It is a substance.
no, lithium sulfate is a salt with a melting point at 1132K
Li(I) lithium iodide is an ionic compound (salt)
Any battery must contain at least two distinct chemical substances, and there is no fixed ratio between the masses of the two substances. Therefore, any battery, including a lithium battery, is a mixture.
Element
Lithium iodide is a chemical compound, not a mixture.
Lithium & Magnesium
Iron, lithium, and neon do not actually mix, nor do they chemically react with each other (although iron and lithium react with other elements such as oxygen). Iron is much denser than lithium, so if you poured these two metals into a container in their molten state, the lithium would just float on top of the iron. And Neon is an inert gas.
Hydrogen bombs usually use the element Lithium to produce Tritium in situ, but it is not in the reactive metallic form. It is in the form of Lithium Deuteride, so that when the Lithium is transformed to Tritium it is already in a Deuterium-Tritium mixture ready to undergo nuclear fusion.
Carbon is not a mixture but an element , one of the basic building blocks. Other such elements are hydrogen, helium, lithium, beryllium, boron, nitrogen, oxygen, fluorine, neon, sodium, magnesium etc.
Lithium Bromine
A mobile phone contains a variety of elements, such as copper, gold, silicon, and lithium. These elements are combined into mixtures, such as the metal alloys used in the phone's casing, and compounds like the semiconductor materials in the microchips. The battery also contains a mixture of elements like lithium and cobalt in the form of lithium-ion compounds.
a chemical reaction occurs. a deadly chemical gas forms. friction is happening inside the mixture. it is becoming very hot. eventually that mixture will explode. it could take seconds or minutes depending upon how much of the mixture was put into place.