Why big oil is wading into lithium

BP AND SHELL, two British oil giants, have long sunk cash into solar and wind farms. Their rivals elsewhere have mostly stuck to their drilling. Investors have rewarded single-mindedness. ExxonMobil, an American firm unapologetically wedded to the black stuff, is worth $510bn, half as much again as the British duo combined. Its share price is up by 50% in the past five years, compared with a rise of 10% for Shell and a fall of 13% for BP.