Phosphorus-Doping-Induced Surface Vacancies of 3D Na 2 Ti 3 O 7 Nanowire Arrays Enabling High-Rate and Long-Life Sodium Storage.

Sodium-ion batteries have attracted interest as an alternative to lithium-ion batteries because of the abundance and cost effectiveness of sodium. However, suitable anode materials with high-rate and stable cycling performance are still needed to promote their practical application. Herein, three-dimensional Na ₂ Ti ₃ O ₇ nanowire arrays with enriched surface vacancies endowed by phosphorus doping are reported. As anodes for sodium-ion batteries, they deliver a high specific capacity of 290 mA h g ^-1 at 0.2 C, good rate capability (50 mA h g ^-1 at 20 C), and stable cycling capability (98 % capacity retention over 3100 cycles at 20 C). The superior electrochemical performance is attributed to the synergistic effects of the nanowire arrays and phosphorus doping. The rational structure can provide convenient channels to facilitate ion/electron transport and improve the capacitive contributions. Moreover, the phosphorus-doping-induced surface vacancies not only provide more active sites but also improve the intrinsic electrical conductivity of Na ₂ Ti ₃ O ₇ , which will enable electrode materials with excellent sodium storage performance. This work may provide an effective strategy for the synthesis of other anode materials with fast electrochemical reaction kinetics and good sodium storage performance.
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