The present invention reports a method for constructing a temperature activated rechargeable battery and apply the device for seasonal electrical energy storage. The battery consists of a metal anode, a metal cathode, a molten salt electrolyte, and a porous separator (Figure 1). The battery operates at an elevated temperature during charging and discharging, at which the molten salt electrolyte is in a liquid state. During idling, the battery will be kept at ambient temperature, and capacity loss due to self-discharge is minimized by freezing the electrolytes.