Electrochemical Quartz Crystal Microbalance Gravimetric and Viscoelastic Studies of Nickel Hydroxide Battery Electrodes

Abstract

The measurement of rheological properties of electrodeposited NiOOH films simultaneous to cyclic voltammetry using an electrochemical quartz crystal microbalance and fast quartz crystal impedance at 10 MHz for thin and thick films are reported. The resulting impedance parameters are analyzed using the model proposed by Martin and Granstaff for multiple viscoelastic layers on a piezoelectric resonator. Nickel battery oxide films show an inversion in mass-to-charge relation as shown previously by Scherson and Hillman in the first reduction-oxidation cycles but without appreciable change in their viscoelastic behavior. Changes in the motional resistance are not recovered in the first cycle during ''break in.'' After hundreds of cycles, NiOOH films undertake an important viscoelastic change, and the aged films become softer. The oxidized state shows always higher shear modulus than the reduced state.Replacement of nickel-cadmium rechargeable battery by metal hydride NiOOH/M͑H͒ with same 1.2 V but nearly twice as much power is a near future target. However, the reversible operation over extended number of cycles of charge and discharge at high rates is a basic need in rechargeable batteries and failures are commonly associated to materials. 1 Redox conversion during charge/discharge cycles of nickel hydrous oxide electrodes in alkaline electrolytes produces changes in the morphology of the material behavior. 2 Contraction of Ni͑OH͒ 2 during discharge and expansion of NiOOH during charging in the brucite-type structure can account as much as 15% with exchange of solvated ions with the alkaline liquid electrolyte.This system has been studied by a large variety of electrochemical and spectroscopic techniques. Among the methods employed to characterize nickel hydrous battery oxides is the use of quartz crystal microbalance. In particular, the electrochemical quartz crystal microbalance ͑EQCM͒ has been used to perform microgravimetric analysis during oxidation/reduction cycles upon the assumption of rigid mass behavior by Gabrielli, 3,4 Scherson, 5 and Hillman. 6 Gabrielli and co-workers 3 detected a mass increase upon oxidation of Ni͑OH͒ 2 and considered the incorporation of alkali cations with different hydration shells into the nickel hydrous oxide. Using alternating current ͑ac͒ modulation of the nickel hydrous layer redox conversion in the 0.01 Hz to 1 kHz frequency range the authors claimed that fast incorporation of alkali cations and slow deprotonation occurs in 5 M KOH. 4 Scherson et al. 5 found that Ni͑OH͒ 2 •H 2 O is the major constituent of freshly prepared films by electroreduction of Ni͑NO 3 ͒ 2 •6H 2 O. The authors also reported that electro-oxidation of the ␣-Ni͑OH͒ 2 film leads to an increase of mass in the first cycles, but a curious mass change inversion occurs in extended redox cycles with ␤-Ni͑OH͒ 2 being formed.Gonsalves and Hillman 6 found from a qualitative analysis of the admittance spectra for the coated and bare quartz crystal that electroprecipitated nickel hydroxide films are rigidly coupled to...

Redox switching and oxygen evolution at oxidized metal and metal oxide electrodes: iron in base

“…The EQCM technique has been used to study both overall thermodynamic changes in ion and solvent populations within electroactive polymer thin films, and the dynamics of ion and solvent motion within these films. For instance Calvo and co-workers 81 have examined the redox switching process involved in the Ni(OH) 2 /NiOOH redox transition, whereas Hillman and co-workers 72 have examined the effect of timescale on redox driven ions and solvent transfers at nickel hydroxide thin film modified electrodes using EQCM and EPBD techniques in tandem. This work has lead to the development of a qualitative picture of the mechanism of mobile species transport and polymer relaxation during redox switching in electroactive polymer thin films which may be readily extended by analogy to microdispersed hydrous transition metal oxide coated electrodes.…”

The Synergistic Influences of OH[sup −] Concentration and Electrolyte Conductivity on the Redox Behavior of Ni(OH)[sub 2]/NiOOH

“…13,14 Recently, the redox transitions among various oxyhydroxides on Ni͑OH͒ 2 ultrathin films were systematically investigated by means of the electrochemical quartz microbalance ͑EQCM͒. [13][14][15][16][17][18] These studies proposed several redox mechanisms involving the exchange of cations, differing in whether H + or OH − is transferred. 18 However, contrary results were usually found when the mass of nickel oxyhydroxides was varied, 14,16,17 probably due to the influences of electronic conductivity of oxyhydroxides and/or the diffusion issues of ionic species involved in the redox transitions.…”

Electrochemical behaviour of nickel surface-alloyed with copper and titanium

“…The redox cycling enhances the effect. The major factors responsible for this behaviour are the contraction/expansion of the Ni(OH) 2 /(NiOOH) brucite-type sheets upon oxidation/ reduction and the injection and release of electrolyte ions and water into and from the layered lattice during redox cycling [8,9,15,[36][37][38]. The presence of Cu, Ti, or Cu and Ti was shown to be effective in preventing/retarding the formation of c-NiOOH.…”