Insight into cations substitution on structural and electrochemical properties of nanostructured Li 2 FeSiO 4 /C cathodes

• Published in: Journal of the American Ceramic Society Vol. 103; no. 3; pp. 1685 - 1697
• Main Authors: Sivaraj, Pazhaniswamy, Abhilash, Karuthedath Parameswaran, Nalini, Balakrishnan, Selvin, Paneerselvam Christopher, Goel, Sunkulp, Yadav, Sudheer Kumar
• Format: Journal Article
• Language: English
• Published: 01.03.2020
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.16805

Abstract Structural instability is the major obstacle in the Li 2 FeSiO 4 /C cathode during charge and discharge process, which can be improved by the substitution of cations in the host cage. In this study, the transition metal ions with different valence (Ag 1+ , Zn 2+ , Cr 3+ , and Ti 4+ ) have been substituted in Li 2 FeSiO 4 /C via modified sol‐gel method and the impact on the structural, electrical, and electrochemical performances has been systematically explored. The Rietveld‐refined XRD pattern and HR‐TEM (SAED) result reveal that all the prepared samples maintain orthorhombic structure (S.G‐ Pmn 2 1 ). The FE‐SEM and TEM micrographs of bare and doped Li 2 FeSiO 4 /C display nanoparticle formation with 20‐40 nm size. Among different cation‐substituted silicates, Li 2 Fe 0.9 Ti 0.1 SiO 4 /C sample exhibits an excellent total conductivity of 1.20 × 10 −4  S cm −1 which is one order of magnitude higher than the bare Li 2 FeSiO 4 /C sample. The galvanostatic charge‐discharge curves and cyclic voltammetric analysis reveal that the Li 2 Fe 0.9 Ti 0.1 SiO 4 /C material provides an excellent initial specific capacity of 242 mAh g −1 and maintains a capacity of 226 mAh g −1 after 50 cycles with capacity retention of 93.38%. The Ti doping is a promising strategy to overcome the capacity fading issues, by preventing the structural collapse during Li‐ion intercalation/de‐intercalation processes in the Li 2 FeSiO 4 /C electrode through the strong hybridization between the 3 d and 4 s orbitals in titanium and 2 p orbital in oxygen.