Identifying the Distribution of Al³⁺ in LiNi_0.8Co_0.15Al_0.05O₂

Abstract

The doping of Al into layered Li transition metal (TM) oxide cathode materials, LiTMO 2 , is known to improve the structural and thermal stability, although the origin of the enhanced properties is not well understood. The effect of aluminum doping on layer stabilization has been investigated using a combination of techniques to measure the aluminum distribution in layered LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) over multiple length scales with 27 Al and 7 Li MAS NMR, local electrode atom probe (APT) tomography, X-ray and neutron diffraction, DFT, and SQUID magnetic susceptibility measurements. APT ion maps show a homogeneous distribution of Ni, Co, Al, and O 2 throughout the structure at the single particle level in agreement with the high-temperature phase diagram. 7 Li and 27 Al NMR indicates that the Ni 3+ ions undergo a dynamic Jahn−Teller (JT) distortion. 27 Al NMR spectra indicate that the Al reduces the strain associated with the JT distortion, by preferential electronic ordering of the JT lengthened bonds directed toward the Al 3+ ion. The ability to understand the complex atomic and orbital ordering around Al 3+ demonstrated in the current method will be useful for studying the local environment of Al 3+ in a range of transition metal oxide battery materials.

Revisiting the charge compensation mechanisms in LiNi0.8Co0.2−yAlyO2 systems

“…This gives a starting point for determining the relationship between the lithium content and the extent of TM and oxygen participation. We primarily focus on the widely reported NCA 1 compound, 6,[40][41][42][43]63 with similar characterization extended to the other Ni-rich systems given in ESI. †…”

Electrochemical behavior of Bi4B2O9towards lithium-reversible conversion reactions without nanosizing

“…Additionally, we observed a strong agglomeration of the Bi nanoparticles ( Figure 7c) after discharge to 1.0 V. Lastly, Bi particles could be also be spotted with SAED in the recharged 3.5 V sample ( Figure S7a evidenced yet due to their most likely nanocrystalline/amorphous nature, similar as observed in the case of transition metal borates. 26 As an attempt to circumvent this issue, Nuclear Magnetic Resonance (NMR), which is a suitable tool for probing local structures [27][28][29][30] and their evolvement upon electrochemical cycling was used taking advantage of the 7 Li nuclei. 31,32 Well-resolved 7 Li NMR measurements were performed for Bi 4 B 2 O 9 samples discharged to 1 V and 1.7 V prior to recharge each of them to 3.5 V as shown in Figure 8.…”

Aluminum-based materials for advanced battery systems

“…LMNCA also exhibited enhanced electron transfer rate constant and diffusion coefficient in comparison with that of the LMNC. Doping with Al provides more chances to improve the electrochemical property of the LMNC [159].…”