A battery is a power source for electrical devices such as cell phones, flashlights, and electric cars that consists of one or more electrochemical cells with external connections. The electrode materials are irreversibly modified after discharge, hence primary (single-use or "disposable") batteries are used once and then destroyed. Secondary (rechargeable) batteries can be discharged and recharged several times with an applied electric current; reverse current can be used to restore the electrodes' original composition.
A solid-state electrolyte (SSE) is a solid ionic conductor electrolyte that is a distinguishing feature of solid-state batteries. It can be used to replace liquid electrolytes in electrical energy storage (EES) systems, such as those found in lithium-ion batteries.