Metal air batteries are one of the most lightweight and most compact battery types, but can have a major limitation: when they do not use it, they quickly suffer because the corrosion vessels are made of metal electrodes. Now MIT researchers have discovered a way to significantly reduce the corrosion, which makes it possible for such batteries to have more shelf life.
Although typical rechargeable lithium-ion batteries simply lose about 5 percent of their charge a month after storage, they are very expensive, bulky, or heavy for many applications. Primary (nonchchargeable) aluminum air batteries are much less expensive and more compact and light, but they can lose 80 percent of their charges per month.
The MIT design overcomes aluminum air batteries with corrosion problem, which introduces an oil barrier between aluminum electrodes and electrolytes – between the two electrodes of liquid fluid aluminum, when the battery is waiting. Oil is quickly pumped and replaced with electrolyte, as soon as the battery is used. As a result, the energy loss decreased by only 0.02 percent per month – over one thousand improvements.
The researches today report in the journal Science Former MIT graduate at Brandon J. Hopkins & # 39; 18, W.M. Professor of Keke Energy Ian Shao-Horon and Mechanical Professor Douglas P. Hart.
Although several other methods were used to store the metal airbags (which may be used by other metals such as sodium, lithium, magnesium, zinc, or iron), these methods can be performed by the Hopkins. Most of the other approaches appear to replace the electrolyte, different, less corrosive chemical formulation, but these alternatives significantly reduce battery power.
Other methods are involved in liquid electrolyte pumping time and storage. These methods still provide an important corrosion and introduce plumbing systems into the battery pack. Because aluminum is hydrophilic (water intake) after the electrolytes, the remaining electrolytes are on the surfaces of the aluminum electrodes. "Batteries have complex structures, so many corners get caught electrolytes", which continues to prevent corrosion, says Hopkins.
The key of the new system is to place a thin membrane between battery electrodes. When using the battery, both sides are filled with the membrane liquid electrolytes, but when the battery is waiting, the oil is followed by the aluminum electrode that protects the aluminum surface on the electrolyte membrane's other side.
The new battery system will also benefit aluminum "Underwater oleophobicity" – when aluminum is immersed in water, it returns to excess oil. As a result, when battery reactors and electrolytes are pumped, the electrolyt can easily remove the oil aluminum surface that restores battery capacity. Ironically, the MIT method of corrosion suppression uses the same aluminum that promotes corrosion conventional systems.
The result is the aluminum air prototype of a much longer term shelter than conventional aluminum air batteries. Researchers have shown that when the battery has been used repeatedly and after one day, the MIT design lasted for 24 days and the usual design was just three. Even when the oil and pump system is included in large-scale aluminum air battery packs, they are still five times lighter and twice as compact as multiple metal-ion battery electric generators, researchers said.
Hart explains that aluminum, except that it is very inexpensive, is one of the "materials on storage of high chemical energy" – that is, it can keep and publish more pounds of energy per pound, only the brom that are expensive and dangerous , Compared to. According to many experts, Aluminum Air Batteries can be the only viable alternative for lithium-ion batteries and car petrol.
Aluminum Air Batteries have been used as a range of extenders for electric vehicles to replenish the built-in rechargeable batteries, add a lot of extra pipe management when the built-in battery life runs out. They also sometimes use electricity sources for remote areas or underwater vehicles. But such batteries can be stored for a long time, as they are unused, as soon as they become the first time they will quickly degrade.
The larger shelf life that this new system could use, aluminum air batteries may be "on the current mark," says Hopkins. This process has already been filed for patents for children.
The research was supported by MIT Lincoln Laboratory.