Pilot‐Scale Synthesis Sodium Iron Fluorophosphate Cathode with High Tap Density for a Sodium Pouch Cell

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 18; no. 45; pp. e2204830 - n/a
• Main Authors: Cao, Yongjie, Li, Xun‐Lu, Dong, Xiaoli, Liao, Mochou, Wang, Nan, Cheng, Jiawei, Xu, Jie, Qi, Yae, Liu, Yao, Xia, Yongyao
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.11.2022
• Subjects: Carbon; cathode materials; Cathodes; Electrochemical analysis; Electrode materials; Electrodes; Energy storage; Fluorides; Iron; iron‐based ferrophosphate; Microspheres; Multi wall carbon nanotubes; Nanotechnology; Nanotubes, Carbon; pouch cells; Sodium; Sodium-ion batteries; Storage batteries; Tap density; wide operating temperature; cathode materials; pouch cells; sodium-ion batteries; wide operating temperature; iron-based ferrophosphate
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202204830

Sodium‐ion batteries (SIBs) have attracted wide interest for energy storage because of the sufficient sodium element reserve on the earth; however, the electrochemical performance of SIBs cannot achieve the requirements so far, especially, the limitation of cathode materials. Here, a kilogram‐scale route to synthesize Na2FePO4F/carbon/multi‐walled carbon nanotubes microspheres (NFPF@C@MCNTs) composite with a high tap density of 1.2 g cm−3 is reported. The NFPF@C@MCNTs cathode exhibits a reversible specific capacity of 118.4 mAh g−1 at 0.1 C. Even under 5 C with high mass loading (10 mg cm−2), the specific capacity still maintains at 56.4 mAh g−1 with a capacity retention rate of 97% after 700 cycles. In addition, a hard carbon||NFPF@C@MCNTs pouch cell is assembled and tested, which exhibits a volumetric energy density of 325 Wh L−1 and gravimetrical energy density of 210 Wh kg−1 (base on electrode massing), and it provides more than 200 cycles with a capacity retention rate of 92%. Furthermore, the pouch cell can operate in an all‐climate environment ranging from −40 to 80 °C. These results demonstrate that the NFPF@C@MCNTs microspheres are a promising candidate cathode for SIBs and facilitate its practical application in sodium cells. A Na‐ion pouch cell consisting of commercialized hard carbon anode and Na2FePO4F/carbon/multi‐walled carbon nanotubes microspheres cathode is assembled and evaluated. This pouch exhibits a maximum specific/volumetric energy density of 210 Wh kg–1 and 325 Wh L–1 based on the mass of active materials with a wide operating temperature range from −40 to 80 °C.