The lithium is also in the anode and cathode, the electricity is generated by lithium traveling from one to another through the electrolyte. The electrolyte is

The lithium is also in the anode and cathode, the electricity is generated by lithium traveling from one to another through the electrolyte. The electrolyte is heavier and bulkier but is picked for the ability to let lithium get through without letting electrons get through. I guess you could call it a lithium solution since lithium passes through it to get between the anode and cathode. The anode and cathode need to be electrically insulated from one another requiring a substantial gap, or else the battery will short out internally or self-discharge if the electrical resistance is too low. That's why it's so big. Of course, reducing that gap is a big area of research. Solid electrolytes in principle might be easier to do this with since they stay put, but stuff cracks when lithium concentrations go up and down. The materials literally swell with lithium at the nanometer scale and then break apart. It's pretty hard, you can't unfortunately just vapor deposit a thin film of a solid electrolyte on the cathode since the materials are a bit too fragile to maintain the electrical resistance required for it to work.