Enhancing the stability of a polycrystalline Ni-rich material upon cycling with an inorganic Li+ conductor binder

Abstract

A critical challenge for commercializing a polycrystalline Ni-rich layered cathode material for Li-ion batteries is the loss of capacity and impedance growth caused by the formation a resistive surface layer on primary grains. Surface modification on secondary particles can partially alleviate the degradation, but it fails to address the surface reconstruction of primary grains upon cycling. Here, we infused the lithium phosphate binder with good structural compatibility with the bulk structure into the grain boundaries of a polycrystalline LiNi_0.9Co_0.05Mn_0.05O₂ material. The key to the process is that the lithium phosphate precursor remains solid until lithium hydroxide melts. The lithium phosphate binder enhances the morphological stability and cycling stability of the polycrystalline material during cycling by increasing its critical pressure. Besides, the lithium phosphate serves as a solid electrolyte, minimizing sluggish kinetics caused by the pseudo-single-crystalline morphology.