Unveiling the role of multifunctional framework for high-energy P2-Na0.8Li0.12Ni0.22Mn0.66O2 cathode materials

Enhancing the interfacial stability between cathode active material and liquid/solid electrolyte is a vital step toward the development of high energy density sodium-ion batteries (SIBs). One of the challenges plaguing this field is an economical and feasible method to construct valid protective layers on cathode materials. Herein, an effective strategy based on synergetic effect of multifunctional framework by simultaneous surface NaTi2(PO4)3 (NTP) coating and bulk Ti4+ doping is designed to improve the performance of P2-Na0.8Li0.12Ni0.22Mn0.66O2 (NLNM@NTP). The combined analysis of in-situ X-ray diffraction (in-situ XRD), scanning transmission electron microscopy (STEM) and density functional theory (DFT) calculations demonstrates that the multifunctional framework optimizes the lattice structure, improves the Ni oxidation states and enhances the stability of crystal and interfacial structure. NLNM@NTP cathode displays high average discharge potential and fast diffusion of Na-ions and electrons. As a result, the NLNM@NTP cathode reveals highly Na storage performance in both liquid-state and solid-state SIBs. The excellent capacity retentions after 500 cycles at 5 C in liquid-state batteries and after 100 cycles at 1 C in solid-state batteries are both close to 100%.