Fig. 4.

Density functional calculations and Bader charge analysis. a, b Calculated free energy diagrams a on the Li₂O₂ $\left(1\overline{1}00\right)$ and b on amorphous Li₂O₂, along with the optimized structures. For the amorphous surface, the most favorable adsorption site was considered to construct the diagram. Lithium is colored in light gray (bulk) and light green (adsorbate); oxygen is colored in dark gray (bulk) and red (adsorbate). c, d The variation in electron density upon the first LiO₂ adsorption on c the crystalline Li₂O₂ $\left(1\overline{1}00\right)$ and d amorphous Li₂O₂ surfaces. The charge density indicated by surface contour is plotted with a threshold value of 0.01e Å⁻³. The newly adsorbing *LiO₂ is denoted explicitly as Li, O₁, and O₂. O₂ which is not shown in c is behind O₁. Lithium is in light green and oxygen in red. e, f Binding energies of e 1st LiO₂ and f 2nd LiO₂ for 16 sites of the amorphous Li₂O₂ surface plotted versus coordination number. Binding energies on the crystalline surface are also shown for comparison, denoted as c-Li₂O₂