Lithium intercalation mechanisms and critical role of multi-doping in LiFexMn2−x−yTiyO4 as high-capacity cathode material for lithium-ion batteries. Issue 23 (19th May 2022)

• Record Type: Journal Article
• Authors: Callegari, D.; Coduri, M.; Fracchia, M.; Ghigna, P.; Braglia, L.; Anselmi Tamburini, U.; Quartarone, E.
• Is Part Of: Journal of materials chemistry. Volume 10:Issue 23(2022)
• Page Start: 8994
• Page End: 9008
• Publication Date: 2022-05-19
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d2tc00573e
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Novel dual-doping strategy for LMO based on partial substitution of Mn with Fe and Ti to design new CAMs for high-capacity cathodes. The cation disordering substitution of Mn allows cycling in a wide V range, higher capacity and improved stability. Abstract : The ever-growing demand for Li-ion batteries requires high-capacity electrode materials that should also be environmentally benign, Co-free, secure and durable, to achieve an optimal compromise between sustainability and functional performances. Spinel LiMn2 O4 (LMO) is a state-of-the-art material, which, in principle, could satisfy such requirements. However, an undesired cubic–tetragonal phase transition favors Jahn–Teller (J–T) spinel distortion, leading to severe capacity reduction upon cycling below 3 V. Here, we propose a novel dual-doping strategy for LMO, based on the partial substitution of Mn(iii ) with Fe(iii ) and Ti(iv ) to design new active materials for high-capacity cathodes, namely LiFe x Mn2− x − y Ti y O4 (LFMT), with Li/Mn ratio ranging between 1 and 1.7. The substitution of Mn with Fe and Ti suppresses the J–T distortion, which is often still evident in the case of Ti-doped LMO. This allows cycling in a wider voltage range (4.8–1.5 V), thus resulting in higher capacity and significantly improved stability. The lithiation mechanisms were investigated by combining ex situ X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS analyses). It demonstrated that the only redox-active metal is Mn, while Fe and Ti are electrochemically inactive. The extensive electrochemical lithiation/delithiation of the LFMT compositions brought unprecedented results, which give evidence of stabilizing cation disorder through the formation of Mn-rich and Mn-poor domains, leading to two spinel phases with different Mn:Ti ratios. These insights into the lithiation mechanism pave the way for a better understanding of the doping chemistry and electrochemistry of Mn-based spinels as cathode materials for Li-ion batteries.