Solvation Structure-Tunable Phase Change Electrolyte for Stable Lithium Metal Batteries

Li⁺ solvation structure (LSS) is considered to be the decisive factor in determining the electrochemical performance of lithium metal batteries. Herein, we propose a phase change electrolyte (PCE) whose LSS can be in operando regulated by changing the physical state of the electrolyte. The primary solvent of a PCE is dimethyl dodecanedioate (DDCA), which stands out among a series of solvents, exhibiting excellent comprehensive performance. The PCE shows high ionic conductivity, lithium transference number, and a wide electrochemical stability window in the solid and liquid states. Moreover, the LSS of the obtained PCE can reversibly transform between the solvent-separated ion pair (SSIP) and contact ion pair (CIP) structure according to its physical state. This characteristic enables PCE to outperform conventional liquid electrolytes in suppressing lithium dendrite growth and dissolution of active anodic materials, especially at varying temperatures. The assembled Li-LiMn₂O₄ full cells display outstanding electrochemical performance, high Coulombic efficiency, and capacity retention.