Improving the Structure and Cycling Stability of Ni-Rich Layered Cathodes by Dual Modification of Yttrium Doping and Surface Coating

Abstract

A crucial challenge for the commercialization of Ni-rich layered cathodes (LiNi0.88Co0.09Al0.03O2) is capacity decay during the cycling process, which originates from their interfacial instability and structural degradation. Herein, a one-step, dual-modified strategy is put forward to in situ synthesize the yttrium (Y)-doped and yttrium orthophosphate (YPO4)-modified LiNi0.88Co0.09Al0.03O2 cathode material. It is confirmed that the YPO4 coating layer as a good ion conductor can stabilize the solid–electrolyte interface, while the formative strong Y–O bond can bridle TM–O slabs to intensify the lattice structure in the state of deep delithium (>4.3 V). In particular, both the combined advantages effectively withstand the anisotropic strain generated upon the H2–H3 phase transition and further alleviate the crack generation in unit-cell dimensions, assuring a high-capacity delivery and fast Li+ diffusion kinetics. This dual-modified cathode shows advanced cycling stability (94.1% at 1C after 100 cycles in 2.7–4.3 V), even at a high cutoff voltage and high rate, and advanced rate capability (159.7 mAh g–1 at 10C). Therefore, it provides a novel solution to achieve both high capacity and highly stable cyclability in Ni-rich cathode materials.

Boron Doping and LiBO2 Coating Synergistically Enhance the High-Rate Performance of LiNi0.6Co0.1Mn0.3O2 Cathode Materials

“…41 In addition, the lower amount of impurity oxygen can inhibit the interfacial side reactions. 12 In addition, as the etching time lasts, two peaks of LBO-0.4 show a slight shift of low binding energy, confirming the effect of boron dopant on the crystal lattice of NCM.…”

A Cobalt‐ and Manganese‐Free High‐Nickel Layered Oxide Cathode for Long‐Life, Safer Lithium‐Ion Batteries

“…[ 32 ] By virtue of this surface‐enriched Ti distribution, pernicious side reactions between electrolyte and the active material might be mitigated, according to literature reports on similar functional elements, such as Y 3+ , Zr 4+ , and Nb 5+ . [ 21,35–38 ]…”

Stabilized Performance of LiNi0.90Co0.07Al0.03O2 Cathodes via Zr4+ Doping upon 4.5 V Application due to the Suppression of H2–H3 Phase Transitions

“…With further extraction of Li + , the irreversible H2–H3 phase transition appears at 4.2 V with large distinction from the former two phase transitions, meanwhile, when compared to the layered material with 30–60% Ni content, the activation voltage decreases ∼0.3 V . The dramatic shrinkage of lattice along the c-direction occurred with the formation of covalent MO–OM peroxide bonds by the oxygen evolution reaction, which is due to the thermodynamic instability of the H3 phase, and this structural change may lead to the capacity decay. , For the NCA cathode, the diffraction peak shifted toward a high angle clearly, when charged to 4.5 V, the 2θ of the (003) peak reached to 19.36°, and a cell volume shrinkage of 5.46% was observed during the H2–H3 phase transition, which was not conducive to the migration of Li ions. However, for Zr-NCA, the (003) peak finally shifted to 2θ = 18.36°, which approached to the original state so that a small volume change of 1.55% was achieved, showing the effect of Zr 4+ doping in suppressing the structural change induced by the irreversible H2–H3 phase transition, which can be regarded as the main reason for the improved capacity retention of the Zr 4+ -doped cathode material because the Zr–O bond offers stronger bonding energy within the lattice.…”