Strong quarterly results expected from Contemporary Amperex Technology Co. Ltd. may widen its market-capitalization lead over electric-vehicle maker BYD Co., reinforcing the companies’ diverging trajectories.

Hang Seng Indexes Co. is adding electric-vehicle battery-maker Contemporary Amperex Technology Co., miner CMOC Group Ltd. and jeweler Laopu Gold Co. to Hong Kong’s equity benchmark gauge, the index compiler said following its quarterly review.

A key Chinese lithium mine run by Contemporary Amperex Technology Co. Ltd. is preparing to reopen as soon as early next month.