  Delivering the full benefits of first principles calculations to battery
materials demands the development of accurate and computationally-efficient
electronic structure methods that incorporate the effects of the electrolyte
environment and electrode potential. Realistic electrochemical interfaces
containing polar surfaces are beyond the regime of validity of existing
continuum solvation theories developed for molecules, due to the presence of
significantly stronger electric fields. We present an ab initio theory of the
nonlinear dielectric and ionic response of solvent environments within the
framework of joint density-functional theory, with precisely the same
optimizable parameters as conventional polarizable continuum models. We
demonstrate that the resulting nonlinear theory agrees with the standard linear
models for organic molecules and metallic surfaces under typical operating
conditions. However, we find that the saturation effects in the rotational
response of polar solvent molecules, inherent to our nonlinear theory, are
crucial for a qualitatively correct description of the ionic surfaces typical
of the solid electrolyte interface.
