Bifunctional Surface Coating of LiAlO₂/Si_1–xAl_xO₂ Hybrid Layer on Ni-Rich Cathode Materials for High Performance Lithium-Ion Batteries

Abstract

As a candidate material for high energy density cathode, nickelrich layered oxide cathode material LiNi 0.6 Co 0.2 Mn 0.2 O 2 has become the current research hotspot for lithium-ion batteries. However, the instability of the surface reaction interface promotes the change of surface structure and bulk structure for LiNi 0.6 Co 0.2 Mn 0.2 O 2 , resulting in poor cycling stability that hindered its practical application. Here, the LiNi 0.6 Co 0.2 Mn 0.2 O 2 surface modified by hybrid coating layer (NCM@LSAO) is reported. In this constructed hybrid layer, the LiAlO 2 with layered structure can be firmly anchored on the NCM surface, and Si 1−x Al x O 2 with high electrical conductivity and chemical stability can be used as a protective layer to inhibit the occurrence of surface side reactions. Hence, combining the advantages of the LiAlO 2 and Si 1−x Al x O 2 coating layer, which can effectively suppress the structural transformation and surface reaction interface failure upon long cycling, thus has improved the electrochemical performance accordingly. As a result, LiAlO 2 /Si 1−x Al x O 2 surface-modified LiNi 0.6 Co 0.2 Mn 0.2 O 2 exhibits excellent rate performance, with a high discharge specific capacity of 153.4 mAh/g even at 10 C. In addition, the cyclic stability is also much improved, which can deliver a high discharge capacity of 130.1 mAh/g after 500 cycles at 5 C, with a capacity retention of 78.5%.

Thermodynamically Stable Dual‐Modified LiF&FeF3 layer Empowering Ni‐Rich Cathodes with Superior Cyclabilities

“…The outer layer of pristine NCM particles is amorphous, corresponding to the impurity layer of lithium oxide residues (LiOH or Li 2 CO 3 ) (Figure 2b). [ 35 ] It was discovered in the NCM@LFF3 sample that a crystallized outer layer with an average thickness of ≈2 nm firmly decorates around the NCM811 particle (Figure 2f). When the coating concentration is 3 wt%, the coating is thin and the composition is difficult to observe, hence, the coating concentration was increased to 5 wt% to validate the presence of the LiF&FeF 3 dual‐modified layer in NCM@LFF5, and TEM and HRTEM images were shown separately in Figure S4 (Supporting Information).…”

“…Further evidence was obtained in the study of CV profiles for the two electrodes at different scan speeds, demonstrating that the LiF&FeF 3 coating layer contributes to increased Li + diffusion (Figure S6, Supporting Information). [ 35,38,39 ] The cycling stability and rate capability can further highlight the excellent electrochemical performance of NCM@LFF samples. To compare the rate performance of NCM811 and dual‐modified samples, the NCM@LFF3 sample is significantly improved, with a capacity of 169.4 mAh g −1 at 10C, owing to the stable LiF&FeF 3 dual‐modified interface that is advantageous for Li + diffusion (Figure 3b).…”