Feasibility to Improve the Stability of Lithium-Rich Layered Oxides by Surface Doping

Abstract

Li-rich layer-structured oxides are considered promising cathode materials for their specific capacities above 250 mAh·g–1. However, the drawbacks such as poor rate performance, fast capacity fading, and the continuous transition metal (TM) migration into the Li layer hinder their commercial applications. To address these issues, surface doping of Ti and Zr was conducted to the Li- and Mn-rich layered oxide (LMR), Li1.2Mn0.54Ni0.13Co0.13O2. The drop of the average discharge potentials of the Ti- and Zr-doped LMR was reduced by 593 and 346 mV in 100 cycles, respectively. With aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy, we clarified that Ti4+ and Zr4+ ions are located near the surface of the material, anchor the surface oxygen, and stabilize the LMR structure. The difference in the strengths of the Ti–O and Zr–O bonds and the doping-resultant electronic structures were determined with density functional theory (DFT) calculations and soft X-ray absorption spectroscopy (SXAS), responsible for the electrochemical performance of surface-doped materials. These findings verify our modification strategies to enhance the cycling performances of the promising LMR cathode materials.

Stabilizing oxygen by high‐valance element doping for high‐performance Li‐rich layered oxides

“…The activity of O in the initial charge process was also probed by sXAS. As shown in Supporting Information: Figure S12, a typical feature peak at ~530.8 eV can be observed when LLO and LLO‐1 are charged at 4.8 V, which represents the characteristic peak of the anionic redox reaction of O 49 . To further explore the systematic evolution of lattice oxygen in the initial charge process, the differential O K‐edge spectra of LLO and LLO‐1 are displayed in Figure 4C,D, respectively.…”

“…As shown in Supporting Information: Figure S12, a typical feature peak at ~530.8 eV can be observed when LLO and LLO-1 are charged at 4.8 V, which represents the characteristic peak of the anionic redox reaction of O. 49 To further explore the systematic evolution of lattice oxygen in the initial charge process, the differential O K-edge spectra of LLO and LLO-1 are displayed in Figure 4C,D, respectively. For both materials, the characteristic peak at 530.8 eV in the differential spectrum gradually increases with the increase of cut-off voltage, indicating the gradually increased activity of oxygen anionic redox.…”

Morphology-Tuned Porous Lithium-Rich Cathode Materials Synthesized via a Solvothermal Approach for Li-Ion Battery Application

“…To address the aforementioned issues, various strategies have been applied, such as surface-coating modification, − heteroatom doping, − preactivation, structure regulation (such as transition-metal elemental gradient design, , defect regulation, , morphology and size control, , etc.). Meanwhile, the structure regulation by different synthesis processes mentioned above is an essential way to improve its intrinsic electrochemical performance.…”

Enhanced Cycling and Structure Stability of an Electron Transfer-Accelerating Polymer Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)-Covered Mn-Based Layered Cathode with Ga3+ Doping for a Li-Ion Battery

“…30−32 It is mainly ascribed to the fact that these expensive cations' substitution in Ni sites enhance the integrated bond dissolution energy of cathodes by dragging the oxygen more tightly. 33 The gallium element located at group IIIA has shown the obvious role on suppressing the unordered transfer of Ni 2+ to the Li + site. Jamil et al found that the appropriate amount of gallium replacement obviously suppressed the H2−H3 phase transformation of Ni-rich LiNi 0.94 Co 0.04 Mn 0.015 O 2 and effectively stabilized the cathode structure during cycling.…”

“…Doping modification is also widely applied to protect cathodes from undergoing irreversible transformation within the particles . The major structure stability could be improved by introducing the expensive cation for partial substitution of Ni 2+ , such as Zr 4+ , Nb 5+ , and W 6+ . − It is mainly ascribed to the fact that these expensive cations’ substitution in Ni sites enhance the integrated bond dissolution energy of cathodes by dragging the oxygen more tightly . The gallium element located at group IIIA has shown the obvious role on suppressing the unordered transfer of Ni 2+ to the Li + site.…”