Medium-temperature molten salt reserve primary cell utilizes low-melting nitrate electrolyte, that is considered suitable for geothermal borehole as well as oil and gas exploration. In this work, Cr3+ and F- ions were introduced into spinel lithium manganate oxides by high-temperature solid-state method and verified by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The effects of fluorine content on the morphology and discharge performance of the LiCr0.1Mn1.9O4-xFx (0 <= x <= 0.5) have been studied in LiCr0.1Mn1.9O4-xFx/LiNO3-KNO3-Ca(NO3)(2)/Li-Mg-B system. Fluoride-doped samples have a significant improvement in discharge performance at the condition of 10 mA.cm(-2) and 250 degrees C because of the stabilization of the crystal structure. Factors of operating temperature and current density have a significant effect on battery discharge performance, and the surroundings of 10 mA.cm(-2) and 200-250 degrees C contributes the battery to achieve high performance. That indicates the LiCr0.1Mn1.9O4-xFx/LiNO3-KNO3-Ca(NO3)(2)/Li-Mg-B battery shows great potential in geothermal borehole as well as oil and gas exploration environment.