Electrochemical Mechanism Analysis of Dual-Site Doped on P2-Na_2/3Ni_1/3Mn_2/3O₂ Enabling Anionic and Cationic Redox with Excellent Electrochemical Performance

Abstract

In recent years, P2-layered manganese-based cathodes have garnered considerable attention because of their exceptional capacity, high energy density, and facile synthesis. Nevertheless, the poor rate capability and inferior capacity retention at high discharge rates have limited their application in commercial batteries. In this work, we report a stable P2-type Na 0.62 K 0.05 Mn 0.67 Ni 0.17 Mg 0.11 Zn 0.05 O 2 layered oxide cathode material with both alkali metal site doping and transition metal site doping and confirm that the synergistic effect of the K−Mg−Zn system suppresses the phase transition of P2−O2 and reduces the activation energy of interfacial charge transfer. Furthermore, the introduction of the K−Mg−Zn system results in favorable cycling stability rate performance of the sample. Specifically, the initial discharge capacity at 0.1C is measured to 140.9 mAh g −1 , with a capacity retention of 95.1% after 100 cycles at 1C. Remarkably, even after 2000 cycles at 20C, the capacity retention remains at 82.8%. Ex situ X-ray photoelectron spectroscopy (XPS) analysis and the density functional theory (DFT) calculation reveal that the charge compensation during the KNMMZ charging and discharging process can be interpreted as the cooperative action of Mn 3+ /Mn 4+ and Ni 2+ /Ni 3+ /Ni 4+ redox couples in the voltage range of 2−4 V, while peaks around 4.2 V are attributed to the anionic redox action. Ex situ X-ray diffraction (XRD) analysis reveals the pronounced capability of KNMMZ to effectively suppress the P2−O2 phase transition. The complex impedance measurements and the galvanostatic intermittent titration technique validate that the K−Mg−Zn system enhances the diffusion of sodium ions. Furthermore, the full cell demonstrates outstanding cyclic electrochemical performance, underscoring its exceptional stability and durability throughout multiple charge−discharge cycles. Consequently, the P2-type Na 0.62 K 0.05 Mn 0.67 Ni 0.17 Mg 0.11 Zn 0.05 O 2 system presents promising prospects for the advancement of high-energy SIBs in practical applications.

Multication-Induced Disorder in an O3-Type NaNi0.4Mg0.1Al0.1Ti0.3Sb0.1O2 Cathode for Sodium-Ion Batteries

“…1,2 However, the implementation of LIBs for large-scale applications is still facing issues due to limited reserves and the high price of lithium. 3,4 Additionally, Co is an invincible component of cathode used in high-capacity LIBs, which is also expensive, toxic, and scant in Earth's crust. In the context of increasing demand for a substantial energy storage system, sodium-ion batteries (SIBs) are favorable substituents to LIBs considering notable characteristics such as Na abundance and wide availability around the globe.…”

“…Lithium-ion batteries (LIBs) have been dominating the market over the past three decades in portable devices. , However, the implementation of LIBs for large-scale applications is still facing issues due to limited reserves and the high price of lithium. , Additionally, Co is an invincible component of cathode used in high-capacity LIBs, which is also expensive, toxic, and scant in Earth’s crust. In the context of increasing demand for a substantial energy storage system, sodium-ion batteries (SIBs) are favorable substituents to LIBs considering notable characteristics such as Na abundance and wide availability around the globe. − Both lithium and sodium have similar physicochemical properties; however, Na inherits a few more beneficial aspects than Li, like high desolvation and activation energies, which promote ion transport. , …”

Ceria Heterostructure Suppresses Oxygen Release of Na-Ion Battery Cathode Materials

“…Recently, manganese-based layered oxides have been reported as a potential cathode candidate for sodium ion batteries because of their high capacity, low cost, and environmental friendliness . Meanwhile, the exploitation of oxygen anionic redox in Na 2/3 TM 1– x Mn x O 2 (TM = Cu, Mg, Zn, Ni, or Li) cathode provided an effective strategy to break through the energy density limitation of the Na-ion batteries. − As an archetypal compound, the Na 2/3 Ni 1/3 Mn 2/3 O 2 (NNM) cathode can achieve an energy density as high as 600 Wh kg –1 through the combination of Ni 2+ /Ni 3+ cationic redox and O 2– /O 2 n– anionic redox. − However, the O 2– /O 2 n– redox is usually accompanied by irreversible oxygen evolution (O 2 n– → O 2 ) from the surface lattice, resulting in undesirable voltage fading and metal dissolution. ,,,− Therefore, stabilizing the surface lattice to suppress oxygen release and metal dissolution is of significant value for the achievement of high energy density SIBs with long cycling stability.…”