Find the hidden power cell
At the entrance of Spider Cave, turn around and look up, you'll see a strong box high up lodged into the rocks. This is the one you'll have to destroy to get the power cell instead. To actually destroy it you'll need yellow eco which can only be found inside Spider Cave, flowing out of some of the vents in the first cavern.
Once you have made your way up to the many ledges on the cave walls (using web trampolines) you'll have to look for a vent that is close to the cave entrance. Once you've done so and started channeling yellow eco, jump down (using spin kick to break your fall) and immediately start running out of the cave into Volcanic Crater. Once you are in view of the strong box use your goggles (Icon|triangle) to aim and shoot it down, releasing the cell inside.