3D hierarchical rose-like NiP@rGO assembled from interconnected nanoflakes as anode for lithium ion batteries.

In recent years, anode materials of transition metal phosphates (TMPs) for lithium ion batteries (LIBs) have drawn a vast amount of attention from researchers, due to their high theoretical capacity and comparatively low intercalation potentials Li/Li. However, in practice, their application remains constrained by poor electrical conductivity, and dramatic volume expansion and severe agglomeration during the lithium process, which leads to questionable kinetic issues and a prompt decline in capacity during cycling. Herein, through an elaborate design, we developed a novel three-dimensional (3D) hierarchical rose-like architecture self-assembled from two-dimensional (2D) NiP nanoflakes immobilized on reduced graphene oxide (rGO) a combination of a hydrothermal process and phosphating treatment. Such a design provides unique superiority for NiP-based anode materials for LIBs. Paraphrasing, the 3D hierarchical structure of NiP distributes the stress on the anode material while cycling and provides more lithium storage space. The rGO not only enhances the conductivity of materials, but also serves as a flexible framework which immobilizes NiP so that it prevents it from pulverization. Therefore, the synergistic effect between them guarantees the integrity of the material structure after a long-term cycling Li intercalation and deintercalation process. When it acted as anode material for LIBs, the as-obtained 3D rose-like NiP@rGO electrode exhibited a noticeable electrochemical performance, which delivers a discharge capacity of 330.5 mA h g at a current density of 100 mA g after 100 cycles and retains 200.5 mA h g at 1000 mA g.