LiCo_1−yB_yO₂ As Cathode Materials for Rechargeable Lithium Batteries

Abstract

Several substituted layered lithium cobaltates of formula Li 0.999 Co 1-y B y O 2 (0.05 e y e 0.35) were synthesized and characterized by X-ray powder diffraction, Raman and FTIR spectroscopy, magnetic measurements, and ESR experiments. The compounds have been investigated as cathode materials in rechargeable lithium batteries and galvanostatic cycling are reported. Structural data showed that particles crystallized in the R3m structural symmetry and single-phased can be grown free of any impurity up to the boron concentration y e 0.25, except for the presence of nickel impurity, as Ni is always present in the cobalt precursors. The voltage profiles of electrochemical cells including these compounds as the cathode were monitored against Li anode. The overall capacity of the oxides has been reduced by the sp metal substitution. However, more stable cycling performances have been observed compared to the performances of the native oxides. At 4.4 V cutoff voltage, the Li//LiCo 0.75 B 0.25 O 2 cell exhibits an almost constant gravimetric capacity of ca. 127 mA h/g up to the 16th cycle. The origin of the benefit of boron doping is discussed.

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

“…An additional proof is provided by the cobalt ions. Co 3+ is in the low spin-state, but Co 4+ in the delithiated samples is in the high-spin state in the samples we have studied (low Co-concentrations 1 − 2y ≤ 0.5), while in the high concentration limit (1 − 2y = 1), it is in the high-spin state in Li x CoO 2 for 0.94 < x < 1.00 for samples that are free of impurity [37,46], and in the low-spin state for 0.50 < x < 0.78 [38]. Ni 3+ is usually in the low spin state in lamellar compounds.…”

An Overview on the Advances of LiCoO2 Cathodes for Lithium‐Ion Batteries

“…Meanwhile, Si 4+ ‐ions lead to a lower impedance and better capacity retention in the voltage of 2.8–4.5 V. B doping stabilizes the structure of LiCoO 2 during cycling, and improve its electrochemical performance. [ 91 ] Julien et al stated that B 3+ ‐ions replaced Co 3+ ‐ions at the octahedral sites, [ 92 ] and thus prevented the first‐order structural transition associated with Li 0.5 CoO 2 . However, due to greatly different radii of B 3+ and O 2− (0.27 vs 1.4 Å), B 3+ is unlikely to stabilize in Co 3+ sites with BO 6 octahedron but triangle BO 3 group.…”

Enabling Stable High‐Voltage LiCoO2 Operation by Using Synergetic Interfacial Modification Strategy

“…To reach this aim, many substantial efforts have been made with different strategies such as cation doping, [ 3b,4 ] surface coating, [ 5 ] morphology control, [ 6 ] electrolyte modification, [ 7 ] separator improvement, [ 8 ] and binder development. [ 9 ] Among them, due to the deep consideration of cost and procedures, modifying the electrolyte to control the LiCoO 2 /electrolyte interface film by using the interphase‐forming functional additives is a promising approach but yet to be developed and optimized further.…”