Researchers at Harvard University in the United States believe they have found a solution to harness the potential of solid-state lithium to build batteries that conserve more energy and charge in less time than conventional lithium-ion cells. Previous attempts have not been successful because of the lack of stability of this type of material.
In lithium metal batteries, ions move from the cathode to the anode during charging. If the anode is made of solid metal, several dendrites form on the surface, growing in the electrolyte and perforating the barrier that separates the cathode from the anode. This invariably causes a short circuit and can even ignite the battery.
Dendrite is an accumulation of lithium crystal that normally starts at the anode and can spread throughout the battery. This is a result of high current charging and discharging, when the combination of electrons and ions in the solid electrolyte forms a layer of solid lithium metal. The addition of these dendrites reduces the capacity of the electrolyte available in the battery, also decreasing its charge storage.
The solution found by the researchers now was to design a multilayer battery, with various materials of different stability between the anode and the cathode. This system prevents the penetration of lithium dendrites, making them remain controlled and stable.
“Our strategy of incorporating instability in order to stabilize the battery seems counterintuitive, but just as a chuck can guide and control a screw that goes into a wall, our multilayer project can also guide and control the growth of dendrites”, says Professor Luhan Ye.
With this unprecedented strategy, the team led by Professor Xin Li was able to design a stable battery that can be charged and discharged more than 10,000 times. In general, a common lithium-ion battery can withstand between 300 and 600 charge and discharge cycles before it begins to lose its energy capacity.
A battery made of solid-state lithium metal could extend the life of electric vehicles to 10 or 15 years, a time very similar to that of gasoline-powered cars. Another advantage is that during this period it would not be necessary to replace the batteries.
Since solid-state batteries have a high current density, future electric-powered cars could have their cells fully charged in ten or 20 minutes, much less than the three or four hours of vehicles equipped with lithium-ion batteries. conventional.
In addition, the longevity of lithium metal batteries is guaranteed by their ability to regenerate. The chemistry used during the manufacturing process is able to fill the holes created by the dendrites, causing the cells to wear very little over time.
“This project shows that lithium metal solid-state batteries can be competitive with commercial lithium-ion batteries and the versatility of multilayers makes this design potentially compatible with current production lines in the battery industry,” adds the professor. Li.