In the last decade, Lithium ion based batteries have emerged as interesting candidates as high-density energy storage devices. The synthesis of polymer electrolytes and the study of their electrochemical properties is currently a very active topic. Poly(ionic liquids) (PILs), in particular, constitute an increasingly sought-after category of materials, as they are expected to replace flammable, leakage-prone organic solvent electrolytes in future energy storage devices. In this work, we have developed two new polymers (PIL’s) from ATRP polymerization for energy storage application with two kinds of end groups: phosphonic (PO3H) or ethyl. An imidazolium group is present on each unit of the polymer backbone with a bromide counter ion to allow supramolecular interactions. Moreover, for few formulations, partial cross-linking of the PIL's has been tested in order to investigate its impact on the gelification process. With addition of water, PIL's form hydrogels which present usual yield stress fluid properties and a so-called sol-gel transition. The study shows that galation mechanism is controlled by three main parameters: polymer concentration, cross-linking amount and the nature of the end group. Using rheological measurements, a phase diagram with two main domains (gel like and viscous liquid behavior) has been obtained. From this diagram, we are able to quantify the contribution of each parameter to the gel formation. Moreover, an interesting transition inside the gel domain with respect to the polymer concentration has been observed and can be attributed to different relaxation mechanisms (from friction to elastic interactions of swollen soft particles) in the gel phase. To summarize, it appears clearly that the nature of end groups is a key to control the hydrogel properties and gel formation. Furthermore, whatever the amount of crosslinking, phosphonic (PO3H) end group enables the formation of a supramolecular network and large variety of hydrogels properties