First-Principles Understanding of the Staging Properties of the Graphite Intercalation Compounds towards Dual-Ion Battery Applications

Abstract

Graphite-based dual-ion batteries are a promising alternative to the lithium-ion batteries for energy storage because of its potentially lower cost, higher voltage, and better safety. Among the most important materials in the dual-ion battery are the graphite and graphite intercalation compounds (GICs), whose properties determine the performance of electrodes. The GICs are formed at both anode and the cathode sides during the charging process in which the graphene sheets and the intercalants are arranged in an ordered way called the staging of GICs. Staging is one of the important structural features of GICs related to the volume expansion of the electrodes, the charging rate, and the capacity of the battery. However, the details of the staging mechanism, such as the structural properties, the electronic structure, and the voltage dependence on the stages are still poorly understood. In this regard, we perform density functional theory studies to explore these issues in GICs. Using staging models, we examine the stability of GICs at different stages of intercalation with a range of species (i.e., Li, Na, K, PF 6 , BF 4 , TFSI, AlCl 4 , and ClO 4 ). We then study the contribution of intercalants to the electronic band structures in GICs. In addition, the voltage profiles of the dual-ion batteries with different intercalation species, intercalation stages, and battery capacities are also analyzed. The present work is important for the better understanding of graphite-based dual-ion batteries and helpful in development of novel energy storage systems.

MoS2/Polythiophene Composite Cathode as a Potential Host for Rechargeable Aluminum Batteries: Deciphering the Impact of Processing on the Performance

“…Such multiple stages of the aluminate ion insertion process is well documented for graphitic materials, which possess similar layered structures. 54,55 This apart, a prominent pair of red-ox peaks in the potential range of ca. 1.8−2.2 V might possibly be attributed to the partial change in the Mo-oxidation states from Mo 4+ to Mo 5+ state and back, possibly owing to the partial lattice insertion of Al 3+ ions.…”

Operandoanalysis of graphite intercalation compounds with fluoride-containing polyatomic anions in aqueous solutions

“…where E(anion:C 24n ), E(C 12 ), and E(anion) are the DFT total energies of anion-GICs, AB-stacking graphite, and isolated anions in a supercell, respectively. Anion in eqn (2) denotes a neutralized anion near graphite electrodes, 24,25 and the solution stabilization of anions was neglected since the water/ lithium ratios were relatively small (about 2.7 and 2.8 in the solutions of 5.2 M LiTFSA and 7.9 M LiOTf, respectively) and TFSA and OTf anions were not strongly coordinated with water molecules in aqueous highly concentrated solutions.…”

“…In addition, Zhou and Sit reported a large variety of formation energies of anion-GICs using DFT calculations: ClO 4 -GIC 4 AlCl 4 -GIC TFSA-GIC 4 BF 4 -GIC 4 PF 6 -GIC. 25 We also calculated the formation energies of GICs with TFSA and OTf anions and found that TFSA-GICs were more stable than OTf-GICs: À0.96 eV for C 24 TFSA (stage 2) and À0.48 eV for C 24 OTf (stage 2). Optimized structures of stage 2 GICs of TFSA and OTf are illustrated in Fig.…”

Stratigraphic analysis of intercalated graphite electrodes in aqueous inorganic acid solutions

“…By applying proper electrochemical (EC) potentials, solvated ClO4and HSO4ions percolate between the HOPG layers. HOPG thus evolves into the so-called graphite intercalated compound (GIC), which shows different transport properties with respect to the pristine sample [13][14][15]. In addition, the presence of ions within the interlayer spacing of graphite helps its delamination in liquid-phase [16].…”