Phosphorus Doped Silicon Nanowires as High‐Performance Li‐Ion Battery Anodes and Supercapacitor Electrodes

Abstract In order to address the challenges of poor cyclic stability and modest rate capability of Si‐based anodes for Li‐ion batteries, n‐type Si nanowires (SiNWs) with varying phosphorus dopant content are developed via hot‐wire‐assisted vapor‐liquid‐solid growth directly on Cu current collectors. The process leads to uniform doping of the crystalline Si (c‐Si) core and amorphous Si (a‐Si) shell, with the increase in dopant content changing the SiNW morphology from “grass‐like” to “solid tube‐like.” Optimal phosphorus concentrations enhance the cyclic stability and rate‐capability, leading to ≈94% capacity retention after 100 cycles at 1C and exhibit 53% of the C/5 capacity at 5C. As a supercapacitor electrode, an areal capacitance of ≈847 mF cm − 2 at 5 mV s −1 is obtained, which is ≈6.5 times higher than their undoped counterpart. An areal energy density of 0.26 mWh cm −2 at a power density of 3.17 mW cm −2 is obtained with a symmetric supercapacitor, which is superior to most Si‐based supercapacitors reported in the literature. Thus, the study helps to develop a correlative understanding of the effect of phosphorus doping and the resultant changes on SiNW morphology and on their electrochemical performances, while also demonstrating the feasibility of their usage in high‐energy‐density Li‐ion batteries and supercapacitors.