<p>High impedance caused by insufficient electrode/electrolyte interfacial compatibility has long been a core challenge for solid-state lithium metal batteries. To optimize the overall interfacial structure, a synergistic strategy must address both the positive and negative electrodes. In this study, a dual in situ cured solid-state polymer electrolyte (DIC-SPE) technique was developed through in situ curing of both the cathode/electrolyte and the lithium metal anode/electrolyte interface. The prepared solid-state electrolyte exhibits an ionic conductivity of 0.12 mS·cm⁻¹ and an electrochemical stability window as high as 5.0&#xa0;V. The as-assembled lithium symmetric battery achieves stable cycling for 400&#xa0;h at a current density of 0.2&#xa0;mA·cm⁻², indicating a favorable suppression for lithium dendrite growth due to the in situ cured anode/solid electrolyte surface. Rate performance and long-cycle tests demonstrate that the LFP/DIC-SPE/Li battery exhibits superior stability compared to ex situ preparation processes: At 30&#xa0;°C, DIC-SPE cell maintains 81.1% capacity retention after 400 cycles at 0.5 C and 91.7% capacity retention after 200 cycles at 1 C. The dual in situ solid-state electrolyte preparation strategy proposed in this study provides a new technical pathway for the development of high-performance and cycling stability solid-state lithium batteries.</p> Graphical Abstract <p></p>