1 research outputs found
High-Performance P2-Phase Na<sub>2/3</sub>Mn<sub>0.8</sub>Fe<sub>0.1</sub>Ti<sub>0.1</sub>O<sub>2</sub> Cathode Material for Ambient-Temperature Sodium-Ion Batteries
High-performance
Mn-rich P2-phase Na<sub>2/3</sub>Mn<sub>0.8</sub>Fe<sub>0.1</sub>Ti<sub>0.1</sub>O<sub>2</sub> is synthesized by a
ceramic method, and its stable electrochemical performance is demonstrated. <sup>23</sup>Na solid-state NMR confirms the substitution of Ti<sup>4+</sup> ions in the transition metal oxide layer and very fast Na<sup>+</sup> mobility in the interlayer space. The pristine electrode delivers
a second charge/discharge capacity of 146.57/144.16 mAĀ·hĀ·g<sup>ā1</sup> and retains 95.09% of discharge capacity at the 50th
cycle within the voltage range 4.0ā2.0 V at C/10. At 1C, the
reversible specific capacity still reaches 99.40 mAĀ·hĀ·g<sup>ā1</sup>, and capacity retention of 87.70% is achieved from
second to 300th cycle. In addition, the moisture-exposed electrode
reaches reversible capacities of more than 130 and 80 mAĀ·hĀ·g<sup>ā1</sup> for C/10 and 1C, respectively, with excellent capacity
retention. The correlation between overall electrochemical performance
of both electrodes and crystal structural characteristics are investigated
by neutron powder diffraction. The stability of pristine electrodeās
crystallographic structure during the charge/discharge process has
been investigated by in situ X-ray diffraction, where only a solid
solution reaction occurs within the given voltage range except for
a small biphasic mechanism occurring at or below 2.2 V during the
discharge process. The relatively small substitution (20%) at the
transition metal site leads to stable electrochemical performance,
which is in part derived from the structural stability during electrochemical
cycling. Therefore, the small cosubstitution (e.g., with Ti and Fe)
route suggests a possible new scope for the design of sodium-ion battery
electrodes that are suitable for long-term cycling