Dynamic Structure Evolution of Extensively Delithiated High Voltage Spinel Li.sub.1+x./sub.Ni.sub.0.5./sub.Mn.sub.1.5./sub.O.sub.4./sub.x < 1.5

0570288 - ÚJF 2024 RIV US eng J - Journal Article
Jobst, N. M. - Paul, N. - Beran, Přemysl - Mancini, M. - Wohlfahrt-Mehrens, M. - Axmann, P.
Dynamic Structure Evolution of Extensively Delithiated High Voltage Spinel Li_1+xNi_0.5Mn_1.5O₄x < 1.5.
Journal of the American Chemical Society. Roč. 145, č. 8 (2023), s. 4450-4461. ISSN 0002-7863. E-ISSN 1520-5126
Research Infrastructure: CICRR - 90241
Institutional support: RVO:61389005
Keywords : compounds * neutron diffraction * entropy method
OECD category: Materials engineering
Impact factor: 15, year: 2022
Method of publishing: Limited access
https://doi.org/10.1021/jacs.2c09621

High voltage spinel is one of the most promising next-generation cobalt-free cathode materials for lithium ion battery applications. Besides the typically utilized compositional range of LixNi0.5Mn1.5O4 0 < x < 1 in the voltage window of 4.90-3.00 V, additional 1.5 mol of Li per formula unit can be introduced into the structure, in an extended voltage range to 1.50 V. Theoretically, this leads to significant increase of the specific energy from 690 to 1190 Wh/kg. However, utilization of the extended potential window leads to rapid capacity fading and voltage polarization that lack a comprehensive explanation. In this work, we conducted potentiostatic entropymetry, operando XRD and neutron diffraction on the ordered stoichiometric spinel LixNi0.5Mn1.5O4 within 0 < x < 2.5 in order to understand the dynamic structure evolution and correlate it with the voltage profile. During the two-phase reaction from cubic (x < 1) to tetragonal (x > 1) phase at similar to 2.8 V, we identified the evolution of a second tetragonal phase with x > 2. The structural evaluation during the delithiation indicates the formation of an intermediate phase with cubic symmetry at a lithium content of x = 1.5. Evaluation of neutron diffraction data, with maximum entropy method, of the highly lithiated phase LixNi0.5Mn1.5O4 with 2 < x < 2.5 strongly suggests that lithium ions are located on octahedral 8a and tetrahedral 4a positions of the distorted tetragonal phase I41amd. Consequently, we were able to provide a conclusive explanation for the additional voltage step at 2.10 V, the sloping voltage profile below 1.80 V, and the additional voltage step at similar to 3.80 V.
Permanent Link: https://hdl.handle.net/11104/0341568