FRANKFURT, Dec 8 (Reuters) - Lithium developer Vulcan Energy Resources (VUL.AX) has secured Volkswagen (VOWG_p.DE) as an additional car industry customer for its environmental-friendly lithium hydroxide for automotive batteries. The binding purchase agreement with Volkswagen for lithium extracted from Germany"s Upper Rhine Valley region by means of geothermal energy has an initial term of five years with commercial delivery to start in 2026, Vulcan said in a statement on Wednesday, without providing contract details. German-Australian company Vulcan last month signed a preliminary lithium supply deal with carmaker Stellantis (STLA.MI), shortly after agreeing a similar deal with rival Renault (RENA.PA) amid a surge in demand for electric vehicles. read more Vulcan, which has supply agreements with Belgian recycling group Umicore (UMI.BR) and South Korea"s LG Chem (051910.KS), says its direct lithium extraction method uses less land, groundwater and energy than the most-common existing methods of open-pit mines and brine evaporation ponds. Geothermal lithium from the Upper Rhine Valley along the French-German border has also attracted interest from utility EnBW (EBKG.DE). read more Other players in the field include mining group Eramet (ERMT.PA), which is extracting lithium from geothermal salt water in a pilot scheme at a geothermal power plant in eastern France. Volkswagen plans to build six large battery cell plants in Europe by the end of the decade as part of its ambition to overtake Tesla (TSLA.O) and become the world"s top electric vehicles seller. read more