Mechano-chemical hydrothermal synthesis of NH4NiPO4·H2O and its transformation to LiNiPO4

Abstract

Powder preparation of materials that can be used in production cathodes can be simplified by development of mechanical synthesis. In this paper, we report a novel approach using mechano-chemical hydrothermal synthesis of NH4NiPO4·H2O (Ammonium Nickel Phosphate Hydrate – ANP) was investigated. This method is easily scalable and is characterized with great repeatability. It uses inexpensive raw materials: NH4H2PO4 and NiCO3·Ni(OH)2·4H2O for one step synthesis without external source of heating. Reaction between substrates was conducted in water environment by planetary ball milling. As a result of high attrition inside milling chamber, both temperature and pressure is rising. By modification of conditions morphology of obtained powders can be modified. The produced ANP powders with phase purity up to 94.3 vol% (XRD measurement), were transformed to LiNiPO4 (Lithium Nickel Phosphate - LNP) by mixing with finely grinded Li2CO3 and calcination at 500 °C for 2 h. It resulted in LNP content of up to 91.2 vol% in final samples (XRD measurement). The mechano-chemical hydrothermal method was proved to be successful in terms of obtaining LNP using a dissolution – precipitation mechanism during wet milling at room temperature.