Can I take a battery, a mobile power supply, a flashlight and the like to fly?

It can be carried, but it should be noted that the rated energy value of lithium-ion batteries cannot exceed the specified value.

According to the Notice on Strengthening the Safety Management of Lithium Batteries in Passengers' Luggage issued by the Civil Aviation Administration of China, personal consumer electronics equipment and spare batteries containing lithium or lithium-ion batteries can be carried on the plane with luggage, but the lithium content of lithium metal batteries should not exceed 2g, and the rated energy value of lithium-ion batteries should not exceed 100Wh. Those exceeding 100Wh but not exceeding 160Wh may be installed on the equipment in checked baggage or hand luggage with the approval of the airline. It is forbidden to use lithium batteries above 160Wh.