Lithium-based batteries are one of the most common types of rechargeable battery used in modern electronics due to their ability to store high amounts of energy. Traditionally, these batteries are made of combustible liquid electrolytes and two electrodes — an anode and a cathode — that are separated by a membrane. After a battery has been charged and discharged repeatedly, strands of lithium called dendrites can grow on the surface of the electrode. The dendrites can pierce through the membrane that separates the two electrodes. This allows contact between the anode and cathode, which can cause the battery to short circuit and, in the worst case, catch fire.
One proposed solution to the volatile liquid electrolytes used in current batteries is to replace them with solid ceramic electrolytes. These electrolytes are highly conductive and non-combustible, and strong enough to resist dendrites. But the contact between the ceramic electrolyte and a solid lithium anode is insufficient for storing and supplying the amount of power needed for most electronics.
Researchers created a new class of material that can be used as a semi-liquid metal anode. The dual-conductive polymer/carbon composite matrix has lithium microparticles evenly distributed throughout. The matrix remains flowable at room temperature, which allows it to create a sufficient level of contact with the solid electrolyte. By combining the semi-liquid metal anode with a garnet-based solid ceramic electrolyte, the cell cycled at 10 times higher current density than cells with a solid electrolyte and a traditional lithium foil anode. This cell also had a much longer cycle life than traditional cells.
The method could be used to create high-capacity batteries for electric vehicles and specialized batteries for use in wearable devices that require flexible batteries. The methods could be extended beyond lithium to other rechargeable battery systems, including sodium metal batteries and potassium metal batteries, and could be used in grid-scale energy storage.