A defect-rich carbon induced built-in interfacial electric field accelerating ion-conduction towards superior-stable solid-state batteries†

The electrochemical performances of composite solid-state electrolytes (CSEs) cannot satisfy the application requirements of solid-state batteries (SSBs) due to the low concentration of movable cations with disordered and slow cation transportation. Herein, a designed CSE with a built-in interfacial electric field (D-CSE) is successfully constructed via defect engineering of electron-conducting carbon. The electrons would transfer and construct a built-in interfacial electric field (IEF) at the phase interface due to the different Fermi energy levels of the defect-rich carbon and polymer matrix. The built-in IEF would promote the dissociation of alkali-metal salts to release free cations and provide an extra driving force to boost the transportation of cations. Additionally, the defect-rich carbon could regulate the distribution of the electric field to enable rapid cation transfer. In terms of sodium, these coupling effects contribute to the high ionic conductivity (0.67 mS cm⁻¹) and transference number (0.77) of the D-CSE. Consequently, D-CSE-based solid-state sodium metal batteries exhibit remarkable cycling stability (0 °C, 80.9%, 500 cycles; 80 °C, 80.1%, 2500 cycles). This strategy of a built-in IEF broadens the perspective of achieving uniform and rapid ion transportation and paves the way for achieving superior-stable SSBs.