Boron Doping and LiBO2 Coating Synergistically Enhance the High-Rate Performance of LiNi0.6Co0.1Mn0.3O2 Cathode Materials
The nickel-rich cathode LiNi0.6Co0.1Mn0.3O2 (NCM613) is a promising cathode material but has poor cycle stability, especially at a high cutoff voltage. Aiming at modulating the unit cell parameters via heteroatom dopants while providing a lithium-ion conductor coating, in this work, boron-based-modified NCM613 has been synthesized with both LiBO2 coating and boron doping via a solid-state method. The optimal modified sample LBO-0.4 exhibits excellent cycle stability at room temperature (2.8–4.5 V) with a retention of 94.8% at 1 C after 100 cycles (versus 79.7% of the pristine sample LBO-0) and 70.7% at 5 C after 1000 cycles (versus a retention lower than 1% for LBO-0). The DLi+ values of LBO-0.4 are significantly higher than those of LBO-0, which is attributed to the enlarged crystal lattice volume generated by the incorporation of B3+ into NCM613. Combined with characterization by Ar sputtering-assisted XPS, TEM, XRD, etc., it is illustrated that LiBO2 coating and B3+ doping can synergistically enhance the electrochemical performance of the NCM613 at a high cutoff voltage, high temperature, and high rate. In addition, DFT calculations disclose that the boron dopant is preferential to locate in the interstice among three Ni atoms of the TM–O layer of NCM, which facilitates the formation of more amount Ni2+, leading to the improved electrochemical performance of NCM613. Such ion doping and surface coating strategy can provide useful guidance on the modification of other layered oxide cathode materials.
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