Stabilized Lithium, Manganese-Rich Layered Cathode Materials Enabled by Integrating Co-Doping and Nanocoating

Abstract

While lithium, manganese-rich (LMR) layered oxide cathode materials offer high energy density (>900 Wh kg–1) and low cost, LMR is susceptible to continuous capacity and voltage decay from the oxygen migration and side reaction with aqueous electrolyte at high voltage. Herein, the integration of Na/F co-doping (CD) and AlF3 coating on LMR is achieved without the need of complex atomic layer deposition. Akin to pristine and CD samples, CD with 1 wt % AlF3 (CD-1.0 wt %) shows excellent electrochemical performance with the capacity and voltage retentions of 93 and 91% after 150 cycles at 0.5C, respectively, and increased ionic conductivity. Spectroscopic analysis indicates that the coating mainly influences the Co distribution, where Co is enriched on the surface, and partial diffusion of Al3+ ions toward the bulk, leading to a slight change of transition-metal (TM) valence states at the nanometer scale and the formation of a stable Li x (CoAl)­O y phase. Post-cycling analysis reveals that CD-1.0 wt % can alleviate the formation of rock-salt structure and Mn dissolution. Besides, little to no metal segregation is detected for the cycled CD-1.0 wt % sample. This finding presents the first instance to apply co-doping and AlF3 coating as a new strategy to enhance the structural homogeneity and takes another step toward their commercial viability.

Upgrading the Performance and Stability of Lithium, Manganese‐Rich Layered Oxide Cathodes with Combined‐Formic Acid and Spinel Coating Treatment

“…The resulting spectra are shown in Figures 4 and S9. Note that the XPS data of PR have been reported in our previous work [38] . For Mn 2p, the main signals are around 642 eV (Mn 2p3/2) and 654 eV (Mn 2p1/2), while the Mn 3+ peaks are located at 642 eV and 653.5 eV.…”

“…Note that the XPS data of PR have been reported in our previous work. [38] For Mn 2p, the main signals are around 642 eV (Mn 2p3/2) and 654 eV (Mn 2p1/2), while the Mn 3 + peaks are located at 642 eV and 653.5 eV. For Mn 4 + state, the peaks are slightly higher at around 643 eV and 655 eV.…”

“…Detailed surface analyses were obtained using X‐ray photoelectron spectroscopy (XPS; PHI 5000 VersaProbe II) and Raman microscopy (Horiba Xplora). The XPS conditions were the same as that reported elsewhere [38] and the corresponding XPS data were fitted using XPSpeak41 software. The obtained spectra were calibrated in reference to the C 1s peak position (284.8 eV).…”

The Effects of Phosphate Impurity on Recovered LiNi0.6Co0.2Mn0.2O2 Cathode Material via a Hydrometallurgy Method

“…Particularly, the Ni 2p 3/2 peak can be deconvoluted into Ni 2+ (854.7 eV) and Ni 3+ (856.5 eV) as displayed in Figure a and Figure S10a. Likewise, as shown in Figure b and Figure S10b, the Co 2p 3/2 peak also can be divided into Co 2+ (782.1 eV) and Co 3+ (780.2 eV), respectively. , The corresponding percentages of each ion are plotted as a histogram given in Figure c,d and Figure S10c,d. An average amount of 42% Ni 2+ and 64% Co 3+ was found when examining the bulk/sub-surface regions of the cathode.…”

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

“…Lattice doping has different effects on LLO characteristics from surface coating: it can improve the structural stability of the material and suppress phase transition during charge/discharge, but it cannot reduce the side reactions at the interface of the active material. , Therefore, a single coating or the elemental doping method does not work optimally for the electrochemical properties of LLO materials. To exploit the advantages of both coating and doping, the strategy of combining surface coating and doping was used to improve the electrochemical properties of LLO materials. ,− …”