Layer-by-Layer Na3V2(PO4)3 Embedded in Reduced Graphene Oxide as Superior Rate and Ultralong-Life Sodium-Ion Battery Cathode

Na3V2(PO4)(3) (NVP) is regarded as a promising cathode for advanced sodiumion batteries (SIBs) due to its high theoretical capacity and stable sodium (Na) super ion conductor (NASICON) structure. However, strongly impeded by its low electronic conductivity, the general NVP delivers undesirable rate capacity and fails to meet the demands for quick charge. Herein, a novel and facile synthesis of layer-by-layer NVP @ reduced graphene oxide (rGO) nanocomposite is presented through modifying the surface charge of NVP gel precursor. The well-designed layered NVP @ rGO with confined NVP nanocrystal in between rGO layers offers high electronic and ionic conductivity as well as stable structure. The NVP @ rGO nanocomposite with merely approximate to 3.0 wt% rGO and 0.5 wt% amorphous carbon, yet exhibits extraordinary electrochemical performance: a high capacity (118 mA h g(-1) at 0.5 C attaining the theoretical value), a superior rate capability (73 mA h g(-1) at 100 C and even up to 41 mA h g(-1) at 200 C), ultralong cyclability (70.0% capacity retention after 15 000 cycles at 50 C), and stable cycling performance and excellent rate capability at both low and high operating temperatures. The proposed method and designed layer-by-layer active nanocrystal @ rGO strategy provide a new avenue to create nanostructures for advanced energy storage applications.