fig5

Figure 5. Charge density difference isosurfaces for various alkali intercalation in -O terminated 1Ti1Nb (1 layer of Ti3C2O2 + 1 layer of Nb2CO2), these configurations possess the largest capacities. (A-D) are charge density difference isosurfaces for 1L Li intercalation, 1L Na intercalation, 2L Li intercalation and 2L Na intercalation in 1Ti1Nb, respectively, for 2L intercalation, we regard 2L alkali atoms as a whole. Isosurface value is set at 0.004 e/bohr3: electron accumulation, yellow; electron depletion, cyan.