Article pubs.acs.org/JPCC
Two-Dimensional Y2C Electride: A Promising Anode Material for NaIon Batteries Jianhua Hou,†,‡ Kaixiong Tu,‡ and Zhongfang Chen*,‡ †
School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, People’s Republic of China ‡ Department of Chemistry, Institute for Functional Nanomaterials and NASA-URC Center of Advanced Nanoscale Materials, University of Puerto Rico, Rio Piedras Campus, San Juan 00931, Puerto Rico ABSTRACT: By means of first-principles computations, we explored the potential of using Y2C monolayer as anode material for rechargeable Na-ion batteries (NIBs). As a two-dimensional electride material, Y2C monolayer is metallic and has a strong in-plane stiffness. Significant interactions between Y2C monolayer and Na atom ensure its high theoretical specific capacity of 564 mA·h/g. The Y2C monolayer also has high Na mobility and rather small average open-circuit voltages. All these characteristics suggest that the Y2C monolayer could be a promising anode material for NIBs.
1. INTRODUCTION Renewable energy sources, such as solar and wind, can reduce our dependence on fossil fuels and greenhouse gas emissions. However, most renewable energy sources are intermittent in their nature, which demands sustainable electrical energy storage (EES) systems for numerous applications.1 As a popular EES system, Li-ion batteries (LIBs) have been used successfully for portable electronic devices and electric vehicles2 since the first commercialization in 1991. Although LIBs potentially give an effective solution to meet the performance targets, the high cost and the limited Li source have spurred the search for alternatives in large-scale EES systems.3 In contrast to Li, low-cost Na resources are unlimited in the Earth’s crust and the ocean. Additionally, Na has many similar chemical properties to Li, which indicates that Na can have the similar storage mechanism as Li in batteries. Thus, Na-ion batteries (NIBs) are an ideal alternative to LIBs. Electrode materials determine the crucial NIBs characteristics, such as capacity, charge/discharge rate, and cycling life. Thus, it is necessary to identify suitable electrode materials for NIBs. For cathodes, by mimicking LIBs, various cathode materials for NIBs, such as iron- and manganese-based layered oxides,4−6 polyanionic compounds,7−9 sulfides,10,11 and fluorides,12,13 have been extensively studied. For anodes, the simple analogy to LIBs is inapplicable. For example, graphite, the most widely used anode for LIBs, is not effective in NIBs because of its electrochemical irreversibility for Na and extremely low capacity (35 mA·h/g).14−16 Although metal anodes (Sn, Sb, etc.) exhibit high capacities of 400−600 mA·h/g,17,18 the large volume change in the charge/discharge process leads to their poor cycling stability. Therefore, it is critical to identify suitable © XXXX American Chemical Society
anode materials with high reversible capacity, fast charge/ discharge rate, and long cycling stability for NIBs. Extensive research efforts have been devoted to developing appropriate anodes for NIBs. Hard carbon19−21 (nongraphitic carbon) is the most widely used anode because of its good conductivity, abundance in nature, and easy process. However, its poor rate performance and fast capacity fading over cycling hinder its development in NIBs.21 Some metal oxides (MOx, M = Ti,22 Fe,23 Co,24 Ni,25 Cu,26 and Sn27) have also been studied as anodes because they show high capacities and energy densities due to multielectron reaction. For instance, SnO2 anode fabricated by in situ hydrothermal method provided a high Na storage capacity (700 mA·h/g at 20 mA/g).27 Besides inorganic materials, organic compounds28−30 are also attractive; however, they suffer from the problems of relatively high solubility and inferior electrical conductivity. Two-dimensional (2D) materials, which can offer high specific surface area and more open ion-transport channels, have shown great promise for NIBs anodes. In 2013, Wang et al.31 reported that the NIBs anode consisting of reduced graphene oxide delivered a high capacity of 141 mA·h/g at 40 mA/g and a long cycle life of over 1000 cycles. Transition-metal disulfides, such as MoS232 and FeS2,33 graphene decorated MoS2,34 and NiS235 nanosheets also showed improved performance. Moreover, MXene (Mn+1Xn: M = Ti, V, Nb, etc.; X = C, N; n = 1−3), a new family of layered compounds, Received: June 17, 2016 Revised: August 1, 2016
A
DOI: 10.1021/acs.jpcc.6b06087 J. Phys. Chem. C XXXX, XXX, XXX−XXX
Article
The Journal of Physical Chemistry C
