The battery is based on a low-cobalt, nickel-rich layered cathode called NCM88, which scientists say provides higher energy density and better stability compared to commercially available organic electrolytes called LP30. HIU Professor Stefano Passerini explained: "In LP30 electrolyte, particle cracks appear on the cathode. The electrolyte reacts in these cracks, disrupting the structure and forming a thick, moss-like lithium-containing layer on the cathode."
According to the researchers, this reaction negatively impacts battery stability and is currently a major obstacle to its technological and commercial maturity. To address this issue, they used a low-volatility and non-flammable ionic liquid electrolyte (ILE) containing two anions: bis(fluorosulfonyl)imide (FSI) and bis(trifluoromethanesulfonyl)imide (TFSI).
They further explained that the combination of the new cathode and electrolyte facilitates the formation of a cathode electrolyte interphase (CEI) layer within the electrolyte. This layer protects the NCM88 surface from harmful reactions with the electrolyte itself, thus preventing the formation of microcracks. This dual-anion electrolyte also reportedly demonstrates compatibility with lithium metal and the high-voltage cathode material used in the device.
This electrolyte achieves an initial specific capacity of 214 mAh g⁻¹ and retains an excellent 88% capacity over 1000 cycles, with an average coulombic efficiency of 99.94%. The research team further noted that the new electrolyte configuration significantly reduces structural changes in the nickel-rich cathode. Coulombic efficiency refers to the ratio of discharge capacity to charge capacity within the same cycle.
All the details about this battery can be found in the paper "Dual anionic liquid electrolyte stabilizes nickel-rich cathodes in lithium metal batteries" recently published in the journal Joule.
