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

Abstract

friendliness. Additionally, there are numerous additional electrochemical battery performance characteristics that play an equally important role such as longterm cycling performance (cycle life), calendar life, Coulombic efficiency (measure for charge loss due to irreversible side reactions), energy efficiency, and the performance at different charge/discharge rates or at different temperatures. From this perspective, researchers constantly explore new anode and cathode materials for existing battery technologies as well as conceive new electrochemical energy storage concepts. In this context, the last two decades have seen a surge of reports on various low-cost anodes and cathodes for Li-ion and post-Li-ion batteries (Na-, K-, Ca-, Mg-, and Al-ion batteries). Moreover, new electrochemical concepts called graphite dual-ion batteries (GDIBs) have recently attracted significant attention. GDIBs show high potential for the use in grid-scale energy storage applications due to their low cost, relatively high energy densities of up to ≈200 Wh kg −1 and cyclic stability (thousands of cycles and potentially more). In this review, we provide an introduction to the basics of GDIBs. In particular, we discuss their operating mechanisms and cover the topic of energy density calculations. In addition, we highlight the importance of correct reporting of the performance metrics with respect to the energy density of GDIBs. Next, we discuss in detail factors governing the electrochemical performance of graphite cathodes in dual-ion batteries, such as graphite structure, morphology, and particle size. The factors that impact the voltage of electrochemical anion intercalation/deintercalation into graphite will be described as well. With respect to the practical application of the GDIBs, the current collector issues and volume changes of GDIBs will be discussed in the final sections. Historical AspectsAlthough GDIBs may appear to be newcomers in battery research, they have a long and tangible history. The concept of GDIBs was introduced in the patents of McCullough et al. [1,2] in 1989. The experimental example consisted of two graphite electrodes acting as an anode and a cathode, and a 15 wt% solution of LiClO 4 in propylene carbonate acting as an electrolyte. The oxidation and reduction of cathodic and anodic graphite electrodes occur with concomitant intercalation of Li + cations and ClO 4 − anions, respectively. The latter process is known as the formation of donor-type (cationic) or acceptor-type (anionic) graphite intercalation compounds (GICs). Some years later, in the 1990s, the intercalation of various anions into graphite Rechargeable graphite dual-ion batteries (GDIBs) have attracted the attention of electrochemists and material scientists in recent years due to their low cost and high-performance metrics, such as high power density (≈3-175 kW kg −1 ), energy efficiency (≈80-90%), long cycling life, and high energy density (up to 200 Wh kg −1 ), suited for grid-level stationary storage of electricity.The key feature of GD...

Challenges and benefits of post-lithium-ion batteries

“…Al-GDIBs are composed of highly abundant elements (H, O, N, C, and Al) and have appropriate energy densities (30-70 W h kg À1 ). [102][103][104][105][106] The basic architecture of an Al-GDIB consists of a graphite cathode, metallic Al current collector, and AlCl 3 -1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) ionic liquid anolyte, as shown in Fig. 3.…”

An Energy‐Dense Solvent‐Free Dual‐Ion Battery

“…Dual‐ion batteries (DIBs) are an emerging class of rechargeable batteries. [ 8–11 ] As the name implies, DIBs rely on the simultaneous storage and release of both cations and anions at the anode and cathode, respectively, unlike rocking‐chair LIBs in which only cations are transferred between electrodes. The advantages of this mechanism are threefold.…”

“…However, the cell‐level energy density of DIBs is inferior (<50 Wh kg −1 , Table S1, Supporting Information). [ 8,9,21 ] This is because the cation/anion content in the system must match the anode/cathode capacity, which inevitably introduces superfluous solvents in most electrolytes. Take the generally adopted diluted electrolyte (≤1 mol dm −3 ) as an example, to supply sufficient charge carriers, the electrolyte itself is deduced to account for >70 wt% over the total cell weight due to the excessive, capacity‐non‐contributing solvents (please see the Excel spreadsheet in the Supporting Information).…”

Aluminum electrolytes for Al dual-ion batteries

“…3 and 4 can be found in ref. 50 . For instance, the gravimetric charge storage capacities of the AlCl 3 : EMIMCl ionic liquid are equal to 19 mAh g −1 and 48 mAh g −1 for r = 1.3 and r = 2, accordingly.…”

“…For instance, the gravimetric charge storage capacities of the AlCl 3 : EMIMCl ionic liquid are equal to 19 mAh g −1 and 48 mAh g −1 for r = 1.3 and r = 2, accordingly. Notably, these capacities define the overall energy density of ADIBs 14,18,[50][51][52][53][54][55][56][57] . Moreover, it should be pointed out that these theoretical capacities are not always achievable experimentally, i.e., they depend on practically relevant experimental conditions and on whether Al 2 Cl 7 − ions can be fully depleted for Al electroplating.…”