A low cost electrolyte of AlCl3/AcAm ionic liquid analogs for high-performance aluminum ion batteries

Abstract

• The species of Al deposited in AlCl 3 /AcAm ILAs was not [AlCl 2 (AcAm) n ] + but Al 2 Cl 7 − . • AlCl 3 /AcAm ILAs exhibits excellent electrochemical performance in Al-graphit cells. • The energy storage mechanism of AlCl 3 /AcAm ILAs in Al-graphite battery is revealed. Rechargeable Aluminum-ion batteries (AIBs) system have been attracting attention owing to its potential high safety, low cost, high theoretical specific capacity high power density and three electron-redox for aluminum (Al) metal anode. Nevertheless, the 1-ethyl-3-methylimidazolium chloride (EMIC) based ionic liquid (IL) electrolyte mainly used in AIBs at present, severely restricting its practical application due to its high cost, low productivity, moisture sensitivity and toxicity. Herein, we report a low-cost AlCl 3 /adelaide (AlCl 3 /AcAm) eutectic ionic liquid analogs (ILAs) electrolyte used to construct practical Al-graphite batteries. The capacity over 72.8 mAh g −1 was well retained within wide current densities range from 50 to 500 mA g −1 . The cathodic capacity remained at ~ 66.8 mAh g −1 (~77% capacity retention) even at a high current density of 500 mA g −1 , and the charge/discharge plateaus were still discerned despite the current density was raised to 500 mA g −1 . By various characterization strategies, the cathodic intercalation/de-intercalation and anodic deposition/dissolution mechanisms are revealed. The active ion of reducing Al is a anionic species of Al 2 Cl 7 - , rather than the cationic species of [AlCl 2 (AcAm) n ] + in AlCl 3 /AcAm ILAs electrolyte. This work provides a new opportunity for the design of new low cost AIBs electrolyte, and opens up a new way for manufacturing better AIBs with high capacity performance.