Niobium oxyphosphate nanosheet assembled two-dimensional anode material for enhanced lithium storage

Abstract

A new-type LIB anode material rGO-supported NbOPO 4 nanosheet exhibits superior rate capability. The lithium storage mechanism study reveals that the 2D structural design and improved electron/ion transport properties result in the high-performance lithium storage. • The new-type two-dimensional anode material NbOPO 4 /rGO was firstly synthesized. • The rGO support improves electron/ion transfer properties of NbOPO 4 /rGO. • The lithiation-generated NbPO 4 contributes to the high-output capacity. The development of high-capacity and high-rate anodes has become an attractive endeavor for achieving high energy and power densities in lithium-ion batteries (LIBs). Herein, a new-type anode material of reduced graphene oxide (rGO) supported niobium oxyphosphate (NbOPO 4 ) nanosheet assembled two-dimensional composite material (NbOPO 4 /rGO) is firstly fabricated and presented as a promising high-performance LIB anode material. In-depth electrochemical analyses and in/ex situ characterizations reveal that the intercalation-conversion reaction takes place during the first discharge process, followed by the reversible redox process between amorphous NbPO 4 and Nb which contributes to the reversible capacity in the subsequent cycles. Meanwhile, the lithiation-generated Li 3 PO 4 , behaving as a good lithium ion conductor, facilitates ion transport. The rGO support further regulates the structural and electron/ion transfer properties of NbOPO 4 /rGO composite compared to neat NbOPO 4 , resulting in greatly enhanced electrochemical performances. As a result, NbOPO 4 /rGO as a new-type LIB anode material achieves a high capacity of 502.5 mAh g −1 after 800 cycles and outstanding rate capability of 308.4 mAh g −1 at 8 A g −1 . This work paves the way for the deep understanding and exploration of phosphate-based high-efficiency anode materials for LIBs.