This study investigates the use of a coating and sintering methods to enhance the durability of Ni-rich single crystals after conversion from Ni-rich polycrystals. LixCoO2 grain boundary coating and LixSnO3 surface dominant coating morphologies were developed to compare the effects after sintering to single crystals. The results showed that the LixSnO3 coated LiNi0.8Co0.1Mn0.1O2 cathode (NCM811) after conversion to single crystal had an improved cycling efficiency over the untreated single crystal sample. However, it had a similar semi-single crystal morphology to the untreated sample. The LixCoO2 coated NCM811 single crystal formation was facilitated by the crystallization of Co in the grain boundaries and resulted in a more robust single crystal particle with high-capacity retention and a high discharge capacity after 50 cycles of 129.11 mAh·g-1 compared to the standard single crystal sample with 117.34 mAh·g-1. This study gives useful insight on the formation of single crystals of Ni-rich cathode materials from their polycrystals.