Tunable Electrochemical Activity of P2–Na_0.6Mn_0.7Ni_0.3O_2–xF_x Microspheres as High-Rate Cathodes for High-Performance Sodium Ion Batteries

Abstract

As an important cathode candidate for the highperformance sodium ion batteries (SIBs), P2-type oxides with layered structures are needed to balance the specific capacities and cycling stability. As a result, a cation and anion codoped strategy has been adopted to tune the electrochemical activity of the redox centers and modulate the structure properties. Herein, a series of P2−Na 0.6 Mn 0.7 Ni 0.3 O 2−x F x (x = 0, 0.03, 0.05, and 0.07) cathodes with microsphere structures are synthesized, using a solid-state reaction in the presence of MnO 2 microsphere self-templates. Compared with the cation-doped Na 0.6 Mn 0.7 Ni 0.3 O 2 , additional Fdoping can affect the lattice parameters and redox centers of Na 0.6 Mn 0.7 Ni 0.3 O 2−x F x . Comprehensively considering the specific capacities, cycling stability, and rate capability, the optimized x value in Na 0.6 Mn 0.7 Ni 0.3 O 2−x F x is determined to be 0.05. In the half cells, Na 0.6 Mn 0.7 Ni 0.3 O 1.95 F 0.05 (F-0.05) maintains a capacity of 90.5 mA h g −1 in the first cycle at 1.0 A g −1 , giving a capacity retention of 78% within 900 cycles. The superior rate capability of F-0.05 is guaranteed by the larger diffusion coefficient of Na + (D Na ) combined with higher charge transfer speed. In addition, when coupled with MoSe 2 /PC anodes, the full cells also exhibit impressive electrochemical performance.

Improving the Na0.67Ni0.33Mn0.67O2 Cathode Material for High-Voltage Cyclability via Ti/Cu Codoping for Sodium-Ion Batteries

“…In recent years, lithium-ion batteries (LIBs) in portable mobile electronics, electrocars, and energy storage devices have undergone rapid development. However, lithium (Li) resource demand for LIBs exceeds the supply, resulting in high Li costs. − Compared with LIBs, sodium-ion batteries (SIBs) have attracted much research because of their similar charge–discharge mechanism and the greater sodium (Na) resources in Earth’s crust. − Now, as more and more researchers have been studying electrode materials for SIBs, it is very important to research and develop a suitable cathode material.…”

Structural degradation mechanisms and modulation technologies of layered oxide cathodes for sodium‐ion batteries

“…A F‐doped Na 2/3 Ni 1/3 Mn 2/3 O 1.95 F 0.05 cathode has been shown to deliver superior high‐temperature performance (75.6% capacity retention after 2000 cycles at 10 C at 55°C). Kang et al [ 111 ] studied crystal modulation and the charge compensation mechanism in P2‐type Na 0.6 Mn 0.7 Ni 0.3 O 2− x F x ( x = 0, 0.03, 0.05, and 0.07) cathodes with microsphere structures. An optimized sample of x = 0.05 delivers capacity retention of 78% after 900 cycles and a superior rate capability with an excellent capacity retention of 63% when the current increases from 0.05 to 2.0 A g –1 .…”

Zn/Ti/F synergetic-doped Na0.67Ni0.33Mn0.67O2 for sodium-ion batteries with high energy density

“…The synergetic-doping of Zn 2+ , Ti 4+ and F − increases oxygen content in the lattice of a crystal structure. 26 As a result, ex situ X-ray diffraction (XRD) measurements indicated that the synergistic effects signicantly alleviated the phase transition of P2 to O2 during cycling. Na 0.67 Ni 0.28 Zn 0.05 Mn 0.62 Ti 0.05 O 1.95 F 0.05 could exhibit a high capacity retention (86%) at 10C (1C = 170 mA g −1 ) over 1000 cycles in half-cells, respectively.…”