Long-range ordering during delithiation of LiMn2O4 cathode material

Abstract

A single crystal of the cubic spinel LiMn 2 O 4 was delithiated electrochemically at 4.06 V vs. Li/Li 1 to probe the structural source of the inflection point at ca. 4.1 V vs. Li/Li 1 in the discharge curve. The phase thus obtained was investigated by single-crystal X-ray diffraction and the structure refined. The structure is closely related to the original cubic structure, but the new space group is rhombohedral R3 ¯m and shows a one-dimensional modulation along the v001w r direction with wave vector q # 0.75c * . The cell parameters are: a ~5.762(1) A ånd c ~14.080(4), and the (3 1 1)-dimensional super space group is R3 ¯m(00c). The modulated phase involves two unique Mn atoms with coordination polyhedra which differ significantly: one has an average Mn-O distance of 2.24(1) A ˚, indicative of a lower oxidation state for the Mn ion; the other has an average Mn-O distance of 1.82(2) A ˚, indicative of a higher oxidation state. Lithium ions appear to be extracted from the structure in a long-range-ordered two-dimensional arrangement between the cubic-close-packed oxygen layers; the manganese atoms are also arranged in charge-ordered Mn 31 /Mn 41 sheets. These two features are the source of the modulation in the structure.

Lithiation of V2O3(SO4)2 – a flexible insertion host

“…The intensities of the reduction peaks are greater than those of the oxidation peaks, suggesting that not all the Li + that was inserted could be extracted. As for the redox processes centred about 3.25 V, the dx/dV curve shows two reduction peaks at 3.23 V and 3.14 V and two oxidation peaks at 3.15 V and 3.11 V. These peaks suggest charge-ordering of the vanadium atoms or vacancy-ordering of Li + which has been reported for Li x Mn 2 O 4 among other systems [28][29][30]. Upon subsequent cycling, the electrode can reversibly insert approximately 1.5 Li + , leading to a reversible capacity of approximately 120 mA h g À1 , which progressively decays upon cycling.…”

Superionics: crystal structures and conduction processes

“…Li 1+x Mn 2−x O 4 ) reduces the transition temperature (from 282 K for x = 0 to 214 K for x = 0.035 [644]) and improves the rechargeable capacity [646]. However, there is increasing evidence that the Li + removal/insertion process involves complex microstructural changes, including ordering of the Li + [647,648] and the formation of additional Li-Mn-O phases [649]. Such issues are increasingly being probed by in situ diffraction studies of electrochemical devices whilst they are charged/discharged within the x-ray [650,651] or neutron [652] beam.…”

Fabrication of all-solid-state rechargeable lithium-ion battery using mille-feuille structure of Li0.35La0.55TiO3

“…Although different active materials should be filled into each 3DOM layer, LiMn 2 O 4 was filled into both 3DOM layers to simplify experimental procedure in this paper. LiMn 2 O 4 shows discharge curve with three plateaus at 3.0, 4.0, and 4.1 V vs. Li/Li + [10,11], thus, LiMn 2 O 4 can work as both cathode and anode. The plateau corresponding to 4.0, and 4.1 V is due to insertion/extraction of Li + into/from cubic spinel LiMn 2 O 4 , respectively.…”

“…On the other hand, another plateau at 3.0 V involves a phase change between cubic and tetragonal phases. These reactions are described as below [10,11]: …”