New acceptor‐type graphite intercalation compounds (GICs) offer candidates of cathode materials for dual‐ion batteries (DIBs), where superhalides represent the emerging anion charge carriers for such batteries. Here, the reversible insertion of [LiCl 2 ] − into graphite from an aqueous deep eutectic solvent electrolyte of 20 m LiCl + 20 m choline chloride is reported. [LiCl 2 ] − is the primary anion species in this electrolyte as revealed by the femtosecond stimulated Raman spectroscopy results, particularly through the rarely observed H–O–H bending mode. The insertion of Li–Cl anionic species is suggested by 7 Li magic angle spinning nuclear magnetic resonance results that describe a unique chemical environment of Li + ions with electron donors around. 2 H nuclear magnetic resonance results suggest that water molecules are co‐inserted into graphite. Density functional theory calculations reveal that the anionic insertion of hydrated [LiCl 2 ] − takes place at a lower potential, being more favorable. X‐ray diffraction and the Raman results show that the insertion of [LiCl 2 ] − creates turbostratic structure in graphite instead of forming long‐range ordered GICs. The storage of [LiCl 2 ] − in graphite as a cathode for DIBs offers a capacity of 114 mAh g −1 that is stable over 440 cycles.

The formation of dimeric or larger cluster metal intercalates within layered hosts may reveal new chemistries for charge storage electrodes. In previous work, we reported a series of novel ternary stage-1 graphite intercalation compounds (GICs) containing alkaline earth metal cations (M = Mg, Ca, Sr, or Ba) and ethylenediamine (en). Pair distribution function (PDF) analyses indicated the presence M-M bonding within the intercalates in the monolayer galleries.

Anion storage in cathode of dual-ion batteries provides leeway for chemistries. For high energy density and better safety, it is desirable but challenging to reversibly intercalate chloride in a graphite cathode because either the oxygen or chlorine evolution reaction can prevail over chloride insertion. The primary barrier is the lack of suitable aqueous electrolytes that suppress these parasitic reactions. Herein, we report an aqueous deep eutectic solvent gel electrolyte that allows reversible chloride storage for graphite based on a chloride-based electrolyte via the formation of iodine-chloride interhalogens. The results suggest three reversible steps: iodine plating on the host surface, oxidation to form I-Cl interhalides, and then intercalation into graphite. As a result, the graphite cathode delivers a high reversible capacity of 291 mAh g(-1) with stable cycling performance. Facilitated by the same mechanism, a porous graphenic carbon delivered a record-high capacity of over 1100 mAh g(-1).

The alkaline earth metals (M=Mg, Ca, Sr, and Ba) exhibit a +2 oxidation state in nearly all known stable compounds, but M-I dimeric complexes with M-M bonding, [M-2(en)(2)](2+), (en=ethylenediamine) of all these metals can be stabilized within the galleries of donor-type graphite intercalation compounds (GICs). These metals can also form GICs with more conventional metal (II) ion complexes, [M(en)(2)](2+). Here, the facile interconversion between dimeric-M-I and monomeric-M-II intercalates upon the addition/removal of en are reported. Thermogravimetry, powder X-ray diffraction, and pair distribution function analysis of total scattering data support the presence of either [M-2(en)(2)](2+) or [M(en)(2)](2+) guests. This phase conversion requires coupling graphene and metal redox centers, with associated reversible M-M bond formation within graphene galleries. This chemistry allows the facile isolation of unusual oxidation states, reveals M-0 -> M2+ reaction pathways, and present new opportunities in the design of hybrid conversion/intercalation materials for applications such as charge storage.

Oxidative anion insertion into graphite in an aqueous environment represents a significant challenge in the construction of aqueous dual-ion batteries. In dilute aqueous electrolytes, the oxygen evolution reaction (OER) dominates the anodic current before anions can be inserted into the graphite gallery. Herein, we report that the reversible insertion of Mg-Cl superhalides in graphite delivers a record-high reversible capacity of 150 mAh g(-1)from an aqueous deep eutectic solvent comprising magnesium chloride and choline chloride. The insertion of Mg-Cl superhalides in graphite does not form staged graphite intercalation compounds; instead, the insertion of Mg-Cl superhalides makes the graphite partially turbostratic.

