Evaluation of suitable methods to synthesize battery active LiNiO₂

Abstract

A detailed investigation has been made on the possibility of synthesizing LiNiO₂ through different methods using a variety of precursors and varying heat treating conditions with a view to identify a suitable method to synthesize LiNiO₂ and to understand the influence of synthesis method and the nature of the precursors towards the performance characteristics of LiNiO₂. In this regard, four different methods,viz., solid-state, organic precursors, solution combustion and microwave methods were adopted involving suitable combinations of lithium and nickel precursors. All the synthesized compounds were characterized for their phase purity (PXRD), local cation environment (FTIR), particle size, surface area, and electrochemical behavior (charge-discharge). Based on the results obtained especially from PXRD and charge-discharge studies, the “all-hydroxide” precursors of Li and Ni were found to be effective in yielding battery active LiNiO₂ as far as the solid-state and microwave-assisted methods are concerned. With regard to solution synthesis methods, citrate precursor and the combustion method involving hydrazine hydrate fuel were found to yield better performing LiNiO₂, compared to the rest of the combinations attempted in both categories. However, among the wet chemistry based solution methods the present study recommends solution combustion method with hydrazine hydrate as fuel to synthesize electrochemically active LiNiO₂ as it was found to exhibit a stable discharge capacity of 177 mAh/g at least up to 20 cycles.