Hydrogenated defective graphene as an anode material for sodium and calcium ion batteries: A density functional theory study

Abstract

Recent experimental studies indicated that hydrogenation improves the performance of graphitic materials used as anodes in lithium and sodium ion rechargeable batteries. Here, results of density functional theory calculations are presented to demonstrate that this is also effective for both sodium and calcium ion batteries. It is shown that this can be explained by the increase in binding strength of the metal adatom to the hydrogenated graphene, compared to its binding to graphene and also an increase in the inter-layer spacing of the layered materials. According to our calculations, whereas Na and Ca bind weakly to the graphene sheet with binding energies of-0.763 and-0.817 eV, they bind more strongly to the single layer of the proposed hydrogenated graphene sheet (C68H4) with binding energies of-1.670 and-2.756 eV, respectively. Furthermore, although Na does not intercalate strongly in the layers of the C68H4 material, up to 16 Ca can intercalate into the bulk layers of this material giving an electrical capacity of 591.2 mAh/g and a 29.3% expansion of the inter-layer distance. Thus, hydrogenated defective graphene provides an anode material that enhances the performance of rechargeable batteries compared to graphene, using metals that are cheaper than lithium.

Adsorption and migration of alkali metals (Li, Na, and K) on pristine and defective graphene surfaces

“…Previous computational studies have focused on graphite and graphene models with a single carbon vacancy (V C ), multiple carbon vacancies, passivated carbon vacancies, and Stone-Wales defects as models for disordered carbons for NIBs. [33][34][35][36][37][38][39] Single and double carbon vacancy defects have been shown computationally to enhance Na ion intercalation. 39,40 Heteroatom doping of graphene, including N, B, S, and P, has also been studied.…”

“…[33][34][35][36][37][38][39] Single and double carbon vacancy defects have been shown computationally to enhance Na ion intercalation. 39,40 Heteroatom doping of graphene, including N, B, S, and P, has also been studied. 8,34,36,[41][42][43][44] N doping has shown to improve Na diffusion in bilayer graphene.…”

N-, P-, As-triphenylene-graphdiyne: Strong and stable 2D semiconductors with outstanding capacities as anodes for Li-ion batteries

“…We then employed first-principles density functional theory (DFT) simulations to explore the mechanical, thermal stability, optical and electronic properties of these novel 2D systems. Because of the fact that 2D materials have currently garnered remarkable attention for the application as anode materials for Li-ion batteries [62][63][64][65][66][67][68][69], we also employed the DFT calculations to explore the possible application of TpG, As-TpG, P-TpG and N-TpG nanosheets as anode materials for Li-ions storage. The acquired results suggest very promising performances of this novel class of 2D materials and will hopefully motivate further theoretical and experimental studies.…”

Potassium‐Ion Storage in Cellulose‐Derived Hard Carbon: The Role of Functional Groups

“…These values are stronger than E coh, which is À 0.93 eV, ensuring that clustering of the K atoms does not occur. [50][51] It is also interesting to see that in contrast to Na which forms NaOH on interaction with the hydroxyl group in the basal plane [52][53] (an unfavourable result in NIBs), K did not form KOH when placed near the hydroxyl groups (Figure 5b). Therefore, this can be considered as an advantage of K over Na in interaction with the hydroxyl group.…”