Kish Graphite Flakes as a Cathode Material for an Aluminum Chloride–Graphite Battery

Abstract

Nonaqueous, ionic liquid-based aluminum chloride-graphite batteries (AlCl-GBs) are a highly promising post-Li-ion technology for low-cost and large-scale storage of electricity because these batteries feature exclusively highly abundant chemical elements and simple fabrication methods. In this work, we demonstrate that synthetic kish graphite, which is a byproduct of steelmaking, can be used as a cathode in AlCl-GB and exhibits high capacities of ≤142 mAh g. The comprehensive characterization of kish graphite flakes and other forms of graphite by X-ray diffraction, Raman spectroscopy, and Brunauer-Emmett-Teller surface area analysis provides solid evidence that the exceptional electrochemical behavior of kish graphite flakes is mainly determined by the high structural order of carbon atoms, a low level of defects, and a unique "crater morphology". In view of the nonrocking chair operation mechanism of AlCl-GB, we have tested the achievable energy densities as a function of the composition of chloroaluminate ionic liquid (AlCl content) and have obtained energy densities of up to 65 Wh kg. In addition, the kish graphite flakes can rapidly charge and discharge, offering high power densities of up to 4363 W kg.

An Aluminum/Graphite Battery with Ultra‐High Rate Capability

“…[23,27,33,35,39] Figure 1c evidences that, at full charge, the NG intercalates 0.05 mole of AlCl 4 À for each mole of carbon (i. e., 110 mAh g À1 capacity), obtaining a C[AlCl 4 À ] 0.05 GIC. This assumption is well supported by literature results, indicating that the AlCl 4 À is the anionic specie intercalated within the graphite planes.…”

Rechargeable Dual‐Ion Batteries with Graphite as a Cathode: Key Challenges and Opportunities

“…[75][76][77][78][79][80][81][82][83][84][85] Aluminum, therefore, does not deposit from neutral or basic melts (excess of EMIMCl). The mixture becomes liquid at room temperature (an ionic liquid) due to the acid-base reaction between AlCl 3 (Lewis acid) and Cl − (Lewis base) forming AlCl 4 − anions charge-balanced with, for instance, EMIM + cation.…”

“…[14] In addition to the intrinsic redox potential of graphite, there are a few other factors contributing toward the experimentally observed voltage of the anion intercalation. Specifically, in the recent publication of Wang et al [75] about the electrochemical performance of graphite in aluminum GDIBs, the constant current-constant voltage (CCCV) charging protocol, which involves constant charging steps in the range of 1.9-2.1 V (terminated at a current drop of 90%), substantially improves the discharge capacity of graphite from 110 to 142 mAh g -1 . These two factors depend differently on the size of the anion.…”

“…Specifically, a high level of CP corresponds to the smaller amount of the defects, the closest interplanar graphene-graphene distance to the ideal value of 0.3354 nm, and the large size of crystallites. [75] Figure 8a shows the chargestorage capacity of graphites using a typical low-acidity formulation of chloroaluminate ionic liquid (AlCl 3 /EMIMCl; r = 1.3), wherein the tested materials exhibit drastic differences. [120][121][122] For instance, the average interplanar spacing distance between graphene layers in graphite crystallites (single graphite monocrystals) and their size can be calculated using XRD analysis.…”

“…Hence, oxidatively stable current collectors such as tungsten, molybdenum, and glassy carbon are employed in GDIBs. [75] Copyright 2017, The American Chemical Society. As reported by Wang et al [103] flexible current collectors were fabricated by a coating of TiN on stainless steel or flexible polyimide substrates by a low-cost, rapid, and scalable method, such as magnetron sputtering.…”