To completely understand the lithium adsorption, diffusion, and capacity on the surface of phosphorene and, therefore, the prospects of phosphorene as an anode material for high performance lithium-ion battery, our group carried out density-functional-theory calculations and studied the lithium adsorption energy landscape, the lithium diffusion mobility, the lithium intercalation, and the lithium capacity of phosphorene. Our calculations show that the lithium diffusion mobility along the zigzag direction in the valley of phosphorene was about 7 to 11 orders of magnitude faster than that along the other directions, indicating its ultrafast and anisotropic diffusivity. The lithium intercalation in phosphorene was studied considering various LinP16 configurations (n=1-16) including the single-side and double-side adsorptions. We found that phosphorene could accommodate up to the ratio of one Li per P atom (i.e., Li16P16). In particular, we found that, even at the high Li concentration (e.g., x = 1 in LixP), there was no lithium clustering, and the structure of phosphorene, when it was fractured, is reversible during the lithium intercalation. The theoretical value of the lithium capacity for a monolayer phosphorene is predicted to be above 433 mAh/g, depending on whether Li atoms are adsorbed on the single-side or the double-side of phosphorene.