T2 and O2 Li[sub 2/3][Co[sub x]Ni[sub 1/3−x/2]Mn[sub 2/3−x/2]]O[sub 2] Electrode Materials

Abstract

The structure and the electrochemical properties of P2-Na 2/3 ͓Co x Ni 1/3Ϫx/2 Mn 2/3Ϫx/2 ͔O 2 and Li 2/3 ͓Co x Ni 1/3Ϫx/2 Mn 2/3Ϫx/2 ͔O 2 (0 р x р 2/3) are investigated by X-ray and neutron diffraction as well as by electrochemical techniques. Li 2/3 ͓Co x Ni 1/3Ϫx/2 Mn 2/3Ϫx/2 ͔O 2 (0 р x р 2/3) can be considered a solid solution between Li 2/3 1ϩ ͓Ni 1/3 2ϩ Mn 2/3 4ϩ ͔O 2 2Ϫ and Li 2/3 1ϩ ͓Co 2/3 3ϩ Mn 1/3 4ϩ ͔O 2 2Ϫ . Samples with x near 0 and with x near 2/3 adopt the T2 structure, while those with intermediate x show a stacking faulted O2 structure. This paper demonstrates that T2-Li 2/3 ͓Co 2/3 Mn 1/3 ͔O 2 is quite different from T2-Li 2/3 ͓Ni 1/3 Mn 2/3 ͔O 2 in its properties. First, neutron diffraction studies indicate that there is no superlattice ordering of Co and Mn in the transition metal layers of P2-Na 2/3 ͓Co 2/3 Mn 1/3 ͔O 2 or T2-Li 2/3 ͓Co 2/3 Mn 1/3 ͔O 2 , as there is in P2-Na 2/3 ͓Ni 1/3 Mn 2/3 ͔O 2 and T2-Li 2/3 ͓Ni 1/3 Mn 2/3 ͔O 2 . Second, the electrochemical results show that all the lithium can be extracted from T2-Li 2/3 ͓Co 2/3 Mn 1/3 ͔O 2 , unlike T2-Li 2/3 ͓Ni 1/3 Mn 2/3 ͔O 2 , from which only one half the available lithium can be extracted.

Investigation of layered intergrowth LixMyMn1?yO2+z (M=Ni, Co, Al) compounds as positive electrodes for Li-ion batteries

“…The potential drop during the 15 minutes of relaxation occurring after each oxidation and reduction (for the same current density) is also larger in materials with high O2 content. This is evident in Figure 3 [6,7]. Further investigation of the effect of structure on phase conversion using 7 Li-MAS NMR and in situ XRD is underway in this laboratory.…”

“…The oxygen arrays in both the O'3 structure of this layered compound and the spinel are cubic close-packed, so that only slight rearrangement of manganese and lithium ions is required for phase conversion to occur. O2 layered lithium manganese oxides, prepared from P2-Na 0.7 MnO 2+z , do not have a cubic closepacked oxygen array and do not convert to spinel under normal cycling conditions [6]. Recently, several layered Li x M y Mn 1-y O 2 compounds (y=0.1, M=Ni, Co, Al) with O2/O3 intergrowth structures have been prepared by ion exchanging P2/P3 sodium-containing precursors [7].…”

On the mechanism of the P2–Na0.70CoO2→O2–LiCoO2 exchange reaction—Part II: an in situ X-ray diffraction study

“…O22LiCoO 2 was the first metastable phase obtained by ion exchange from sodium to lithium reaction in P22Na 0:70 CoO 2 [1]. In addition to LiCoO 2 , T # 22Li 2=3 ½Ni 1=3 Mn 2=3 O 2 [2] and recently found T # 22Li 2=3 ½Co 2=3 Mn 1=3 O 2 [3] are well crystallized. All other phases: O22LiMnO 2 [4], Li 0:70 ½Mg 0:30 Mn 0:70 O 2 [5] and those belonging to the Li 2=3 ½Ni 1=3Àx Co x Mn 2=3 O 2 and Li 2=3 ½Ni 1=3Àx=2 Co x Mn 2=3Àx=2 O 2 families exhibit more or less stacking faulted structures [6].…”

“…6 presents thus the ideal P2 phase packing and an example of P2-O2 intergrowth, with the associated stacking vectors (R ij ) and probabilities (a ij ). To built up the P2-O2 intergrowth using DIFFaX, three AB-type slabs and three BA-type slabs were used: one of each for the P2 description (slabs (1) and (2)) and the others for the two O2 descriptions (growth from a BA-type slab (slabs (3) and (4)) and from AB-type slab (slabs (5) and (6))). In order to take into account the difference in interslab distances between P2 and O2, the stacking vectors are (a; b; c hex:ðP2Þ /2) and (a 0 ; b 0 ; c hex:ðO 2 Þ =2Þ in P2 and O2 domains, respectively.…”

First principles study of Li diffusion inI-Li2NiO2structure

“…Particular attention has been given to the Ni +2 / Ni +4 double redox couple, which has been shown to exchange two electrons in layered LiNi 0.5 Mn 0.5 O 2 , [1][2][3][4][5][6] LiNi 1/3 Co 1/3 Mn 1/3 O 2 , 7,8 Li͑Ni x Li 1/3−2x/3 Mn 2/3−x/3 ͒O 2 , 9 LiNi 2/3 Sb 1/3 O 2 , 10 and spinel LiNi 0.5 Mn 1.5 O 4 . 11 Multielectron redox reaction can provide a way to overcome the capacity limitation caused by the usual limit of one electron per transition metal in an acceptable voltage range that applies to cations in most of cathode materials.…”