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

LiNi 0.5 Co 0.2 Mn 0.3 O 2 is 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 LiCoO 2 in high‐end digital field. Herein, three‐in‐one modification, Na‐doping and Al 2 O 3 @Li 3 BO 3 dual‐coating simultaneously, is explored for single‐crystalline LiNi 0.5 Co 0.2 Mn 0.3 O 2 (N‐NCM@AB), which exhibits excellent high‐voltage performance. N‐NCM@AB displays a discharge‐specific capacity of 201.8 mAh g −1 at 0.2 C with a high upper voltage of 4.6 V and maintains 158.9 mAh g −1 discharge capacity at 1 C over 200 cycles with the corresponding capacity retention of 87.8%. Remarkably, the N‐NCM@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 Li 3 BO 3 relieves the charge transfer resistance with surface coating, whereas the outer surface Al 2 O 3 coating 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 high‐voltage performance of NCM cathode in Li‐ion batteries.