Self-Supported NaTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub> Nanorod Arrays: Balancing Na<sup>+</sup> and Electron Kinetics via Optimized Carbon Coating for High-Power Sodium-Ion Capacitor
Ming Chen, Qinnan Zhou, Asma Iqbal, Xuejiao Liu, Ali Nazakat, Changyu Yan, Heng Tian, Wenqian Li, Yuchi Zhang, Boxu Dong, Jiantao Zai, Xuefeng Qian
Abstract
The NaTi2(PO4)3 (NTP) anode materials exhibit high Na+ diffusion dynamics; carbon-based materials can effectively improve its limited electronic conductivity. However, the low Na+ diffusion of NTP/C composite materials from inhomogeneous carbon mixing or uncontrollable carbon coating cannot keep up with fast electron transfer, leading to undesirable electrochemical performances. Herein, a uniform and controllable carbon layer is designed on the self-supported-coated NTP nanorod arrays with binder-free (NTP@C NR) to improve Na+ and electron kinetics simultaneously. As a result, the NTP@C NR electrodes possess initial coulombic efficiency (ICE = 97%), good rate capabilities (89.1 mA h g–1 at 100 C), and stability with ≈78.4% of capacity retention rate at even 30 C over 1200 cycles. The sodium-ion capacitors with NTP@C NR as an anode and commercially activated carbon as a cathode exhibit ∼9180.0 W kg–1 of power density at 10 A g–1 and super high retention of ≈94.5% at 1 A g–1 over 7000 cycles. This work will help balance transport kinetics between the ion and electron for materials applied in storage devices.