Enhanced electrochemical performance of Li-CO₂ batteries enabled by MWCNT/Ru catalyst and NASICON-type LASTP solid electrolyte

The use of conventional Li-CO₂ batteries (LCBs) is limited by high charge overpotentials for Li₂CO₃ decomposition, cathode passivation by these insulating products, and safety and stability risks posed by traditional liquid electrolytes. To address these limitations, this paper reports the synthesis and evaluation of a Ru-decorated multi-walled carbon nanotube (MWCNT/Ru) cathode combined with a Si-doped NASICON-type LiAlSiTi(PO₄)₃ (LASTP) solid electrolyte for enhancing the performance of LCBs. The MWCNT/Ru composite was synthesized using a wet-chemical method, producing uniformly dispersed metallic Ru nanoparticles. The LASTP electrolyte, synthesized via a solution-based method, exhibited a dense, crack-free microstructure with high ionic conductivity (1.07 × 10^–3 S/cm) and robust structural integrity and chemical stability for Li. Electrochemical evaluations confirmed exceptional battery performance, with a discharge capacity of 32,168 mAh g⁻¹ and stable cycling over 380 cycles at a high current density of 200 mA g⁻¹, highlighting the synergistic effects of the Ru catalyst and LASTP electrolyte. Post-cycling characterizations verified the integrity of the cathode surface and its overall state and confirmed the highly reversible formation and decomposition of Li₂CO₃. The proposed integrated cathode–electrolyte design effectively addresses the aforementioned challenges of traditional LCBs, offering a promising pathway toward practical, high-performance energy-storage solutions.