Local structure and electrochemistry of LiNi y Mn y Co1 − 2y O2 electrode materials for Li-ion batteries

Abstract

A series of LiNi x Mn y Co z O 2 (x=y, z=1−2y) oxides have been synthesized by "chimie douce" and investigated as positive electrodes in rechargeable lithium batteries. Layered LiNi y Mn y Co 1−2y O 2 materials with high homogeneity and crystallinity were synthesized using the wet-chemical method assisted by carboxylic acid as the polymeric agent. The long range and local structural properties are investigated with experiments including Xray diffraction, Fourier transform infrared spectroscopy, and electron paramagnetic resonance spectroscopy. The evolution of the structure is discussed as a function of the cobalt content that confers layer-like behavior on the framework. Electrochemical performance of LiNi y Mn y Co 1−2y O 2 oxides is tested in cells using nonaqueous 1 M LiPF 6 dissolved in ethylene carbonate-diethyl carbonate. Charge-discharge profiles are investigated as a function of the rate capability and the voltage window. A relation is found between the gravimetric capacity and the cation disorder of the positive electrode as indicated by structural analysis. Fast lithium extraction attributed to the larger interslab space has been observed in the cobalt-rich oxides.

Fundamental Linkage Between Structure, Electrochemical Properties, and Chemical Compositions of LiNi1–x–yMnxCoyO2 Cathode Materials

“…Since the content of Ni 2+ is in principle equal to the content of Mn 4+ , Mn–Co (representing the value of x – y in LiNi 1– x – y Mn x Co y O 2 ) is used as the cation mixing indicator. The effectiveness of this indicator is shown in Figure c, which uses data both from the literatures − and our own Rietveld refinement results. It clearly shows a monotonic increase of cation mixing ratio as the Mn–Co content increases.…”

“…(c) Correlation between Mn–Co content and Li/Ni mixing ratio. Detailed NMC stoichiometry information is: 2008EA and 2005JPS (LiNi 0.5 Mn 0.5 O 2 ); , 2008Ionics (LiNi 0.25 Mn 0.25 Co 0.5 O 2 , LiNi 0.3 Mn 0.3 Co 0.4 O 2 , LiNi 0.33 Mn 0.33 Co 0.33 O 2 , LiNi 0.4 Mn 0.4 Co 0.2 O 2 ); 2018RSI (LiNi 0.85 Co 0.15 O 2 , LiNi 0.94 Co 0.06 O 2 , LiNi 0.6 Mn 0.2 Co 0.2 O 2 , LiNi 0.7 Mn 0.15 Co 0.15 O 2 , LiNi 0.8 Mn 0.1 Co 0.1 O 2 , LiNi 0.9 Mn 0.05 Co 0.05 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 , LiNi 0.68 Mn 0.22 Co 0.1 O 2 ); 2001ESL (LiNi 0.25 Mn 0.25 Co 0.5 O 2 , LiNi 0.375 Mn 0.375 Co 0.25 O 2 ); and refinement by author (LiNi 0.5 Mn 0.3 Co 0.2 O 2 , LiNi 0.67 Mn 0.25 Co 0.08 O 2 , LiNi 0.70 Mn 0.22 Co 0.08 O 2 , LiNi 0.73 Mn 0.18 Co 0.09 O 2 , LiNi 0.76 Mn 0.14 Co 0.1 O 2 , LiNi 0.8 Mn 0.1 Co 0.1 O 2 ).…”

Magnetic properties of LixNiyMnyCo1−2yO2 (0.2≤1−2y≤0.5, 0≤x≤1)

“…[52]. In particular, the reduction of the concentration of the Ni(3a) defects upon the introduction of cobalt in Li(Ni,Mn)O 2 is benefit to the rate capabilities.…”

Aging of LiNi1/3Mn1/3Co1/3O2 cathode material upon exposure to H2O

“…1a and b, the Bragg lines are well indexed in the R3m space group with the hexagonal ordering. No impurity phases are detected and the powders are well crystallized in the˛- NaFeO 2 type structure [12,13]. The (0 0 6)/(1 0 2) and (1 0 8)/(1 1 0) doublets are both well separated, which indicate a good hexagonal ordering of Li 1 + x (Ni 1/3 Mn 1/3 Co 1/3 ) 1 − x O 2 after aging process [14,15].…”