RESTRAINT TOOL, BATTERY SYSTEM, AND FLYING BODY

There is provided a restraint tool which restrains a lithium metal battery including a plurality of battery cells, including: a restraint member which includes: a plate-shaped member which is made of a rubber-based material and include a plate-shaped base and a plurality of protrusions on the base; and a frame member into which the plate-shaped member is fitted; and a fixing member which fixes the plate-shaped member fitted into the frame member in a pressurized state in which the plate-shaped member is pressed against the lithium metal battery. In the restraint tool, due to elasticity of the plate-shaped member, a pressure applied by the restraint tool to the plurality of battery cells in charging the plurality of battery cells is 5 MPa or less, and a pressure applied by the restraint tool to the plurality of battery cells in discharging the plurality of battery cells is 0.1 MPa or more.