Electric potential
The negative ones are attracted to the positive ones but cannot get to them because there is a wall between them in the battery. So you make them go 'around the house and through the back door' i.e. you make a circuit which goes from the negative side to the positive side. Then the negative ions go through the wire and mix with the positive ones. When all the negative ones go to the other side the battery is flat and needs to be recharged. Think of a turbine in water. Water passes through it moving down and turns it. When the negative ions move through the wire they go through things like bulbs, microwaves etc. Instead of moving them, they collide into them, but only some go through. When they collide they produce light and heat. The reason why we have electrical appliances today is because these negative ions collide into the positive ions in a circuit.