Heat is the worst enemy of your smartphone battery. Batteries exposed to hot temperatures lose their ability to store energy; the hotter the temperature, the faster they lose their storing ability. Extreme heat also has the potential to shorten overall battery performance. It can cause permanent battery failure or eventually explode if it’s exposed for a long period of time.
In the cold, when the temperatures drop low enough, your smartphone could think its battery is empty even if it’s fully charged. The colder it gets, the least amount of energy that the battery can provide. In addition, the internal resistance of the battery grows, causing the output voltage to drop. When the voltage drops below the threshold – Your smartphone thinks the battery is empty, even if it’s fully charged.
The ideal temperature for your smartphone CPU should be as cool as possible (which usually means normal room temperature) since a hot-running Electronics components could cause problems ranging from unwanted system crashes, to physical damage to the smartphone processor itself. Most modern smartphones have a protection feature which automatically shuts them down if they get too hot, so actual damage is unlikely unless it’s kept exposed to longer periods of high heat. In general you should consider 60 degrees Celsius as absolute maximum for long periods.
LCD screens uses liquid crystal molecules for display, when they are aligned perfectly, that alignment generates the desired pattern. However, exposure to freezing conditions can disturb molecular order, hence leading to dimming, screen blackouts and permanent damage. These common faults are widely known to the snowboarding community and north arctic residents who spend most of their time in subzero conditions.
Exposing your smartphone to hot & cold temperatures over and over again could cause your smartphone PCB’s to expand and shrink due temperatures changes. These changes could lead to cracks over time, which will cause poor circuit connections and eventually permanent smartphone failure.