a, b, SEM image of LAGP before cycling (scale bar, 2 μm) (a) and after 10 cycles (scale bar, 2 μm) (b). c, d, SEM image of C-LiXZM before cycling (scale bar, 500 nm) (c) and after 100 cycles (scale bar, 500 nm) (d). The original morphology of LAGP was not maintained after cycling, whereas the outline of the crystal face of LiXZM is still clear. e, f, XRD patterns of LAGP (e) and LiXZM (f) after cycling. The crystallinity of LAGP decreased considerably, indicating the poor stability of LAGP, whereas no structural change was observed in LiXZM even after 100 cycles. g, h, Ge 3d XPS spectra of LAGP before (g) and after (h) cycling. i, j, Al 2p XPS spectra of C-LiXZM before (i) and after (j) cycling. k, l, Si 2p XPS spectra of C-LiXZM before (k) and after (l) cycling. When in contact with the Li metal surface, Ge4+ in LAGP is easily reduced, whereas no structural change occurs in LiXZM even after 100 cycles. m, n, Al 2p (m) and Si 2p (n) XPS spectra of the lithium anode before and after cycling. No Al and Si species appeared on the surface of lithium metal after cycling, which further confirmed the stability of LiXZM towards lithium metal. o, Results of scratch and Vickers hardness tests of LiXZM and LAGP.