Ind. Eng. Chem. Res. 2004, 43, 4957-4963
4957
Rationalization of the Industrial Nickel Hydroxide Synthetic Process in View of Optimizing Its Electrochemical Performances M. Casas-Cabanas,† J. C. Hernandez,‡,§ V. Gil,§ M. L. Soria,‡ and M. R. Palacı´n*,† Institut de Cie` ncia de Materials de Barcelona (CSIC), Campus UAB E-08193 Bellaterra, Catalonia, Spain, Sociedad Espan˜ ola del Acumulador TUDOR (Exide Technologies), Autovı´a A-2, km 42 E-19200 Azuqueca de Henares, Guadalajara, Spain, and Electro Mercantil Industrial S.L., Hierro 38, 28850 Torrejo´ n de Ardoz, Madrid, Spain
A thorough study of all the steps involved in a typical industrial nickel hydroxide based active material preparation process has been carried out. The influence of the parameters involved in the reaction, graphite addition, sedimentation, washing, and homogenization steps upon the properties of the final product was determined. The results indicate that no significant particle growth takes place during the sedimentation step and it could thus be suppressed from the process, a fact that would result in cost and time savings. On the other hand, the sometimes disregarded final homogenization step turned out to be crucial in view of obtaining optimal electrochemical performances. Indeed, simple low cost additional milling treatments were found to significantly increase the electrochemical yields and are advisable for implementation in the industrial process. Introduction Nickel based batteries (Ni/Cd, Ni/MH, or Ni/H2) are still widely used for very diverse applications ranging from portable electronics to satellites. Ni/Cd is the second most widely used rechargeable battery for industrial applications after Pb/acid and presents better high-rate and low-temperature performances. Other beneficial features are a flat discharge voltage, long life, continuous overcharge capability, low maintenance requirements, and excellent reliability.1 Even if the crystal chemistry of the nickel oxyhydroxide electrode (NOE) is complex and not fully understood,2,3 the Ni/ MH system is currently the most viable one for hybrid electric vehicle applications.4 Nickel based cells and batteries are available in many different sizes using diverse electrode technologies such as pocket plate, pasted, or sintered. The formulation of the positive electrode active material is highly dependent on the electrode technology used. Among these, either pocket plate or pasted electrodes are those most commonly used for Ni/Cd and Ni/MH batteries. In the first case, the active material consists of a mixture of slightly cobalt doped (