consisting of the top Y (YT) and bottom Y (YB) atomic layers and the middle C atomic layer, forming octahedral symmetry (Figure 1A,B). The optimized lattice parameters in the
has been demonstrated to be emerging anode materials for NIBs.36 More recently, 2D electrides37−41 (Ca2N, Sr2N, Ba2N, Y2C, etc.), peculiar ionic crystals in which electrons serve as anions and are confined within the interlayer space, have been attracting much attention due to their high electron mobility and the low work function. In 2015, Hu et al.41 predicted that Ca2N and Sr2N can be used as anode materials for NIBs. Ca2N and Sr2N exhibit maximum theoretical capacity of 1138 and 283 mA·h/g, adsorption energies of −0.23 and −0.13 eV, and diffusion barrier of 0.08 and 0.02 eV, respectively. Y2C is a typical rare-earth carbide with the anti-CdCl2 type structure, which is rather similar to the structures of Ca2N and Sr2N.38,39,41 Then is the Y2C monolayer suitable for NIB anode material? Here, we carried out density functional theory (DFT) computations to investigate the feasibility of using the Y2C monolayer as anode materials for NIBs. Our computations showed that the Y2C monolayer has bigger Na adsorption energy (−0.32 eV) and lower diffusion barrier (0.01 eV) than both Ca2N and Sr2N monolayers, and a high theoretical specific capacity of 564 mA·h/g. Moreover, the average open-circuit voltage (OCV) of the Y2C monolayer is relatively low. All these characteristics suggest that the Y2C monolayer could be a promising anode material for NIBs.
Figure 1. Optimized structure of the Y2C monolayer (3 × 3 supercell). (A) Top view and (B) side view of the Y2C monolayer, which consists of a triple layer with top Y atom (YT)−C− bottom Y atom (YB) stacking sequence. (C) Considered adsorption sites on the surfaces of the Y2C monolayer (top view). Sites 1, 2, and 3 are on top of C, YT, and YB, respectively. Sites 4, 5, and 6 are on top of the bridge sites. Site 7 is on top of the center of the triangle.
monolayer, a = b = 3.578 Å, are slightly shorter than experimental values measured for the bulk (3.617 Å).38,41 The Y−C bond length (2.464 Å) is close to the Ca−N bond (2.440 Å) in Ga2N monolayer,42 and slightly shorter than the Sr−N bond (2.617 Å) in Sr2N monolayer.42 To examine the dynamical stability of the Y2C monolayer, we calculated its phonon dispersion curves from 2 × 2 supercell using Vienna ab initio simulation package.49 The phonon dispersion curves along the high-symmetry lines in first Brillouin zone are shown in Figure 2A. There is no appreciable imaginary frequency in the phonon dispersion curves, which suggests that the Y2C monolayer is kinetically stabile. An ideal 2D material as NIB anode should be a freestanding membrane in which the in-plane stiffness is strong enough to avoid curling and allows the material to withstand its own weight or external load. The in-plane stiffness of the Y2C monolayer is characterized by the Young’s modulus, which is defined as
2. COMPUTATIONAL DETAILS Our DFT computations were carried out by using an allelectron method within a generalized gradient approximation for the exchange-correlation term, as implemented in the DMol3 code.43,44 The double numerical plus polarization (DNP) basis set and Perdew−Burke−Ernzerhof (PBE) functional were adopted.45 The accuracy of DNP basis sets is comparable to that of Pople’s 6-31G** basis set. Especially, to accurately account for the long-range electrostatic interactions between Na atoms in high concentrations, we adopted the PBE +D2 method with the Grimme vdW correction.46 Selfconsistent field computations were performed with a convergence criterion of 10−6 a.u. on the total energy and electron density. To ensure high-quality numerical results, we chose the real-space global orbital cutoff radius as high as 5.6 Å in all the computations. The Brillouin zone was sampled with 4 × 4 × 1 Monkhorst−Pack47 k-point mesh for the structural optimization and with 8 × 8 × 1 mesh for the electronic structure calculations. The thickness of the vacuum region is greater than 15 Å. The transition states were located by computing the minimum-energy path (MEP) for the Na diffusion processes using the nudged elastic band method,47,48 which starts by inserting a series of image structures between the initial and final states of the reaction. An artificial spring force then is introduced between all nearest-neighboring image structures. The MEP can be obtained by optimizing these image structures simultaneously as the true force on the image structures has a zero projection in the direction perpendicular to the path.
