Influence of cobalt ions on the electrochemical properties of lamellar manganese oxides

Abstract

Abstract. Evaluation of Co-doping on the electrochemical properties of the sol-gel birnessite and the new lithiated manganese oxide Li0.45MnO2+ 5 is reported. For both compounds the synthesis of Co-doped materials via a solution technique is described. We demonstrate the interest of Co-doped structures with the selected content of 0.15 Co per mole of oxide as the optimum composition. In the case of Li0.45Mnl_yCOyO2+ 8, prepared at 300 ~ a mixture of a lamellar phase and a cubic one is identified while the Co-doped birnessite appears as a single phase. A probable substitution of Mn by Co ions explains the better specific capacity of 185 mAh/g found and the excellent stability observed over 40 cycles in the voltage range 4.2-2.0 V.

Variation of the MnO2 Birnessite Structure upon Charge/Discharge in an Electrochemical Supercapacitor Electrode in Aqueous Na2SO4 Electrolyte

“…However, the ion-exchange of Mg 2+ is almost complete in our experimental conditions, either during soaking or upon electrochemical cycling in a sodium-containing electrolyte. It would be interesting to investigate other doping cations such as chromium or cobalt, which have demonstrated improved cycling stability in lithium ion batteries applications. ,,,, The Na + intercalation/deintercalation in/from an Mg-doped Na-birnessite electrode upon cycling in 0.5 M Na 2 SO 4 electrolyte is confirmed by EDX analysis. The electrodes were subjected to 50 cyclic voltammetry cycles between −0.05 and 0.85 V at a scan rate of 2 mV/s, and the scan was stopped either at the reduced state (−0.05 V) or at the oxidized state (0.85 V) prior to analysis by EDX.…”

Chemistry and Electrochemistry of Low-Temperature Manganese Oxides as Lithium Intercalation Compounds

“…Figure 6 presents the best results obtained for the optimal composition of 15% for cobalt ions in Li 0.45 Mn 0.85 Co 0.15 O 2 (sample C) in the potential window 4.2-2.5 V. 26 The material is first charged to 4.2 V, allowing the extraction of 0.15 Li ions at around 4 V (Fig. 6a).…”

Synthesis and Substitution Chemistry of Redox-Active Manganese/Cobalt Oxide Nanosheets

“…Modulation of the properties can be achieved by the elemental substitution or doping of the redox-active nanosheets, as has been reported for bulk materials. For example, the influence of cobalt doping on the electrochemical properties of layered manganese oxide has been studied to improve the cycle performance of lithium-ion batteries. − The doping of different elements into redox-active nanosheets and its effect on the crystal structure, optical properties, and redox properties have been scarcely examined, although such properties would be largely modified. Examples of redox-active nanosheets doped with different elements include MnO 2 nanosheets partly substituted with Co, Co/Ni, or Ru .…”

“…In the present study, we synthesize Co-substituted MnO 2 nanosheets (Mn 1– x Co x O 2 ) through the synthesis, protonation, and exfoliation of layered manganese oxide doped with cobalt. The starting material was synthesized by following the reported procedure. − Although protonation of the starting material has been studied, the influence of the doping amount on the crystal structure and the valence of constituent elements has not been reported . Although the synthesis of MnO 2 nanosheets doped with cobalt has been examined via a bottom-up process, there is no direct evidence for the doping of Co into the lattice of MnO 2 nanosheets.…”