Construction of 3D architectures with Ni(HCO 3 ) 2 nanocubes wrapped by reduced graphene oxide for LIBs: ultrahigh capacity, ultrafast rate capability and ultralong cycle stability.

Rechargeable lithium-ion batteries (LIBs) have been the dominating technology for electric vehicles (EV) and grid storage in the current era, but they are still extensively demanded to further improve energy density, power density, and cycle life. Herein, a novel 3D layered nanoarchitecture network of Ni(HCO3 )2 /rGO composites with highly uniform Ni(HCO3 )2 nanocubes (average diameter of 100 ± 20 nm) wrapped in rGO films is facilely fabricated by a one-step hydrothermal self-assembly process based on the electrostatic interaction and coordination principle. Benefiting from the synergistic effects, the Ni(HCO3 )2 /rGO electrode delivers an ultrahigh capacity (2450 mA h g-1 at 0.1 A g-1 ), ultrafast rate capability and ultralong cycling stability (1535 mA h g-1 for the 1000th cycle at 5 A g-1 , 803 mA h g-1 for the 2000th cycle at 10 A g-1 ). The detailed electrochemical reaction mechanism investigated by in situ XRD further indicates that the 3D architecture of Ni(HCO3 )2 /rGO not only provides a good conductivity network and has a confinement effect on the rGO films, but also benefits from the reversible transfer from LiHCO3 to Li x C2 ( x = 0-2), further oxidation of nickel, and the formation of a stable/durable solid electrolyte interface (SEI) film (LiF and LiOH), which are responsible for the excellent storage performance of the Li-ions. This work could shed light on the design of high-capacity and low-cost anode materials for high energy storage in LIBs to meet the critical demands of EV and mobile information technology devices.