Y2D =
2 1 ∂ Es A 0 ∂ε 2
ε= 0
where ε is the axial strain, Es is the total strain energy (per unit cell), and A0 is the area of the equilibrium surface. From the energy curve under biaxial strains (Figure 2B), Y2D value, 5.38 eV/Å2, is obtained for the Y2C monolayer. According to the elastic theory, we can estimate the bending of a square Y2C flake with one edge L fixed. The out-of-plane deformation can be calculated by the formula H/L ≈ (ρgL/Y2D)1/3,50 where g is the gravitational acceleration and ρ is the density of the Y2C monolayer. For a large Y2C monolayer flake of length L ≈ 100 μm, the H/L value is about 3.0 × 10−4, which indicates that it is strong enough to form a free-standing membrane. 3.2. Single Na Atom Adsorption on the Y 2 C Monolayer. To safely avoid the interaction between two Na atoms, we used a 3 × 3 supercell of Y2C monolayer. To find the favorable adsorption site, all the possible sites are chosen, as described in Figure 1C. The adsorption energy (Ead) of Na atom was defined as
3. RESULTS AND DISCUSSION 3.1. Optimized Structure and In-Plane Stiffness of Y2C Monolayer. Compared with magnetic bulk Y2C,41 Y2C monolayer is verified to be nonmagnetic by spin polarization test computations, which is consistent with the previous result.38 The optimized Y2C structure is a three-layer sandwich B
DOI: 10.1021/acs.jpcc.6b06087 J. Phys. Chem. C XXXX, XXX, XXX−XXX
Article
The Journal of Physical Chemistry C
In comparison, for Li atom, only three adsorption sites can be obtained, and all the absorption energies are positive, which indicates that energetically it is not favorable for Li atom to adsorb on Y2C monolayer. The smaller charge transfer from Li to Y2C monolayer (qe = 0.15 |e|) may explain the unfavorable Li adsorption. Generally, electrical conductivity is a vital factor in deciding the electrochemical performance of an electrode. To check the conductivity, we computed the density of states (DOS) and partial DOS (PDOS) of Y2C with Na adsorbed in the most favorable site (site 1), and compared with the pristine Y2C monolayer (Figure 3). Encouragingly, the metallic character of
Figure 2. (A) Phonon dispersion curves of the Y2C monolayer. (B) Elastic energy of the Y2C monolayer under biaxial strain along x and y directions.
Ead = E NaY18C9 − E Y18C9 − E Na
where ENaY18C9 and EY18C9 are the total energies of the Y2C monolayer with and without Na atom adsorption and ENa is the energy per atom for the bulk. According to this definition, a more negative adsorption energy indicates a more favorable exothermic reaction between Y2C and Na. For comparison, single Li atom adsorption on the Y2C monolayer was also considered. After geometry optimizations, we only obtained four stable adsorption sites (Figure 1C and Table 1). The Na atom prefers
Figure 3. Density of states (DOS) and partial density of states (PDOS) for (A) pristine and (B) Na-adsorbed Y2C monolayer.
