Propylene carbonate (PC) is regarded as a promising solvent for replacing ethylene carbonate due to its high dielectric constant and wide working temperature range. However, the co-intercalation behavior between PC and Li + on graphite poses limitations to its further application. In this study, a weakly solvating solvent of methyl trifluoromethyl carbonate (FEMC) and lithium bis(oxalato)difluorophosphate (LiDODFP) synergistically enable reversible cycling of low-concentration PC-based electrolytes on graphite. Nuclear magnetic resonance spectroscopy and theoretical calculations indicate that FEMC partially substitutes PC in the solvation structure and interacts with PC through intermolecular forces, facilitating desolvation of Li + . Moreover, the utilization of LiDODFP enhances the solvation structure of Li + , effectively resolving the compatibility issue between graphite and PC. This electrolyte exhibits exceptional oxidative stability and nonflammability properties. At a cut-off voltage of 4.5 V, the NCM811/graphite full cell exhibits 88.86% capacity retention after 300 cycles at 25 °C, and retains 76.23% capacity after 100 cycles at 60 °C; even at −40 °C, it still delivers a capacity of 67 mAh g −1 . This work presents a novel strategy for developing low-concentration, wide-temperature-applicable, high-safety, and high-voltage PC-based electrolytes.
Solid-state batteries , which exhibit characteristics including uniform Li deposition, non-flammability and low interfacial resistance, are desirable for novel energy storage devices. Herein, a self-standing, fireproof and electrochemically stable organic-inorganic composite ionogel electrolyte was carefully designed and prepared by using polymerized ionic liquid (PIL), ionic liquid (IL), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium aluminum titanium phosphate (LATP) nanoparticles . The incorporation of LATP nanoparticles into polymer backbone was found to facilitate ionic transport due to the homogenous Li + distribution, which would further boost the ionic conductivity and mechanical properties. In addition, the introduction of IL favored the reduction of interface resistance. Benefiting from the nonflammability, the thermal shrinkage performance of as-prepared electrolyte could stand over a broad operating temperature range. A Li/Li symmetric cell containing optimized PIL-14 wt% LATP could be cycled steadily for over 2000 h at 50 °C. A lithium metal battery containing composite ionogel electrolyte exhibited an outstanding specific capacity of 145 mAh g −1 and 95% capacity retention at 50 °C even after 100 cycles. This study indicates that the co-employment of IL and inorganic nanoparticle is an effective strategy for the construction of organic-inorganic hybrid electrolytes for high-safety solid-state lithium metal batteries (LMBs).
A novel hydrophilic polytetrafluoroethylene (PTFE)-supported gel polymer electrolyte (GPE) membrane based on the cross-linked poly(ethylene glycol) and poly(glycidyl methacrylate) block copolymer (PEG– b –PGMA) is successfully prepared by cationic ring-opening polymerization and followed by in situ cross-linking process. The poly(ethylene glycol) side chains of PEG– b –PGMA interact with the liquid electrolyte and hold it inside the membrane, while the hydrophilic and highly-porous PTFE membrane offers mechanical support for the cross-linked GPE. The ionic conductivity of the optimized GPE-3 reaches 1.30×10 −3 S cm −1 at 25 °C and is high enough to be applied in lithium secondary batteries . The GPE is electrochemically stable up to 4.5 V versus Li/Li + . Moreover, the optimized GPE membrane demonstrates non-flammability and good dimensional stability at elevated temperature, which can improve the safety of the cell. The Li/LiFePO 4 cell using the GPE-3 exhibits stable cycling behavior and superior rate performance comparable to the cell based on conventional liquid electrolyte. Therefore, the reported GPE is very promising for the use in rechargeable lithium batteries .
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