Boosting High-Voltage and Ultralong-Cycling Performance of Single-Crystal LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2) Cathode Materials via Three-in-One Modification

摘要

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.