A Comparative First-Principles Study on Sodiation of Silicon, Germanium, and Tin for Sodium-Ion Batteries

Abstract

Sodium-ion batteries (NIBs) have recently received great attention as a potential complement to existing lithium-ion battery (LIB) technology. Due to the difference between Na and Li in nature, what has been an attractive anode material for LIBs may or may not be utilized for NIBs.Using density functional theory calculations, we examine and compare the sodiation behaviors of Si, Ge, and Sn, in comparison also to their lithiation processes if needed. We evaluate single Na incorporation in the host matrices (M = Si, Ge, Sn) and also discuss the formation of Na-M alloys in terms of structural evolution and energetics, along with their mechanical and diffusion properties. While the alloy systems considered in this work appear to undergo similar transformation during sodiation and lithiation, the M networks tend to lose connectivity more rapidly in the former. At Na/Li:M = 1:1 ratio, the M networks in a-NaM alloys already disintegrate into compact isolated clusters while those in a-LiM still maintain extended connectivity via puckered conformation. This unique difference in their specific atomic arrangements contributes to the more rapid softening, larger volume expansion, and faster increase in Na diffusivity with sodiation in comparison to the case of lithiation.

Feasibility of Reversible Electrochemical Na-Storage and Cyclic Stability of Amorphous Silicon and Silicon-Graphene Film Electrodes

“…• C. In a more recent work, Chou et al 24 predicated that the Na diffusion coefficient is likely to be of the order of ∼ 10 −26 m 2 s −1 , but again in c-Si. Our observations of electrochemical Nastorage behavior in a-Si continuous film electrodes (as reported in the previous section) suggest that electrochemical Na-storage in a-Si may also be diffusion limited.…”

Recent Progress in Electrode Materials for Sodium‐Ion Batteries

“…In particular, P-based materials have exhibited exceptionally high capacity. Although a host metal with larger atomic size can take more Na ions with a higher average voltage and lower Na diffusion activation barrier according to the study by Chou et al, [ 472 ] black P is an exception, which can react with up to 3 Na ions and forms Na 3 P in the fully discharged state despite its location in period 3. This behavior of black P results from its layered structure with relatively large available space for Na ions, whereas other metals/ metalloids (Si, Ge, Sn, As, Sb, Bi) form the diamond structure in their ground state.…”

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

“…Indeed, it is well known that in the dilute regime Li and Na occupy tetrahedral interstitial sites in Si and Ge, while Mg may occupy substitutional sites. Our study in a way bridged the many single-atom insertion studies [59][60][61] and a handful of studies modeling higher charge states and thereby shed light on initial stages of lithiation, sodiation, and magnesiation [64,98]. It follows from Figure 7 that lithiation of Ge is slightly favored (Eb = −0.04 eV for single Li insertion) while sodiation and magnesiation are strongly disfavored (Eb > 0).…”

“…The idea of applying U correction to s, p states has since been gaining some traction [97]. Germanium has an important advantage over its group IV neighbor silicon as a potential battery electrode material: compared to Si, Ge provides higher ionic diffusivities and more stable insertion sites for Li/Na/Mg (i.e., the intercalation of Na and Mg can be easier in Ge compared to Si) Germanium has an important advantage over its group IV neighbor silicon as a potential battery electrode material: compared to Si, Ge provides higher ionic diffusivities and more stable insertion sites for Li/Na/Mg (i.e., the intercalation of Na and Mg can be easier in Ge compared to Si) [98], and its isotropic expansion (reported for Li) can reduce the mechanical stresses generated during intercalation, compared to the anisotropic swelling of Si [68]. In [37], we performed a comparative ab initio study of lithiation, sodiation, and magnesiation of Ge, in which we showed that there exists competition between interstitial and substitutional sites for Li/Na/Mg insertion, with preferred sites dependent on the type of inserted atom type and concentration.…”

“…Energies 2017, 10, 2061 13 of 32 [98], and its isotropic expansion (reported for Li) can reduce the mechanical stresses generated during intercalation, compared to the anisotropic swelling of Si [68]. In [37], we performed a comparative ab initio study of lithiation, sodiation, and magnesiation of Ge, in which we showed that there exists competition between interstitial and substitutional sites for Li/Na/Mg insertion, with preferred sites dependent on the type of inserted atom type and concentration.…”