The implementation of battery storage in solar energy and battery backup systems is becoming an increasingly popular option, if not, a necessity. Two of the most common batteries implemented in these systems are lithium-ion and lead acid batteries. This NEW series gives an overview of both lithium-ion and lead acid batteries, as well as elaborates on their operating principle.
In Part 1, we tackle lithium-ion batteries. Part 2 discusses lead acid batteries, and summarises a comparison of both. Consider this comparison of these batteries to help you in selecting the correct type of battery for your home or business…
Lithium-ion (li-ion) batteries are used as an energy storage means for off-grid solar products or battery backup systems. These batteries have higher efficiency, higher depth of discharge capacities, high capacity, and a long life cycle. Lithium-ion batteries do not suffer from high self-discharge rates and the memory effect experienced by both Nickel-Cadmium (NiCd) and Nickel metal hydride (NiMH) batteries. The charging efficiency of the battery is excellent, with some reaching up to 99%, and these batteries do not contain toxic heavy metals like sealed lead acid (SLA) and NiCd.
How does a Li-ion Battery Work?
All li-ion batteries consist of three functional layers which are the positive electrode (cathode), the negative electrode (anode) and the separator. The separator is usually a polymeric membrane which is saturated with a liquid electrolyte which allows for lithium-ion transport but prevents direct contact between the electrodes.
When the battery is charging, lithium ions will move from the positive electrode to the negative electrode and moves from the negative electrode to the positive when discharging. Electrons will move through the external circuit in the same direction as the lithium ions when driven by an external charger or by its stored chemical energy when the battery is discharging.
The below diagram depicts lithium ion and electron flow in a cell with an external circuit.
What are the types of Lithium-Ion Batteries?
Li-ion batteries are classified according to the composition of their positive electrodes. The following are the various Li-ion batteries used:
Lithium Cobalt Oxide (LCO) was the first commercialized cathode material and is still used by consumers today. It has a high energy density but is not suited for use in off-grid products as it has a lower cycle life and the safety of it is poor.
Lithium Manganese Oxide (LMO) batteries possess the advantages of being a battery that has a good thermal stability as well as safety, but it has the disadvantage of having a lower cycle life. The use of this type of battery has declined in commercial use and has been replaced by combining the manganese oxide with nickel and cobalt (NMC).
Lithium Nickel Manganese Cobalt Oxide (NMC, NCM) blended batteries possess advantages of having a good cycle life, improved safety, and high energy density. Varying the ratios of Nickel, Manganese and cobalt in the battery will result in the emphasis of certain qualities that target specific applications including off-grid products.
Lithium-Ion Phosphate (LiFePO4) batteries consist of qualities that make them suited for off-grid products where cost, safety, stability, and cycle life are primary requirements. These batteries have a lower energy density than competing Li-ion chemistries and majority of cases a lower cell output voltage which is acceptable for most applications.
Watch this space for Part 2 of the series, where we tackle lead acid batteries and then summarise the two.
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