A Smart Large-Scale Synthesis of Na1.0Li0.2Ni0.25Mn0.75O2 as Cathode for Na-Ion Batteries

Sodium-ion batteries (NIBs) represent one of the alternatives to lithium-ion batteries (LIBs), especially for large-scale energy storage. The interest in these batteries arises due to the intrinsic characteristics of sodium: it is cheap, abundant and, above all, environmentally friendly. Among the possible Na-based materials that could be used as cathode in NIBs, it was decided to investigate the performance of Na1.0Li0.2Ni0.25Mn0.75O2 (NLNMO) spinel. NLNMO is a P2-type layered oxide and has attracted great attention as a cathode for NIBs. Despite its presenting some critical issues, especially regarding stability at high working voltage, it proved to be the most promising candidate among the materials belonging to this family. The activity carried out in the work envisaged the production of 1 kg of NLNMO suitable to be used as a cathode material in NIBs. The fundamental requirement was to obtain a high-quality material, at least equal to that synthesized on a laboratory scale. The most critical steps of the synthesis were studied for the possible scale-up step, namely the mixing of the reagents and the heating step. The laboratory scale synthesis was studied in terms of feasibility and scalability and the most critical points for a large-scale transition were analysed. In particular, the quantity of water to be added in the dissolution phase and the operating conditions of the heat treatment were optimized. To validate the performance of the NLNMO obtained on large-scale, it was used to prepare electrodes that were tested in battery. The electrochemical performances of these electrodes were then compared with those exhibited by the material prepared by laboratory-scale.