Ionic liquids and their derivatives for lithium batteries: role, design strategy, and perspectives

Abstract

Lithium-ion batteries (LIBs) are the predominant power source for portable electronic devices, and in recent years, their use has extended to higher-energy and larger devices. However, to satisfy the stringent requirements of safety and energy density, further material advancements are required. Due to the inherent flammability and incompatibility of organic solvent-based liquid electrolytes with materials utilized in high energy devices, it is necessary to transition to alternative conductive mediums. The focus is shifting from molecular materials to a class of materials based on ions, including ionic liquids (ILs) and their derivatives such as zwitterionic ILs, polymerized ILs, and solvated ILs, which possess high levels of safety, stability, compatibility, and the ability to rationally design ILs for specific applications. Ion design is crucial to achieve superior control of electrode/electrolyte interphases (EEIs) both on anode and cathode surfaces to realize safer and higher-energy lithium-metal batteries (LMBs). This review summarizes the different uses of ILs in electrolytes (both liquid and solids) for LMBs, reporting the most promising results obtained during the last years and highlighting their role in the formation of suitable EEIs. Furthermore, a discussion on the use of deep-eutectic solvents is also provided, which is a class of material with similar properties to ILs and an important alternative from the viewpoint of sustainability. Lastly, future prospects for the optimization of IL-based electrolytes are summarized, ranging from the functional design of ionic structures to the realization of nanophases with specific features.

Controlling the Potential of Affordable Quasi‐Solid Composite Gel Polymer Electrolytes for High‐Voltage Lithium‐Ion Batteries

“…In response to these challenges, research endeavors are shifting towards developing safer alternatives to liquid electrolytes, with a focus on solid-state batteries (SSBs). [7][8][9] To mitigate the limitations linked with liquid electrolytes and enhance the security of Li metal anodes, pure solid electrolytes (SEs) have emerged as a promising solution.…”

In Situ Polymerized Zwitterionic Copolymer Ionic Gel Electrolytes with High Performance for Lithium-Ion Batteries

“…Recent studies have reported several brand-new methods, among which the use of ionic liquids to modify solid electrolytes to obtain “ionic gel electrolytes” has attracted widespread attention . Ionic liquids (ILs) have noncombustion, nonvolatility, high thermal stability, and a broad electrochemical stability window. − Ionic gel electrolyte (IGE) using an ionic liquid as a plasticizer can largely avoid the risk of using organic solvent, which is considered a kind of safe electrolyte system with great application potential. , …”

“…26−28 Ionic gel electrolyte (IGE) using an ionic liquid as a plasticizer can largely avoid the risk of using organic solvent, which is considered a kind of safe electrolyte system with great application potential. 29,30 But traditional polymer matrices, such as PAN and PVDF, only have limited IL content. To maximize the benefits of ILs, it is significant to select the appropriate matrix.…”

The deconstruction of a polymeric solvation cage: a critical promotion strategy for PEO-based all-solid polymer electrolytes

“…Solid-state lithium batteries are considered promising candidates for next-generation secondary batteries as they can perfectly balance the constantly increasing demand for battery energy density and safety. 1–5 Various types of solid-state electrolytes (SSEs) have been proposed and developed, yet many concerns still remain in terms of the transition of electrolytes from the liquid to solid state, severely hindering the commercialization of solid-state batteries, with key issues including low σ at room temperature, poor electrolyte/electrode interface compatibility, and narrow electrochemical stability window. Benefiting from the excellent toughness and strength of polymers, SPEs with better fabrication and mechanical flexibility are considered interfacial friendly and more compatible with existing lithium battery production processes, and are thus considered one of the most commercially viable options.…”