Effects of 30° partial dislocation and stacking fault on Na and Mg storage and diffusion in Si anode

While the perfect Si can't be used to store Na and Mg interstitials in Na-ion batteries (NIBs) and Mg-ion batteries (MIBs), the defects of 30 degrees partial dislocation and stacking fault (SF) may improve the performance of Si anode according to the multi-scale simulation results. It is found that both 30 degrees partial dislocation and SF can provide more stable sites to accommodate impurities and enhance the binding strengths. The 30 degrees partial dislocation can drastically promote the binding energies of Na (Mg) to the value of 0.72 (0.622) eV and 0.684 (0.6) eV at Oct-A and Oct-B, respectively. Moreover, it is thermodynamically and kinetically favorable for Na and Mg concentrating in the defect areas. On the other side, the migration barriers of Na and Mg in the 30 degrees partial dislocation and SF are much higher than the defect-free Si. Those defects may restrict the diffusion of interstitials and turn into limiting factors of charge/discharge rate of NIBs and MIBs. (C) 2016 Elsevier B.V. All rights reserved.