Polyelectrolyte gels are soft materials that consist of an electrically charged polymer network that is swollen with fluid. When placed in a salt solution, ions will migrate towards the gel to screen the electric charges on the polymers. The resulting diffuse layer of charge is called an electric double layer (EDL). It is commonly assumed that the EDL plays a passive role in the macroscopic behaviour of the gel. Therefore, in mathematical models, the EDL is often neglected and the gel is assumed to be electrically neutral. In this talk, I will revisit these assumptions by using matched asymptotic expansions and numerics to determine the structure of the EDL and its impact on the bulk response of the gel. Surprisingly, the EDL can play a fundamental role in controlling the macroscopic properties of the gel. Electrically charged, spatially localised patterns can emerge from the EDL and invade the bulk, triggering a breakdown of electroneutrality throughout the gel. I will conclude by arguing that these spatially localised instabilities provide a new interpretation of the volume phase transition, which occurs when the gel volume changes discontinuously in response to an infinitesimal stimulus.