HOUSTON : Exxon Mobil said on Wednesday it has signed a non-binding lithium supply deal with battery parts maker LG Chem, the oil giant's second agreement to supply the electric vehicle battery metal from its proposed Arkansas project. Exxon last year announced plans to extract lithium from the Smackover Formation, an underground deposit of salty water known as brine that stretches from Florida through Arkansas and into Texas, using at least one type of direct lithium extraction (DLE)