Lithium metal batteries promise significantly more energy storage than today's standard lithium-ion cells, but they have long struggled with a stubborn problem: the electrolyte solution that shuttles lithium ions back and forth tends to break down during charging, especially at high voltages. That breakdown shortens battery life and limits how these cells can be used in practice.
A study published in Nature describes a new approach to this problem. Researchers built an electrolyte containing what they call a targeted ligand anti-solvent, or TLAS, added to an ether-based electrolyte that is already rich in anions. Ether-based electrolytes have previously shown promise for lithium metal electrodes, but they suffer during the charging of high-voltage full cells, when solvent and anion molecules must detach from lithium ions released by the positive electrode. This detachment process accelerates the oxidative breakdown of the electrolyte, and repeated cycling further consumes electrolyte components, steadily degrading the battery's chemical stability.
How the new electrolyte behaves differently
According to the researchers, the TLAS molecule largely stays out of the way under normal, static conditions, since it associates only weakly with lithium ions. But under the strong electric field generated inside a high-voltage full cell, the orientation and distribution of the TLAS molecules change substantially, and their ability to coordinate with lithium ions becomes active specifically at the surface of the positive electrode.
This dynamic behavior allows the electrolyte to bypass the usual cycle of solvent and anion molecules detaching and reattaching at the positive electrode, a process that in conventional electrolytes drives much of the degradation. By avoiding this repeated reconstruction, the new electrolyte reduces deterioration of the interphase layer that forms between the electrode and electrolyte.
Performance results
Using this gradient solvation electrolyte, the team built a lithium metal pouch cell with an energy density of 450 watt-hours per kilogram that sustained more than 750 charge cycles while retaining 80% of its original capacity. In a separate test, a cell with a higher energy density of 605 watt-hours per kilogram achieved 150 cycles while retaining 96% of its capacity.
The researchers describe the gradient solvation strategy as a feasible pathway for electrolyte engineering more broadly in metal-ion batteries, suggesting the approach could extend beyond lithium metal systems. The full datasets underlying the study are included with the published article and its supplementary information, with additional data available from the corresponding author on request.