Local Electron Spin‐State Modulation at Mn Site for Advanced Sodium‐Ion Batteries with Fast‐Kinetic NaNi0.33Fe0.33Mn0.33O2 Cathode

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Abstract
O3‐type cathode material with high theoretical capacity possesses significant potential for sodium ion batteries (SIBs). However, the irreversible phase transition, structural volume change and poor Na+ transmission efficiency, caused by Jahn–Teller distortion of Mn3+, lead to the inferior cycling lifespan. Herein, the nonequilibrium‐driven local electron spin‐state modulation at Mn site with Sn4+ substitution is proposed to stabilize the NaNi0.33Fe0.33Mn0.33O2 cathode. With this, the controlled irreversible phase transition and volume expansion during charge/discharge and fast Na+ transportation channel is achieved. Therefore, the modulated NaNi0.33Fe0.33Mn0.33O2 cathode can contribute to improved capacity of 144.8 mAh g−1 at 0.1 C rate and long‐term cycling over 200 cycles with 80.1% retention by comparison with the counterpart (132.5 mAh g−1 at 0.1 C) and 54.1% retention. Noted that the elevated Na+ diffusion kinetics corresponding to high‐rate capability is also demonstrated (93.2 mAh g−1 at 10 C rate). Furthermore, the full battery equipped with hard carbon anode shows an energy density of 381.05 Wh kg−1 and the 76.8% retention after 200 cycles. This work highlights the regulation of electron spin‐state from the insight of modification Jahn–Teller effect would shed a new perception on the design for the advanced layered cathode materials and SIBs.
Funding Information
  • National Natural Science Foundation of China (52162030)
  • Major Science and Technology Projects in Yunnan Province (202202AG050003)

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