High Partial Molar Volume Polymer Electrolyte for Upgraded Lithium Metal Batteries

Lithium (Li) metal batteries combined with solid electrolytes represent a highly promising technology for high‐energy‐density storage systems. However, their cycling performance encounters inferior stability due to the continuous growth of Li‐dendrites. The initial motivation for Li‐dendrite growth theoretically arises from the high chemical potential difference (∆μ) at the electrolyte/Li metal interface, yet the effectiveness of ∆μ regulation lacks experimental validation. Here, we experimentally present the impact of ∆μ on the growth of Li‐dendrites through manipulation of the partial molar volume of Li+ (V_(Li^+ )) in the polymer electrolyte. By weakening Li‐O coordination structure, the as‐produced high‐V_(Li^+ ) polymer electrolyte (108.5 cm3/mol) shows 83% decrease in ∆μ (289 J/mol) compared with conventional counterparts, thereby enabling stable cycling for >10 months in a Li||Li cell and >2000 cycles in a Li||Cu cell with an average Coulombic efficiency (CE) of 96%. To one's delight, a practical cylindrical Li||Li[Ni0.5Co0.3Mn0.2]O2 cell with capacity of 0.62 Ah delivers excellent cycle stability with negligible capacity attenuation over 95 cycles at 0.2 C. The beneficial role of high V_(Li^+ ) is leveraged to introduce a new dimension in polymer electrolyte engineering, highlighting the underexplored design strategy of regulating interfacial ∆μ to rejuvenate practical lithium metal batteries.