The invention provides a mixed water system ionic battery and application thereof. The battery comprises a positive electrode, a negative electrode, a diaphragm and quaternary mixed electrolyte, wherein the negative electrode takes a carbon composite NaTi2(PO4)3 material as a negative active substance; the diaphragm is arranged between the positive electrode and the negative electrode; the quaternary mixed electrolyte is prepared from water, a material selected from one or more of urea, N,N-dimethyl formamide, dimethyl sulfoxide, diethyl carbonate and dimethyl carbonate, a material selected from one or more of sodium perchlorate and sodium nitrate as well as a material selected from one or more of lithium perchlorate or lithium nitrate. The materials of the battery are non-toxic, pollution-free, non-combustible, non-explosible, safe and reliable, the output voltage of the total battery can reach 1.65 V, the energy density is up to 50 Wh/kg, and the service life is up to 1000 times or longer. Compared with the conventional water system ionic battery, the battery provided by the invention has high circulation stability; the manufacturing process is simple; the raw materials are cheapand have wide sources; the energy density is high; the problems that the conventional water system ionic battery has short circulation life and low energy density can be solved effectively.