Reader question: Are LFP batteries better than NMC?

A reader sent us this question:

Hi team

The new Xpeng G6 offers 2 models. The base model has a LFP battery and the top model has a NMC battery with bigger range. Other than range what are the benefits of one over the other?

I understand LFP is safer (less risk of fire) and can be charged fully and can be fast charged with less risk of long term damage to battery. I also understand NMC is recommended to only slow charge to full and mostly to charge to 80%.

Are there any other reasons to prefer one over the other?

Thanks for your fabulous website. I am a daily reader.

Des

Hi Des – you ask a good question! There is a lot of confusion about the merits (or otherwise) of the two main types of EV battery. The short answer is that it’s a matter of ‘horses for courses’, but neither is a short-priced favourite.

The longer answer, is, er, a bit longer. I’ll start by explaining the broad differences between LFP and NMC battery chemistries and then look at whether those differences make any significant impact on EV choice.

LFP stands for lithium iron phosphate (chemical formula: LiFePO₄). LFP refers to the material the cathode (positive end of a cell) is made of. NMC refers to a range of related battery cathode materials involving mixtures of nickel, manganese and cobalt. (General chemical formula: LiNi_xMn_yCo_1-x-yO₂).

As you can see from the chemical formulae – NMC batteries include both cobalt and nickel in the mixture, LFP do not. As cobalt and nickel are supply constrained, they are both relatively expensive. This makes NMC batteries more expensive to produce than LFP. On the other hand, both are lithium-based batteries, so many of their energy storage and use properties are similar.

As LFP batteries are made from readily available (and cheaper) materials, they are cheaper to produce, but the down-side is LFP chemistry results in a lower energy density. (i.e. how many kWh of electrical energy storage you can squeeze into a given volume or mass). This does however make LFP ideal for producing cheaper lower range EVs. (As compared to fitting an EV with an NMC battery of the same kWh rating).

On the other hand, where the space for a battery is constrained and/or to reduce the overall mass of the car: NMC is the choice as you can get more kWh into a smaller space. It will also be lighter than an equivalent kWh size LFP one.

This is the main reason manufacturers choose one chemistry over the other. Longer range EVs generally come with NMC batteries and shorter-range ones LFP. The other reason an EV may be fitted with an LFP battery is that China leads the world in LFP battery chemistries – so pretty much any EV from a Chinese manufacturer will have an LFP battery unless they are really constrained for space in the longest range versions (such as the long-range Xpeng G6 you mention).

Now we come to the marketing. Yes, LFP batteries have longer lives. (Around 2,500 to 9,000 charge-discharge cycles versus roughly 1,000 to 3,000 cycles for NMC). However – if on average you charge your EV once every week or two from 0 – 100% (which is well above the average use): in 20 years that equates to 520 to 1,040 cycles.

This means for the vast majority of car owners, the lifespan difference between the two is irrelevant. On the other hand, high-mileage trucks may be better served with LFP batteries, provided the weight penalty was not an issue. (It is worth noting here that the next generation of LFP batteries will likely have both a higher energy density and a reduced life of around 5,000 cycles maximum).

The other big marketing ploy from the LFP EV manufacturers is the hyping of a fire safety difference between the two. Yes, LFP is regarded as something like 10 times less likely to go into thermal runaway than NMC. The big BUT here is that BEVs are far less likely to burn than an ICE vehicle (see articles here and here) – so if you are happy to drive a petrol car now, a battery EV is a much safer choice already, irrespective of chemistry.

Fundamentally, despite the marketing (and trolling): when it comes to EVs and fires, it is not a choice between a ‘likely fire with NMC’ and ‘no fire with LFP’. Both battery chemistries are much less fire-prone than ICE vehicles, plus LFP is not ‘fireproof’.

Charging speed is also slightly different between the two: NMC cells have both a higher individual cell voltage and can be charged faster than LFP, so for really fast-charging cars like the Hyundai Ioniq 5 that has a 77kWh, 800V battery for up to 230 kW DC charging – NMC is the only choice.

On the other hand, smaller batteries naturally don’t take as long to charge, so whilst an LFP battery may have a lower DC charge rate, the difference in time won’t be very noticeably for a 40 to 50kWh battery of either chemistry.

In regards to charging to 100% or not being a reason to choose between the two: NMC batteries last best (degrade least) if they are normally kept between 20% and 80%.

That doesn’t mean you can’t go below/above these (say for a long trip): just don’t leave them below 10% or above 90% for extended periods. LFP on the other hand is supposed to be more tolerant of being left at 100% – however the car manufacturers also specify that they need to be regularly cycled up to 100% for the battery management system to operate effectively.

One other point to make is when using a DC fast charger, the 80% rule is etiquette (not battery longevity management) and applies to both NMC and LFP. This is because after around 80%, both start to slow down their charge rate. As a result, to get the quickest charging time (and let others get a charge sooner) NEVER charge at a DC charger past 80% unless there is no-one else there AND you really need the extra to get to where you are going.

(By the way: After around 90%, for a three phase AC charging capable EV – an AC charger will in all likelihood be as fast or faster anyway). In addition, the stats coming in now are that neither battery type degrades faster due to lots of DC charging – so charging speed affecting NMC life more than LFP is looking like a Furphy.

Summing up – larger, faster charging (and more expensive) EVs use NMC batteries to take advantages of the characteristics inherent in NMC chemistries. Smaller battery EVs employ LFP because they can be made cheaper and are less constrained by the need to squeeze in as many kWh of storage as can be fitted into the available space.

LFP also has the advantage of some reduction in (the extremely unlikely) fire risks of an EV as well as reputedly being more tolerant of being left at 100% charge. On the other hand, LFP does have the disadvantage of a slower DC charge rate and slowed AC and DC charge rates in cold weather.

Put in terms of BEV choice: if you want a super-fast charging, long range EV, your choices will all have NMC batteries. If you are looking at a cheaper EV with reasonable (but not the longest) range and a slightly slower DC charge rate – your choices will likely all have LFP batteries.

If your choice of BEV is from Europe, it is more likely to have NMC whatever its range, and the reverse if it comes from China. However, as LFP evolves, it may very well catch up to NMC in energy density and charge speed – meaning that being cheaper, LFP may very well win out in the end. We shall have to wait and see there.

Personally, I wouldn’t choose a car based on its battery chemistry. Choose one that does what you want in terms of driving range, price, charging speed and brand … and the chemistry will follow as it will have been chosen by the manufacturer to be the best one they make for the use-case.