Na-site coordination environment regulation of Mn-based phosphate cathodes for sodium-ion batteries with elevated working voltage and energy density

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 12; no. 11; pp. 6681 - 6692
• Main Authors: Wang, Kairong, Gao, Chenxi, Tu, Jian, Guo, Kunkun, Ding, Yuan-Li
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 12.03.2024
• Subjects: Batteries; Carbon nanotubes; Cathodes; Coordination; Cycles; Diffusion barriers; Electric potential; Energy storage; Hybrids; Potassium; Sodium; Sodium channels (voltage-gated); Sodium-ion batteries; Structural stability; Voltage
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d3ta07300a

Mn-based sodium superionic conductor (NASICON) phosphate cathodes have been considered as new promising candidates for high-energy, low-cost and relatively environmentally friendly sodium-ion batteries (SIBs). Such cathodes, however, suffer from limited Na + mobility owing to rigid coordinated environments of Na + ions at Na(1) sites and low intrinsic electronic conductivity due to the blocked electronic pathways caused by the big size and isolating nature of PO 4 3− groups in the NASICON structure, leading to low utilization, poor rate capability and cycling performance. To address the above issues, a facile and efficient strategy to regulate the Na-site coordination environment in Na 4 MnV(PO 4 ) 3 (NMVP) has been reported by introducing K + at Na(1) sites for realizing a flexible Na-site coordinated environment and enhancing Na + diffusion. Combining theoretical calculation and experimental results, it is corroborated that the K + dopant at Na(1) sites can efficiently reduce the Na + diffusion energy barrier and increase structural stability and working voltage. By synergistically utilizing the modulation of the Na-site coordination environment and 3D conductive networks, the optimized Na 3.8 K 0.2 MnV(PO 4 ) 3 /carbon nanotube hybrids exhibit superior rate capability and cycling performance with 216% capacity improvement at 15C, and 52.5% increase in energy density in contrast to pristine counterparts, and a capacity retention of 81% after 2300 cycles at 10C, revealing their great potential for practical and cost-effective energy storage applications. The Na-site coordination environment of the Na 4 MnV(PO 4 ) 3 cathode is regulated for the first time for largely improving electrochemical properties via K + doping.