Na_2/3Li_1/9[Ni_2/9Li_1/9Mn_2/3]O₂: A High-Performance Solid-Solution Reaction Layered Oxide Cathode Material for Sodium-Ion Batteries

Abstract

Designing high-performance layered cathodes, in particular the P2-type groups, is still challenging for sodium-ion batteries. Taking advantage of the well-known Li/Ni mixing in Ni-rich layered cathodes for Li-ion batteries, a layered Na 2/3 Li 1/9 [Ni 2/9 Li 1/9 Mn 2/3 ]O 2 cathode with a superior rate and long-cycle performance is developed through Li-ion incorporation. Neutron diffraction indicates that the introduced Li ions occupy the intrinsic Na + vacancies in the Na layer and transition metal layer concurrently. A facile solid-solution reaction mechanism upon cycling is also revealed by in situ X-ray diffraction, and ex situ X-ray photoelectron spectroscopy results demonstrate that the Ni 2+ /Ni 4+ pairs participate in the electrochemical reactions, while the Mn ions remain unchanged. This material delivers ∼91.6% of the theoretical capacity initially and 64 mAh g −1 reversible capacity even at 20 C (∼58.2% of the capacity at 0.1 C) with 74.5% capacity retention after 1500 long-term cycles in the voltage range of 2.0−4.2 V. This approach can optimize the material structure design, providing some insights into designing high-rate and long-cycle life oxide cathodes for sodium-ion batteries.

In‐Plane BO3 Configuration in P2 Layered Oxide Enables Outstanding Long Cycle Performance for Sodium Ion Batteries

“…Moreover, even at relatively small discharge current of 2 C, the long cycle performance differences is also very large (Figure 3h). The NNCMB cathode material demonstrate an excellent capacity retention of 92.5% after 500 cycles and 80.1% after 1000 cycles at 2 C which is well comparable with those of the reported Na‐storage layered oxide cathodes, [ 39–50 ] as seen in Table S4 (Supporting Information). While for NNCM, after 500 cycles, the capacity shows a significant attenuation, indicating B doping can significantly improve the long cycle performance of P2‐Na 0.67 Ni 0.3 Co 0.1 Mn 0.6 O 2 materials.…”

Structural Evolution of Air-Exposed Layered Oxide Cathodes for Sodium-Ion Batteries: An Example of Ni-doped NaxMnO2

“…The electrochemical performance of NMNO_B in the 2.5–4.1 V potential window was also evaluated by means of GITT (Figure ). The Na + diffusion coefficients calculated from the profiles shown in Figure a (in the order of 10 –14 to 10 –15 cm 2 s –1 , apart from the first values of the reduction process, as shown in Figure b) are comparable with those of many other layered oxides − that typically exhibit high sodium diffusion due to their structure particularly favorable to Na-ion intercalation. From GITT analysis, it further came out that, at a current density of 10 mA g –1 , the material exhibits a very low overpotential (40 mV), which demonstrates the good kinetic properties of the material.…”

Facilitating Layered Oxide Cathodes Based on Orbital Hybridization for Sodium‐Ion Batteries: Marvelous Air Stability, Controllable High Voltage, and Anion Redox Chemistry

“…The continuous degradation between the cathode and the electrolyte can cause the accumulation of unfavorable products and result in the formation of an inhomogeneous solid electrolyte interface (SEI), which hinders Na + transport and restricts its practical application. [25][26][27][28] iii) During anionic redox reactions, the irreversible loss of lattice oxygen at the material surface leads to low initial Coulombic efficiency, and the migration of transition metal ions causse slow diffusion kinetics, which ultimately generates severe capacity decline during long cycling. [29,30] Presently, a large number of researchers proposed a series of strategies from the perspective of atomic orbitals, but no one has specifically summed them up.…”