Multiscale structural NaTi₂(PO₄)₃ anode for sodium-ion batteries with long cycle, high areal capacity, and wide operation temperature

Abstract

Though plenty of research has been conducted to improve the low intrinsic electronic conductivity of NASICON-structured NaTi₂(PO₄)₃ (NTP), realizing sodium-ion batteries with high areal/volumetric capacity still remains a formidable challenge. Herein, a multiscale design from anode material to electrode structure is proposed to obtain a gadolinium-ion-doped and carbon-coated NTP composite electrode (NTP-Gd-C), in which gadolinium ion doping, oxygen vacancy, optimized structure, N-doped carbon coating, and bridging on the three-dimensional network are simultaneously achieved. In the whole electrode, the excellent hierarchical electronic/ionic conductivity and structural stability are simultaneously improved via the synergistic optimization of NTP-Gd-C. As a result, excellent electrochemical performances of NTP-Gd-C electrode with a high areal/volumetric capacity of 1.0 mAh cm^–2/142.8 mAh cm^–3, high rate capability (58.3 mAh g^–1 at 200 C), long cycle life (ultralow capacity fading of 0.004% per cycle under 10,000 cycles), and wide-temperature electrochemical performances (97.0 mAh g^–1 at 2 C under –20°C) are achieved. Moreover, the NTP-Gd-C//Na₃V₂(PO₄)₃/C full cell also delivers an excellent rate capacity of 42.0 mAh g^–1 at 200 C and long-term high-capacity retention of 66.2% after 4000 cycles at 20 C.

Keywords

high areal/volumetric capacity / multiscale structure / NaTi₂(PO₄)₃ / Na⁺ storage mechanism / sodium-ion batteries