Fast Lithium Ion Diffusion in the Ternary Layered Nitridometalate LiNiN

Abstract

The structure, Li+ diffusion dynamics, and magnetic properties of the layered nitridonickelate(II), LiNiN, have been investigated by powder X-ray diffraction, 7Li solid-state NMR, and SQUID magnetometry and compared and contrasted with those of the Li+ fast ion conductor, Li3N. The replacement of Li+ by Ni2+ with concomitant generation of Li+ vacancies has profound effects on ionic diffusion and electronic properties. The nitridonickelate, akin to its binary parent, displays rapid Li+ ion diffusion but, by contrast, the diffusion process is confined only to the Li-N planes. Further, replacement of Li by Ni leads to a transition from semiconducting to metallic behavior, likely mediated through the creation of infinite, 1D Ni-N chains of increased covalency.

Electronic structure and vacancy formation of Li3N

“…An increase in Li vacancy concentration corresponds to high Li ion mobility and thus high ionic conductivity. 21 The vacancy formation energy in the Li͑1͒ site is about 1.7 eV higher than that in the Li͑2͒ site. Therefore, removal of the lithium between the Li 2 N layers is a very energetically unfavorable process since the two nearly triply negative nitrogen ions would now be repelled by their own ionic charges and by the effective negative charge of V Li͑1͒ − vacancy.…”

Lithium nitrides as sustainable energy materials

“…In fact, LiNiN serves as an excellent model compound as one moves from the parent unsubstituted Li 3 N across a ternary solid solution (Li 3‐x‐y M x N) to a “fully substituted” ternary compound (where the Li layer has been completely replaced) 7. Li solid‐state NMR combined with diffraction methods is extremely useful in unraveling the structural changes as one progresses through this substitutional process, but, moreover, gives an intimate insight into the changes in Li + ionic diffusion behavior 45,46. Figure 4 gives an example of this local structural evolution and also reveals how the diffusion mechanisms change.…”

Enhanced H-storage property in Li–Co–N–H system by promoting ion migration

“…As well demonstrated, doping Li 3 N with transition metal produces defective Li 3−x−y M x N structure where transition metal partially and aliovalently replaces interlayer Li. As a result of the ensuing Li vacancies randomly distributed within [Li 2−y N] planes, Li + mobility is markedly improved as compared with parent Li 3 N [17][18][19]. Motivated by these findings as well as the ion migration model, we mechanically prepare Li 3−x−y Co x N samples and investigate their H-storage properties, especially in comparison with Li 3 N.…”

“…Closely related to this idea, the lithium (transition) metal nitrides Li 3−x−y M x N (M = Co, Ni and Cu, x = 0-0.6, y = vacancy) have been extensively investigated as promising anode materials in lithium secondary batteries [15][16][17][18][19]. As well demonstrated, doping Li 3 N with transition metal produces defective Li 3−x−y M x N structure where transition metal partially and aliovalently replaces interlayer Li.…”