LATP-coated NCM-811 for high-temperature operation of all-solid lithium battery

To achieve high-temperature operation of all-solid lithium batteries (ASLBs), LATP (Li1.3Al0.3Ti1.7(PO3)4) was coated on the surface of a high-nickel cathode material, NCM-811 powder (LiNi0.8Co0.1Mn0.1O2), by evaporation-induced self-assembly (EISA). Using EISA, the fine LATP precursor in ethanol was deposited on NCM-811 powder at loadings of 0.1–3 wt%, after which the precursor was dried and calcined at 750 °C. Although the X-ray diffraction (XRD) patterns of the coated samples were not significantly changed, the main peaks of NCM-811 were slightly shifted to lower angle by increasing LATP amount on NCM-811. Therefore, due to cation mixing in LATP-coated NCM-811, the lattice constant increased slightly, accompanied by a decrease in the factor c/3a. Transmission electron microscopy (TEM) showed that the thickness of the coating was 2, 5, and 8 nm for 0.5 wt%-, 1 wt%-, and 3 wt%-LATP-coated NCM-811, respectively. The LATP-coated NCM-811 samples were utilized as the active material in the composite cathode for ASLBs. The electrochemical behavior of single cells (LATP-coated NCM//composite solid electrolyte sheets//lithium metal) was evaluated at 70 °C. The cycle capacity retention was higher for the cell employing the cathode with 0.5 wt%-LATP-coated NCM-811 than for the other cells, with an initial discharge capacity of 138 mAh g−1 in the range of 3.0–4.1 V and capacity retention of 85% over 45 cycles. Moreover, the cycle retention of the cell was significantly improved compared with the electrochemical behavior of the existing ASLBs in which the cathode is prepared by simply mixing LATP powder with polyethylene oxide/salt and NCM-811 powder.