Lithium−Cobalt Citrate Precursors in the Preparation of Intercalation Electrode Materials

Abstract

Noncrystalline solids with LiCoC 6 H 5 O 7 ‚5H 2 O and (NH 4 ) 3 LiCo(C 6 H 5 O 7 ) 2 compositions were obtained by ethanol dehydration of concentrated lithium-cobalt citrate solutions. Electron spectroscopy of solutions and solid citrates, as well as IR spectroscopy of solid citrates, reveals that in LiCoC 6 H 5 O 7 ‚5H 2 O one triionized citrate ion chelates Co 2+ while two triionized citrate ions surround Co 2+ in (NH 4 ) 3 LiCo(C 6 H 5 O 7 ) 2 . Lithium-cobalt citrates were used as precursors in the formation of lithium-cobalt mixed oxides. At 400 °C, thermal decomposition of LiCoC 6 H 5 O 7 ‚5H 2 O yields a mixture of pseudo-spinel and rhombohedral LiCoO 2 . From (NH 4 ) 3 -LiCo(C 6 H 5 O 7 ) 2 , monophase powders of rhombohedral LiCoO 2 were obtained at 400 °C, which consist of hexagonal individual particles with a diameter of 80-120 nm. This product can be annealed up to 800 °C without marked structural changes. The rhombohedral LiCoO 2 was used as active cathode material in lithium cells. Cyclic voltammogams showed little changes in the main cathodic and anodic peaks with synthesis temperature. The loss of cell capacity is limited in electrodes prepared at 400 °C from citrate precursors as compared with products of low-temperature synthetic procedures previously reported.

Synthesis of LiCoO2 via a facile hydrothermal-assisted route

“…20) In addition, these methods require difficult condition or a large quantity of solvent and organic materials. 12) To the best of our knowledge, there are few reports concerning synthesis of LiCoO 2 via a hydrothermal-assisted route. In this study, a facile hydrothermal-assisted route using cobalt naphthenate was developed to synthesize LiCoO 2 with various calcination temperatures for the first time, in which plate-like ¢-Co(OH) 2 prepared by hydrothermal reaction was used to as precursor.…”

Cathodes for lithium ion batteries: the benefits of using nanostructured materials

“…Solid state reactions to afford LiCoO 2 may start from many different precursors, such as, Li 2 35 Owing to insufficient mixing, low reactivity of the starting materials and calcinations at 850-900 o C for several hours, LiCoO 2 produced by solid state reactions usually has non-homogeneity, irregular morphology and a broad particle size distribution, which characteristics influence significantly on the electrochemical properties of the product. Taking into account these advantages, alternative methodologies for the solidstate preparations are been proposed in order to synthesize lithium cobalt oxides at micrometer scale, such as solgel, [104][105][106][107][108][109] water-in-oil emulsion process, 110 emulsion drying method, 111 and electrostatic spray deposition. [112][113][114] Although these methods require a much lower calcination time and shorter calcination temperature, the synthesis of particles with size under 100 nm is very hard due to their tendency to agglomerate; therefore, the search for new synthetic methodologies or even the modification of the old ones is still necessary.…”

Preparation of an Li0.7Ni0.8Co0.2O2 Electrode Material From a New Li–Co–Ni Mixed‐Citrate Precursor

“…The thermal decomposition of this amorphous citrate yields a LiCoO 2 phase with an "ideal" trigonal α-NaFeO 2 -type structure. [29] Although the method employed by Zhecheva et al [29] is efficient for the preparation of lithium cobalt oxides, there is no evidence of its application to systems involving other metal such as nickel, or when a substitution of cobalt by nickel must take place. The aim of the present work is to extend Zhecheva's method [29] to the synthesis of LiNi 0.8 -Co 0.2 O 2 by using, in this case, a new precursor consisting of a mixed nickel-cobalt citrate of appropriate stoichiometry.…”

“…[29] Although the method employed by Zhecheva et al [29] is efficient for the preparation of lithium cobalt oxides, there is no evidence of its application to systems involving other metal such as nickel, or when a substitution of cobalt by nickel must take place. The aim of the present work is to extend Zhecheva's method [29] to the synthesis of LiNi 0.8 -Co 0.2 O 2 by using, in this case, a new precursor consisting of a mixed nickel-cobalt citrate of appropriate stoichiometry. We intend to optimize the synthesis conditions to reach a well-defined crystalline phase of the mixed citrate that could produce the ideal trigonal Li-Co-Ni oxide (rich in nickel) by a new chemical route followed by thermal decomposition.…”