Hydrothermal crystallization of Pmn21 Li2FeSiO4 hollow mesocrystals for Li-ion cathode application

摘要: Abstract Lithium transition metal orthosilicates such as Li2FeSiO4 (LFS) have been recognized promising cathode materials for application in Li-ion batteries because of their high theoretical energy density, safety, and benign/abundant element composition. Their development, however, has hampered by the challenge obtaining phase-pure defect-free nanoparticles non-optimized crystal properties an adverse effect on structural stability electrochemical performance. Considering sustainable potential hydrothermal synthesis producing electrode materials, here we employ this process to systematically study critical parameters optimal control particle size, morphology, phase purity, defects crystallized orthorhombic system with space group Pmn21. It is shown that via a combination elevated FeSO4 concentration regime use EDTA complexing agent, Pmn21 formation can be controlled. Synchrotron-based XRD Rietveld refinement 57Fe Mossbauer spectroscopy reveal significant reduction Li-Fe antisite presence Fe3+. Additionally, promotes unique peanut-shell looking hollow mesocrystals are advantageous maximizing electrode/electrolyte contact resulting higher storage capacity than dense LFS particles. On basis detailed XRD, SEM, TEM characterizations, four-step crystallization mechanism proposed explain mesocrystals. These findings bring new insight into our pursuit optimization material batteries.