Lithium-ion batteries are literally everywhere – from laptops and cell phones to hybrids and electric cars. They offer great capacity and current output for a lightweight and small size. Lithium-ion batteries are deep-cycle by origin, so they can be fully charged and discharged, and thus used for solar energy storage.
Lithium-ion batteries have four main components:
- Anode (positive cobalt-oxide electrode) and cathode (negative graphite electrode) which store the lithium;
- Separator which blocks the flow of electrons inside the battery;
- Electrolyte carrying positively charged lithium ions from the anode to the cathode and vice versa through the separator;
- Two current collectors (positive and negative).
While the battery is discharging, the anode releases lithium ions to the cathode, generating a flow of electrons from one side to the other. When the battery is getting charged, lithium ions are released by the cathode and received by the anode. The battery is fully charged when no more ions flow. If all the ions have moved back, it means that the battery is fully discharged.
There are three types of lithium-ion batteries: cylindrical such as in a remote control, pouches such as in smartphones and tablets, and prismatic such as in electric vehicles. The former type often has corrugated sides, which create air gaps between adjacent cells and can aid in cooling. This feature makes them suitable for solar energy storage.
Lithium-ion refers to a variety of lithium-based battery chemistries. Lithium iron phosphate (LFP) batteries are considered to be the best solar battery type. Unlike regular lithium ion batteries, LFPs have a higher cell density, which makes them more compact. Moreover, they last longer due to the electrolyte's properties, and are not classified toxic.