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⁺ ( $V_{{\mathrm{Li}}^{+}}$ ) in the polymer electrolyte. By weakening Li-O coordination structure, the as-produced high- $V_{{\mathrm{Li}}^{+}}$ polymer electrolyte (108.5 cm³ mol^-1) shows 83% decrease in ∆µ (289 J mol^-1) 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[Ni_0.5Co_0.3Mn_0.2]O₂ cell with capacity of 0.62 Ah delivers excellent cycle stability with negligible capacity attenuation over 85 cycles at 0.2 C. The beneficial role of high $V_{{\mathrm{Li}}^{+}}$ 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.