Topotactic Two-Phase Reactions of Li[Ni[sub 1/2]Mn[sub 3/2]]O[sub 4] (P4[sub 3]32) in Nonaqueous Lithium Cells

Abstract

Li͓Ni 1/2 Mn 3/2 ͔O 4 was prepared by a two-step solid state reaction and characterized by X-ray diffraction ͑XRD͒, infrared ͑IR͒-Raman, and electron diffraction ͑ED͒. Li͓Ni 1/2 Mn 3/2 ͔O 4 having characteristic eight absorption bands in 400-800 cm Ϫ1 in IR spectrum, extra lines in XRD, and extra spots in ED was analyzed in terms of a superlattice structure. Analytical results on the structural data indicated that Li͓Ni 1/2 Mn 3/2 ͔O 4 ͑cubic: a ϭ 8.167 Å) was a superlattice structure based on a spinel framework structure having a space group of P4 3 32 ͑or P4 1 32) in which nickel ions were located at the octahedral 4͑b͒ sites, manganese ions were at the octahedral 12͑d͒ sites, and lithium ions were at the 8͑c͒ sites in a cubic-close packed oxygen array consisting of the 8͑c͒ and 24͑e͒ sites. Well-defined Li͓Ni 1/2 Mn 3/2 ͔O 4 was examined in nonaqueous lithium cells and showed that the cell exhibited extremely flat operating voltage of about 4.7 V with rechargeable capacity of 135 mAh/g based on the sample weight. The reaction mechanism of Li͓Ni 1/2 Mn 3/2 ͔O 4 was examined and shown that the reaction at ca. 4.7 V consisted of two cubic/cubic two-phase reactions, i.e., ᮀ͓Ni 1/2 Mn 3/2 ͔O 4 (a ϭ 8.00 Å) was reduced to Li͓Ni 1/2 Mn 3/2 ͔O 4 (a ϭ 8.17 Å) via ᮀ 1/2 Li 1/2 ͓Ni 1/2 Mn 3/2 ͔O 4 (a ϭ 8.09 Å). Results on the detailed reversible potential measurements indicated that the flat voltage at ca. 4.7 V consisted of two voltages of 4.718 and 4.739 V. The reaction of Li͓Ni 1/2 Mn 3/2 ͔O 4 to Li 2 ͓Ni 1/2 Mn 3/2 ͔O 4 is also examined and showed that the reaction proceeded in a cubic (a ϭ 8.17 Å)/tetragonal (a ϭ 5.74 Å, c ϭ 8.69 Å) two-phase reaction with the reversible potential of 2.795 V. From these results, characteristic features of topotactic two-phase reactions of Li͓Ni 1/2 Mn 3/2 ͔O 4 ( P4 3 32) were discussed by comparing with the results on LiMn 2 O 4 (Fd3m).

Electrochemical Performance and Phase Transitions between 1.5 and 4.9 V of Highly-Ordered LiNi0.5Mn1.5O4with Tailored Morphology: Influence of the Lithiation Method

“…The calculated c/a ratio values are in good agreement with those reported in literature for highly-ordered lithiated spinel (space group P4 3 32). [20][21][22] The c/a values calculated for electrochemically-and chemically-obtained Li-rich phases are comparable and constant for the entire composition range, indicating that the Li insertion leads to a direct cubic-tetragonal phase transition without formation of intermediate phases, regardless of the lithiation method used.…”

“…[19][20][21][22][23][24] The reasons of the different processes revealed by electrochemical analysis at low-potentials are currently under investigation and will be the subject of a later communication. From a practical point of view, it is clear that the overall capacity can be controlled by selecting the potential cutoff.…”

Oxygen Lattice Instability as a Capacity Fading Mechanism for 5 V Cathode Materials

“…These two anodic signals have frequently been reported for Li-Ni-Mn spinels ͑particularly for LiNi 0.5 Mn 1.5 O 4 ). Recently, Ariyoshi et al 22 showed that the lithium deinsertion reaction at ca. 4.7 V involves two cubic/cubic two-phase reactions.…”

Temperature-dependent oxygen behavior of LixNi0.5Mn1.5O4 cathode material for lithium battery

“…One is the face-centered cubic (FCC) with the space group Fd3m and the other is the primitive simple cubic (SC) with the space group P4 3 32. [30][31][32][33] For the FCC structure, the unit cell consists of the Li ion-occupied tetrahedral 8a sites, Mn/Ni ion-occupied octahedral 16d sites, and O-occupied cubic close-packed 32e sites. The Mn/Ni ions in 16d sites are randomly distributed and thus the FCC spinel is often called the disordered structure.…”