Stabilized Performance of LiNi_0.90Co_0.07Al_0.03O₂ Cathodes via Zr⁴⁺ Doping upon 4.5 V Application due to the Suppression of H2–H3 Phase Transitions

Abstract

The layered structured cathode material Li-Ni 0.90 Co 0.07 Al 0.03 O 2 (NCA) has good prospects for its high energy density for the application in electric vehicles (EVs) but suffers from rapid capacity decay at a high working voltage. In this work, Zr-doped LiNi 0.90 Co 0.07 Al 0.03 O 2 (Zr-NCA), with excellent performance at 4.5 V, has been successfully synthesized through a nanomilling-assisted solid-state reaction. The doped material presents an initial capacity of 225.9 mA h•g −1 and a coulombic efficiency of 89.29% at 4.5 V, and an improved capacity retention by 22.84% after 100 cycles at 0.5 C is also observed. Such a big promotion can be ascribed to the fact that the irreversible phase transition from the second hexagonal to third hexagonal (H2−H3) phase is suppressed by strong Zr−O bonds. The substitution of zirconium ions also expands the thickness of the lithium slab, which thereafter causes a rapid Li-ion migration; thus, the doping of Zr 4+ in the NCA cathode also creates a promoted rate behavior with a capacity of 144.7 mA h•g −1 at 5 C. The method of lattice doping to improve electrochemical performance of NCA at 4.5 V has been displayed, showing high potential for the mass production of cathode materials with a high energy density.

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

“…Two pairs of diffraction peaks referring to (006)/(102) and (108)/(110) have good splitting, indicating that the synthesized LLO materials have a highly ordered layered structure and good crystallinity. Compared to pristine LLO, the enlarged (003) and (104) peaks of the modified samples have a slight shift toward the lower angle (Figure b), thus inferring a slight increase in the lattice parameters due to the doping of Cd 2+ . With the increase in the Cd 2+ ratio, the leftward shift of the modified samples becomes larger, and the results manifest that the lattice parameters of the material become larger.…”

Enhancing the Electrochemical Performance of Ni-Rich LiNi0.88Co0.09Al0.03O2 Cathodes through Tungsten-Doping for Lithium-Ion Batteries

“…Remarkably, W-doped NCA exhibits a larger unit cell volume than that of pristine NCA cathodes. The expansion of unit cells benefits the migration of Li + and is conducive to rate performance [41]. In addition, the magnified XRD patterns in Figure 3b shows full width at half maxima broadening, the magnitude of which is proportional to the W content.…”

“…The capacity of NCA is 142.3 mAh g −1 at 5 C, which is 69.7% of its value at 0.1 C (204.3 mAh g −1 ). The improved rate performance is primarily related to the slight expansion of the lattice structure by Wdoping, which results in the increase in the distance between the lithium layers and the rapid deintercalation of Li + from the layered structures[41]. Combining the results of cycling and rate measurements, it is considered that the appropriate W dopant (1.0 mol%) could better enhance the electrochemical performances of the cathodes compared to others.To investigate the electrochemical performance of NCA and W1.0-NCA, cyclic voltammetry during the third initial cycle was performed at a scanning rate of 0.1 mV s −1 , shown in Figure6.…”

Ta Doping Improves the Cyclability and Rate Performance of a Nickel-Rich NCA Cathode via Promoted Electronic and Cationic Conductivity

“…The measurements were performed in the range of 2.8–4.8 V with a scan rate of 0.1 mV·s –1 , and the results are shown in Figure . Three pairs of redox peaks are presented in the CV curves for both samples, corresponding to three phase transition processes from left to right, from the first hexagonal phase to the monoclinic phase (H1-M), from the monoclinic phase to the second hexagonal phase (M-H2) and from the second to the third hexagonal phase (H2–H3), respectively. − It is well-known that electrode polarization also affects the cyclic stability of the electrode, and the degree of polarization can be assessed by comparing the potential difference (ΔV) between the highest points of the oxidation and reduction peaks . The ΔV of the three pairs of redox peaks are also denoted in the figure.…”