Electrochemical cells & Fuel Cells
http://www.envocare.co.uk/batteries.htm
http://electronics.howstuffworks.com/everyday-tech/battery.htm
http://depts.washington.edu/matseed/batteries/MSE/classification.html
http://humantouchofchemistry.com/how-do-rechargeable-batteries-work.htm
Fuel Cells:
http://www.envocare.co.uk/fuel_cells.htm
http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell.htm