Referring to FIG. 1, the polymeric material 100 may be includes a hydrogel structure, which may include (but not limited to) a polyacrylate-based material or sodium polyacrylate (PANa). These polymers or hydrogel structures include a hydrophilic functional group which may facilitate retaining water or an ionic solution including a plurality of chemical ions 104, while allowing the mobile ions 104 to move within the hydrogel structure. Therefore the polymeric material 100 includes an ion-conductivity which is sufficient for being used as an electrolyte in a battery device.

Preferably, hydrogel may be used as a host of water and free-moving ions due to its high absorbency, behind which the driving force is an osmotic pressure difference arising from the concentration of ionic groups inside the hydrogel network.

With reference to FIGS. 2A and 2B, the water absorbency of different hydrogel may vary with species. PANa, as a superabsorbent polymer, may absorb water 220 times the weight of its own in less than 2 h. On the other hand, as another example hydrogel, polyacrylic acid (PAA) may absorb water 45 times the weight of its own. The superabsorbency of PANa is further revealed by the fact that it may absorb water vapor in the air up to ?30% wt., depending on the relative humidity in the ambient environment.

Hydrogel may also change its structure in response to the absorbed content. Referring to FIG. 2B, the initially dry PANa film 100 becomes soft and flexible after absorption of water vapor from the ambient air. Thus the ion-conducting material is mechanically flexible.