Structure Solution of Metal-Oxide Li Battery Cathodes from Simulated Annealing and Lithium NMR Spectroscopy

Abstract

Discerning the arrangement of transition metal atoms in Li[Ni x Mn y Co z O 2 ] cathode materials has remained an open problem for many years despite the commercial importance of some stoichiometries and the even more promising characteristics of others. We present a method for structural determination in this class of cathode materials. A simple definition of the total energy, based on the chemical principle of electroneutrality, is used in combination with a simulated annealing algorithm to generate model structures. The method reproduces the well known structure of Li[Li 1/3 Mn 2/3 O 2 ] and produces structures of the disordered Li[Ni x Mn x Co 1-2x O 2 ] phases (where x = 0.02, 0.1, 0.33) that are verified by detailed 7 Li NMR spectra. For each Li[Ni x Mn x Co 1-2x O 2 ] phase, the solution is found to be heavily disordered, yet retaining significant ion pairing. Since the underlying notion of favoring charge-neutral regions is generic, we anticipate its utility in a much broader family of materials.

Evolution of Structure and Lithium Dynamics in LiNi0.8Mn0.1Co0.1O2 (NMC811) Cathodes during Electrochemical Cycling

“…Deviations may result from partial ordering of TM ions within their layers, arising from the occurrence of Ni 2+ −Mn 4+ pairs or larger clusters of certain TM ions as described for related NMC materials. 30,33 In order to calculate the spectra in the case of mobile lithium ions for x > 0.1, a formula given by Norris was employed. 24 It allows rapid computation of chemical exchange line shapes even when several hundred sites are involved, under the assumption that all Li sites participate in the exchange and that the same hopping rate occurs between all sites.…”

Challenges in Developing Electrodes, Electrolytes, and Diagnostics Tools to Understand and Advance Sodium‐Ion Batteries

“…[490][491][492][493] Together with electrochemical devices, solid-state NMR spectroscopy can track dynamic processes for both crystalline and amorphous electrode materials during the electrochemical process. 485,[494][495][496][497][498][499][500][501][502][503][504][505][506][507][508][509][510][511][512] Atoms with a nuclear spin I≠0 possess a magnetic moment and are, in principle, detectable by NMR spectroscopy. Although Na 23 NMR is usually conducted in SIBs systems, many other nuclei (e.g., I=1/2 isotopes like 1 H, 13 C, 19 F, 29 Si, 31 P, and 119 Sn as well as quadrupolar nuclei with I > 1/2 like 2 H, 17 O, 25 Mg, 27 Al, 33 S, 39 K, 43 Ca, 51 V, and 67 Zn) can also provide useful insights.…”

Charge transport modelling of Lithium-ion batteries

“…Many authors including [38,77,84] discuss the challenges associated with formulating mathematical models that couple phenomena occurring at vastly disparate lengthscales. There is also current impetus to experimentally characterise and develop new modelling approaches to better understand chemical structure within electrode materials [44,52], mechanical and thermal effects [72], chemical degradation [7,67,71,85,100], and to also develop battery management systems to optimally control batteries for use in electric vehicles [53,62].…”