A Novel Moisture‐Insensitive and Low‐Corrosivity Ionic Liquid Electrolyte for Rechargeable Aluminum Batteries

Abstract

Rechargeable aluminum batteries (RABs) are extensively developed due to their cost‐effectiveness, eco‐friendliness, and low flammability and the earth abundance of their electrode materials. However, the commonly used RAB ionic liquid (IL) electrolyte is highly moisture‐sensitive and corrosive. To address these problems, a 4‐ethylpyridine/AlCl3 IL is proposed. The effects of the AlCl3 to 4‐ethylpyridine molar ratio on the electrode charge–discharge properties are systematically examined. A maximum graphite capacity of 95 mAh g−1 is obtained at 25 mA g−1. After 1000 charge–discharge cycles, ≈85% of the initial capacity can be retained. In situ synchrotron X‐ray diffraction is employed to examine the electrode reaction mechanism. In addition, low corrosion rates of Al, Cu, Ni, and carbon‐fiber paper electrodes are confirmed in the 4‐ethylpyridine/AlCl3 IL. When opened to the ambient atmosphere, the measured capacity of the graphite cathode is only slightly lower than that found in a N2‐filled glove box; moreover, the capacity retention upon 100 cycles is as high as 75%. The results clearly indicate the great potential of this electrolyte for practical RAB applications.

Engineering Active Sites of Polyaniline for AlCl2+ Storage in an Aluminum‐Ion Battery

“…[21] Generally, the soluble halides of Al element undergo asymmetric cleavage in solution to generate [AlX 2 + ] and [AlCl 4 À ] ions (Supporting Information, Figure S29). [22] In our case, AlCl 4 À anions cannot react with the electronegative ÀNHÀ in PANI(H + ) because of the electrostatic repulsion, and cationic chloroaluminate (AlCl 2 + ) will interact with À NH À groups of PANI(H + ) during the discharge process. It can be confirmed by the FTIR and TEM elemental mapping images with the corresponding EDS (Supporting Information, Figures S30 and S31).…”

Deep eutectics and analogues as electrolytes in batteries

“…The electrolyte with AlCl3 to EP ratio equal to 1.3 turned out to be the optimal composition in Al|graphite cells in terms of capacity and rate capability (95 mAh g −1 at 25 mA g −1 and 32% capacity retention at 300 mA g −1 , against 41, 55, and 80 mAh g −1 , with 20%, 25%, and 26% retention, for molar ratios of 1.1, 1.2 and 1.4, respectively). 204 The cell with AlCl3:EP 1.3:1 also exhibited decent cycling stability, with ≈85% of the initial capacity retained after 1000 charge-discharge cycles at a rate of 100 mA g −1 . This electrolyte also possesses additional upsides.…”

“…In this framework, a more severe substitution includes the use of 4-ethylpyridine (EP) as a neutral ligand to form a new electrolyte in combination with AlCl3. 204 Increasing AlCl3 ratio from 1.1 to 1.4 leads to an improvement in ionic conductivity (from 0.71 to 0.91 mS cm -1 ) due to the increase of ionic species, and a slight increase in viscosity (from 17.8 to 23.6 mPa s), probably due to enhanced interactions/aggregations between ions at high concentrations (Table 5). Contrary to previous studies, regardless of the AlCl3 to EP ratio, Al 2 Cl 7 − anions were not detected, then the deposition is expected to accur via the following reaction: 204…”

Ionic Liquid‐Based Stimuli‐Responsive Functional Materials

“…These properties make ILs an environmentally benign media for catalytic reactions, a supported liquid membrane for gas separation, and an excellent electrolyte for electrochemistry and energy‐related applications. [ 30–35 ] ILs have received a great deal of attention in the past decade and many reviews focused on these topics are available. [ 36–39 ] It should be noted that IL‐based stimuli‐responsive functional materials have been rarely elaborated until now.…”