Novel Mn2+-doped NASICON glass-ceramic electrolyte with engineered columnar microstructure for high lithium-ion conductivity

Abstract

Glass-ceramic electrolytes are poised to revolutionize energy storage as breakthrough candidates for next-generation all-solid-state lithium batteries. This study introduces a high-performance and new Mn-doped NASICON-type (Li1.2Mn0.1Ti1.9(PO4)3) phase within a glass-ceramic electrolyte, synthesized via a melt-quenching and crystallization protocol. Crystallization analysis reveals a surface-to-bulk phase transformation via a one-dimensional nucleation process, with a low activation energy of 161.68 kJ.mol-1, enabling a Li-enriched NASICON matrix at reduced temperatures. Structural characterization through Rietveld-refined XRD, and 7Li and 31P MAS NMR spectroscopy, verified Mn2+ substitution within the crystal lattice, causing bottleneck size expansion and weakened Li+-O bonding, enhancing ion mobility. FT-IR and Raman spectra further confirm the successful formation of the Li-rich NASICON phase. SEM/TEM imaging revealed a unique columnar grain morphology that reduces grain boundary areas and porosity, while the residual glass phase (11.2%) enhances interfacial Li⁺ transfer. The optimized LMnTP-0GC composition (30Li2O-20TiO2-20MnO-30P2O5) delivered high-ionic conductivity (2.73×10-4 S.cm-1at RT), low electronic leakage (3.425×10-8 S.cm-1), and near-unity Li⁺ transference number (0.9998) outperforming undoped LiTi2(PO4)3 and Mn-enriched counterparts. The Li|LMnTP-0GC|Li cell achieves 2 mA.cm-2 CCD and stable cycling for 200 h, while the Li|LMnTP-0GC|LFP cell delivers 130.00 mAh.g-1 with 96.40% retention after 50 cycles at 0.1C