Potentially temperature-resistant inorganic perovskite/silicon tandem solar cells (TSCs) are promising devices for boosting efficiency past the single-junction silicon limit. However, undesirable non-radiative recombination generally leads to a significant voltage deficit. Here, we introduce an effective strategy using nickel iodide, an inorganic halide salt, to passivate iodine vacancies and suppress non-radiative recombination. NiI2-treated CsPbI3-xBrx inorganic perovskite solar cells with a 1.80 eV bandgap exhibited an efficiency of 19.53% and a voltage of 1.36 V, corresponding to a voltage deficit of 0.44 V. Importantly, the treated device demonstrated excellent operational stability, maintaining 95.7% of its initial efficiency after maximum power point tracking for 300 h under continuous illumination in a N2 atmosphere. By combining this inorganic perovskite top cell with a narrower bandgap silicon bottom cell, we for the first time achieved monolithic inorganic perovskite/silicon TSCs, which exhibited an efficiency of 22.95% with an open-circuit voltage of 2.04 V. This work provides a promising strategy for using inorganic passivation materials to achieve efficient and stable solar cells.