The unipolar resistive switching behavior of Pt/LixZn1-xO/Pt structures fabricated via radio-frequency magnetron sputtering is investigated. Various Li doping concentrations influence the defect types (i.e., VO, Lii, and LiZn) in LixZn1-xO films for adjustable resistance ratio. The resistance ratio reaches 108 due to the minimized leakage current in the high-resistance state (HRS) at 6 at. % Li dopants. The dominant conduction mechanisms are explained in terms of Ohmic behavior and Poole-Frenkel (PF) emission. The coefficient r of the PF emission in the HRS is evaluated to confirm that the total number of defects in LixZn1-xO films decreases with increasing Li content.