NiCl2 has been widely studied as a new cathode material for thermal batteries due to its high theoretical discharge voltage and specific energy. However, LiCl generates during the discharge process of NiCl2 cathode, which results in composition segregation and larger polarization resistance of the molten salt electrolyte containing LiCl. It makes a significant reduction for the discharge performance of NiCl2 cathode. In this contribution, NiF2 was adopted as an additive to construct a NiCl2/NiF2 dual active composite cathode in order to suppress the composition segregation of molten salt electrolyte during the discharge process. The research results show that when the content of NiF2 is 30wt%, the specific discharge capacity and specific energy density of NiCl2/NiF2 composite cathode respectively reach 291.2 mAh·g-1 and 0.701 Wh·g-1 at the cut-off voltage over 2 V and the discharge current density of 100 mA·cm-2. The specific energy density of NiCl2/NiF2 composite cathode is 1.67 and 2.11 times of NiCl2 and NiF2 cathode, respectively.