Electron Beam Modification of Solid Polymer Electrolytes for Solid-State Lithium Metal Batteries

Solid polymer electrolytes (SPEs) offer flexibility and processability but suffer from low ionic conductivity and inadequate mechanical strength. Here, a facile, solvent-free electron beam (EB) irradiation method is introduced to modify poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (PDADMATFSI)-based SPEs for lithium metal batteries. At an optimal dose, EB irradiation simultaneously generates polar carbonyl groups and induces a crosslinked network. The carbonyl groups facilitate lithium-ion transport and contribute to forming a robust, Li₂O-rich solid electrolyte interphase. Concurrently, the crosslinked architecture enhances mechanical integrity and suppresses the growth of lithium dendrites. As a result, Young's modulus increases from 170 to 921 MPa, ionic conductivity rises from 4.7 × 10^-4 to 8.2 × 10^-4 S cm^-1, the lithium-ion transference number (t_Li ⁺) improves from 0.29 to 0.48, and the dielectric constant increases from 6.5 to 16.6. Consequently, Li||Li symmetric cells with modified SPE cycle stably for 2000 h (0.05 mA cm^-2), 600 h (0.1 mA cm^-2), and 180 h (0.2 mA cm^-2), with a critical current density of 1.1 mA cm^-2. Li||NCM811 (LiNi_0.8Co_0.1Mn_0.1O₂) full cells deliver 83.7% capacity retention after 300 cycles at 1C and superior rate performance. This work demonstrates that EB irradiation is a promising and effective strategy for developing high-performance solid-state lithium metal batteries.