Solvate Ionic Liquids for Li, Na, K, and Mg Batteries

Abstract

From the viewpoint of element strategy, non‐Li batteries with promising negative and positive electrodes have been widely studied to support a sustainable society. To develop non‐Li batteries having high energy density, research on electrolyte materials is pivotal. Solvate ionic liquids (SILs) are an emerging class of electrolytes possessing somewhat superior properties for battery applications compared to conventional ionic liquid electrolytes. In this account, we describe our recent efforts regarding SIL‐based electrolytes for Li, Na, K, and Mg batteries with respect to structural, physicochemical, and electrochemical characteristics. Systematic studies based on crystallography and Raman spectroscopy combined with thermal/electrochemical stability analysis showed that the balance of competitive cation−anion and cation−solvent interactions predominates the stability of the solvate cations. We also demonstrated battery applications of SILs as electrolytes for non‐Li batteries, particularly for Na batteries.

Advances in sodium secondary batteries utilizing ionic liquid electrolytes

“…The lowest eutectic temperature of 36 1C was observed for the Na[FSA]/ K[FSA]/Cs[FSA] system at a molar ratio of 40 : 25 : 35. 144 Solvate ILs are another category in this field, 95,145,146 although the number of solvate ILs investigated for Na secondary batteries is currently limited. Solvate ILs are formed by Lewis basic species such as oligoethers interacting with metal salts at equimolar concentrations.…”

Toward High‐Energy‐Density Lithium Metal Batteries: Opportunities and Challenges for Solid Organic Electrolytes

“…The ever‐growing consumer electronic market, such as portable electronics, wearable devices, and the commercialization of electric vehicles (EVs) have greatly motivated the pursuit of efficient, safe batteries that can be used for long service times. Although great efforts have been made to develop other alternative batteries, such as using Na, K, or Mg as anodes, they are still nascent compared with Li batteries. Li metal is known for its extremely high theoretical specific capacity (≈3860 mAh g −1 ) due to its low density (0.53 g cm −3 ) and ultranegative electrochemical potential (−3.04 V vs standard hydrogen electrode).…”

Sulfonylamide‐Based Ionic Liquids for High‐Voltage Potassium‐Ion Batteries with Honeycomb Layered Cathode Oxides

“…Ionic liquids are a burgeoning class of safe electrolytes that have particularly been sought to address the stability of cathode materials under high‐voltage operation conditions in batteries such as the lithium‐, sodium‐, magnesium‐ and aluminum‐ion technologies, but not yet as prolific in the nascent potassium‐ion battery research. Ionic liquids, which comprise (in)organic anions and organic cations, are characterized by a suite of unique properties; prime amongst them being their good thermal stability, low flammability and low volatility.…”

“…Potassium-based oxides tend to show low average voltage; however, this prevailing notion was recently obliterated by the design of tellurium-doped K 2/ potassium metal anode continues to cast doubt on the safety of electrolytes based on organic solvents. [14] Ionic liquids are a burgeoning class of safe electrolytes that have particularly been sought to address the stability of cathode materials under high-voltage operation conditions in batteries such as the lithium-, sodium-, magnesium-and aluminum-ion technologies, [15][16][17][18] but not yet as prolific in the nascent potassium-ion battery research. Ionic liquids, which comprise (in)organic anions and organic cations, are characterized by a suite of unique properties; prime amongst them being their good thermal stability, low flammability and low volatility.…”