Lithium is the lightest metal in the periodic table, and also it is the lowest density of any metal and can even float on the water. It can be used in rechargeable batteries. Normally lithium battery can last for around 2 to 3 years or you can recharge it for 300 to 500 times.
When you discharge a lithium battery, its voltage remains relatively constant. But a lead-acid battery decrease its voltage while discharge. Lithium battery storage capability measured as Amp-Hour, Ah, which can use hundred per cent of its storage capability. But a lead-acid battery can only use up to around 30%.