Doping and Coating Synergy to Improve the Rate Capability and Cycling Stability of Lithium-Rich Cathode Materials for Lithium-Ion Batteries

Abstract

Layered lithium-rich oxide (LLO) with high energy density is considered as the cathode material for the next generation of lithium-ion batteries. However, low initial Coulombic efficiency, poor cycling performance, and rate performance have hindered the commercialization of LLO. Herein, we propose an effective one-pot co-precipitation method to improve the rate capability and cycling stability of LLO materials. The addition of Cd 2+ ions in LLO can affect the formation and growth of primary grains, which leads to structural reconstruction phenomena. Finally, the Cd element exists in the LLO material in the form of ion doping and CdO coating. The Cd-modified LLO material shows porous microspheric morphology, large layer spacing, and well crystallization. The role of Cd doping is to improve the electronic conductivity of LLO and increase the electrochemical potential. CdO nanoparticles covered on the surface and dispersed in the interior of the LLO material particles prevent the native material from being corroded by the electrolyte and contribute to the structural stability of the active material during cycling. Under the synergistic effect of these two modification methods, the surface and internal kinetics of the LLO materials are enhanced, their rate performance and cycling stability are improved, and the electrodes exhibit excellent structural stability after cycling. Density functional theory analysis results prove that Cd doping can suppress the structural change during the charging process and possess lower formation energy.

In Situ Reconstruction of the Spinel Interface on a Li-Rich Layered Cathode Material with Enhanced Electrochemical Performances through HEPES and Heat Treatment Strategy

“…It can directly detect the oxygen coordination environment around manganese ions in LLO due to the [Mn 3+ O 6 ] octahedron. 9 The Raman bands reflect the vibrational modes of polyhedral units, which is achieved by detecting the coordination proximity of O around Li + and TM ions. 26 As shown in Figure 1b, the peaks at about 370, 430, and 480 cm −1 are recognized as the vibration of Li 2 MnO 3 components.…”

“…Compared with the XRD technique, Raman spectroscopy can provide a wider range of structural information about the material. It can directly detect the oxygen coordination environment around manganese ions in LLO due to the [Mn 3+ O 6 ] octahedron . The Raman bands reflect the vibrational modes of polyhedral units, which is achieved by detecting the coordination proximity of O around Li + and TM ions .…”

“…The modification of LLOs has been focused on stabilizing the structure, reducing the corrosion of the active material by the electrolyte, and increasing the migration rate of Li + ions and electrons . Doping and surface coating are considered effective strategies to improve the irreversible capacity loss in the cycle as well as the rate performance of LLOs. , However, doping is prone to cause surface structure damage and transition metal (TM) dissolution, and surface coating agents could reduce the specific capacity of the electrode material. Recently, the formation of the spinel phase on the surface of LLOs has attracted much attention. , Because the spinel phase can act as a protective layer to inhibit the release of surface lattice oxygen and provide three-dimensional (3D) diffusion channels, which facilitate the migration of Li + ions, and thus the existing problems can be significantly improved. , Li + ions were taken away from the cathode materials by pretreating the LLO materials with weak acids (such as (NH 4 ) 2 SO 4 , (NH 4 ) 2 S 2 O 8 , and oleic acid), − or strong acids (such as HNO 3 , H 3 PO 4 , and H 2 SO 4 ). − Because oxygen vacancies can suppress irreversible oxygen loss during cycling, it helps to improve the ICE .…”

Understanding the Impact of Fe‐Doping on the Structure and Battery Performance of a Co‐Free Li‐Rich Layered Cathodes

“…[12,25,26] Several strategies have been proposed to improve their electrochemical behavior, being the most popular a balanced doping of the TM blend. [27][28][29][30][31] In this context, also our group proved that the over-lithiation combined with Al doping could be a good strategy to mitigate the voltage decay upon cycling in battery and improve the structural stability. [32,33] In this study, we investigate the effect of iron doping on the electrochemical and chemical-physical properties of an overlithiated LRLO.…”

Cd-Doped Li4–xCdxTi5O12 (x = 0.20) as a High Rate Capable and Stable Anode Material for Lithium-Ion Batteries

“…To the best of our knowledge, Cd 2+ ( r = 0.78 Å, CN = 4) doped LTO has not been reported thus far. As recently reported, Cd 2+ as a dopant in the lattice of layered lithium-rich oxide (LLO) and Li 2 FeSiO 4 compounds enhances the electronic conductivity and helps to boost the rate performance at high currents with the stable cycling performance for LIBs. , Herein, we have reported a series of [Li 3– x Cd x ] 8 a [LiTi 5 ] 16 d [O 12 ] 32 e (0 ≤ x ≤ 0.2) samples, where Cd 2+ was doped into the tetrahedral Li­(8 a ) site, and thoroughly examined their effect on the electrochemical performances in Li half cell for the first time. The Cd 2+ -doped LTO (i.e., Cd-LTO) electrodes demonstrated remarkable improvement in capacity, cycling, and rate performance in the Li half cell.…”