Origin and regulation of interfacial instability for nickel-rich cathodes and NASICON-type Li1+xAlxTi2-x(PO4)3 solid electrolytes in solid-state lithium batteries

Abstract

Li1.3Al0.3Ti1.7(PO4)3 (LATP)-based all-solid-state lithium battery (ASSLB) assembled with Ni-rich layered cathode (NCM), of much interest because of its high energy-density and safety, presents many challenges, one of which is poor interfacial instability resulting in large interfacial resistance. Nevertheless, the mechanism of electro-chemical side reactions on the interfacial deterioration hasn't been much investigated specifically, despite their close relationships in electrochemical performance. Herein, we report that the fundamental origin of interfacial chemical reactions is the migration of Ni2+ from the nickel-rich cathodes to the NCM/LATP interface, for the first time, and the simultaneous chemical reaction with Ti4+ in LATP, followed by the decomposition of LATP. In view of this, an elaborately designed regulation strategy, in-situ construction of the layered perovskite La4NiLiO8 buffer layer, is proposed to effectively reduce the content of Ni2+ on the surface of the nickel-rich cathodes and alleviate the chemical reaction between Ni2+ and Ti4+, thereby improving the interfacial stability between NCM and LATP. As a result, the assembled ASSLBs with the La4NiLiO8 buffer layer exhibit high initial discharge ca-pacity (171.49 mAh/g) and excellent cycling performance with 89.47 % capacity retention after 100 cycles at 0.1C.