Sodium-ion battery (SIB) is especially attractive in cost-effective energy storage device as an alternative to lithium-ion battery. Particularly, metal phosphides as potential anodes for SIBs have recently been demonstrated owing to their higher specifi c capacities compared with those of carbonaceous materials. Unfortunately, most reported metal phosphides consist of irregular particles ranged from several hundreds nanometers to tens of micrometers, thus delivering limited cyclic stability. This paper reports the sodium storage properties of additive-free Cu 3 P nanowire (CPNW) anode directly grown on copper current collector via an in situ growth followed by phosphidation method. Therefore, as a result of its structure features, CPNW anode demonstrates highly stable cycling ability with an ≈70% retention in capacity at the 260th cycle, whereas most reported metal phosphides have limited cycle numbers ranged between 30 and 150. Besides, the reaction mechanism between Cu 3 P and Na is investigated by examining the intermediate products at different charge/discharge stages using ex situ X-ray diffraction measurements. Furthermore, to explore the practical application of CPNW anode, a pouch-type Na + full cell consisting of CPNW anode and Na 3 V 2 (PO 4 ) 3 cathode is assembled and characterized. As a demonstration, a 10 cm × 10 cm light-emmiting diode (LED) screen is successfully powered by the Na + full cell. Figure 6. a) Schematic representation of the pouch-type CPNW/NVP Na + full cell. b) Cycling performance of the CPNW/NVP Na + full cell at current densities of 600 mA g −1 . c,d) Optical images showing a fl exible LED screen powered by the pouch-type CPNW/NVP Na + full cell. wileyonlinelibrary.com

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Advanced anode materials for next generation lithium ion batteries have attracted great interest due to the ever increasing demand for powerful, light-weight, and compact electrical devices. In this work, graphene nanosheets decorated with ultra-small Fe3O4 nanoparticles (USIO/G) were synthesized via a facile hydrothermal method. Compared with other reported Fe3O4-based anode composites, USIO/G demonstrated superior cyclic ability and excellent rate capability owing to its ultra-small size of active lithium storage sites, Fe3O4, with an average diameter less than 5 nm. Furthermore, graphene nanosheets played an important role in the overall electrochemical performance of the composite by enhancing the electrical conductivity, forming a flexible network, and providing extra lithium storage sites. The obtained composites were tested for electrochemical performance for a total number of 2120 cycles: a rate capability test with current densities ranged from 90 to 7200 mA g(-1) for 920 cycles, followed by a cycling test at 1800 mA g(-1) for 1200 cycles. For the rate capability test, steady reversible capacities were delivered under each current density with final reversible capacities of 1177, 1096, 833, 488, 242, and 146 mA h g(-1) at 90, 180, 900, 1800, 3600, and 7200 mA g(-1), respectively. The subsequent cyclic test demonstrated the superior cyclic stability of USIO/G and a reversible capacity of 437 mA h g(-1) at the 2120(th) cycle was delivered.