  We study a symmetric diffusion $X$ on $\mathbb{R}^d$ in divergence form in a
stationary and ergodic environment, with measurable unbounded and degenerate
coefficients $a^\omega$. The diffusion is formally associated with $L^\omega u
= \nabla\cdot(a^\omega\nabla u)$, and we make sense of it through Dirichlet
forms theory. We prove for $X$ a quenched invariance principle, under some
moment conditions on the environment; the key tool is the sublinearity of the
corrector obtained by Moser's iteration scheme.
