Poly(ionic liquid)‐Based Hybrid Hierarchical Free‐Standing Electrolytes with Enhanced Ion Transport and Fire Retardancy Towards Long‐Cycle‐Life and Safe Lithium Batteries

Abstract

Ionic liquid electrolytes (ILEs), owing to their wide electrochemical window, high ionic conductivity, and low volatility, have been extensively applied in the field of energy storage devices. However, it is extremely significant and greatly challenging to seek the counterbalance of good mechanical properties and excellent electrochemical performances, including a high transference number of ILEs for safe flexible lithium batteries. In this work, a novel hybrid poly(ionic liquid)-based quasi-solid electrolyte containing silica nanoparticles (SiO 2 -PIL-QSE) is fabricated through the one-step in situ polymerization of the ionic liquid covalently tethered to silica nanoparticles (SiO 2 -IL-TFSI), which fills a poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) porous membrane prepared through phase inversion. The hybrid hierarchical porous architecture endows the SiO 2 -PIL-QSE with excellent thermal stability, good fire safety (i. e. nonflammable and low shrinkage), improved mechanical strength, and excellent electrochemical performance, including a high room-temperature ionic conductivity of 1.69 mS cm À 1 , a superior electrochemical window up to 5.5 V, as well as a high lithium-ion transference of 0.46. Accordingly, the LiFePO 4 j SiO 2 -PIL-QSE j Li cell can maintain a discharge specific capacity of 133.7 mAh g À 1 at 0.1 C at 25°C with a capacity retention ratio of 91.9 % after 400 cycles. The excellent performances and good applicability in the pouch-type battery of SiO 2 -PIL-QSE indicate a good prospect in the field of flexible solidstate polymer batteries (SSPB).[a] T.

Highly Conductive, Flexible, and Nonflammable Double-Network Poly(ionic liquid)-Based Ionogel Electrolyte for Flexible Lithium-Ion Batteries

“…The interfacial stability between the electrolyte and the lithium anode was estimated by galvanostatic cycling measurements with a current density of 0.1 mA/cm 2 , as shown in Figure d,e. A sharp voltage drop occurs at 190 h for the PP separator absorbed LE as the signal of short-circuit, indicating that the separator is penetrated by unstoppable lithium dendrites during the lithium deposition and stripping. , Substituting the LE with IL, no short-circuit can be found in the DN-Ionogel after 350 h, suggesting that the application of IL can significantly suppress the growth of lithium dendrites. Meanwhile, the DN-Ionogel exhibits long-term cycling stability with no evidence of voltage fluctuation (∼64 mV).…”

Influence of Polarizability on the Structure, Dynamic Characteristics, and Ion-Transport Mechanisms in Polymeric Ionic Liquids

“…Solid polymer electrolytes (SPEs) have been proposed as one potential candidate for alleviating some of the issues plaguing the electrolytes in LIBs. − As a family member of SPEs, polymeric ionic liquids (polyIL) exhibit the attractive combination of physicochemical and ion-transport characteristics of ILs and enhanced mechanical properties of polymers. − As a result, such materials exhibit high conductivities and lower glass-transition temperatures even at high charge densities. Consequently, polyILs have attracted considerable interest as potential electrolytes for LIBs. − …”

Mechanisms of Ion Transport in Lithium Salt-Doped Polymeric Ionic Liquid Electrolytes

“…Polymerized ionic liquids (polyILs) are macromolecules that incorporate traditional ionic liquid (monomeric IL) monomers as their repeating units. PolyILs inherit the unique physicochemical properties of ILs and the mechanical stability characteristics of solid polymer electrolytes, thereby endowing desirable performance features. − Among different applications, such materials are emerging of significant interest in pursuit of safe electrolyte materials for lithium ion batteries. − …”