Although lithium-ion batteries are the best in terms of efficiency, they are amongst the worst in terms of cost. On top of that, lithium reserves around the world are rapidly depleting. The world is in need of a more cost-effective, environmentally-friendly alternative, which is why a team of researchers are developing a battery based on the abundant element of sodium. So far, the researchers have been able to create a sodium-based battery that can store the same amount of energy as a lithium-based battery at less than 80 percent of the cost.