Strange idea to save money. One can make there own selenium toners, right. So, if I substitute some lithium, powder form, for the selenium, what would result? Just curious, as I am not a chemist. That and lithium does not seem to have many uses in photo chemistry.
Lithium is a soft silvery metal that reacts explosively with water. It is the third element in the periodic table of elements and its chemistry bares no resemblance to that of selenium. That being said, as PE points out selenium is a toxic metal similar to arsenic in its toxicity. Selenium toner is not that expensive and people reuse the toner many times. So the actual cost per print is not that much. Use a commercial toner rather than run the risk of making your own.