SYDNEY—Lithium is one of Janus Henderson Investors’ top commodity bets for 2024, despite the metal having a rocky run in recent months as investors fret that the energy transition is happening more slowly than thought.

Prices of lithium have fallen to around two-year lows as supply, including from Australia, outpaces demand for a metal that’s a key component of electric-vehicle batteries and other technology such as smartphones. Electric-vehicle sales in the U.S. have plateaued in recent months, wrong-footing some automakers that had anticipated stronger demand.