NaTi2(PO4)3 hollow nanoparticles encapsulated in carbon nanofibers as novel anodes for flexible aqueous rechargeable sodium-ion batteries
Bing He, Kuibo Yin, Wenbin Gong, Yuwei Xiong, Qichong Zhang, Jiao Yang, Zhixun Wang, Zhe Wang, Mengxiao Chen, Ping Man, Philippe Coquet, Yagang Yao, Litao Sun, Lei Wei
Abstract
NASICON‐structured NaTi2(PO4)3 (NTP) is an attractive anode material for aqueous rechargeable sodium-ion batteries (ARSIBs) thanks to its three-dimensional open framework and appropriate negative voltage window. Nevertheless, the lack of flexible and high-performance binder-free NTP-based anodes remains stumbling blocks to the development of wearable ARSIBs. Herein, hollow-structure NTP evenly encapsulated in cross-linked porous N-doped carbon nanofiber (HNTP@PNC) is prepared through electrospinning technology and subsequent carbonization treatment, directly acting as binder-free anode for flexible ARSIBs. Benefiting from its unique hollow structure, continuous conductive network and favorable synergistic effect, the HNTP@PNC electrode displays as high as of 108.3 mAh g−1 rate capacity at 5.50 A g−1 and an impressive cycling stability of 97.2% capacity retention after 3000 cycles. Further, theoretical calculations reveal that NTP with NC coating significantly enhances electronic conductivity and accelerates Na+ diffusion kinetics. Pairing with potassium zinc hexacyanoferrate free-standing cathode, a prototype quasi-solid-state ARSIB with a high-voltage discharge plateau of 1.6 V is successfully constructed, achieving a high volumetric capacity of 24.5 mAh cm−3 and an admirable energy density of 39.2 mWh cm−3, outperforming most reported flexible aqueous rechargeable energy-storage devices. These exciting results provide valuable intuition into the design of novel binder-free NTP-based anodes for next-generation wearable ARSIBs.