Direct recycling of lithium-ion is a promising method for manufacturing sustainability. It is more efficient than classical methods because it recovers the functional cathode particle without decomposition into substituent elements or dissolution and precipitation of the whole particle. This case study of cathode-healing™ applied to a battery recall demonstrates an industrial model for recycling of lithium-ion, be it consumer electronic or electric vehicle (EV) batteries. The comprehensive process includes extraction of electrolyte with carbon dioxide, industrial shredding, electrode harvesting, froth flotation, cathode-healing™ and finally, building new cells with recycled cathode and anode. The final products demonstrated useful capability in the first full cells made from direct recycled cathodes and anodes from an industrial source. The lessons learned on recycling the prototypical chemistry are preliminarily applied to EV relevant chemistries.

The electric vehicle and energy storage industries will generate over one-million tons per annum of lithium-ion for recycling in the next decade. There are significant technology gaps in the recovery of lithium-ion battery materials that threaten the sustainability of these industries. Cathode healing is introduced here as a new approach to produce low cost (i.e. < $10/kg), recycled, battery grade electrode material. The soft-chemical treatment non-destructively recycles cathodes. Two examples are shown in this work: LiNi0.5Co0.2Mn0.3O2 and LiNi0.6Co 0.2Mn0.2O2 (NCM 523 and NCM 622). The cathodes were harvested from end-of-life cells and further processed with cathode-healing methods to reproduce recycled electrodes with performance equivalent to the original manufactured baseline material. The so-called healed cathodes were built into 2Ah test cells and compared side-by-side with the baseline. Healed NCM 523 performed like the baseline, recording over 2,100 charge-discharge cycles to reach 80% of original capacity. The cathode healing process was modified to fully recover end-of-life NCM 622. Powder X-ray diffraction and X-ray photoelectron spectroscopy data support the lithium capacity measurements with structural models. These analyses show that cathode healing reverses cation mixing by oxidizing nickel to reproduce well-ordered, high-capacity material. These examples show the technical feasibility and low-cost opportunity for cathode healing to enable sustainability in the electric vehicle and energy storage industries.

A series of new ternary graphite intercalation compounds (GICs) containing alkaline earth metal cations (M = Mg, Ca, Sr, Ba) and ethylenediamine (en) are reported. These GICs are deep blue to green in color and can be prepared as phase-pure compounds by the direct reaction of graphite powder with the metal in liquid en at mild temperatures (25-100 degrees C) under an inert atmosphere. X-ray diffraction and thermal analyses were employed to determine the structural and compositional details. [Mg-2(en)(2.0)] C-26 and [Ba-2(en)(2.0)]C-34 can be obtained as stage-1 GICs with gallery expansions of 0.55 and 0.46 nm, respectively, indicating the presence of intercalate monolayers with en cointercalates oriented perpendicular to the encasing graphene layers. Reactions with Ca and Sr metals form [Ca(en)(2.0)]C-26 and [Sr(en)(2.0)]C-22, which are stage-1 GICs with intercalate bilayers and gallery expansions of 0.76 nm. Titration indicates that each metal intercalate is associated with a 2-electron reduction process. Details on the effects of reaction time, temperature, and starting stoichiometry on reaction rates and product staging are reported.

There has been a major effort recently to develop new rechargeable sodium-ion electrodes. In lithium ion batteries, LiC6 forms from graphite and desolvated Li cations during the first charge. With sodium ions, graphite only shows a significant capacity when Na+ intercalates as a solvated complex, resulting in ternary graphite intercalation compounds (GICs). Although this chemistry has been shown to be highly reversible and to support high rates in small test cells, these GICs can require >250% volume expansion and contraction during cycling. Here we demonstrate the first example of GICs that reversibly sodiate/desodiate without any significant volume change. These pillared GICs are obtained by electrochemical reduction of graphite in an ether/amine co-solvent electrolyte. The initial gallery expansion, 0.36 nm, is less than half of that in diglyme-based systems, and shows a similar capacity. Thermal analyses suggest the pillaring phenomenon arises from stronger co-intercalate interactions in the GIC galleries.

