Lithium Manganese Nickel Oxides Li x  ( Mn y Ni1 − y  ) 2 − x  O 2 : I. Synthesis and Characterization of Thin Films and Bulk Phases

Abstract

The series Li(Mn Ni1_ )2_O2 for x s 1.33 and 0.38 y 0.50 shows a very close relationship to its parent series LiNi202. The refineà lattice parameters for at least 0.93 x 1.26 are a linear function of the concentration ratio Li/(Mn + Ni) which in turn is proportional to the averaged valence state of the transition metals. Li(Mn9Ni1_9)202 is able to reversibly coprecipitate/reinsert Li20 and release/absorb 02. This self-regulation mechanism seems to always adjust the number of cations to an undisturbed oxygen sublattice according to the rule "cations/anions = 1," which holds true at least for temperatures up to 800°C and oxygen partial pressures above i0 atm. Samples prepared in air and under 02 did not show nucleation of Li20, not even for x> 1.0. The series Li(Mn6Ni1_6)202 where 0.38 y 0.50 crystallizes in a rhombohedral unit cell (space group R3m) for x < 1.15 and transforms into a single monoclinic phase (space group C2/c) for x> 1.25. The similarity between LiNi2_02 and Li,(Mn0Ni1_9)202 strongly suggests a rhombohedralcubic transition at x 0.6 for the latter series. Derived from the linear dependence of the X-ray density on the stoichiometric parameter x, an equation was found with which the lithium concentration of Li(Mn9Ni,_0)202 thin film phases over the entire range 0 x 1.33 can be determined accurately without extensive ion-beam analysis. XPS measurements on a film with the bulk stoichiometry Li110Mn039Ni05102 gave evidence for Mn4 and Mn3, but no indication was found for nickel valence states other than Ni2. In order to meet the above-given stoichiometry, the averaged nickel valence state had to increase with film depth. lnfroduction In recent years, LiNiO2 has been used as a cathode material in high-voltage lithium-ion and lithium batteries.1-4 Electrochemical experiments, however, showed that a slight deviation from the ideal starting stoichiometry LiNiO2 resulted in a poor cell performance caused by Ni2 defects on Li sites.5 Moreover, upon extensive lithium deintercalation wherein x in LiNi02 approaches zero and the nickel valence state comes close to its maximum of +4, nickel ions migrate from their nickel layer sites into the vacancies of the lithium layers. Such nickel migration creates severe diffusional limitations to lithium reinsertion thereby reducing cell performance. 6 These drawbacks stimulated our research on the partially substituted manganese derivatives of LiNiO2, namely, Li(Mn.4Ni1_9)202. In particular, it was felt that the introduction of Mn" "buffer ions," which easily form under typical solid-state preparation conditions such as annealing at 700°C in air; would lift the electrochemically detrimental effect Ni2-defects impose on chemically prepared LiNiO2 cathodes. That is, Mn" ions could help balance the two oxygen anions without the need of Ni2 occupying Li sites. * Electrochemical Society Active Member. The purpose of this paper is to describe the synthesis and characterization of Li(Mn0Ni10)202 in thin-film and bulk forms. Our electrochemical studies of the thin films are reporte...

Characterization of the surface of positive electrodes for Li-ion batteries using 7Li MAS NMR

“…1 leaves no ambiguity as for the difference in surface reactivity of the two compounds. Such observation is in perfect agreement with previous results obtained using different techniques such as XPS and Fourier transform infrared (FTIR) [25][26][27][28][29].…”

“…5). This confirms previous results concerning the higher stability of LiFePO 4 compared to LiNi 1/2 Mn 1/2 O 2 and their different surface chemistry [25][26][27][28][29][30], as suggested by XPS or FTIR.…”

Optimization and Characterization of Lithium Ion Cathode Materials in the System (1 – x – y)LiNi0.8Co0.2O2 • xLi2MnO3 • yLiCoO2

“…Two-dimensional layered materials based on Mn were explored by Peter Bruce et al [17]. Additional improvements in the layered insertion materials were proposed by Ohzuku et al for cathode materials with composition LiNi 0.5 Mn 0.5 O 2 [18], in addition to the investigation of the system Li x (Mn y Ni 1-y ) 2-x O 2 by Bates [19]. Ohzuku reported novel LiMn 1/3 Ni 1/3 Co 1/3 O 2 which was investigated further [20].…”

Thin-film lithium and lithium-ion batteries

“…Results and discussion intercalation compounds, allowing us to investigate the electrochemical properties of the pure phases free 3.1. Crystalline LiCoO : lithium, lithium-ion, and 2 of binders [1][2][3][4][10][11][12][13][14] and to perform in situ lithium free cells experiments such as X-ray diffraction [11] and X-ray absorption [15] as a function of the lithium conPolycrystalline films of LiCoO deposited by rf 2 centration in these materials. magnetron sputtering exhibited a strong preferred The purpose of this paper is to summarize the orientation or texturing after annealing at elevated results of recent studies of lithium, lithium-ion, and temperatures [17][18][19].…”

“…For example, the comparison of the results and work in progress on the structure and X-ray diffraction pattern of a 4-mm thick film with electrochemical properties of thin films of layered that of a powdered (random) sample (Fig. 2), shows Li-Ni-Mn oxides [13,14] and amorphous [1,10] and that within the sensitivity of the measurement, none crystalline V O will not reviewed. The paper will of the grains had their (003) planes oriented parallel 2 5 conclude with a brief discussion of applications and to the substrate.…”