Y2C monolayer persists after Na adsorption, considerable electronic states are at the Fermi level, and the metallic states are mostly contributed by the 4d state of the Y atom. Therefore, the metallicity of the pristine and Na-adsorbed Y2C monolayer endows a highly desirable characteristic for their applications as NIB anodes. 3.3. Na Atom Diffusion on the Y2C Monolayer and in Bulk Y2C. The charging/discharging rate of an electrode material is closely related to the Na mobility; thus, it is necessary to estimate the diffusion of Na atom on the surface of Y2C monolayer. We used the same 3 × 3 supercell containing 18 Y and 9 C atoms to examine the Na diffusion. Obviously, on Y2C monolayer the Na atoms can diffuse between two neighboring energetically most favorable adsorption sites (site 1). Such a diffusion has three possible paths, that is, C → YB → C (P1), C → C (P2), and C → YT → C (P3), respectively (Figure 4A). Among these three pathways (Figure 4B), even the highest barrier, 0.11 eV for P3 path, which can be understood by the repulsion between the Na ion and YT ion, is rather small. The barriers along the P1 and P2 paths, 0.01 eV for both cases, are even lower than those on Sr2N monolayer (0.016 eV)42 and on Ca2N monolayer (0.08 eV).42 According
Table 1. Calculated Adsorption Energies (Ead), Distances from Li/Na to C Atom Layer (dC), and Hirshfield Charge Transfer (qe) for Li/Na Li
Na
ads. site
Ead (eV)
dLi−C (Å)
q
Ead (eV)
dLi−C (Å)
q
1 2 3 6
0.01
4.152
0.151
0.02 0.03
4.146 4.182
0.151 0.151
−0.32 −0.21 −0.31 −0.30
4.486 4.548 4.463 4.467
0.188 0.187 0.187 0.186
to be adsorbed at the top site of the C atom (site 1) with an absorption energy of −0.32 eV, which is almost 1.5 and 3 times stronger than those of Ca2N (−0.23 eV)42 and Sr2N (−0.13 eV),42 respectively. The distance from Na atom to the C atomic layer (dC), 4.49 Å, is also shorter than the corresponding values in the Ca2N and Sr2N monolayers.42 According to Hirshfeld charge population analysis,47 about 0.19 |e| charge transfers from Na to Y2C monolayer. C
DOI: 10.1021/acs.jpcc.6b06087 J. Phys. Chem. C XXXX, XXX, XXX−XXX
Article
The Journal of Physical Chemistry C
Figure 4. (A) Schematic figure of the three Na diffusion pathways on the Y2C monolayer, where the black, red, and blue colored lines represent P1, P2, and P3 paths, respectively. (B) Corresponding diffusion profiles for Na on Y2C monolayer. (C) The most favorable configuration of the bulk Y2C with an inserted Na atom, and the Na diffusion pathway. (D) Corresponding Na diffusion profiles in the bulk Y2C.
where again ENa is the energy per atom in the bulk Na metal and ENa2nY2C and ENa2(n−1)Y2C are the total energies of the Y2C monolayer with n and n − 1 Na layers. The number “2” in the formula represents two adsorbed Na atoms in each layer. Like Ca2N monolayer,42 the Y2C monolayer can absorb two Na atoms layers on each side. The first layer of Na atoms is adsorbed on the top sites of the C atom with the Eave value of −0.45 eV. Then the second layer of Na atoms is absorbed on the top sites of the YB atom, and the Eave is −0.03 eV. Consequently, a unit cell could accommodate up to 4 Na atoms, which corresponds to a chemical stoichiometry of Na4Y2C. As Na4Y2C represents the highest Na storage capacity, we can easily deduce that the Y2C monolayer has a theoretical capacity of 564 mA·h/g, which is lower than the theoretical capacity (1138 mA·h/g) of the Ca2N monolayer,42 but higher than the theoretical capacity (283 m· Ah/g) of the Sr2N monolayer.42 Finally, we computed the average open-circuit voltage (OCV) for Na intercalation on Y2C monolayer. Because the charge/discharge processes of Y2C follow the common half-cell reaction vs Na/Na+,
