T. Vo, T. Phung, H. Truong, L. Nguyen, O. Nguyen, and P. Le, “Physical-chemical and electrochemical properties of sodium ion conducting polymer electrolyte using copolymer poly(vinylidene fluoride- hexafluoropropylene) (PVDF-HFP)/ polyethylene oxide (PEO)”, Science and Technology Development Journal, vol. 22, no. 1, pp. 147-157, Mar. 2019.