Full picture discovery for mixed-fluorine anion effects on high-voltage spinel lithium nickel manganese oxide cathodes

Abstract

Small amounts of fluorine substituting for oxygen deficiencies could reduce Mn dissolution, enhancing the cyclability in spinel-type lithium nickel manganese oxides (LiNi 0.5 Mn 1.5 O 4). Fluorine anion incorporation simultaneously enhances the Crate capability and specific capacity fading. We used experimental and theoretical approaches to obtain a full picture of the mixedanion effects for LiNi 0.5 Mn 1.5 O 4 − x F x cathode materials. The fluorine anion reduced the activation barrier for lithium-ion hopping along the most energetically preferable 8a-16c-8a route, enhancing the Crate capability. Simultaneously, the coordination bond of the linear F −-Mn 3+-F − (Mn@2F diagonal) arrangement increased the oxidation potential to 5.1 V (vs Li + /Li). This hampered full extraction of Li + from the spinel lattice, which was triggered by the oxidation of Mn 3+ below the cutoff voltage (3.5-4.8 V (vs Li + /Li)), leading to a capacity loss.

Fluorine-Doped LiNi0.8Mn0.1Co0.1O2 Cathode for High-Performance Lithium-Ion Batteries

“…To investigate the replacement of oxygen with Fions at the oxygen sites, XPS analysis was performed ( Figure 3 and Figure S1). In the O1s spectra, the characteristic peaks at 528-530 and 531-533 eV correspond to bonds between the transition metal (M) and oxygen and oxygen vacancies, respectively (Figure 3a (Table S2) [32][33][34][35]. Furthermore, the Ni2p spectrum of NCMF consisted of characteristic peaks at 854-856 and 858-859 eV, which corresponded to Ni−O and M−F bonds, respectively ( Figure 3b).…”

Synthesis, Modification, and Lithium‐Storage Properties of Spinel LiNi0.5Mn1.5O4

“…The molten salt method is a facile preparation method based on low melting point salt, which can be applied to prepare pure phase LNMO cathode material. Kim et al [71] . prepared LNMO 4‐ δ by the LiCl‐KCl flux growth method, and the LNMO 4‐ δ crystals were then reacted with LiF in KCl flux (800 °C, 20 hours) at different LiF concentrations to obtain LNMOF samples with different fluorine substitution amounts (Figure 6a–d).…”

“…Compared with cation doping, anion doping can avoid occupying the sites of Li and TM, and effectively reduce the dissolution of surface Li and TM [106] . F‐doping LNMO can play a certain role in stabilizing the spinel structure [107] by inhibiting the generation of impurities such as NiO, effectively retarding the polarization phenomenon, thereby reducing the energy loss caused by polarization and material resistance to electrolytes [71] . Kim et al [71] ,.…”

“…F‐doping LNMO can play a certain role in stabilizing the spinel structure [107] by inhibiting the generation of impurities such as NiO, effectively retarding the polarization phenomenon, thereby reducing the energy loss caused by polarization and material resistance to electrolytes [71] . Kim et al [71] ,. with experimental and theoretical methods, studied the mixed anion effect of LiNi 0.5 Mn 1.5 O 4− x F x cathode materials.…”

Molecular gate effects observed in fluoroalkylsilane self-assembled monolayers grafted on LiNi0.5Mn1.5O4cathodes: an application to efficient ion-exchange reactions

“…Furthermore, the insertion of small quantities of transition metal substitutes, such as Zr, 17 Al, 18 Zn, 19 and Cu, 19 in transition metal sites increased the local electron density and lattice strength, thereby effectively suppressing the Mn dissolution and improving the cycle life of the battery. In addition to the benefit of cation substitution analogies, multianion systems further enhanced battery performances owing to the F-doped 20 and S-doped 21 LNMO surface. Utilizing multiple anions with different electronegativities and polarizabilities as compared to those of oxides, facilitates the excellent controllability of chemical bonds and electronic structures to offer unique coordination and crystal structures.…”