Enhanced lithium storage capability of Ni-rich LiNi0.9CoxMn0.1−xO2(0 ≤ x ≤ 0.1) cathode by co-operation of Al-doping and V-coating

Abstract

The Nickel-rich layer materials LiNixCoyMn1−x−yO2 (x ≥ 0.9) are usually accompanied by structural instability and inevitable capacity loss due to surface degradation during long cycles. The Al-V dual-modification is used in this research to enhance the stability of the structure and the electrochemical capacity of LiNi0.9Co0.05Mn0.05O2 (NCM). First, Al source was added during the co-precipitation synthesis of the precursors. Then, the Al-doped precursors were treated at 720 ℃ for 10 h with slight excess lithium to prevent volatilization of lithium during the sintering process. Finally, Al-doped LiNi0.9Co0.04Mn0.03Al0.03O2 (NCMA) materials were treated with V2O5 at 450 ℃ for 4 h. During calcination, Li3VO4-coated LiNi0.9Co0.04Mn0.03Al0.03O2 materials (NCMAV) were generated by employing residual lithium. Meantime, the Al-V dual-modification helps reduce the mingling degree of Ni2+/Li+ and promotes the diffusion of Li+. Hence, the Al-V dual-modified NCMAV displays a superior rate capability of 162.2 mAh g−1 at 5 C, remaining predominant capability retention of 90.5% after 100 cycles at 4.3 V. Compared with NCMAV, the discharge capability of pure NCM is 140.3 mAh g−1 and its capability retention is 81.6% at 5 C. This dual-modification strategy provides a facile and scalable method to achieve massive application of NCM LIBs with high density and excellent cycling stability.