Xiaoya Gao,Zhimin Li,Honglin Yan,Dongyan Zhang,Yuan Wang,Yuan Ha
Ni-rich layered LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA) cathode materials have attracted extensive attention in power lithium ion batteries on account of their high specific capacities and low voltage delay. However, they still suffer from inferior cycling stability, especially operating at a high cutoff voltage. In this paper, a surface modification strategy was proposed by utilizing Al(PO 3 ) 3 as a coating material to enhance the cycling performance of NCA in 2.7–4.6 V (vs. Li/Li + ). The surface modification effects of Al 3+ lattice doping and Al(PO 3 ) 3 coating were verified to be well achieved. In particular, besides the functions in stabilizing surface crystal structure of the NCA and isolating the erosion from electrolyte, the Al(PO 3 ) 3 coating could eliminate the residual lithium on the NCA surface to in-situ generate the Li 3 PO 3 which was conductive to the rate performance. Accordingly, the Al(PO 3 ) 3 -modified NCA cathode delivered excellent cycling performance, of which the initial discharge capacity was 235.9 mAh . g −1 at high cutoff voltage of 4.6 V, with a capacity retention of 71.6% after 100 cycles at 1 C. This work demonstrates the feasibility of surface modification on NCA via the phosphate coating with multiple functions, and provides an efficient approach to improve the cycling stability of Ni-rich layered cathode materials at higher cutoff voltage.
Interfacial modification is one of the most important technologies to improve the overall electrochemical properties of Ni-rich cathodes. Herein, a novel strategy of in situ planting of an electrolyte film-forming additive on a single crystal NCM811 surface is proposed by consuming the residual lithium to develop a functional Al(Li)BOB nano-layer. Different from traditional physical coating, this approach cleverly consumed the undesirable residual lithium on the NCM811 surface. The in situ grown 30–50 nm Al(Li)BOB layer on the single crystal NCM811 cathode surface contributes to its much enhanced electrochemical performances. At a high operating voltage (charge voltage limit of 4.5 V vs. Li/Li+), the capacity retention is greatly increased from 57.0% to 83.5% after 295 cycles. Meanwhile, the incorporation of aluminum is effective in improving the thermal stability of the Ni-rich cathode. The novel interfacial strategy by in situ implanting of an electrolyte additive is of important significance for solving the critical interfacial issue for Ni-rich cathode materials.
The layered lithium nickel-rich cathodes have become one of the most promising candidates for next-generation lithium-ion batteries with high energy density , However, the nickel-rich cathode suffers from a rapid decay of capacity due to their intrinsic instability and undesirably residual lithium compounds originated from LiNiO 2 structural changes on the surface, hindering large-scale commercial application. Herein, a continuous and uniform oxygen vacancy enriched-MoO 3-x coating was successfully synthesized and reacted residual lithium compounds as a functional layer on the cathode. Such chemically reconstructed coating (Li 2 MoO 4 ) strategy endows the 1 wt% MoO 3-x coated NCA cathode with a fast Li + ions transport and enhanced structural stability , leading to an outstanding discharge capacity of 214.0 mAh g −1 at 0.1C (1C = 270 mA g −1 ), a better capacity retention of 80.3 % after 120 cycles at 0.5C, and an excellent high rate capability of 120 mAh g −1 at 5C cycled in voltage range of 2.75 V–4.3 V. This work provides an effective strategy to modulate surface structure towards advanced Ni-rich cathodes for high-performance lithium-ion batteries.
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