Electrochemical performance comparison between β-type mixed nickel cobalt hydroxides prepared by various synthesis routes

• Published in: Solid state sciences 2001-01, Vol.3 (1), p.65-80
• Main Authors: Cressent, Angèle, Pralong, Valérie, Audemer, Albane, Leriche, Jean-Bernard, Delahaye-Vidal, Agnès, Tarascon, Jean-Marie
• Format: Article
• Language: English
• Subjects: Applied sciences; Cobalt co-precipitate; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Exact sciences and technology; Lithium-based precursor; Ni-MH batteries; Nickel hydroxide and oxyhydroxide
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/S1293-2558(00)01125-0

Cobalt is usually co-precipitated with nickel to improve the nickel hydroxide electrode capacity. Herein, we present the acquirement of β-type mixed Ni/Co phases by three different synthetic routes. The first method consists of the electrochemical removal of Li from LiNi 1– x Co x O 2 compounds to form Ni 1– x Co x O 2 compounds that are then reduced in a KOHhydrogen peroxide medium to produce Ni 1– x Co x (OH) 2. The second method deals with the aging of α-type mixed Ni/Co hydroxides in 8M KOH solution at 60 °C. Finally, the third method consists of the direct precipitation of Ni and Co sulfates using the right sequence and amount of NH 4OH and NaOH bases. A constant capacity was found, independently of the amount of Co, for samples prepared from a lithiated precursor, in total contrast with samples prepared from the aging and precipitation processes that show a maximum capacity near x=0.1. We explain such a different electrochemical behavior, based on material morphology and surface area arguments. Moreover, we show that cobalt addition in the nickel network enhances the stability of the β(III) phase.