Ionothermal synthesis and lithium storage performance of core/shell structured amorphous@crystalline Ni–P nanoparticles

A new strategy for synthesizing Ni–P alloy nanoparticles with a core-shell structure is proposed, which involves a facile ionothermal process in a deep eutectic solvent (DES). The architecture of the core-shell structured Ni–P alloys is featured as amorphous spherical cores homogeneously wrapped by self-generated crystalline Ni3P shells of different thickness, which rely on the molar ratio of Ni2+/H2PO2− in the choline chloride (ChCl)/ethylene glycol (EG) based eutectic mixture. As an anode for lithium ion batteries, cyclic voltammetry curves, electrochemical impedance spectra, and cyclability of the novel structured Ni–P nanoparticles were evaluated. It was found that the sample with a thicker crystalline shell exhibited improved capability and reversibility over the sample with a thinner one, especially at a higher discharge–charge current density. It was suggested that the crystalline shell can enhance the conductivity of the amorphous cores, suppress the aggregation of active particles and increase the structural stability during cycling.