Lithium Iron Phosphate vs. Lithium-Ion: Differences and Advantages

Lithium Ferro Phosphate technology (also known as LFP or LiFePO4), which appeared in 1996, is replacing other battery technologies because of its technical advantages and very high level of safety.

Due to its high power density, Lithium Iron Phosphate (LiFePO4) technology is well-suited for medium-power traction applications such as robotics, Automated Guided Vehicles (AGVs), and e-mobility, as well as heavy-duty traction applications like marine traction and industrial vehicles.

The long service life and deep cycling capability of LiFePO4 also make it ideal for energy storage applications, including stand-alone systems, off-grid setups, self-consumption with battery storage, and general stationary storage.

In summary, the major advantages of Lithium Iron Phosphate technology include:

- Exceptional safety (no thermal runaway)

- Very low environmental toxicity (uses iron, graphite, and phosphate)

- Calendar life exceeding 10 years

- Cycle life ranging from 2,000 to several thousand cycles

- Operational temperature range up to 70°C

- Low internal resistance, maintaining stability or even improving over cycles

- Constant power delivery throughout the discharge range

- Easy recycling process

Chemistries of Lithium Iron Phosphate and Lithium-Ion Batteries

The charge and discharge rates of batteries are defined by their C-rates. A battery’s capacity is typically rated at 1C, meaning a fully charged 1Ah battery should deliver 1A for one hour. If discharged at 0.5C, it provides 500mA for two hours, and at 2C, it delivers 2A for 30 minutes.

Lithium-Ion (Li-ion)  

Lithium-ion batteries can be made using two different cathode chemistries: lithium manganese oxide (LiMn2O4) or lithium cobalt dioxide (LiCoO2), both paired with a graphite anode. Li-ion batteries have a specific energy of 150-200 watt-hours per kilogram and a nominal voltage of 3.6V. Their charge rate ranges from 0.7C to 1.0C, as charging beyond this range can cause significant damage. The discharge rate for lithium-ion batteries is typically 1C.

Lithium Iron Phosphate (LiFePO4)  

Lithium iron phosphate batteries feature an iron phosphate cathode and a graphite anode. They have a specific energy of 90-120 watt-hours per kilogram and a nominal voltage of 3.20V or 3.30V. The charge rate for LiFePO4 is 1C, with a discharge rate ranging from 1C to 25C.

What Are The Energy Level Differences?

There are significant differences in energy when comparing lithium-ion and lithium iron phosphate. Lithium-ion has a higher energy density at 150/200 Wh/kg versus lithium iron phosphate at 90/120 Wh/kg. So, lithium-ion is normally the go-to source for power hungry electronics that drain batteries at a high rate.

On the other hand, the discharge rate for lithium iron phosphate outmatches lithium-ion. At 25C, lithium iron phosphate batteries have voltage discharges that are excellent when at higher temperatures. The discharge rate doesn't significantly degrade the lithium iron phosphate battery as the capacity is reduced.

Safety Advantages of Lithium Iron Phosphate (LiFePO4)

Lithium iron phosphate (LiFePO4) is increasingly chosen by manufacturers for applications where safety is a priority. It offers excellent thermal and chemical stability, staying cool even at higher temperatures. LiFePO4 is also incombustible, reducing risks during rapid charging, discharging, or short-circuit incidents. Unlike other battery chemistries, LiFePO4 does not experience thermal runaway, as its phosphate cathode does not burn or explode during overcharging or overheating, ensuring the battery remains stable and cool.

In contrast, lithium-ion batteries, particularly those using lithium cobalt dioxide (LiCoO2) for the cathode, lack the same safety advantages. While they have a higher energy density, this comes at the cost of stability. Lithium-ion batteries heat up more quickly during charging and can experience thermal runaway, making them less safe in certain conditions.

Another safety benefit of LiFePO4 is its ease of disposal. Lithium-ion batteries, especially those with lithium cobalt dioxide chemistry, are considered hazardous materials. Exposure to these batteries can cause eye and skin irritation and, if ingested, may lead to severe medical issues. Therefore, special disposal protocols are required. In contrast, LiFePO4 batteries are non-toxic and easier to dispose of, posing fewer environmental risks.

Applications for Lithium Iron Phosphate and Lithium-Ion

Lithium iron phosphate is highly sought after for applications where safety, longevity, and moderate energy density are prioritized. It is ideal for electric motors in vehicles, medical devices, and military applications, especially in environments with higher temperatures. LiFePO4 is also well-suited for stationary applications due to its slightly heavier and bulkier design compared to lithium-ion, although it can still be used in some portable devices.

However, LiFePO4 may not be the best choice for applications where portability is critical, such as smartphones, laptops, and tablets, where lithium-ion batteries are preferred. Lithium-ion batteries are also the go-to choice for high-performance devices that require maximum energy density, providing the best performance from the first use.

Beyond energy density, safety, and portability, manufacturers also consider production costs and disposal. LiFePO4 batteries are generally more cost-effective due to their safer chemistry, which reduces recycling and disposal costs. As a result, many manufacturers opt for LiFePO4 when seeking a more affordable and safer battery solution.

Lithium Offering a Range of Benefits

Advancements in battery technology have made lithium chemistry a leading choice for high-energy devices that require portability. With its long shelf life and ability to provide a continuous power supply over extended periods, both lithium-ion and lithium iron phosphate (LiFePO4) batteries are reliable alternatives for various applications.

Although lithium batteries tend to be more expensive than nickel-metal hydride (NiMH) and nickel-cadmium (NiCd) batteries, their long lifespan helps offset the initial higher costs. Manufacturers considering whether to use lithium-ion or LiFePO4 should evaluate the following key factors:

- Highest energy density: Lithium-ion

- Good energy density and lifecycle: Lithium iron phosphate

- Stable chemical and thermal properties: Lithium iron phosphate

- No thermal runaway and safe when fully charged: Lithium iron phosphate

- Portability and lightweight: Lithium-ion

- Long lifespan: Both lithium-ion and lithium iron phosphate

- Lower costs: Lithium iron phosphate

In addition to these factors, manufacturers should consider the operating environment and potential vibration issues, as these can impact performance. In such cases, the superior chemical and thermal stability of lithium iron phosphate may make it the better choice compared to lithium-ion.