Si-doped NASICON-type Li1.4Al0.4Ti1.6(PO4)3 solid electrolytes for enhanced stability and performance of Li-CO2 batteries

• Published in: Journal of alloys and compounds 2025-01, Vol.1010, p.177722, Article 177722
• Main Authors: Yu, Dohyeon, Na, Dan, Kim, Hwan, Son, Dong Ick, Lee, David D., Seo, Inseok
• Format: Article
• Language: English
• Subjects: Inorganic solid electrolyte; Li-CO2 battery; NASICON; Si doped
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2024.177722

Li-CO2 batteries (LCBs) have attracted significant research interest owing to their potential as energy storage devices and their contribution to carbon neutrality. In this study, we synthesized a solid electrolyte using Si-doped Li1.4Al0.4Ti1.6(PO4)3 (LASTP), by incorporating Si into the NASICON-structured LATP. Through Si doping, P in the tetrahedral PO4 units within the NASICON framework is substituted with Si, and bridging oxygen bonds are formed after high-temperature heat treatment The LASTP powder synthesized via a solution-based method exhibited uniform particle size and composition, and the resulting pellet achieved high densification and the formation of interconnected structures. The pellet exhibited an ionic conductivity of approximately 8.8 × 10−4 S/cm at 25℃. The LCB utilizing LASTP demonstrated a maximum discharge capacity of 23,887 mAh/g and successfully operated for 200 cycles at a current density of 100 mA/g with a cut-off capacity of 500 mAh/g. The post-cycling analysis of the cathode confirmed the reversible reactions of the LCB. Additionally, comparative post-cycling XPS analysis of LATP and LASTP revealed that Si doping in LASTP mitigated the reduction of Ti4+ to Ti3+, thereby enhancing the chemical stability of the solid electrolyte. Also, the structural stability of the solid electrolyte was enhanced owing to the formation of new bonds, surpassing the cycle performance and full-depth capacity of LCBs using conventional solid electrolytes. The introduction of structurally and chemically stabilized LASTP enabled the realization of long-lasting, high-capacity LCBs. [Display omitted] •Li-CO2 battery developed with Si-doped Li1.4Al0.4Ti1.6(PO4)3 solid electrolyte.•The ionic conductivity of LASTP is 8.8 × 10−4 S/cm.•Bridging oxygen bonds formed during sintering enhance structural stability.•Si doping mitigates the reduction of Ti4+ to Ti3+ within the NASICON structure.•LASTP battery demonstrates 23,887 mAh/g capacity and 200 cycles at 100 mA/g.