to the Arrhenius equation, the diffusion constant (D) is proportional to exp(−Ea/kBT), where Ea and kB are the activation energy and Boltzmann constant, respectively. Therefore, we can estimate that at room temperature the Na mobility on Y2C monolayer can be more than 1.2 times faster than that on Sr2N monolayer and 15 times faster than that on Ca2N monolayer. Therefore, once used as the anode material in NIBs, good high-rate performances can be expected for Y2C monolayer. As a comparison, we investigated the Na atom diffusion barrier in the bulk Y2C. First, we calculated the lattice constants of the bulk Y2C. Our optimized lattice constants of bulk Y2C (a = b = 3.625 Å and c = 17.964 Å, respectively) agree well with the experimental values (3.616 and 17.965 A, respectively41). When a single Na atom is inserted into a 2 × 2 × 1 supercell of bulk Y2C consisting of 12 C and 24 Y atoms, there are seven possible sites for Na adsorption (Figure 1C). To determine the most favorable insertion site, we considered all these seven possible sites, and found that Na prefers to occupy an interstitial site where Na is collinear with YT and YB (see Figure 4C). The distance between Na and YT (4.418 Å) is almost the same as that between Na and YB (4.428 Å). In the bulk Y2C, the Na atom can diffuse from the interstitial site to its neighboring interstitial site. The single-atom diffusion in the bulk along this pathway needs to overcome a barrier of 0.39 eV (Figure 4D), which is much larger than the barriers on the Y2C monolayer. 3.4. Na Storage Capacity of Y2C Monolayer and Average Open-Circuit Voltage. Next, we explored the Na storage capacity and the average open-circuit voltage of Y2C monolayer. To estimate the maximum possible storage of Na, we calculated the average adsorption energies of Na atoms layer by layer. In our calculations, the unit cell is employed and the Na atom layers are absorbed on both sides of the monolayer. The average adsorption energy (Eave) for the outermost Na atom layer is defined as
Y2C + χ Na + + χ e− ↔ Naχ Y2C
with volume and entropy effects both neglected, the OCV for Na intercalation in Y2C monolayer can be computed from the energy difference based on the equation below VOCV = (E Y2C + χE Na − E NaχY2C)/χ e
where EY2C and ENaχY2C are the total energies of the Y2C monolayer without and with Na intercalation and ENa is the energy per atom in the bulk Na metal. As mentioned above, the Y2C monolayer can absorb two layers of Na atoms. Therefore, when Y2C monolayer absorbs the first and second Na layers, corresponding to the case of Na2Y2C and Na4Y2C, the computed average OCVs are 0.45 and 0.24 V, respectively. In addition, we examined the evolution of the average adsorption energy of Na atom in NaxY8C4 (x = 2, 4, 6, ..., 16) by constructing 2 × 2 supercell. The optimized structures with
Eave = (E Na 2nY2C − E Na 2(n−1)Y2C − 2E Na)/2 D
DOI: 10.1021/acs.jpcc.6b06087 J. Phys. Chem. C XXXX, XXX, XXX−XXX
Article
The Journal of Physical Chemistry C Notes
different Na atom content are shown in Figure 5A, while the evolution of the average adsorption energy of Na atom for all
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS This work was supported by the China Scholarship Council, NSF (Grant EPS-1002410), and Department of Defense (Grant W911NF-15-1-0650).
■
(1) Chen, H.; Cong, T. N.; Yang, W.; Tan, C.; Li, Y.; Ding, Y. Progress in Electrical Energy Storage System: A Critical Review. Prog. Nat. Sci. 2009, 19, 291−312. (2) Zu, C. X.; Li, H. Thermodynamic Analysis on Energy Densities of Batteries. Energy Environ. Sci. 2011, 4, 2614−2624. (3) Yabuuchi, N.; Kubota, K.; Dahbi, M.; Komaba, S. Research Development on Sodium-Ion Batteries. Chem. Rev. 2014, 114, 11636− 11682. (4) Yabuuchi, N.; Hara, R.; Kajiyama, M.; Kubota, K.; Ishigaki, T.; Hoshikawa, A.; Komaba, S. New O2/P2-Type Li-Excess Layered Manganese Oxides as Promising Multi-Functional Electrode Materials for Rechargeable Li/Na Batteries. Adv. Energy Mater. 