Exxon Mobil XOM.N sent a contingent as part of its foray into the battery metals sector. By Ernest Scheyder LAS VEGAS, June 22 (Reuters) - Lithium producers are growing anxious that delays in mine permitting, staffing shortages and inflation may hinder their ability to supply enough of the battery metal to meet the world's aggressive electrification timelines. Those growth projections assume a best-case scenario, even as mining companies face difficulty hiring technical talent, rising costs and delay times for crucial equipment.