LONDON, March 28 (Reuters) - Chemicals group Johnson Matthey has secured a site in Poland to produce ultra-high energy battery materials and signed a 10-year supply deal with Canada's Nemaska Lithium as it seeks to grow its exposure to the electric vehicle market.

Plant construction should begin this year at Konin, about 200 kilometres west of Warsaw, and it would have the potential to produce up to 100,000 million tonnes per year, Johnson Matthey said in a statement on Thursday.