2014, 4, 1301453. (5) Ma, X.; Chen, H.; Ceder, G. Electrochemical Properties of Monoclinic NaMnO2. J. Electrochem. Soc. 2011, 158, A1307−A1312. (6) Zhao, J.; Zhao, L.; Dimov, N.; Okada, S.; Nishida, T. Electrochemical and Thermal Properties of α-NaFeO2 Cathode for Na-Ion Batteries. J. Electrochem. Soc. 2013, 160, A3077−A3081. (7) Zaghib, K.; Trottier, J.; Hovington, P.; Brochu, F.; Guerfi, A.; Mauger, A.; Julien, C. Characterization of Na-Based Phosphate as Electrode Materials for Electrochemical Cells. J. Power Sources 2011, 196, 9612−9617. (8) Moreau, P.; Guyomard, D.; Gaubicher, J.; Boucher, F. Structure and Stability of Sodium Intercalated Phases in Olivine FePO4. Chem. Mater. 2010, 22, 4126−4128. (9) Saravanan, K.; Mason, C. W.; Rudola, A.; Wong, K. H.; Balaya, P. The First Report on Excellent Cycling Stability and Superior Rate Capability of Na3V2 (PO4)3 for Sodium Ion Batteries. Adv. Energy Mater. 2013, 3, 444−450. (10) Kim, J. S.; Ahn, H. J.; Ryu, H. S.; Kim, D. J.; Cho, G. B.; Kim, K. W.; Nam, T. H.; Ahn, J. H. The Discharge Properties of Na/Ni3S2 Cell at Ambient Temperature. J. Power Sources 2008, 178, 852−856. (11) Kim, J. S.; Kim, D. Y.; Cho, G. B.; Nam, T. H.; Kim, K. W.; Ryu, H. S.; Ahn, J. H.; Ahn, H. J. The Electrochemical Properties of Copper Sulfide as Cathode Material for Rechargeable Sodium Cell at Room Temperature. J. Power Sources 2009, 189, 864−868. (12) Nishijima, M.; Gocheva, I. D.; Okada, S.; Doi, T.; Yamaki, J. I.; Nishida, T. Cathode Properties of Metal Trifluorides in Li and Na Secondary Batteries. J. Power Sources 2009, 190, 558−562. (13) Yamada, Y.; Doi, T.; Tanaka, I.; Okada, S.; Yamaki, J. I. LiquidPhase Synthesis of Highly Dispersed NaFeF3 Particles and Their Electrochemical Properties for Sodium-Ion Batteries. J. Power Sources 2011, 196, 4837−4841. (14) Slater, M. D.; Kim, D.; Lee, E.; Johnson, C. S. Sodium-Ion Batteries. Adv. Funct. Mater. 2013, 23, 947−958. (15) Wen, Y.; He, K.; Zhu, Y.; Han, F.; Xu, Y.; Matsuda, I.; Ishii, Y.; Cumings, J.; Wang, C. Expanded Graphite as Superior Anode for Sodium-Ion Batteries. Nat. Commun. 2014, 5, 4033. (16) Liu, Y.; Merinov, B. V.; Goddard, W. A. Origin of Low Sodium Capacity In Graphite and Generally Weak Substrate Biding of Na and Mg among Alkali and Alkaline Earth Metals. Proc. Natl. Acad. Sci. U. S. A. 2016, 113, 3735−3739. (17) Liu, Y.; Xu, Y.; Zhu, Y.; Culver, J. N.; Lundgren, C. A.; Xu, K.; Wang, C. Tin-Coated Viral Nanoforests as Sodium-Ion Battery Anodes. ACS Nano 2013, 7, 3627−3634. (18) Zhu, Y.; Han, X.; Xu, Y.; Liu, Y.; Zheng, S.; Xu, K.; Hu, L.; Wang, C. Electrospun Sb/C Fibers for a Stable and Fast Sodium-Ion Battery Anode. ACS Nano 2013, 7, 6378−6386.
Figure 5. (A) Schematics of NaxY8C4 (top view and side view) and (B) the variation of average adsorption energy with increasing Na content in Y2C monolayer.
these configurations is shown in Figure 5B. The general trend is that the Na average adsorption energies decrease with increasing the increasing Na content x. Especially, when the second Na layer (x = 10−16) is added, the Na average adsorption energies are significantly lower than those in the first Na layer (x = 2−8) because at high Na concentrations the distances between Na atoms are shorter, leading to stronger repulsive electrostatic interactions.
4. CONCLUSION In summary, we investigated the possibility of using Y2C monolayer as NIB anode material by means of the firstprinciples computations. We systematically examined single Na atom adsorption energy, diffusion barrier, and the maximum specific capacity as well as average open-circuit voltage of Y2C monolayer. Our computations showed that Y2C monolayer is metallic and can be strong enough as a freestanding membrane, and the excellent electrical conductivity is maintained after Na atom adsorption. With the exceptional characteristics, such as high Na adsorption energy, low Na diffusion barrier, and high theoretical capacity, the Y2C monolayer is rather promising as anode material for NIBs.
