The original study abstract is a little more clear. The main concern is grid storage batteries and EV batteries.

Given that the sharp increase in copper demand is primarily driven by batteries, the extra copper needs for electrification can be significantly reduced if the need for electrical storage is minimized. This can be achieved by generating electricity through a mix of nuclear, wind, and photovoltaics; managing power generation with backup electric plants fueled by methane from abundant resources of natural gas; and transitioning to a predominantly hybrid transportation fleet rather than fully electric vehicles.