Electrochemical behaviour of solid lithium nickelate (LiNiO2) in an aqueous electrolyte system

Lithium nickelate was synthesized by self-propagating high-temperature comb ustion. The electrochemical behaviour of the product was studied by cyclic voltammetry of microparticles immobilized on the surface of graphite electr odes. Whereas numerous previous studies have dealt with non-aqueous electro lyte solutions, here the behaviour of lithium nickelate in contact with aqu eous electrolyte solutions was investigated. It could be shown that protons are intercalating upon reduction of the Ni(III) to Ni(II) and deintercalat ing upon oxidation. This insertion electrochemistry is chemically reversibl e. Within 1600 oxidation-reduction cycles, the response diminished only by about 10%. Scanning electron microscopy reveals a considerable recrystalliz ation during the electrochemical cycles. Energy dispersive X-ray detection proved that no metal cations are intercalating. The electrochemical system is accessible only in very alkaline solutions as it shifts to more positive values with decreasing pH.