■
REFERENCES
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected] (Z.C.). E
DOI: 10.1021/acs.jpcc.6b06087 J. Phys. Chem. C XXXX, XXX, XXX−XXX
Article
The Journal of Physical Chemistry C (19) Alcántara, R.; Lavela, P.; Ortiz, G. F.; Tirado, J. L.; Menéndez, R.; Santamaría, R.; Jimenez-Mateos, J. M. Electrochemical, Textural and Microstructural Effects of Mechanical Grinding on Graphitized Petroleum Coke for Lithium and Sodium Batteries. Carbon 2003, 41, 3003−3013. (20) Stevens, D.; Dahn, J. High Capacity Anode Materials for Rechargeable Sodium-Ion Batteries. J. Electrochem. Soc. 2000, 147, 1271−1273. (21) Luo, W.; Bommier, C.; Jian, Z.; Li, X.; Carter, R.; Vail, S.; Lu, Y.; Lee, J. J.; Ji, X. Low-Surface-Area Hard Carbon Anode for Na-Ion Batteries via Graphene Oxide as a Dehydration Agent. ACS Appl. Mater. Interfaces 2015, 7, 2626−2631. (22) Huang, J. P.; Yuan, D. D.; Zhang, H. Z.; Cao, Y. L.; Li, G. R.; Yang, H. X.; Gao, X. P. Electrochemical Sodium Storage of TiO2(B) Nanotubes for Sodium Ion Batteries. RSC Adv. 2013, 3, 12593−12597. (23) Jiang, Y.; Hu, M.; Zhang, D.; Yuan, T.; Sun, W.; Xu, B.; Yan, M. Transition Metal Oxides for High Performance Sodium Ion Battery Anodes. Nano Energy 2014, 5, 60−66. (24) Rahman, M. M.; Glushenkov, A. M.; Ramireddy, T.; Chen, Y. Electrochemical Investigation of Sodium Reactivity with Nanostructured Co3O4 for Sodium-Ion Batteries. Chem. Commun. 2014, 50, 5057−5060. (25) Sun, W.; Rui, X.; Zhu, J.; Yu, L.; Zhang, Y.; Xu, Z.; Madhavi, S.; Yan, Q. Ultrathin Nickel Oxide Nanosheets for Enhanced Sodium and Lithium Storage. J. Power Sources 2015, 274, 755−761. (26) Liu, H.; Cao, F.; Zheng, H.; Sheng, H.; Li, L.; Wu, S.; Liu, C.; Wang, J. In Situ Observation of the Sodiation Process in CuO Nanowires. Chem. Commun. 2015, 51, 10443−10446. (27) Su, D.; Ahn, H.-J.; Wang, G. SnO2@Graphene Nanocomposites as Anode Materials for Na-Ion Batteries with Superior Electrochemical Performance. Chem. Commun. 2013, 49, 3131−3133. (28) Zhao, L.; Zhao, J.; Hu, Y. S.; Li, H.; Zhou, Z.; Armand, M.; Chen, L. Disodium Terephthalate (Na2C8H4O4) as High Performance Anode Material for Low-Cost Room-Temperature Sodium-Ion Battery. Adv. Energy Mater. 2012, 2, 962−965. (29) Abouimrane, A.; Weng, W.; Eltayeb, H.; Cui, Y.; Niklas, J.; Poluektov, O.; Amine, K. Sodium Insertion in Carboxylate Based Materials and Their Application in 3.6 V Full Sodium Cells. Energy Environ. Sci. 2012, 5, 9632−9638. (30) Castillo-Martínez, E.; Carretero-González, J.; Armand, M. Polymeric Schiff Bases as Low-Voltage Redox Centers for SodiumIon Batteries. Angew. Chem., Int. Ed. 2014, 53, 5341−5345. (31) Wang, Y. X.; Chou, S. L.; Liu, H. K.; Dou, S. X. Reduced Graphene Oxide with Superior Cycling Stability and Rate Capability for Sodium Storage. Carbon 2013, 57, 202−208. (32) Mortazavi, M.; Wang, C.; Deng, J.; Shenoy, V. B.; Medhekar, N. V. Ab Initio Characterization of Layered MoS2 as Anode for SodiumIon Batteries. J. Power Sources 2014, 268, 279−286. (33) Hu, Z.; Zhu, Z.; Cheng, F.; Zhang, K.; Wang, J.; Chen, C.; Chen, J. Pyrite FeS2 for High-Rate and