The breakthrough of electric cars is held back by only one barrier: the lack of a light, compact and affordable battery. The lithium-air battery, which we wrote about earlier, promises at least ten times the capacity for the same weight. Will this be the breakthrough we've been waiting for for years?
Lithium air batteries are potentially capable of vastly increasing capacity compared to lithium-ion batteries currently in use. This is because lithium air batteries use the oxygen from the air instead of a heavy molecule that absorbs the electrons from the lithium. Lithium is then converted into lithium peroxide, Li2O2. So much for the theory. The weight efficiency of such a battery is enormous: lithium, the lightest metal that exists under Earth conditions, has an atomic mass of 6, so here it absorbs one electron per three atomic mass units. In comparison: the well-known “heavy” lead-sulphate battery from cars with an internal combustion engine requires around 150 atomic mass units, with a lower source voltage. Practice is much more unruly. It is true that progress has been made in the inflow of air into the battery and actually getting the oxygen to react with the lithium, but there is an annoying problem: oxygen also reacts with the parts of the battery where this is not intended.
Finally long life lithium air battery?
As a result, the lithium air battery can only be recharged a few times before it gives up. Now researchers have found a material that does not react with oxygen, which also keeps the battery functioning multiple times. Even more good news is that the battery can theoretically store more than ten times the energy of a lithium-ion battery of the same mass, thereby preventing an oxygen radical from forming in the process of converting lithium to lithium peroxide. . A radical is an incomplete molecule with an unbound electron and is therefore chemically extremely aggressive. This radical attacks the electrolyte that transports charged ions from one electrode to another. The formation of the oxygen radical is inevitable, but the sensitivity of the electrolyte to oxygen radicals can be avoided.
Hardly any loss of capacity after a hundred charges
The authors discovered a mixture of a hydrocarbon (tetraethylene glycol dimethyl ether) and the lithium salt LiCF3SO3 that proved resistant to the radical. This worked well at room temperature and, even better, it turned out to pass through the oxygen reactions so quickly that hardly any intermediates could be measured. LiCO3+, which is formed when oxygen with lithium and the carbon electrode reacts (a sign that the electrode is being attacked), was not found, the authors said. This was also found in the test set-up: after the hundredth charge, there was hardly any loss of capacity compared to the twentieth charge. For a car, that easily means a service life of at least two years. The material was also found to perform well with different loads.
Extremely high energy density
Although the electrode material is not always the heaviest part of the battery, which makes comparison difficult, this does offer the necessary perspectives. At a high discharge rate, according to the authors, the battery is capable of storing 13.5 kWh per kg of electrode. That's more chemical energy than there is in a gallon of gasoline or diesel and, since electric motors are nearly 100% efficient, means that the range of such a car will be more than ten times that of a gasoline car. The authors are more cautious and assume a factor of ten lower, but even then this technique would far exceed existing batteries, with a capacity of around 0.15 kWh per kg. In short, let's hope this technique lives up to these claims.
This would completely solve the peak-oil problem - solar panels are already cheap enough to compete with petroleum as an energy source.