Synergistic dual-additive engineering in composite-polymer-electrolyte empowering long-lifespan all-solid-state Li–Se batteries

Abstract

In this study, we propose dual-additive engineering by introducing lithium nitrate (LiNO₃) and lithium difluorophosphate (LiDFP) into a composite-polymer-electrolyte (CPE) denoted as DA. This approach aims to simultaneously stabilize both the solid electrolyte interphase (SEI) and cathode electrolyte interface (CEI) layers in the newly developed all-solid-state lithium–selenium batteries (ASSLSeBs). These batteries are constructed by using a selenium-embedded carbon cathode (Se@MPC) and CPE. The comprehensive characterization studies of electrode|electrolyte interfaces including electrochemical symmetric/asymmetric cell analysis, potential-resolved in situ electrochemical impedance spectroscopy (PRIs-EIS), and ex situ X-ray photoelectron spectroscopy (XPS) precisely revealed the synergistic effect of LiNO₃ and LiDFP. This effect enables the formation of robust, inorganic-rich interfaces composed of Li₂O, Li₃N, LiF, and Li₃PO₄, which significantly enhance interfacial lithium-ion transport. As a result, dendritic growth and interface degradation are suppressed. The ASSLSeBs with the DA achieve an unprecedented lifespan of 3000 cycles at a high rate of 2C, with a decay rate of 0.001% per cycle. This work offers a promising guideline for interfacial engineering performed with an additive-based approach, paving the way for the design of high-performance all-solid-state batteries.