In this study, alkali cellulose-6-phosphate (A-CP) was prepared by the treatment of cellulose-6-phosphate (CP) with an aqueous solution of sodium hydroxide. X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), 13C, 31P, and 23Na Nuclear Magnetic Resonance (NMR) spectroscopies were used to characterize the studied polymers. The CP and A-CP crystallize in the monoclinic system of the P21 space group (cellulose Iβ). CP and A-CP, with relative densities of 70% and 77%, respectively, were shaped into cylindrical pellets by uniaxial pressing and sintering at 423 K of the A-CP. Electrical conductivity measurements of CP and A-CP were carried out using complex impedance spectroscopy between 298 K and 433 K in the frequency range of 13 MHz - 5 Hz. The influence of aqueous NaOH on the structure, thermal stability, and electrical conductivity of cellulose phosphate was observed. In contrast to CP, A-CP was stable up to temperatures exceeding 433 K and showed fast ionic conductivity σ393 K = 2.03 × 10−6 S.cm−1 with an activation energy (Ea) of 0.73 eV.