Aqueous hybrid Zn-based batteries (ZIBs), as a highly promising alternative to lithium-ion batteries for grid application, have made considerable progress recently. However, few studies have been reported that investigate their working mechanism in detail. Here, the operando synchrotron X-ray diffraction is employed to thoroughly investigate the operational mechanism of a hybrid LiFePO4(LFP)/Zn battery, which indicates only Li+ extraction/insertion from/into cathode during cycling. Based on this system, a cheap electrolyte additive, sodium dodecyl benzene sulfonate, is proposed to effectively enhance its electrochemical properties. The influence of the additive on the Zn anode and LFP cathode is comprehensively studied, respectively. The results show that the additive modifies the intrinsic deposit pattern of Zn2+ ions, rendering Zn plating/stripping highly reversible in an aqueous medium. On the other hand, the wettability of the LFP electrode is visibly a meliorated by introducing the surfactant additive, accelerating the Li-ion diffusion at the LFP electrode/electrolyte interface, as indicated by the overpotential measurements. Benefiting from these effects, the Zn/LFP batteries deliver high rate capability and cycling stability in both coin cells and pouch cells.