Tertiary-Amine Based Network Polymer Electrolyte for Improving the Cyclic Stability of Na Metal Batteries with Large Capacity

Polymer-based sodium metal battery (SMB) has a great development prospect due to its low cost, good safety, and high theoretical energy density. However, sodium (Na) metal electrode suffers low cyclic stability due to the naturally-formed unstable solid electrolyte interface (SEI). Herein, 3D network polymer, poly-bis(3-(2-methylaziridin-1-yl) propanoate (PBMP) is synthesized, for mechanically robust gel polymer electrolyte (GPE), in which the tertiary-amine functional group with low-valence N prefers to react with Na metal to produce a thin and ion-conducive SEI, realizing Na+ fast and uniform plating/stripping. The assembled Na/GPE/Na3V2(PO4)3 full battery shows an ultrahigh capacity retention of 97.8% after 2000 cycles under 2 mA cm-2, which is the top-level of GPE-SMB. This work provides a new strategy to construct advanced SEI by regulating functional groups of network polymer for GPE-SMBs with high safety. In the PBMP-based gel polymer electrolyte, a polymer and inorganic-rich SEI layer structure is constructed on Na metal to extraordinarily extend its cycle life to 6000 cycles, which is a new strategy to construct advanced SEI by a tertiary-amine functional group of network polymer with low-valence N. image