Superior lithium storage in Fe2O3 nanoporous arrays endowed by surface phosphorylation and bulk phosphorous doping

Fe2O3 film anodes are promising for application in lithium-ion micro-batteries in terms of their high theoretical capacity, earth-abundancy, and being environmentally friendly. Nevertheless, the low intrinsic electronic conductivity, sluggish Li+ diffusion, and unstable electrode–electrolyte interface stemming from cycling within Fe2O3 film limit its cyclic stability and rate capability. Herein, extraordinary cyclability and rate performance boosting of nanoporous Fe2O3 film anode are achieved using facile phosphorous heteroatom doping. The unique P-Fe2O3 nanoporous film can reversibly exhibit a capacity of 725 mAh/g at 248 mA g−1 for 300 cycles with a capacity retention of 94.5 %, which is approximately 15 times higher than that without P doping. Moreover, the P-Fe2O3 nanoporous film can retain a capacity of 401 mAh/g at a high rate of 2.48 A/g and the initial coulombic efficiency can reach 90.4 %. Experimental results and density functional theory analysis verify that the enhanced performance derives from the synergistic effect of surface phosphorylation layer and bulk P doping defect, which can promote electron and Li+ transportation meanwhile enhancing surface faradaic redox sites. The insight from this work can provide a new avenue for the rational design of other advanced film electrodes through defect and surface engineering simultaneously.