Researchers at the Karlsruhe Technology Institute and the Helmholtz Institute Ulm (HIU) have developed a new lithium-metal battery that offers a specific energy of 560 Wh/kg with good stability.
The researchers used a low-cobalt, nickel-rich layered cathode (NCM88), which offers high energy density. With the commonly used organic electrolyte LP30, however, the stability is unacceptable. The researchers instead used a non-volatile, non-flammable ionic liquid electrolyte with two anions. With the NCM88 cathode and the liquid electrolyte, the lithium-metal battery initially has a storage capacity of 214 mAh/g, and 88% of the capacity is retained over 1,000 charging cycles. The Coulombic efficiency, which indicates the ratio between the withdrawn and supplied capacity, averages 99.94%.
“In the LP30 electrolyte, particle cracks occur on the cathode. The electrolyte reacts within these cracks and destroys the structure. In addition, a thick, moss-like lithium-containing layer forms on the anode,” says Stefano Passerini, Director of the HIU. The article Dual-anion ionic liquid electrolyte enables stable Ni-rich cathodes in lithium-metal batteries summarizing the research was published in the research journal Joule.