context: When cycled at 4.5 V, as shown in Fig. 6(a), P2-NMZ10 has 68% capacity retention after 200 cycles, while P2-NMM10 only has 51% capacity retention after 200 cycles, indicating that the Zn-doped sample possesses superior cyclability. Our detailed structural analysis reveals that the dopant precipitates in P2-NMZ10 samples are more stable upon continuous cycling, while the precipitates in P2-NMM10 samples are not stable. As shown in Fig. 6(b–d), the morphology of Mg-enriched precipitates changes obviously with increasing cycle numbers, especially from 100 cycles to 200 cycles, and finally high density intragranular cracks and nano-voids (revealed in Li-rich layered cathodes ) are developed after 200 cycles. Note that bulk degradations initiate from the grain interior after prolonged cycles (see more examples in Fig. S11(a and b)†). For the P2-NMZ10 sample, the precipitates are quite stable once formed. As illustrated in Fig. 6(e–g), the lamellar morphology and the density of the precipitates remain similar up to 200 cycles. More P2-NMZ10 examples are shown in Fig. S11(c and d).† The stabilized structure enables the stable cyclability of P2-NMZ10. Therefore, a good dopant should form high-density stable nano-precipitates so that the bulk structure does not degrade upon prolonged cycling.
answer: Li-rich layered