exhibits a high specific capacity of 138 mA h g −1 with remarkable cycling stability at 0.5 C and 30 °C (94% capacity retention after 800 cycles). More impressively, the pouch cell based on QSPE-PU40 delivers good flexibility and high safety. Such a QSPE is expected to provide an effective strategy where SPEs are applied in solid-state lithium batteries at ambient temperature and even flexible batteries for next-generation wearable devices.

Thermally Stable Ceramic-Salt Electrolytes for Li Metal Batteries Produced from Cold Sintering Using DMF/Water Mixture Solvents

“…DMF and DMSO remain in the grain boundary after CSP is complete, which produces a highly concentrated DMF (or DMSO)-LiTFSI phase, and it enables fast Li ion conduction at the grain boundary of LAGP. Based on this mechanism, we attribute the better thermal stability of CSP LAGP-LiTFSI DMF/H2O, compared with CSP LAGP-LiTFSI DMSO/H2O, to the strong solvation ability of DMF [53,54]. To verify the hypothesis, we simply measured the solubility of LiTFSI in DMF and DMSO solvents by preparing highly concentrated LiTFSI solutions (5~16 M conc.)…”

Poly(vinylidene fluoride-co-hexafluoropropylene)-Based Solid Polymer Electrolyte Incorporated with UiO-66 for Lithium Metal Batteries

“…In this study, we use an octahedral UiO-66 prepared and synthesized via hydrothermal methods as a filler for a poly­(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP) polymer electrolyte. PVDF-HFP-based polymer electrolytes have garnered attention for their attributes, including a high dielectric constant (ε r ∼ 8–10), robust electrochemical stability (4–5 V), and excellent thermal stability. − Its high dielectric constant accelerates the dissociation of lithium salts, and lithium salts coordinate with residual dimethylformamide (DMF) forming Li­(DMF) x TFSI, − which combines with the UiO-66 and PVDF-HFP matrix to form a CSPE. The uniform distribution of MOF fillers within the CSPE contributes to a denser structure within the solid-state polymer electrolyte system.…”

A Biodegradable High-Performance Microsupercapacitor for Environmentally Friendly and Biocompatible Energy Storage

“…In addition, the environmental and biological hazards of both electrodes and electrolytes must also be fully considered. For example, most of liquid electrolytes use toxic organic solvents, such as ethylene carbonate and 1,3-dioxolane, − and some electrode materials contain heavy-metal elements, such as Co and Mn, that can affect cell survival and lead to tissue lesions. , To overcome these issues, some biodegradable or highly biocompatible materials have been applied to the preparation of harmless and biodegradable substrates or encapsulation materials, including natural polysaccharide represented by cellulose, starch, and chitosan, animal and plant proteins represented by silk protein and gelatin, and some synthetic biodegradable polymers represented by polycaprolactone (PCL) and polylactic acid (PLA) . Aiming to nontoxic electrodes, graphene and activated carbon (AC), which contain no heavy-metal elements and are highly chemically inert, are gradually being selected for preparing environmentally friendly and biosafe electrode materials. − Moreover, aqueous electrolytes, usually Na 2 SO 4 , LiCl, and NaCl solutions, are also being developed to replace environmentally harmful organic electrolytes.…”