High-performance LiCoO2 by molten salt (LiNO3:LiCl) synthesis for Li-ion batteries
2005; Elsevier BV; Volume: 147; Issue: 1-2 Linguagem: Inglês
10.1016/j.jpowsour.2005.01.019
ISSN1873-2755
AutoresK. S. Tan, M. V. Reddy, G. V. Subba Rao, B. V. R. Chowdari,
Tópico(s)Extraction and Separation Processes
ResumoIn an effort to increase and sustain the reversible capacity of LiCoO2 on cycling, LiCoO2 is prepared by using the molten-salt of the eutectic LiNO3–LiCl at temperatures 650–850 °C with or without KOH as an oxidizing flux. The compounds are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), chemical analysis, surface area and density techniques. Cathodic behaviour was examined by cyclic voltammetry (CV) and charge–discharge cycling. The 850 °C-synthesized LiCoO2, which has excess lithium incorporated in to it, shows a reversible capacity, with ∼98% coulombic efficiency, of 167 (±2) mAh g−1 at a specific current of 30 mAg−1 in the range 2.5–4.4 V up to 80 cycles with no capacity-fading. When cycled to a higher cut-off voltage (4.5 V), a capacity of 192 (±2) mAh g−1 versus Li is obtained at the fifth cycle, but capacity-fading is observed, viz., ∼ 6% after 60 cycles. On the basis of the CV and capacity–voltage profiles, this is attributed to the non-suppression of the hexagonal (H1) ↔ (H1-3) structural transition. A similar capacity-fading, i.e., ∼5–6%, during 5–40 cycles, is also observed in the LiCoO2 prepared at 650 and 750 °C when cycled up to only 4.3 V and this is ascribed to the non-suppression of the H1 ↔ M ↔ H1 phase transitions (M = monoclinic).
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