The development of high-performance battery separators using solid electrolyte polymers in a continuous industrial process is a promising field of research when considering economical and ecological aspects. These solid polymer electrolytes should be permeable to ionic current but electrically insulating, all the while maintaining sufficient mechanical resistance. To enhance mechanical properties, dispersion of nanometrics fillers (nanocrystalline cellulose) in a polymer is the chosen pathway. Nanocrystalline cellulose is a type of filler with lengths between 100 and 300 nm and diameters between 5 and 20 nm. They are obtained after acid hydrolysis which removes the amorphous parts of the cellulose elementary fibril. Thus, nanocrystalline cellulose has a high crystallinity which leads to a high elastic modulus. A homogeneous dispersion of these fillers allows the formation of a percolating network at low concentrations (thanks to their high form factor), which greatly enhances the mechanical properties of the matrix. The goal is to carry out this dispersion in molten polymer through extrusion, as opposed to the well-established solvent evaporation process. The main difficulties are the aggregation of cellulose whiskers which occurs through hydrogen bonding and the concentrated medium in which these fillers are dispersed. To achieve dispersion, both the internal mixer and a miniextruder have been used. Different protocols as well as a copolymer have been tested to promote dispersion. Results have shown that there is orientation of the fillers thus increasing the concentration necessary to obtain a percolating network. In this presentation we will show that we have found a way to overcome the orientation issue and have managed to disperse nanocrystalline cellulose with no modification of the surface or addition of plasticizer.