Plants use sunlight energy to take carbon dioxide and water molecules are rearrange them to make oxygen gas and glucose, which stores the energy (battery). Animals/humans
"burn" the glucose using oxygen, and then we help to recycle the carbon dioxide and
water when we breathe out.
So why does the sun have to keep supplying more energy? Why isn't the energy also
recycled when the atoms are recycled?

Inside every cell of all living things, energy is needed to carry out life processes. Energy is required to break down and build up molecules and to transport many molecules across plasma membranes. All of life’s work needs energy. A lot of energy is also simply lost to the environment as heat. The story of life is a story of energy flow — its capture, its change of form, its use for work, and its loss as heat. Energy, unlike matter, cannot be recycled, so organisms require a constant input of energy. Life runs on chemical energy.