An alkaline battery is a type of primary battery that derives energy from the reaction between zinc metal and manganese dioxide, and has an electrolyte with a pH value above 7, typically potassium hydroxide (KOH) . Compared to other types of batteries, alkaline batteries have a higher energy density and longer shelf life, yet provide the same voltage. They are available in both disposable and rechargeable versions, with the disposable version being the most popular household battery. The positive electrode of an alkaline battery is manganese dioxide (MnO2), while the negative electrode is zinc. The concentration of the alkaline electrolyte of potassium hydroxide remains constant during discharge, as only the zinc and MnO2 are consumed. Alkaline batteries have a higher voltage than lithium batteries, but their voltage and mAh capacity decline as the battery discharges, making them better suited for applications that require fast bursts of power, such as camera flashes. The usage of alkaline batteries is limited to specific applications, but they remain the most frequently consumed battery chemistry due to their wide availability, range of suitable applications, and reliability in many different environments and climates.