It is not difficult in the sense of being technically challenging but in the sense that it has very low yields. It doesn't exist naturally in huge concentratio

It is not difficult in the sense of being technically challenging but in the sense that it has very low yields. It doesn't exist naturally in huge concentrations (you can't just get a chunk of Lithium) you either extract it from a huge volume of evaporated salt brine, or you filter through huge amounts of ore to yield something rich in lithium.