Long-Life Rechargeable Sodium Batteries. Energy Environ. Sci. 2015, 8, 1309−1316. (34) David, L.; Bhandavat, R.; Singh, G. MoS2/Graphene Composite Paper for Sodium-Ion Battery Electrodes. ACS Nano 2014, 8, 1759− 1770. (35) Wang, T.; Hu, P.; Zhang, C.; Du, H.; Zhang, Z.; Wang, X.; Chen, S.; Xiong, J.; Cui, G. Nickel Disulfide−Graphene Nanosheets Composites with Improved Electrochemical Performance for Sodium Ion Battery. ACS Appl. Mater. Interfaces 2016, 8, 7811−7817. (36) Xie, Y.; Dall’Agnese, Y.; Naguib, M.; Gogotsi, Y.; Barsoum, M. W.; Zhuang, H. L.; Kent, P. R. C. Prediction and Characterization of MXene Nanosheet Anodes for Non-Lithium-Ion Batteries. ACS Nano 2014, 8, 9606−9615. (37) Lee, K.; Kim, S. W.; Toda, Y.; Matsuishi, S.; Hosono, H. Dicalcium Nitride as a Two-Dimensional Electride with an Anionic Electron Layer. Nature 2013, 494, 336−340. (38) Inoshita, T.; Jeong, S.; Hamada, N.; Hosono, H. Exploration for Two-Dimensional Electrides Via Database Screening and Ab Initio Calculation. Phys. Rev. X 2014, 4, 031023.
(39) Tada, T.; Takemoto, S.; Matsuishi, S.; Hosono, H. HighThroughput Ab Initio Screening for Two-Dimensional Electride Materials. Inorg. Chem. 2014, 53, 10347−10358. (40) Walsh, A.; Scanlon, D. O. Electron Excess in Alkaline Earth SubNitrides: 2D Electron Gas or 3D Electride? J. Mater. Chem. C 2013, 1, 3525−3528. (41) Zhang, X.; Xiao, Z.; Lei, H.; Toda, Y.; Matsuishi, S.; Kamiya, T.; Ueda, S.; Hosono, H. Two-Dimensional Transition-Metal Electride Y2C. Chem. Mater. 2014, 26, 6638−6643. (42) Hu, J.; Xu, B.; Yang, S. A.; Guan, S.; Ouyang, C.; Yao, Y. 2D Electrides as Promising Anode Materials for Na-Ion Batteries from First-Principles Study. ACS Appl. Mater. Interfaces 2015, 7, 24016− 24022. (43) Delley, B. From Molecules to Solids with the Dmol3 Approach. J. Chem. Phys. 2000, 113, 7756−7764. (44) Delley, B. An All-Electron Numerical Method for Solving the Local Density Functional for Polyatomic Molecules. J. Chem. Phys. 1990, 92, 508−517. (45) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865. (46) Grimme, S. Semiempirical Gga-Type Density Functional Constructed with a Long-Range Dispersion Correction. J. Comput. Chem. 2006, 27, 1787−1799. (47) Olsen, R.; Kroes, G.; Henkelman, G.; Arnaldsson, A.; Jónsson, H. Comparison of Methods for Finding Saddle Points without Knowledge of the Final States. J. Chem. Phys. 2004, 121, 9776−9792. (48) Henkelman, G.; Jónsson, H. Improved Tangent Estimate in the Nudged Elastic Band Method for Finding Minimum Energy Paths and Saddle Points. J. Chem. Phys. 2000, 113, 9978−9985. (49) Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-energy Calculations Using a Plane-wave Basis Set. Phys. Rev. B: Condens. Phys. Rev. B: Condens. Matter Mater. Phys. 1996, 54, 11169−11186. (50) Booth, T. J.; Blake, P.; Nair, R. R.; Jiang, D.; Hill, E. W.; Bangert, U.; Bleloch, A.; Gass, M.; Novoselov, K. S.; Katsnelson, M. I.; Geim, A. K. Macroscopic Graphene Membranes and Their Extraordinary Stiffness. Nano Lett. 2008, 8, 2442−2446.
F
DOI: 10.1021/acs.jpcc.6b06087 J. Phys. Chem. C XXXX, XXX, XXX−XXX
