Double transition metal-containing M₂TiAlC₂o-MAX phases as Li-ion batteries anodes: a theoretical screening

Figures & data

Table 1. Lattice constants, cell volume, and formation energies, $\mathrm{\Delta }{E}_{M_{2}TiAl{C}_2}$, of M₂TiAlC₂ MAX phases (M = Cr, V, Mo, Ti, Nb, Ta, Hf, Zr, Sc, Y, and La).

M2TiAlC2	a (Å)	c (Å)	V (Å^3)	$\mathrm{\Delta }{E}_{M_{2}TiAl{C}_2}$ (eV/atom)
Cr2TiAlC2	2.904	17.793	519.659	−0.447
V2TiAlC2	2.965	18.077	550.494	−0.691
Mo2TiAlC2	3.002	18.743	584.885	−0.526
Ti3AlC2	3.072	18.730	612.781	−0.841
Nb2TiAlC2	3.105	18.896	630.824	−0.732
Ta2TiAlC2	3.131	18.904	641.779	−0.641
Hf2TiAlC2	3.250	19.314	706.742	−0.695
Zr2TiAlC2	3.259	19.565	719.659	−0.779
Sc2TiAlC2	3.190	20.173	712.566	−0.623
Y2TiAlC2	3.403	21.258	852.427	−0.260
La2TiAlC2	3.460	22.704	940.866	−0.050

Figure 1. The density of states of (a) Ti₃AlC₂, (b) Zr₂TiAlC₂, (c) Hf₂TiAlC₂, (d) Sc₂TiAlC₂ and (e) Y₂TiAlC₂.

Figure 2. The charge differences of Ti₃AlC₂ and M₂TiAlC₂ MAX phases at the same isosurface with isovalue are 0.05 electrons/bohr³.

Figure 3. Structure of M₂TiAlC₂ MAX phases and initial lithium storage sites, where the black dotted line represents different interstices.

Table 2. Charge transfer with reference to isolated atoms (in electrons; calculated by the Bader approach) for lithiation of M₂TiAlC₂ MAX phases.

Type	Elements	Hf2TiAlC2	Sc2TiAlC2	Y2TiAlC2	Zr2TiAlC2	Ti3AlC2
Lithiation	Ti	−1.46	−1.49	−1.49	−1.45	−1.46
	C	1.73	1.8	1.81	1.81	1.64
	Al	0.82	0.95	0.93	0.86	0.69
	Outsides M	−1.37	−1.48	−1.49	−1.47	−1.22
	Li	−0.72	−0.72	−0.74	−0.72	−0.69

Figure 4. (a) The lithiation formation energy for M₂TiAlC₂ for every inserting Li. The bonding length between the (b) M and Li, (c) Al and Al, (d) Al and Li as the function with the inserted Li number.

Figure 5. (a) The three types of Li diffusion pathways and (b) the diffusion energy barrier for M₂TiAlC₂.