Amorphous (Glassy) Carbon, a Promising Material for Sodium Ion Battery Anodes: a Combined First-Principles and Experimental Study

Abstract

We present a comparative, combined ab initio and experimental study of sodium and lithium storage in amorphous (glassy) carbon (a-C) vs. graphite. Amorphous structures are obtained by fitting stochastically generated structures to a reference radial distribution function.Li insertion is thermodynamically favored in both graphite and a-C. While sodium insertion is thermodynamically unfavored in graphite, a-C possesses multiple insertion sites with binding energies stronger than Na cohesive energy, making it usable as anode material for Na-ion batteries. Binding energy of Na is predicted to be stronger than the Na cohesive energy for Na concentrations corresponding to a capacity of about 200 mAh/g. These results are confirmed by experimental measurements using highly amorphous carbon, in which a specific capacity of 173 mAh/g for Na is obtained after 100 cycles.

Insertion of Mono- vs. Bi- vs. Trivalent Atoms in Prospective Active Electrode Materials for Electrochemical Batteries: An ab Initio Perspective

“…For Li, this meant increased voltages. Computed voltage-capacity curves for lithiation and sodiation agreed well with experimentally measured curves using thoroughly amorphized carbon [25]. Our calculations also showed a significant magnitude of strengthening of insertion energy of Mg and K by amorphization [27], as is also shown in Figure 3, implying the possibility of electrochemical activity after amorphization.…”

“…Here, we only introduce key computed quantities which are important for a material's performance as an active electrode material and which are discussed in Sections 2 and 3. To analyze the thermodynamics of interaction of a potential electrode material with Li, Na, K, Mg, or Al, we use the binding energy E b (n) of n of these atoms to the active material, which is effectively the defect formation energy (E f , which is the term used in many studies [11][12][13]15,16,[19][20][21][22][23][24][25]). It is computed as:…”

“…Our calculations also suggest that a-C might work for Mg with initial voltages on the order of 0.7 V (−Eb/2). To generate the amorphous structures used in [25,27], we developed an approach in which we made structures directly reproducing the density and the radial distribution function (RDF) known experimentally. To this end, a cubic simulation cell was set up into which a number of C atoms were placed corresponding to the desired density.…”

Amorphous Vanadium Oxide Thin Films as Stable Performing Cathodes of Lithium and Sodium-Ion Batteries

“…Such increase in ionicity might originate from vanadium reduction to V(III) in addition to local vanadium-oxygen coordination changes, i.e. further amorphisation [5, 27–29]. Overall charge-discharge features of a-VOx-6 Pa are similar to other a-VOx materials synthesised by different routes in other works as referred in the present work.…”

Recent Progress in Electrode Materials for Sodium‐Ion Batteries

“…[ 138,269, The storage of Na in carbon materials such as hard carbon, amorphous carbon, defected graphene, and functionalized graphite has been observed to be thermodynamically feasible. [ 325,326,274,276 ] In the early works by Doeff et al, they demonstrated that the extent of Na intercalation in carbon materials varies depending on the carbon structure; NaC 70 , NaC 30 , and NaC 15 were formed for graphite, petroleum coke, and Shawinigan black, respectively. [ 277 ] The inserted Na ions were also reversibly extracted from the carbon materials.…”