Ionogel Electrolytes for High‐Performance Lithium Batteries: A Review

Abstract

Ionic liquids (ILs) are important electrolytes for applications in electrochemical devices. An emerging trend in ILs research is their hybridization with solid matrices, named ionogels. These ionogels can not only overcome the fluidity of ILs but also exhibit high mechanical strength of the solid matrix. Therefore, they show promise for applications in building lithium batteries. In this review, various types of solid matrices for confining ILs are summarized, including nonmetallic oxides, metal oxides, IL‐tethered nanoparticles, functionalized SiO2, metal–organic frameworks, and other structural materials. The synthetic strategies for ionogels are first documented, focusing on physical confinement and covalent grafting. Then, the structure, ionic conductivity, thermal stability, and electrochemical stability of ionogels are addressed in detail. Furthermore, the authors highlight the potential applications of state‐of‐art ionogels in lithium batteries. The authors conclude this review by outlining the remaining challenges as well as personal perspectives on this hot area of research.

Electrolytes for Rechargeable Lithium–Air Batteries

“…In solid composite electrolytes, the enhancement in ionic conductivity is attributed to the inhibition of crystallization in the polymer phases. In solid–liquid composite electrolytes, the functionalized passive ceramic fillers with functional groups grafted on their surface can promote the dissociation of lithium salts, which is beneficial to increase the amount of free Li + in the electrolyte . The ionic transport in these electrolytes appears to occur along the surface of the fillers or through the interfacial region.…”

“…In solid composite electrolytes,the enhancement in ionic conductivity is attributed to the inhibition of crystallization in the polymer phases.Insolid-liquid composite electrolytes,the functionalized passive ceramic fillers with functional groups grafted on their surface can promote the dissociation of lithium salts, which is beneficial to increase the amount of free Li + in the electrolyte. [183,184] Thei onic transport in these electrolytes appears to occur along the surface of the fillers or through the interfacial region. Other materials such as CNTs,g raphene, microporous molecular sieves,z eolites,a nd metal-organic frameworks with specific structures and components can also serve as passive fillers to elevate the total conductivity of solid-state electrolytes by providing low-energy conduction pathways.…”

Silica gel solid nanocomposite electrolytes with interfacial conductivity promotion exceeding the bulk Li-ion conductivity of the ionic liquid electrolyte filler

“…Polymer electrolytes are more mechanically compliant but do not yet exhibit high enough ionic conductivity at room temperature. Very interesting new materials in this regard are silica gel electrolytes, which have also been referred to as "ionogels," where an ionic liquid electrolyte (ILE) is confined in a nanoporous silica matrix (1). The extremely high porosity of the silica matrix (70 to 90%) gives these nanocomposite electrolyte materials a gel-like consistency and thus making them mechanically compliant similar to polymer electrolytes.…”

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

“…The particle gap of particle‐rich PIL coating formed on the lithium electrode is much smaller than the strict nucleation size of the lithium dendrite, which can completely stabilize the electrodeposition of the lithium metal/electrolyte surface and promote the formation of SEI film on the Li surface . Moreover, the porous architecture provides continuously paths to regulate the lithium ion transport in the electrolyte and reduces the driving force for forming electric convection and dendrites . So, short‐circuit can be avoided and the safety of battery in the practical use is ensured.…”