Supplementary information files for Synthesis and spectroscopic identification of nickel and cobalt layered hydroxides and hydroxynitrates

Supplementary files for article Synthesis and spectroscopic identification of nickel and cobalt layered hydroxides and hydroxynitratesThe formation of different nickel and cobalt layered hydroxide phases by a variety of solution and solid-state synthesis methods have been investigated. Initially, the preparative conditions were refined to generate single-phase products from metal(II) nitrate hexahydrate starting materials and were characterised by powder X-ray diffraction, vibrational spectroscopy and thermogravimetric analysis. As well as the brucite type β-M(OH)2 and the hydrotalcite-like [M(OH)2-x(H2O)x]x+ alpha-phases (where M = Ni, Co), two different hydroxynitrate phases were isolated with the generic formula M(OH)2-x(NO3)x with x = 0.67 and 1.0 (where M = Ni, Co). The reduction of symmetry of the nitrate anion from D3h to C2v allows the alpha-phases to be distinguished from the two different layered hydroxynitrate phases by both infrared and Raman spectroscopy through the loss of symmetry and concomitant splitting of the degenerate bands. The symmetric N-O stretch enables the two hydroxynitrate phases to be distinguished from one another through the sharp absorption bands at ca. 1000 cm-1 (x = 0.67) and ca. 1050 cm-1 (x = 1.0). The thermogravimetric analysis data of the phases showed key differences between the layered hydroxides, with anhydrous phases having singular weight losses over short temperature ranges and hydrated phases having multiple losses over more extended temperature ranges.</p

Determination of layered nickel hydroxide phases in materials disordered by stacking faults and interstratification

The formation of stacking faults and phase interstratification disorder in the layered nickel(II) hydroxides during the chemical precipitation synthesis of the materials using nickel(II) nitrate and potassium hydroxide solutions has been investigated in the temperature range of 5°C to 95°C and time intervals from 1 hour to 1 week. Stacking faulted materials were identified by broadening of the 00l reflections, while interstratified materials were identified through the splitting of the 001 into two lines. In contrast to the disorder concepts presented in previous studies of these materials, this work has shown through vibrational spectroscopy that both the alpha-phase and beta-phase hydroxides are present in materials described with stacking fault disorder, while layered hydroxysalts were additionally present in the materials considered to be interstratified. Standard mixtures of Ni3(OH)4(NO3)2 and β-Ni(OH)2 were prepared to investigate if the intensity of particular vibrational bands could be correlated with the proportion of the particular phases in mixtures. The intensities of the C2v nitrate infrared and Raman bands at 990 cm-1 and 1315 cm-1 were shown to correlate with the amount of layered hydroxynitrate incorporated in the phase, theoretically providing a method to determine the components in mixed compositions. Since disorder and phase impurities in layered nickel hydroxide materials affect both their electroactive stability and performance as cathode materials, this work has important implications in several research fields.</p

Synthesis and spectroscopic identification of nickel and cobalt layered hydroxides and hydroxynitrates

The formation of different nickel and cobalt layered hydroxide phases by a variety of solution and solid-state synthesis methods have been investigated. Initially, the preparative conditions were refined to generate single-phase products from metal(II) nitrate hexahydrate starting materials and were characterised by powder X-ray diffraction, vibrational spectroscopy and thermogravimetric analysis. As well as the brucite type β-M(OH)2 and the hydrotalcite-like [M(OH)2-x(H2O)x]x+ alpha-phases (where M = Ni, Co), two different hydroxynitrate phases were isolated with the generic formula M(OH)2-x(NO3)x with x = 0.67 and 1.0 (where M = Ni, Co). The reduction of symmetry of the nitrate anion from D3h to C2v allows the alpha-phases to be distinguished from the two different layered hydroxynitrate phases by both infrared and Raman spectroscopy through the loss of symmetry and concomitant splitting of the degenerate bands. The symmetric N-O stretch enables the two hydroxynitrate phases to be distinguished from one another through the sharp absorption bands at ca. 1000 cm-1 (x = 0.67) and ca. 1050 cm-1 (x = 1.0). The thermogravimetric analysis data of the phases showed key differences between the layered hydroxides, with anhydrous phases having singular weight losses over short temperature ranges and hydrated phases having multiple losses over more extended temperature ranges.</p

Supplementary information files for Determination of layered nickel hydroxide phases in materials disordered by stacking faults and interstratification

Supplementary files for article Determination of layered nickel hydroxide phases in materials disordered by stacking faults and interstratificationThe formation of stacking faults and phase interstratification disorder in the layered nickel(II) hydroxides during the chemical precipitation synthesis of the materials using nickel(II) nitrate and potassium hydroxide solutions has been investigated in the temperature range of 5°C to 95°C and time intervals from 1 hour to 1 week. Stacking faulted materials were identified by broadening of the 00l reflections, while interstratified materials were identified through the splitting of the 001 into two lines. In contrast to the disorder concepts presented in previous studies of these materials, this work has shown through vibrational spectroscopy that both the alpha-phase and beta-phase hydroxides are present in materials described with stacking fault disorder, while layered hydroxysalts were additionally present in the materials considered to be interstratified. Standard mixtures of Ni3(OH)4(NO3)2 and β-Ni(OH)2 were prepared to investigate if the intensity of particular vibrational bands could be correlated with the proportion of the particular phases in mixtures. The intensities of the C2v nitrate infrared and Raman bands at 990 cm-1 and 1315 cm-1 were shown to correlate with the amount of layered hydroxynitrate incorporated in the phase, theoretically providing a method to determine the components in mixed compositions. Since disorder and phase impurities in layered nickel hydroxide materials affect both their electroactive stability and performance as cathode materials, this work has important implications in several research fields.</p

Synthesis and spectroscopic identification of nickel and cobalt layered hydroxides and hydroxynitrates

The formation of different nickel and cobalt layered hydroxide phases by a variety of solution and solid-state synthesis methods have been investigated. Initially, the preparative conditions were refined to generate single-phase products from metal(II) nitrate hexahydrate starting materials and were characterised by powder X-ray diffraction, vibrational spectroscopy and thermogravimetric analysis. As well as the brucite type β-M(OH)2 and the hydrotalcite-like [M(OH)2-x(H2O)x]x+ alpha-phases (where M = Ni, Co), two different hydroxynitrate phases were isolated with the generic formula M(OH)2-x(NO3)x with x = 0.67 and 1.0 (where M = Ni, Co). The reduction of symmetry of the nitrate anion from D3h to C2v allows the alpha-phases to be distinguished from the two different layered hydroxynitrate phases by both infrared and Raman spectroscopy through the loss of symmetry and concomitant splitting of the degenerate bands. The symmetric N-O stretch enables the two hydroxynitrate phases to be distinguished from one another through the sharp absorption bands at ca. 1000 cm-1 (x = 0.67) and ca. 1050 cm-1 (x = 1.0). The thermogravimetric analysis data of the phases showed key differences between the layered hydroxides, with anhydrous phases having singular weight losses over short temperature ranges and hydrated phases having multiple losses over more extended temperature ranges.</p