New graphite intercalation compounds (GICs) containing 1-alkyl-2,3-dimethyl imidazolium cations (Im(1-1-a), a = alkyl length) are obtained from [Na(ethylenediamine)(1.0)]C-15 by cation exchange. Exchange reactions occur rapidly, but require higher temperature than for substituted alkylammoniums. Powder X-ray diffraction, thermogravimetry and structural modeling indicate that [Im1-1-4]C-47 is a stage-2 GIC with 0.36 nm monolayer galleries and cations oriented parallel to graphene sheets. [Im1-1-12]C-44 is a stage-1 GIC with a gallery expansion of 0.40 nm. The lower sheet charge density for [Im1-1-12] C-44 is commensurate with its larger intercalate. Imidazolium cations without alkyl substitution at the imidazolium ring C2 do not form stable GICs by this route. (C) 2018 Elsevier B.V. All rights reserved.

Nickel rich electrodes are of interest for use in next generation electric vehicle applications. Both new-scrap from original manufacturing and old-scrap from end of life batteries may require fees for processing because such "cobalt-lite" formulations have a low value of recoverable elements. For these materials, direct recycling technologies for recovery of electrode particles are not constrained by cobalt content. Coating of cathodes with molecular barriers is a strategy to improve the safety and life for of these electrodes. Coated cathodes can be adopted not only to improve 'first-life' cell performance, but also, when coupled with direct recycling technologies, facilitate the `next-life' of low cost lithium-ion cathodes from scrap material. This paper demonstrates direct recycling of bare NMC 622 from used cells, and direct recycling of a similar, coated material.

The first structural and compositional details of a low-stage graphite interaction compound (GIC) containing Mg are reported, with the GIC obtained by combining magnesium metal and graphite powder in ethylenediamine (en) at 100 °C under an inert atmosphere. Thermal analyses indicate the bottle-green stage 1 product has a composition of [Mg(en)1.0]C13. X-ray diffraction shows a c-axis expansion of 0.55 nm, indicating the presence of intercalate monolayers with the en cointercalate oriented perpendicular to the encasing graphene layers. Redox titration indicates two electrons are transferred per Mg. A structural model is proposed with dimeric [Mg2(en)2]2+ intercalate species.

Diffusion of alkali metals in graphite layers is significant for the chemical and electrochemical properties ol graphite intercalation compounds (GICs). Crown ethers co-intercalate into graphite with alkali metal (Na and K) cations and form ternary GICs. The structures and molecular dynamics of 15-crown-5 and 18-crown-6 ether coordinating to Na+ or K+ in GICs were investigated by DFT calculations and H-1 solid state NMR analyses. DFT calculations suggest a stacked structure of crown ether-metal complex with some offset. H-1 NMR shows two kinds of molecular motions at room temperature: isotropic rotation with molecular diffusion and axial rotation with fluctuation of the axis. The structure and dynamics of crown ether molecules in GIC galleries are strongly affected by the geometry of the crown ether molecules and the strength of the interaction between alkali metal and ligand molecules.

By 2025, the lithium-ion battery and disposal markets are forecast to reach $ 93 billion and $14 billion respectively. Logistics contribute to these costs, but processing takes its toll with energy intensive industrial smelting and/or hydrometallurgical technologies. As traction and storage cathode materials use less cobalt, these recycle technologies require centralized, large scale facilities to meet economic viability based upon the metal. Cobalt dilute or cobalt free applications may therefore require disposal fees, which is not helpful for circular economic sustainability for the advanced lithium-ion battery industry. Another technological approach is necessary to address this challenge for the industry. Direct recycling has potential for cost effective recycling of lithium-ion cathodes, which is demonstrated for NMC532 and NMC622 in this work. In the first example, NMC 532 electric vehicle grade cells were faded to 80% of their original capacity. The cells were pulverized and cathodes captured and treated and packaged. Afterwards, in a manufacturing setting, 2.2 Ah cells were built using the recycled cathode and graphite. Recycled cathode demonstrated both performance and manufacturability like new material. In side by side cycle testing, both tallied 2,500 cycles at C/10 to reach 80% of original capacity. In the second example, starting with faded cells, NMC 622 is similarly regenerated to original capacity and rate capability. Physical characterization of NMC622 before and after processing shows the treatment reverses ageing in the surface region of the electrode particles resulting in renewed performance. These examples show the ease and flexibility of hydrothermal and calcination processes to restore electrochemical performance to NMC cathode materials. A comparable industrial process is alumina production from bauxite, which has a world-wide production over 60,000 tons and demonstrates the scalability and low cost potential for direct recycling. The development of distributed direct recycling services reduces both logistical and production costs relative to the current approach. Direct recycling technologies provide a viable foundation for the future waste management services for the lithium-ion battery market. Figure 1

