A novel silicon-doped 2D Ti2C MXene monolayer as high capacity stable anode material for lithium ion batteries: Insight from density functional theory study

Although MXene is still considered as the newcomer of the 2D nanomaterials family for energy storage application, pristine MXene is unable to satisfy the capacity demand of energy storage devices like alkali-ion batteries. Here, we present a DFT based investigation with GGA-PBE exchange-correlation functional on pristine and Si-doped Ti2C system for potential application as anode materials in lithium ion batteries. This work explores the structural, electronic and adsorption behavior of pristine and Si-doped Ti2C nanosheets. All predicted Si-doped Ti2C MXenes adsorbed Li-atoms with favorable adsorption energy (Ead) without any structural deformation, exhibiting good structural stability. For three distinct adsorption sites, the Ead are calculated as −1.48 eV, −1.55 eV and −1.57 eV which indicates that Ead is higher when lithium ion is adsorbed at the titanium atomic sites. The calculated specific capacity for pristine Ti2C is 331.6 mAh/g, which is less than conventional graphite anode material. But after doping Si atoms, the specific capacity increases up to 439.4 mAh/g for Si-doped Ti2C and enhance the storage capacity up to 32% for lithium ion batteries. The predicted Voc for pristine nanosheet is 2.26 V and for the mono- and di-Si doped nanosheets 2.24 V and 2.14 V, respectively. Besides, the nanosheets remain metallic during lithiation process after doping silicon.