energy storage
A Better Lithium Battery by Kevin Zanjani
In recent years, Lithium Iron Phosphate (LiFePO4) batteries have gained traction as a viable replacement for SLA/AGM batteries for energy storage applications. If that first sentence didn’t make much sense to you, don’t worry; you’ll be a little wiser by the time you read all the way to the end. You probably know them as the batteries that you use to power your snow blower, your electric car, or R/C vehicles. Technically, these batteries are known by their chemical makeup: LFP, Lithium Iron Phosphate, Lithium Ferrous Phosphate, LiFe, and LiFePO4. There’s a reason this battery technology is used so widely in so many applications - it has a tremendous degree of thermal and chemical stability. Just as importantly, this technology is also intrinsically safer because of an ultra-stable Fe-P-O chemical bond. If you’re a consumer trying to better understand the offerings out there – even if you’re a storage system provider who needs to explain the benefits of your system to a potential buyer – you run across terminology like charge cycles and lifespan. Essentially, these terms describe how much use you’ll get from the battery; every time you use up all the power in the battery and then recharge it until it’s ready to go again, it’s called a charge cycle. Due to the nature of chemicals, you don’t actually recharge the battery to a full 100 percent – each cycle “refills” the battery capacity
just short of the last full amount. How many times you’re able to complete this cycle is what defines the battery’s lifespan. The battery chemistry of a LiFePO4 appears to offer 3,000+ charge cycles, with manufacturers’ data showing at least 8 years in lifespan. In other words, based on average use (and what you’re using that battery for) it should last 8 years before you’ll need to replace it. Compared to other competing battery chemistries like Li-Ion Polymer (and chemistries based on LiCoO2, among others) LiFePO4 is considered to be robust in terms of cycle life and performance. Another kind of battery, SLA/AGM (used in cars and golf carts, etc.) pose dangers because they can sulfate, vent, or leak. Part of the inherent safety of LiFePO4 batteries is due to their non-toxic chemistry and tight chemical bond. LiFePO4 batteries are also a lot lighter -
Figure 1: LiFePo4 Batteries Provide a Flat Discharge Curve allowing for > 95% Depth of Discharge
Figure 2: LiFePo4 Batteries Offer Enhanced Energy Performance at Low Temperatures
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JANUARY • FEBRUARY2021 /// www.nacleanenergy.com
