Hierarchical Microspheres Based on α-Ni(OH)₂ Nanosheets Intercalated with Different Anions: Synthesis, Anion Exchange, and Effect of Intercalated Anions on Electrochemical Capacitance

Abstract

Metal oxides and metal hydroxides are interesting, low cost, and low toxicity energy storage materials for electrochemical capacitor applications. Many studies to date have been directed toward replacing RuO 2 1,2 with NiO, 3,4 Co 3 O 4 , 5 MnO 2 , 6 Co(OH) 2 , 7 or Ni(OH) 2 . 8 In recent years Ni(OH) 2 has received much attention due to its superior theoretical electrochemical properties. In particular, β-Ni(OH) 2 has been extensively studied. Despite being a metastable phase, α-Ni(OH) 2 presents itself as a promising material for secondary battery 9 and electrochemical capacitor applications. 10 Two polymorphic forms of layered nickel hydroxide (Ni(OH) 2 ) exist: the αand β-phases. Control over morphology, basal spacing, and types of inorganic materials present is facilitated in the α-Ni(OH) 2 phase; thus manipulation of magnetic, electrical, and ion transport properties can be realized. Both forms have hexagonal crystal structures in which Ni(OH) 2 layers are stacked along the c-axis. A main feature differentiation between these phases is the presence of intercalated species (water and/or anions) within the interlayer galleries of α-Ni(OH) 2 . β-Ni(OH) 2 has a brucite-like structure (a = 3.12 Å, c = 4.6 Å; JCPDS Card No. 14-0117) comprised of perfectly stacked Ni(OH) 2 layers which do not contain water or any charge-balancing anions between its layers. α-Ni(OH) 2 , on the other hand, is a hydrotalcite-like structure (JCPDS Card No. 38-0715) comprised of randomly stacked Ni(OH) 2Àx layers along the c-axis intercalated with water or anions. The basal spacing of α-Ni(OH) 2 can be adjusted from 31.7 to 7.5 Å by adjusting the species intercalated in the interlayer galleries. 11 The size and morphology of α-Ni(OH) 2 particles are affected by several factors: inorganic precursor, solvent, temperature, concentration, and surfactant template. Yang et al. reported the synthesis of α-Ni(OH) 2 with nanoribbon and nanoboard-type structures by a hydrothermal process. 12 Cao et al. reported various α-Ni(OH) 2 morphologies for alkaline rechargeable batteries by reverse micelle/microemulsion and a hydrothermal method. 13 Ida et al. reported the synthesis of layered nickel hydroxide intercalated with dodecyl sulfate, and then successfully eliminated dodecyl sulfate molecules between the Ni(OH) 2 layers, resulting in the formation of hexagonal α-Ni(OH) 2 nanosheets that are potentially useful in ultrathin film devices. 14 In our previous paper we demonstrated a simple, effective coprecipitation synthetic method using alcohol and a dodecyl

The Preparation of Nickel Hydroxide Based on Infinite Dilute Method and Its Electrochemical Performance

“…Furthermore, two broad and asymmetric peaks are observed at about 33.7 and 60.0°, corresponding to nonbasal spacing and which are present in turbostratic materials. 8 This turbostratic behavior has also been observed in other A-Ni(OH) 2 .…”

Nickel hydroxides and related materials: a review of their structures, synthesis and properties

“…(i) Surfactant-intercalated α-derivative structures α-Ni(OH) 2 -like materials in which the intercalated water is replaced with surfactant molecules have been prepared using cetyltrimethylammonium bromide [100], dodecyl sulfate [82,92,[100][101][102][103][104][105][106], dodecylbenzene sulfonate [103], p-aminobenzoate [18] and Tween 80 [100]. The polar or ionic regions of the surfactant molecules interact with the Ni(OH) 2 sheets and the non-polar regions fill the interlayer space.…”

Ultrasound-assisted hexamethylenetetramine decomposition for the synthesis of alpha nickel hydroxide intercalated with different anions

“…The γ-NiOOH and β-NiOOH are the corresponding oxidized forms with oxidation states of +3.5 and +3.0, respectively. The α-to-γ transition has attracted quite attention in the recent years due its greater charge exchange (433 [2] vs 289 mA h g −1 of β-to-β [3]). Unfortunately, the α-form has an inherent instability and eventually converts to the β-form [4].…”

“…In a recent study, α-Ni(OH) 2 was prepared following a surfactant-assisted method to control the interlayer spacing and to exchange the intercalating anions [3]. The cyclic voltammetry results demonstrated that the largest specific capacitance was obtained for the chloride-intercalated products (805 F g −1 ), while the smallest value was obtained for the sulfate-intercalated case (221 F g −1 ) [3].…”

“…In a recent study, α-Ni(OH) 2 was prepared following a surfactant-assisted method to control the interlayer spacing and to exchange the intercalating anions [3]. The cyclic voltammetry results demonstrated that the largest specific capacitance was obtained for the chloride-intercalated products (805 F g −1 ), while the smallest value was obtained for the sulfate-intercalated case (221 F g −1 ) [3]. While the reasons behind this observation could be related to the anionic size differences, the specific capacitance for the nitrate-and acetate-intercalated samples was not in order with the anion size [3].…”