Localization of electrons within interlayer stabilizes NASICON-type solid-state electrolyte

Although Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolyte has the advantages of high ionic conductivity, low cost, and satisfying air stability, it is thermodynamically unstable with lithium metal, which could reduce the Ti4+ to Ti3+ and form a highly resistive interface, leading to the fast degradation of battery performance. Herein, through an in-depth study on the degradation mechanism of LATP by delocalized π electrons in succinonitrile (SN), we propose a novel plastic composite interlayer (PCI) based on succinonitrile and polyacrylonitrile, which can not only realize a rapid and uniform transmission of lithium ions but also localize π electrons, inhibit the continuous deterioration of LATP. Compared with previous battery tests at elevated temperatures or by adding liquid components, the PCI-based Li|Li symmetric cell has achieved a cyclability for more than 300 h at room temperature. Moreover, the discharge capacity of the all-solid-state battery based on PCI still retains 87.9% after 170 cycles at 0.1C, which is in sharp contrast to the 38.6% capacity retention after 50 cycles of LFP/SN/LATP/SN/Li battery. These results show that PCI, as an effective anode interlayer, paves a way for high-performance solid-state batteries based on NASICON-type electrolytes.