Lithium disilicate as an alternative silicate battery material. A theoretical study

Advanced atomistic simulations are used to study the ion transport in the Na-and K-doped lithium disilicate Li2Si2O5 which is considered as a potential battery material for solid state alkali batteries. In order to evaluate the ease with which Li2Si2O5 can store Na and K ions, the Na and K incorporation mechanisms into Li2Si2O5 are studied by using lattice statics simulations. Our calculations revealed that the defect formation energies for K and Na doping of Li2Si2O5 amount to 0.49 eV/dopant and 0.96 eV/dopant, respectively. The Li ion diffusion in Li2Si2O5 is significantly enhanced upon Na and K doping. The activation energies of Li ion diffusion in all samples are in the range of 0.5-0.6 eV, while for conduction 0.4-0.5 eV. At higher dopant concentrations, K doping increases the Li ion diffusion/ conduction, reaching their improved transport properties at x = 0.14 with low activation energy for diffusion and conduction. At a low dopant concentration of x = 0.02, Na doping also improves the Li ion diffusion/conduction. Our results demonstrate the potential of the doped lithoum disilicate Li2Si2O5 as an effective material for alkali ion batteries and strongly suggest experimental verification.