Synthesis and electrochemical properties of nanocrystalline Li[Ni_xLi_(1−2x)/3Mn_(2−x)/3]O₂prepared by a simple combustion method

Abstract

Nanocrystalline Li[Ni x Li (122x)/3 Mn (22x)/3 ]O 2 powders were prepared by a simple combustion method and investigated using X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), scanning electron microscopy (SEM), particle size analysis (PSA), and galvanostatic charge/discharge cycling. According to the XRD analysis, single-phase compounds with a layered structure were obtained for powders with 0 ¡ x ¡ 0.25, while mixtures were obtained for powders with 0.30 ¡ x ¡ 0.50. Rietveld analysis revealed that single-phase Li[Ni x Li (122x)/3 Mn (22x)/3 ]O 2 is basically a layered rock-salt structure in which a small amount of Ni occupies the 3a sites. The initial discharge capacity of a Li/Li[Ni x Li (122x)/3 Mn (22x)/3 ]O 2 cell with x ~0.20 was about 288 mA h g 21 , corresponding to about 91% of the theoretical value, when it was cycled in the voltage range of 4.8-2.0 V with a specific current of 20 mA g 21 at 30 uC. As far as we know, charge/discharge cycling on an Li/Li[Ni 0.20 Li 0.20 Mn 0.60 ]O 2 cell gives the highest discharge capacity of 288 mA h g 21 among the LiMO 2 -based (M ~Co, Ni, and Mn) cathode materials. A very promising factor for high-rate capability applications was an excellent rate capability in continuous cycling at specific currents ranging from 20 mA g 21 to 900 mA g 21 , due to the nanocrystalline particle size of 80-200 nm. The origin of the 4.5 V plateau was investigated by means of weight loss measurement and XAS for the charged/discharged electrodes. The weight loss measurement for the charged electrodes gave indirect evidence that the 4.5 V plateau did not originate from the ejection of oxygen. In XAS, the Mn oxidation state of 41 did not change during the charge/discharge process, and surprisingly the Ni did not further oxidize beyond about 31.

Relationship between Electrochemical Pre-Treatment and Cycle Performance of a Li-Rich Solid-Solution Layered Li1^|^minus;^|^alpha;[Ni0.18Li0.20+^|^alpha;Co0.03Mn0.58]O2 Cathode for Li-Ion Secondary Batteries

“…One limitation of this approach, however, is the low electronic and Li + ion conductivities intrinsic to the family of Li-rich solid-solution layered cathode materials. 24 These poor transportation abilities could be derived from the existence of transition metal ions in the Li + layers and/or Li + in the transition metal layers. Initially, the current density limits that can be used during conventional pre-cycling to obtain Electrochemistry, 80(8), 561565 (2012) stable capacities were explored.…”

Synthesis and Characterization of High‐Energy, High‐Power Spinel‐Layered Composite Cathode Materials for Lithium‐Ion Batteries

“…The 0.5LIR · 0.5LNMO composite material exhibited an excellent high-rate cycling stability in the series with 81% capacity retention after 300 cycles at 20C. [ 36,40 ] Hence, by carefully tailoring the " x " values, composite cathodes offering high energy as well as high power could be designed to meet the current Li-ion battery demands. Figure 1 , were synthesized via an already existing coprecipitation method.…”

Effects of surface area on electrochemical performance of Li[Ni0.2Li0.2Mn0.6]O2 cathode material

“…Li[Ni 0.2 Li 0.2 Mn 0.6 ]O 2 is a promising cathode material with a high discharge capacity of [200 mAh g -1 and stable cyclic performance [21][22][23][24]. Surface area of the sample powders was controlled by changing the molar ratio of nitrate/acetate sources and adding an organic solvent.…”

“…Once ignition occurs, thermal decomposition spontaneously occurs over the reactants, since the fuel (acetate sources) closely coexists with the oxidizing agent (nitrate sources) in a homogeneously mixed state. At this point, the intensity of the production of the gases is a key factor in controlling the particle size and surface area [21].…”

“…The electrochemical cell was assembled in a dry room using above cathode material. We used a 1 M LiPF 6 solution in 1:1 volumetric 3 Results and discussion Small XRD peaks between 20 and 25°(marked as *) are attributed to superlattice ordering of Li and Mn in the transition-metal containing layers [21][22][23]. Except for the superlattice ordering peaks, the diffraction patterns of the five samples are indexed well with that of a hexagonal a-NaFeO 2 structure (space group R-3m).…”