  We present a new theoretical and computational framework for modelling
electro-chemo-mechanical fracture. The model combines a phase field description
of fracture with a fully coupled characterisation of electrolyte behaviour,
surface chemical reactions and stress-assisted diffusion. Importantly, a new
physics-based formulation is presented to describe electrolyte-containing phase
field cracks, appropriately capturing the sensitivity of electrochemical
transport and reaction kinetics to the crack opening height. Unlike other
existing methods, this approach is shown to accurately capture the results
obtained with discrete fracture simulations. The potential of the
electro-chemo-mechanical model presented is demonstrated by particularising it
to the analysis of hydrogen embrittlement in metallic samples exposed to
aqueous electrolytes. The finite element implementation takes as nodal
degrees-of-freedom the electrolyte potential, the concentrations of relevant
ionic species, the surface coverage, the concentration of diluted species, the
displacement field and the phase field order parameter. Particular attention is
devoted to improve stability and efficiency, resulting in the development of
strategies for avoiding ill-constrained degrees of freedom and lumped
integration schemes that eliminate numerical oscillations. The numerical
experiments conducted showcase the ability of the model to deliver
assumptions-free predictions for systems involving both free-flowing and
crack-contained electrolytes. The results obtained highlight the role of
electrolyte behaviour in driving the cracking process, evidencing the
limitations of existing models.
