Path Less Traveled: A Contemporary Twist on Synthesis and Traditional Structure Solution of Metastable LiNi₁₂B₈

Abstract

Achieving kinetic control to synthesize metastable compounds is a challenging task, especially in solid-state reactions where the diffusion is slow. Another challenge is the unambiguous crystal structure determination for metastable compounds when high-quality single crystals suitable for single-crystal X-ray diffraction are inaccessible. In this work, we report an unconventional means of synthesis and an effective strategy to solve the crystal structure of an unprecedented metastable compound LiNi12B8. This compound can only be produced upon heating a metastable layered boride, HT-Li0.4NiB (HT: high temperature), in a sealed niobium container. A conventional heating and annealing of elements do not yield the title compound, which is consistent with the metastable nature of LiNi12B8. The process to crystallize this compound is sensitive to the annealing temperature and dwelling time, a testament to the complex kinetics involved in the formation of the product. The unavailability of crystals suitable for single-crystal X-ray diffraction experiments prompted solving the crystal structure from high-resolution synchrotron powder X-ray diffraction data. This compound crystallizes in a new structure type with space group I4/mmm (a = 10.55673(9) Å, c = 10.00982(8) Å, V = 1115.54(3) Å3, Z = 6). The resulting complex crystal structure of LiNi12B8 is confirmed by scanning transmission electron microscopy and solid-state 11B and 7Li NMR spectroscopy analyses. The extended Ni framework with Li/Ni disorder in its crystal structure resulted in the spin-glass or cluster glass type magnetic ordering below 24 K. This report illustrates a “contemporary twist” to traditional methodologies toward synthesizing a metastable compound and provides a recipe for solving structures by combining the complementary characterization techniques in the cases where the traditionally used single-crystal X-ray diffraction method is nonapplicable.

Layered Li–Co–B as a Low-Potential Anode for Lithium-Ion Batteries

“…14,15 However, in the LiNiB delithiation experiments, only about 50% of Li can be removed from the parent structure before irreversible phase transition happened in layered Ni−B structures. 9,11,16 Therefore, LiNiB as the electrode material of LIBs did not have high capacity.…”

“…A variety of new materials have been predicted based on these algorithms, many of which further have been successfully synthesized by subsequent experiments. An example closely related to lithium-ion batteries (LIBs) is LiNiB. − Using the adaptive genetic algorithm (AGA), , one of the evolutionary algorithms, the LiNiB family of lithium-rich nickel boride polymorphs with a new layered structure were theoretically predicted and further synthesized by using salt-like LiH as a precursor . Theoretical calculation studies found that layered LiNiB had a lower voltage platform than graphite and had the potential as a high-performance anode material for LIBs because layered materials significantly shorten the ion diffusion length, accelerating the reaction kinetics, and have high mechanical strength, structural integrity, and stability during charging/discharging. , However, in the LiNiB delithiation experiments, only about 50% of Li can be removed from the parent structure before irreversible phase transition happened in layered Ni–B structures. ,, Therefore, LiNiB as the electrode material of LIBs did not have high capacity.…”

Breaking New Ground: MBene Route toward Selective Vinyl Double Bond Hydrogenation in Nitroarenes

“…Mixing of Li and Ni in the same crystallographic sites has also been observed in another compound in the Li–Ni–B systemLiNi 12 B 8 . In that case, in addition to two fully occupied Li sites, 5 Li/Ni mixed occupied sites were confirmed by solid-state 7 Li NMR . Mixing of Li sites with other transition metals, particularly with Mn, Co, and Ni, was also observed in layered oxide cathodes for lithium-ion batteries …”

“…We corrected data for a trace amount of ferromagnetic impurity using the Honda-Owen method , and obtained intrinsic M/H ( T ) that was fitted with the modified Curie–Weiss equation, χ = χ 0 + C /( T – Θ ) (Table S4, Figure , Figure S19). Such analysis yielded an effective moment of 0.1–0.2 μ B per transition metal in Li 0.01 Ni 0.7 Co 0.3 B, which is comparable to the effective moment per Ni atom in other Li–Ni–B compounds with a spin glass-like state below 30 K. , On the other hand, the contribution of the temperature-independent term (χ 0 ) in the case of Li 0.01 Ni 0.7 Co 0.3 B is negligible, while the Weiss constant, Θ , approaches 0. In summary, the magnetic properties of Li 0.04 Ni 0.7 Co 0.3 B and Li 0.01 Ni 0.7 Co 0.3 B with a CoB-like structure differ from nonmoment bearing CoB and NiB and resemble those of HT -Li 0.4 NiB with a potential low-temperature magnetic transition and a small effective moment per transition metal.…”

“…Upon prolonged exposure to air, the latter compounds convert into novel layered borides RT -Li 0.6 NiB and HT -Li 0.4 NiB, whose structures consist of randomly distributed atomically ordered substructures Li­[NiB] n ( n = 1, 2, 3). Upon further heating in a sealed niobium container, HT -Li 0.4 NiB transforms into another novel metastable boride: LiNi 12 B 8 , the synthesis of which is sensitive to slight changes in dwelling temperature and annealing time. Magnetic property measurements revealed that the 4 parent compounds ( RT -LiNiB, HT -LiNiB, RT -Li 1+x NiB, and HT -Li 1+y NiB) are temperature-independent paramagnets, while the 3 metastable borides RT -Li 0.6 NiB, HT -Li 0.4 NiB, and LiNi 12 B 8 exhibit spin-glass like behavior at low temperatures. − , Therefore, we were interested in how the substitution of Ni for Co affects the topology of the [NiB] layers, electronic structure, and resulting magnetic properties.…”