We report that crystalline 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), an organic solid, is highly amenable to host divalent metal ions, i.e., Mg2+ and Ca2+, in aqueous electrolytes, where the van der Waals structure is intrinsically superior in hosting charge-dense ions. We observe that the divalent nature of Mg2+ causes unique squeezing deformation of the electrode structure, where it contracts and expands in different crystallographic directions when hosting the inserted Mg-ions. This phenomenon is revealed experimentally by ex situ X-ray diffraction and transmission electron microscopy, and is investigated theoretically by first-principles calculations. Interestingly, hosting one Mg2+ ion requires the coordination from three PTCDA molecules in adjacent columns of stacked molecules, which rotates the columns, thus reducing the (011) spacing but increasing the (021) spacing. We demonstrate that a PTCDA Mg-ion electrode delivers a reversible capacity of 125 mA h g(-1), which may include a minor contribution of hydronium storage, a good rate capability by retaining 75 mA h g(-1) at 500 mA g(-1) (or 3.7 C), and a stable cycle life. We also report Ca2+ storage in PTCDA, where a reversible capacity of over 80 mA h g(-1) is delivered.

The exploration of electrode materials in the paradigm of battery research has been shifting towards finding materials that are completely renewable, do not contain any transition metals, and are readily available. Recently, we have explored using pure polycyclic aromatic hydrocarbons (PAHs) as electrode materials for dual-ion batteries, where for the first time we demonstrated a crystalline coronene electrode showing flat plateaus at around 4.1 V in charge and discharge in a standard alkyl carbonate electrolyte. A voltage of 4.1 V avoids the use of expensive ionic liquids that are used with the conventional graphite anion insertion electrodes, which insert anions at much higher voltages of above 5.0 V. This electrode delivers a reversible discharge capacity of ~ 40 mA h g-1. We have further demonstrated that perylene and triphenylene, both PAH crystalline solids, exhibit even higher capacities than coronene, ~80 and ~100 mA h g-1, respectively. We are striving to investigate and identify a trend to elucidate structure-property relationships of PAHs that we believe can create a paradigm shift in dual-ion batteries based on pure hydrocarbons as the electrode materials.

New graphite intercalation compounds (GICs) containing N,N-n-alkyl substituted pyrrolidinium cation intercalates (Pyn.m, n, m = alkyl chain lengths) are obtained via cationic exchange from stage-1 donor-type GIC [Na(ethylenediamine)1.0]C15. Powder X-ray diffraction and thermogravimetric analyses are used to determine the GIC structures and compositions. [Py4.8]C47·0.71DMSO and [Py8.8]C48 with intercalate monolayers are obtained as stage-1 GICs with gallery expansions of 0.48 nm, whereas [Py1.18]C47 and [Py12.12]C80·0.25DMSO form stage-1 GICs with intercalate bilayers and gallery expansions of 0.81 nm. The gallery dimensions require that alkyl chain substituents orient parallel to the encasing graphene sheets. Smaller intercalate cations such as Py1.4, Py4.4, and Py1.8 either form high-stage GICs or do not form stable intercalation compounds. These results, along with those reported for graphite intercalation of other quaternary ammonium cations, indicate trends in graphite chemistry where larger intercala...

Crown ethers are well established as cointercalates in many layered hosts, but there are no reports of crown ethers incorporated into graphite. Here, we describe the preparation of the first graphite intercalation compounds (GICs) containing crown ethers. These GICs are obtained either by reductive intercalation of an alkali metal-amine complex followed by cointercalate exchange or by the direct reaction of graphite with a crown ether, alkali metal, and an electrocatalyst. Structural and compositional characterization of these new GICs using powder X-ray diffraction, thermal analysis, and GC/MS indicates the formation of well-ordered, stage-1 bilayer galleries.