Boosting High-Voltage and Ultralong-Cycling Performance of Single-Crystal LiNi0.5Co0.2Mn0.3O2 Cathode Materials via Three-in-One Modification

LiNi0.5Co0.2Mn0.3O2is extensively researched as one of the most widely used commercially materials for Li-ion batteries at present. However, the poor high-voltage performance(≥4.3 V) with low reversible capacity limits its replacement for LiCoO2in high-end digital field. Herein, three-in-one modification, Na-doping and Al2O3@Li3BO3dual-coating simultaneously, is explored for single-crystalline LiNi0.5Co0.2Mn0.3O2(N-NCM@AB), which exhibits excellent high-voltage performance. N-NCM@AB displays a dischargespecific capacity of 201.8 mAh g-1at 0.2 C with a high upper voltage of4.6 V and maintains 158.9 mAh g-1discharge capacity at 1 C over 200 cycles with the corresponding capacity retention of 87.8%. Remarkably, the NNCM@AB ||graphite pouch-type full cell retains 81.2% of its initial capacity with high working voltage of 4.4 V over 1600 cycles. More importantly, the fundamental understandings of three-in-one modification on surface morphology, crystal structure, and phase transformation of N-NCM@AB are clearly revealed. The Na+doped into the Li–O slab can enhance the bond energy, stabilize the crystal structure, and facilitate Li+transport.Additionally, the interior surface layer of Li+-ions conductor Li3BO3relieves the charge transfer resistance with surface coating, whereas the outer surface Al2O3coating layer is beneficial for reducing the active materials loss and alleviating the electrode/electrolyte parasite reaction. This three-in-one strategy provides a reference for the further research on the performance attenuation mechanism of NCM, paving a new avenue to boost the highvoltage performance of NCM cathode in Li-ion batteries.