Enhancing Kinetics in Sodium Super Ion Conductor Na<sub>3</sub>MnTi(PO<sub>4</sub>)<sub>3</sub> through Microbe-Assisted and Structural Optimization
Caixia Li, Shuping Pu, Jiapin Liu, Yun Huang, Jiepeng Chen, Xinyan Xiang, Lei Fu, Chao Zou, Xing Li, Mingshan Wang, Yuanhua Lin, Haijun Cao
Abstract
Sodium (Na) super ion conductor (NASICON) structure Na 3 MnTi(PO 4 ) 3 (NMTP) is considered a promising cathode for sodium-ion batteries due to its reversible three-electron reaction. However, the inferior electronic conductivity and sluggish reaction kinetics limit its practical applications. Herein, we successfully constructed a three-dimensional cross-linked porous architecture NMTP material (AsN@NMTP/C) by a natural microbe of Aspergillus niger (AsN), and the structure of different NMTP cathodes was optimized by adjusting different transition metal Mn/Ti ratios. Both approaches effectively altered the three-dimensional NMTP structure, not only improving electronic conductivity and controlling Na + diffusion pathways but also enhancing the electrochemical kinetics of the material. The resultant AsN@NMTP/C-650, sintered at 650 °C, exhibits better electrochemical performance with higher reversible three-electron reactions corresponding to the voltage platforms of Ti 4+/ 3+, Mn 3+/ 2+, and Mn 4+/ 3+ around 2.1, 3.6, and 4.1 V (vs Na + /Na), respectively. The capacity retention rate is up to 89.3% after 1000 cycles at a 2C rate. Moreover, a series of results confirms that the Na 3.4 Mn 1.2 Ti 0.8 (PO 4 ) 3 cathode has the most excellent electrochemical performance when the Mn/Ti ratio is 1.2/0.8, with a high capacity of 96.59 mAh g –1 and 97.1% capacity retention after 500 cycles.