Safety
LiFePO4 batteries are safer than Li-ion due to the strong covalent bonds between the iron, phosphorus, and oxygen atoms in the cathode. The bonds make them more stable and less prone to thermal runaway and overheating, issues that have led to lithium-ion batteries having a reputation for a higher risk of battery fires.
Stability is why LFPs are the standard in off-grid and solar power applications. When the batteries are in the home, there is no room for error concerning overheating and other issues. Homeowners can confidently store their LiFePO4 battery in the house without worrying about fire safety issues.
Energy Density
Li-ion batteries typically have a higher energy density than LFPs. The energy density of a battery is a measure of how much energy it can store per unit of volume or weight. Li-ion batteries can store more power per volume or weight unit than LFPs.
For example, the energy density of a typical Li-ion battery is around 45–120 Wh per lb (100-265 Wh per kg), while the energy density of a LiFePO4 battery is about 40–55 Wh per lb (90-120 Wh per kg). The expansive energy density range of Li-ion batteries is due to this statistic encompassing all types of Li-ion batteries, including technologies only suitable for electric cars and other applications.
For off-grid power solutions, LiFePO4 remains supreme, even when considering the slightly lower energy density. This difference is negligible as you move into larger stationary power solutions. For instance, the EcoFlow Power Kits are set-it-and-forget-it battery solutions. You won’t notice a slight difference in energy density.
Weight
The weight of a battery bank has some correlation to energy density, as mentioned above. LiFePO4 battery banks may weigh slightly more than comparable Li-ion batteries, while some LFPs may be lighter because the metals used in their construction are lighter.
Either way, any slight variation in weight pales in light of the other enormous advantages of LFPs.
Li-ion batteries with higher energy densities—such as nickel-cobalt-aluminum (NCA) and nickel-cobalt-manganese (NCM)—are no longer considered ideal for off-grid and solar applications. Instead, home power solutions use safer, longer-lasting technologies like LiFePO4. A safer battery is more important than a slight difference in weight.
LFPs are still incredibly light, considering how much power they pack. The EcoFlow DELTA 2 Portable Power Station contains 1024 Wh of energy storage capacity. It weighs only 27 lbs (12 kg) — light enough to comfortably carry around the house or toss in the back of a car.
Temperature Range
LiFePO4 batteries offer a wider operating temperature range. They can function well in temperatures ranging from -4°F (-20°C) to as high as 140°F (60°C).
In contrast, Li-ion batteries have a much smaller temperature range of 32°F (0°C) to 113°F (45°C). Users need to store Li-on batteries in climate-controlled spaces during the depths of winter or the heat of summer.
LiFePO4 batteries are safe to store in the house, shed, garage, or other indoor space without air conditioning. They’re less susceptible to temperature changes, giving you more options for locating the battery without potential damage or reduced efficiency.
Lifespan
Many Li-ion batteries can go through around 500 charge and discharge cycles before degrading in performance. LiFePO4 batteries can go through thousands of cycles before their performance begins to drop.
For example, the DELTA Pro Portable Power Station has a charge cycle rating of 6500 cycles before it reaches 50% capacity. Smaller options tend to have lower lifespans, such as the EcoFlow RIVER 2 Pro Portable Power Station, which has a cycle life rating of 80%+ capacity after 3000 cycles. However, that is still a reliable lifespan. After this time, the battery will still function at a minimum of 80% of the original 768 Wh capacity. Even after this slight drop in performance, you may still receive years of use from your LFP battery bank!
This much longer lifespan means that LiFePO4 will reduce the environmental impact resulting from e-waste. The lack of nickel and cobalt also makes them more environmentally friendly.
You can use your LFP battery bank for 5 or 6 times longer than a Li-ion model, and you won’t waste money on replacements.
Cost
The cost per watt-hour of LiFePO4 and Li-ion batteries can vary wildly depending on the manufacturer, market demand, and capacity. LiFePO4 batteries don’t use nickel or cobalt, materials that can fluctuate dramatically in supply and price.
LiFePO4 is still a relatively new battery chemistry, meaning there are fewer manufacturers and less supply, which can make LiFePO4 batteries slightly more expensive Wh for Wh.
However, it is possible to find affordable options for LFP batteries. The EcoFlow RIVER 2 Portable Power Station is one example. With a 256Wh LiFePO4 battery, it costs less than $1 per Wh.
Even if there is a slightly higher cost than comparable Li-ion battery packs, the advantages of LFP outweigh the price difference. Any extra costs go toward added safety, longer lifespan, and other invaluable benefits.
Self-Discharge Rate
LiFePO4 batteries have a self-discharge rate of around 1-3% per month, depending on usage, temperature, and other factors. The low self-discharge rate means you can leave the battery in storage for months. It will still supply substantial power even after a period of disuse.
To follow best practices, top off your battery at least every few months to keep it optimized for use.
Voltage
LiFePO4 batteries have a lower nominal voltage than Li-ion batteries, typically around 3.2V per cell, compared to 3.6V to 3.7V per cell for Li-ion batteries.
The voltage can impact the design of battery packs and the voltage requirements of devices that use them.