A microcomposite structure for use as a component of a lithium battery is formed from a liquid phase mixture by the removal of a solvent. The microcomposite structure includes a continuous reticulated solid polymer phase, a formed in situ gel-electrolyte phase, and a solid phase surfactant at the interface between the gel and polymer phases for stabilizing the gel phase within the pores of the solid polymer phase. The liquid phase mixture comprises a polymer blend, an aprotic solvent system for the polymer blend, a substantially dissolved anionic surfactant, and a phase separation liquid that is miscible with the aprotic solvent system, but in which the polymer blend is substantially insoluble. The microcomposite structure is formed by casting the liquid phase mixture on a surface and removing solvent until the microcomposite structure forms.