A Hydride Route to Ternary Alkali Metal Borides: A Case Study of Lithium Nickel Borides

Abstract

Ternary lithium nickel borides LiNi3B1.8 and Li2.8Ni16B8 have been synthesized by using reactive LiH as a precursor. This synthetic route allows better mixing of the precursor powders, thus facilitating rapid preparation of the alkali‐metal‐containing ternary borides. This method is suitable for “fast screening” of multicomponent systems comprised of elements with drastically different reactivities. The crystal structures of the compounds LiNi3B1.8 and Li2.8Ni16B8 have been re‐investigated by a combination of single‐crystal X‐ray/synchrotron powder diffraction, solid‐state 7Li and 11B NMR spectroscopies, and scanning transmission electron microscopy. This has allowed the determination of fine structural details, including the split position of Ni sites and the ordering of B vacancies. Field‐dependent and temperature‐dependent magnetization measurements are consistent with spin‐glass behavior for both samples.

Computationally Driven Discovery of a Family of Layered LiNiB Polymorphs

“…We have shown previously [10] that this route is feasible for the preparation of previously reported ternary lithium nickel borides using am ixable LiH precursor.I nt he case of the LiNi 3 B 1.8 phase,this route is considerably faster than the route based on an elemental Li metal precursor (annealing for 20 h vs.9 0days). We have shown previously [10] that this route is feasible for the preparation of previously reported ternary lithium nickel borides using am ixable LiH precursor.I nt he case of the LiNi 3 B 1.8 phase,this route is considerably faster than the route based on an elemental Li metal precursor (annealing for 20 h vs.9 0days).…”

“…[9,10] In Figure 1, all stable compounds are represented by solid red triangles,and metastable phases with formation energies above the convex hull are represented by hollow blue triangles.B esides the experimentally discovered and characterized LiNi 3 B 1.8 ,L i 2.8 Ni 16 B 8 ,a nd Li 3 Ni 20 B 6 phases, [9,10] the equiatomic LiNiB compound was predicted to be stable.T he possible existence of ac ompound with ac omposition similar to LiNiB was pointed out earlier by Jung,[9a] but no crystal structure was reported. [9,10] In Figure 1, all stable compounds are represented by solid red triangles,and metastable phases with formation energies above the convex hull are represented by hollow blue triangles.B esides the experimentally discovered and characterized LiNi 3 B 1.8 ,L i 2.8 Ni 16 B 8 ,a nd Li 3 Ni 20 B 6 phases, [9,10] the equiatomic LiNiB compound was predicted to be stable.T he possible existence of ac ompound with ac omposition similar to LiNiB was pointed out earlier by Jung,[9a] but no crystal structure was reported.…”

“…[8,10] TheNi 6 B 2 unit is found in the structure of binary Ni 2 Bboride (CuAl 2 structure type), whereas the Li layer is similar to that in Li metal (at room temperature cubic Li has the structure of W, whereas hexagonal Li is isostructural to Mg at low temperatures;s ee Figure S8). [8,10] TheNi 6 B 2 unit is found in the structure of binary Ni 2 Bboride (CuAl 2 structure type), whereas the Li layer is similar to that in Li metal (at room temperature cubic Li has the structure of W, whereas hexagonal Li is isostructural to Mg at low temperatures;s ee Figure S8).…”

“…Such slabs are randomly distributed and have az igzag arrangement of the projected Ni columns (single,d ouble,o rm ultiple;F igure 6c). [10] TheMAS 7 Li NMR spectrum of HT-LiNiB is distinct from that of RT-LiNiB.There are two 7 Li peaks with a2:1.9 ratio at approximately 55-65 ppm, two peaks at approximately 95 and 110 ppm with a1 .7:1 ratio,a nd an additional peak at approximately 0ppm (Figure 7; see also Figure S12). 7 Li and 11 Bmagic-angle spinning (MAS) solid-state NMR spectroscopy further shed light on the Li and Bcoordination environment in RT-LiNiB and HT-LiNiB structures (Figure 7).…”

“…Previously,weutilized alkali-metal hydrides AH(A = Li, Na, K) as mixable salt-like precursors for the fast experimental exploration of ternary systems containing alkali metals. [10,11] Herein, we report the computationally driven experimental discovery of two polymorphs of the novel transitionmetal boride LiNiB with au nique layered crystal structure. [10,11] Herein, we report the computationally driven experimental discovery of two polymorphs of the novel transitionmetal boride LiNiB with au nique layered crystal structure.…”