Li de-intercalation mechanism in LiNiMnO cathode material for Li-ion batteries

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

“…First, the analysis of the magnetic properties in ionic intercalation compounds is quantitative, because the orbital momentum is quenched, and the magnetic moment of the ions is reduced to the spin-only value, whether the materials are lamellar like in the present case [36] or olivine compounds [41]. This holds true for ions in the high-spin state of the 3(d 7 ) configuration such as Fe 2+ [41] or the Ni 4+ case met in the present work [20,35,36]. This is also true for the Mn 4+ ion in the 3(d 3 ) configuration [20,26,35,36].…”

“…In the case of Ni 4+ , the result was already known [20,35,36], but in the case of Co 4+ the result is not trivial since Co 4+ is in the high-spin state in Li x CoO 2 for 0.94 < x < 1.00, and low-spin state for 0.50 < x < 0.78 [38,39]. We shall return to this feature in the discussion.…”

“…We know from earlier works [20,35,36] that Ni 3+ ions is in the low spin state (spin S = 1/2) and Ni 4+ is in the high spin state (S = 2) in the materials of this family. Therefore, eff is:…”

Ion Distributions and the Electrochemical Properties of LiNi_0.5Mn_0.5O₂ Prepared by Ion-Exchange for Positive Electrode

“…9 3 were mixed and then calcinated at 873 K for 12 h. The obtained powders were pressed into disks under a pressure of 0.490 MPa and sintered at 1173 K for 24 h in air. Finally, the precursor was allowed to react at 423, 553, 623, 723 K for from 10 min to 40 h by 0.5 M LiCl in 1-hexanol (the boiling point is 430 K) and the molten salt containing LiNO 3 and LiCl (eutectic point is 517 K).…”

“…6 We have reported the charging mechanism of Li 1¹x Ni 0.5 Mn 0.5 O 2 that a charging reaction proceeds with an oxidation of Ni 2+ to Ni 3+ , but not to Ni 4+ while maintaining oxidation state of Mn 4+ up to x = 0.5. 8,9 However, this material showed a rechargeable capacity corresponding to x = 0.7 in the voltage range of 2.5 to 4.3 V. O K-edge absorption spectra for Li 1¹x Ni 0.5 Mn 0.5 O 2 showed a slight shift towards lower energy for beyond the composition of x = 0.5. The first principle calculations indicated a remarkable difference between x = 0 and x = 0.5 in a valence band state distribution of oxygen respectively.…”