Exploring pristine and transition metal doped SiP₂ monolayer as a promising anode material for metal (Li, Na, Mg) ion battery

Following the successful synthesis of SiP2 monolayers, the two-dimensional (2D) SiP2 monolayer could potentially be used in various fields including photocatalyst water splitting, phototransistor, and thermoelectric applications. However, 2D SiP2 has not been explored as an electrode in the field of rechargeable batteries. In this study, we investigate the structural and electronic properties of 2D SiP2 monolayers. This study also covers the analysis of doping effects on pristine SiP2 where we substitute the phosphorus atom with a transition metal (Cr, Mn, Co, Ni). Further, we show its potential application as an anode material for lithium, sodium, and magnesium ion batteries. We analyze the adsorption and diffusion behavior of the alkali metal atoms. The magnesium ion shows a maximum adsorption energy of -3.2 eV, followed by -2.42 eV and -2.22 eV for the Li and Na ions respectively. The calculated minimum diffusion barrier for Li and Na is 0.9 eV and 0.28 eV, while the Mg ion shows an ultra-low diffusion barrier of 0.06 eV which is the signature of the SiP2 monolayer. The predicted open circuit voltage falls between 0.6 to 0.9 volts for all the metal atoms. The specific capacity shown by the SiP2 monolayers towards Li, Na and Mg are 209 mA h g(-1), 188 mA h g(-1) and 373 mA h g(-1), respectively.