Galaxies at z>5 are the dominant sources for cosmic reionization, but current knowledge on these galaxies are restricted by the limited data available. JWST and next generation of ground-based telescopes allow us to probe z>5 galaxies in the rest-frame optical at higher resolution via deeper observations. I will present a new suite of high-resolution cosmological zoom-in simulations of z>5 galaxies, using realistic models of the multi-phase ISM, star formation, and stellar feedback from the FIRE project. These simulations form a more realistic sample of model galaxies and can provide useful predictions for future observations. By post-processing with Monte Carlo radiative transfer code, we compute the escape fraction of ionizing photons from these galaxies. I will show that using canonical stellar population model, the escape fractions cannot exceed a few percent, because most photons from young stars are absorbed by their birth clouds, which are destroyed on a time-scale comparable or longer than the lifetime of most massive stars. However, recent stellar population models including binary interaction can produce hot stars, and more ionizing photons at much later times. These photons can escape the galaxy very easily, and thus provide sufficient photons to cosmic reionization.