LiFePO4 Batteries vs NMC Batteries: Which is Better?
With the ever-growing demand for electric vehicles and energy storage systems, lithium batteries are getting more and more attention. Lithium batteries are more efficient than other typical lead-acid batteries and are much lighter. But there are many different types of lithium batteries which can be confusing.
The word “lithium battery” itself is a generic term for a variety of different types of batteries that use lithium ions during charging/discharging. The word “lithium” refers to the type of ion that moves between the positive and negative electrodes when charging or discharging.
The most common types of rechargeable lithium-ion batteries are Lithium Nickel Manganese Cobalt Oxide (NMC), Lithium Iron Phosphate (LFP) Lithium Cobalt Oxide (LiCoO2), and Lithium Manganese Oxide (LMO).
In this article, we will focus on two different chemistries: LiFePO4 and NMC. Both have their advantages and disadvantages that make them suitable for certain applications.
Lithium Iron Phosphate (LiFePO4 or LFP) Battery
A Lithium Iron Phosphate battery is a type of rechargeable battery that uses lithium iron phosphate (LiFePO4) as its cathode material and carbon graphite for its anode. These batteries offer high safety and are highly stable in high-temperature environments.
LFP has a nominal voltage of 3.2V per cell. LFP is the safest type of lithium battery because it has extremely low thermal runaway. LFP also has a long lifespan with up to 8000 cycles at 100% depth of discharge (DOD).
Ni-Mn-Co Battery
Ni-Mn-Co is a type of lithium-ion battery that uses nickel, manganese, and cobalt as its main materials. They are suitable for applications where high capacity is required, such as electric vehicles, power tools, and consumer electronics.
NMC batteries have a nominal voltage of 3.6v per cell and have good power performance due to their higher operating voltage compared to other chemistries. NMC batteries typically have about 500-700 cycles at 100% DOD, making them half as durable as LFP battery.
LiFePO4 vs NMC: A Technical Look at the differences
So now that we have a basic understanding of the primary lithium chemistries, let’s get into the nitty-gritty of what makes each type of battery unique. What advantages or disadvantages does each of these chemistries bring to the table? Here are the technical differences between the two battery types:
1. Cycle Life
Cycle life is the number of times a battery can be charged and discharged before it loses a significant amount of its capacity. The key term here is “significant amount.” A significant amount is defined as 20%. That means that if a battery starts with a capacity of 100 Amp-hours (Ah), after 500 cycles, it will only be able to store 80Ah. After 1000 cycles, it will only store 64Ah, etc. LiFePO4 batteries have a very similar cycle life to NMC at low depths of discharge (DOD). At 100% DOD, however, LiFePO4 can last over 10x longer than NMC.2. Energy Density
One of the main reasons why Lithium-Ion technology is so popular is due to its high energy density, or how much energy can be stored in a given space. When compared to traditional lead-acid batteries, lithium-ion batteries offer twice as much energy density per charge. Amongst their lithium counterparts, LiFePO4 offers even more energy density than NMC and has a lifespan up to 10 times that of traditional lead-acid batteries. This means that for a given amount of storage space, you would get more energy out of a LiFePO4 battery than a regular NMC battery.3. Charging Efficiency
Charging efficiency is defined as the energy that goes into the battery (measured in watt-hours) divided by the energy that comes out of the battery (also measured in watt-hours). LiFePO4 batteries have a charging efficiency of about 95%. This means that 95-watt hours go into the battery for every 100-watt hours taken out. NMC batteries have a charging efficiency of about 85%. This means that 85-watt hours go into the battery for every 100-watt-hours taken out. When comparing these two chemistry types, it can be seen that LiFePO4 is 10% more efficient at charging than NMC.4. Raw Materials
The big difference between NMC and LFP cells is the raw materials. As previously mentioned, NMC uses nickel, cobalt, and manganese in their cathode formulation. LFP uses iron phosphate. The raw materials for iron phosphate are considerably cheaper than those for NMC—about a third of the price or less. The cost of raw materials is the most significant cost associated with manufacturing lithium-ion batteries; therefore, the low-cost raw materials used in LFP cells make them a more economical choice. In addition, NMC will often use lithium compounds such as carbonates and hydroxides, which tend to be cheaper than the phosphates that are used for LiFePO4 synthesis. This means that production costs are lower for NMC cells, which helps explain why they are so common in high-volume devices such as electric vehicles (EVs). Other factors such as cathode material costs also play a part in determining price differences.5. Self-Discharge
Self-discharge is the loss of charge in a battery over time. The rate of self-discharge varies depending on the chemistry and temperature of the battery. Higher temperatures cause an increased rate of self-discharge, while colder temperatures slow it. Lithium iron phosphate batteries have a very low self-discharge rate. In fact, they have one of the lowest rates of any lithium battery chemistry, losing a maximum 5% capacity per month at room temperature (25°C/77°F). Nickel manganese cobalt cells have a much higher self-discharge rate, losing 20–40% capacity per month at room temperature. They also see a much greater increase in self-discharge at high temperatures than lithium iron phosphate batteries.6. Polymer vs. Liquid Electrolyte
One of the most significant differences between the two cathode types is their electrolyte type. The NMC cell uses a liquid electrolyte, whereas the LiFePO4 cell uses a solid polymer electrolyte. The polymer electrolyte is present on the inside of the cell as a thin layer coating the entire inside surface area of the case. This creates a very uniform and consistent environment for the chemistry to operate in and also provides good thermal conductivity from the cathode to the metal case. NMC cells, on the other hand, utilize a liquid electrolyte that can be made up of multiple components, depending on the cell manufacturer.Environmental Impact and Recycling
LiFePO4 is an iron-based battery with more environmentally friendly properties than NMC. The cathode material of LiFePO4 is made from iron, which is one of the most plentiful elements on earth. It is also very easy and cheap to recycle, which makes LiFePO4 a better choice for environmental concerns than NMC batteries which are comprised of nickel, manganese, and cobalt (NMC). NMC chemical components are not as abundant as iron. This means they will be harder to get in the future, meaning once they are depleted, they will be significantly harder to replace than LiFePO4 batteries. Moreover, NMC cells contain a mixture of metals that pose risks to our environment when discarded improperly. If an NMC cell is punctured or damaged, it can easily catch fire. This poses an enormous fire risk in landfills and recycling facilities, where fires can quickly spread to other combustible materials. To make matters worse, NMC contains cobalt — a rare metal that is mined largely in Africa. Because of its high toxicity levels, environmental groups have raised concerns over the negative impact this has on miners and local communities.Which is better for you to choose?
As with any decision, there are trade-offs. Both LFP and NMC have their pros and cons in terms of performance, life, cost, and safety. Since some applications require a higher amount of energy whereas other applications require high power output, the choice between the two depends on your requirements. Broadly speaking, LFP has a longer cycle life than NMC but offers lower energy density. This means that for applications where higher energy density is required, such as electric vehicles, NMC is generally chosen over LFP. However, for applications where longevity is essential such as grid storage or uninterruptible power supplies (UPS), LFP is usually preferred over NMC. Here are other reasons why LiFePO4 may be a better option:- LiFePO4 batteries are safer compared to NMC batteries
- Lifepo4 batteries have longer lifespans
- LFP batteries are the most stable chemistry for Lithium-Ion.
- LFP is environmentally friendly.
- Compared to other lithium-ion batteries, LFP batteries have a higher discharge rate.
- While NMC batteries can undergo thousands of cycles before failing, LFP batteries can undergo tens of thousands of cycles without degradation.
- Lithium iron phosphate batteries are also less likely to have thermal runaway (fire).