Fuel cell is very complex, involving chemical thermodynamics, electrochemistry, electrocatalysis, materials science, power systems and automatic control and other disciplines of the theory, with high power generation efficiency, less environmental pollution and so on.
It looks from the appearance of positive and negative and electrolyte, like a battery, but in essence it can not "storage" but a "power plant."
Simply put, fuel cell (Fuel r nCell) is a kind of power generation device that converts chemical energy existing in fuel and oxidant directly into electrical energy.