The quest for the perfect battery continues. Increasingly often called the Holy Grail of energy storage, it needs to be energy dense, cheap, and durable. Existing batteries usually fail in at least one of these respects, with lithium-ion ones being on the expensive side despite their energy density and durability, and lead-acid batteries, for example, having short lives and low energy density. Now a team of scientists from Stanford say they may have come up with the Holy Grail: a battery that is simultaneously energy dense, cheap, and durable. An important bonus is that the battery is easily scalable.
The battery developed by the lab of a materials science professor, Yi Cui, and his team, led by Wei Chen, uses manganese as electrolyte in a water-based solution. When the battery charges, electrolysis breaks down the water from the solution into hydrogen and oxygen. The manganese from the electrolyte solution binds with the oxygen and sticks to the carbon cathode. Hydrogen gas is the form in which the energy is stored in the battery. During discharge, the manganese ions dissolve back into the electrolyte solution and the oxygen and hydrogen turn back into water.
According to the team, their battery has an energy density of 140 Wh/kg and has a lifecycle of 10,000 charge/discharge cycles. As for cost, the senior author of the study estimated that storing enough electricity to power a 100-W lightbulb for 12 hours would cost a penny. And what’s perhaps best about this battery is that it could be easily used to store energy from renewable sources, to discharge it during peak demand hours. This will replace the on-demand power plants that are commonly used right now, but at the expense of higher CO2 emissions.
The Department of Energy has recognized the benefits of battery storage and has devised requirements for grid-scale storage that all battery makers are in a rush to fulfill. These include the capacity to store and discharge a minimum of 20 kW per hour, durability of at least 5,000 cycles, and a lifespan of at least 10 years. As for cost, the DoE estimates US$100 per kWh as the maximum to make such storage commercially viable.
The Stanford lab battery is cheaper than other alternatives because it uses abundant elements such as manganese and hydrogen. Because of its relatively simple structure it can also easily be scaled, and it has the durability. But scalability would come at a cost: the prototype uses platinum as catalyst—and platinum, while relatively cheap right now, is nowhere near as cheap as manganese and has brought the total cost of the water-based battery to over the US$100 maximum. Besides, building a grid-scale battery of this kind could prove costlier than the prototype, but the researchers are already looking into ways to reduce the cost of their invention.
They have already found an alternative to the platinum catalyst and are now working on the cathode, testing different materials, to improve the battery’s performance further. The invention certainly sounds promising and possibly superior to other recent battery prototypes that fell short of requirements in one of the three aspects that make up the perfect battery. Now it just needs to prove viable outside the lab.
By Irina Slav for Oilprice.com
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