Lithium-ion batteries (LIB) batteries were initially made for use in laptops, cell phones, and other consumer electronics but they have grown to become a major battery technology for power storage systems. In addition, they have become the most common battery type in modern electric cars.
Batteries play the same role in inverter and solar systems, namely, they provide the DC that is to be converted to AC by the inverter for use in appliances. Lithium-ion also store energy produced from solar panels for later use. All batteries have essentially the same components: electrolytes, positive and negative terminals, and separators integrated into ‘cells’.
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These components are often differentiated based on the nature of the material from which they are made. The most important and definitive component of all batteries, the electrolytes, may be in liquid form as in lead-acid batteries or in the semi-solid gel form. In the case of LIB, lithium salts dissolved in an organic solvent are used. Also, there may be variances in the type of electrodes or terminals. For LIB, the positive electrode is a metal oxide, and the electrolyte is a lithium salt in an organic solvent. (Water is not used as a solvent as lithium reacts vigorously with water.)
The most popular negative electrode used in the manufacture of LIB is graphite.
The positive electrode is generally one of the three-layered materials of lithium salts. Recently, graphene-containing electrodes (based on 2D and 3D structures of graphene) have also been used as components of electrodes for lithium batteries.
The electrolyte is typically a mixture of organic carbonates containing mixtures of lithium salts. A modified variant of Li-ion batteries, the lithium polymer battery, or more correctly lithium-ion polymer battery (abbreviated as LiPo, LIP, Li-poly, lithium-poly, and others), uses a polymer electrolyte instead of a liquid electrolyte.
Advantages of lithium-ion
- Their main attraction is that they do not require constant maintenance. They are a type of sealed maintenance-free battery types.
- Also, they weigh far less than other types of rechargeable batteries of the same size and output capacities. The reason is that the electrodes of a lithium-ion battery are made of lightweight materials. It takes up less space and is thus more suitable when there are space considerations.
- They do not have to completely discharge before recharging, as with some other battery technologies. They have a very much longer life than other battery types.
- Comparatively, Li-ion batteries charge extremely faster than other rechargeable batteries. The reason why lead-acid batteries require a three-stage charging profile where each stage progressively lowers the charge current and can be bulk-charged up to 80%, then absorption-charged from 80% to about 95%, and then float-charged to 100%. Li-ion batteries however do not have such a similar three-stage charging and can be bulk-charged all the way up to 100%.
- Li-ion batteries can withstand very rugged power conditions than other types of batteries. They can supply electricity to very high-power appliances.
- Under the same conditions, LIB is far more efficient than lead-acid batteries. Lead-acid batteries only have a charge efficiency of 85%. This means that for every 1A sent to the batteries, only .85A are store for use. Lithium batteries however have a charge efficiency of 99% so nearly every amp sent to them is store and usable. Therefore, a lead-acid battery bank will require a 15% larger – and more expensive – solar array to charge it as fast as a comparably sized lithium battery bank.
- The lifespan of lithium batteries is significantly higher than that of normal lead-acid batteries! Some manufacturers warranty their Li-ion batteries to last 10,000 cycles. Most lead-acid batteries are only rated for 400 cycles or less. This means li-ion batteries will last ten times longer than their lead-acid The lifespan of lithium batteries is significantly higher than that of normal lead-acid batteries! Some manufacturers warranty their Li-ion batteries to last 10,000 cycles. Most lead-acid batteries are only rated for 400 cycles or less. This means li-ion batteries will last ten times longer than their lead-acid
Disadvantages of lithium-ion
- The single most important disadvantage of LIB is its cost. They cost up to three times the cost of conventional batteries per Ah.
- They are extremely sensitive to high temperatures. Heat causes lithium-ion battery packs to degrade much faster than they normally would.
- They have a very low shelf life thus when in storage, they have to be recharged from time to time. Also, they have to be stored under temperatures lower than 40 degrees. (The shelf life of a battery is the time an inactive battery can be stored before it becomes unusable. It is usually considered as having only 80% of its initial capacity. The conditions under which a battery is stored either by the dealer or the user will determine its shelf life and in turn, eventual lifespan.
- Again, if lithium-ion completely discharges, it will be permanently damaged. Typically, this is accounted for as many inverters will automatically shut down when their batteries are being discharged below their depth of discharge because the batteries may be permanently damaged if fully discharged.
- They require an onboard protection circuit to maintain the battery voltage. This makes them even more expensive than they already are because of their manufacturing costs. The goal of the protection circuit is to limit the peak voltage of each cell during charge and prevent the cell voltage from dropping too low on discharge. In addition, it helps to monitor the cell temperature to prevent temperature extremes. With these precautions in place, the possibility of metallic lithium plating occurring due to overcharge is virtually eliminated.
- There is a small chance that, if a lithium-ion battery pack fails, it will burst into flame.
- There are often transportation restrictions on the shipment of larger quantities. (This restriction does not apply to personal carry-on batteries.)