Adjusting Oxygen Redox Reaction and Structural Stability of Li- and Mn-Rich Cathodes by Zr-Ti Dual-Doping

Abstract

Li-and Mn-rich cathodes (LMRs) with cationic and anionic redox reactions are considered as promising cathode materials for high-energy-density Li-ion batteries. However, the oxygen redox process leads to lattice oxygen loss and structure degradation, which would induce serious voltage fade and capacity loss and thus limit the practical application. High-valent and electrochemical inactive d 0 element doping is an effective method to tune the crystal and electronic structures, which are the main factors for the electrochemical stability. Herein, noticeably inhibited oxygen loss, reduced voltage fade, enhanced rate performance, and improved structure stability and thermal stability of LMRs have been realized by Ti 4+ and Zr 4+ dual-doping. The underlying modulation mechanisms are unraveled by combining differential electrochemical mass spectrometry, soft X-ray absorption spectroscopies, in situ XRD measurements, etc. The dual-doping reduces the covalency of the TM-O bond, mitigates the irreversible oxygen release during the oxygen redox, and stabilizes the layered framework. The expanded lithium layer facilitates the lithium diffusion kinetics and structure stability. This study may result in the fundamental understanding of crystal and electronic structure evolution in LMRs and contribute to the development of high capacity cathodes.

Significant Enhancement of the Capacity and Cycling Stability of Lithium-Rich Manganese-Based Layered Cathode Materials via Molybdenum Surface Modification

“…Figure 4 a shows the initial charge/discharge profiles of batteries with LMR or LMR-Mo as cathodes, respectively. Generally, the charging process of lithium-rich manganese-based layered cathode materials can be divided into two stages [ 48 , 49 , 50 , 51 ]. In the first stage (potential < 4.45 V), the Li+ are released and charge compensation is achieved by transition metal ion oxidation in LiTMO 2 , specifically Ni 2+ /Ni 4+ and Co 3+ /Co 4+ ; the Li 2 MnO 3 phase does not participate in the reaction and only plays the role of stabilizing the material’s structure.…”

Fabrication of submicron Li‐rich Li2(Ti,Zr)O3 solid solution ceramics with sluggish grain growth rate

“…In fact, the Zr in Li 2 TiO 3 has a large solubility limit of 50% and should not be easily segregated. Thus, another possibility is that the stronger bonds increase the thermal activation needed for diffusion, 33 as the bond energy of Zr–O bond is higher than that of the Ti–O bond 34 …”

“…Thus, another possibility is that the stronger bonds increase the thermal activation needed for diffusion, 33 as the bond energy of Zr-O bond is higher than that of the Ti-O bond. 34 Solid tritium breeding materials will be used in hightemperature conditions for a prolonged time in a fusion reactor. It is important to obtain ceramics with small initial grain size, but also the size of grains should not easily grow up during the operation.…”

Li-Rich Layered Oxides: Structure and Doping Strategies to Enable Co-poor/Co-free Cathodes for Li-Ion Batteries

“…The most relevant beneficial effect of this strategy is the remarkable reduction of the voltage decay: this behavior can be correlated to the improvement in the LRLO structure stability upon cycling, in fact, postmortem XRD patterns and Raman spectra showed the superior structural retention of Li1.28Mn0.54Ni0.13Co0.02Al0.03O2 compared to Li1.2Mn0.54Ni0.13Co0.13O2. Feng et al [98] used Ti and Zr co-doping to hinder oxygen losses during the first charge: the optimized material has an initial Coulombic efficiency of 84.2% and a suppressed voltage decay. Furthermore the specific capacity is 229 mAhg -1 with a capacity retention of 84% over 400 cycles.…”