The pledge would mark the first commitment from the G7 to quit coal-fuelled power - use of which needs to decrease if the world is to avoid the worst impacts of climate change.
"There are very concrete declarations and agreements for the expansion of renewable energies, but also for example for phasing out coal," Lemke said.
The final communique of the three-day G7 meeting in Berlin this week would also include a strong emphasis on protecting biodiversity and fighting plastic pollution, she said.
Lemke was speaking as Germany hosted G7 energy, climate and environment ministers for talks held against a backdrop of spiralling energy costs and fuel supply worries sparked by the war in Ukraine.
The conflict has triggered a scramble among some countries to buy more non-Russian fossil fuels and burn coal to cut their reliance on Russian supplies, raising fears that the crisis could undermine efforts to fight climate change.
Germany has said finding alternative fossil fuels would not come at the expense of environmental goals.
The final communique will be published later on Friday.