Today, lithium batteries are being used for the electrification of an increasingly wide range of applications. While they initially involved telephones, computers and small tooling applications, they have gradually evolved towards the electrification of hybrid or full-electric vehicles, and today a growing number of manufacturers of industrial machines and electric vehicles are turning to this technology for the electric transition of their fleets, in a wide variety of sectors, such as logistics, material handling, construction, aerial platforms, agriculture, airport vehicles and shipping, to mention only some of them.
Now more than ever, therefore, choosing the right lithium battery for your vehicle has become a complex but necessary task, especially in view of the latest provisions from the European Parliament, which has approved a ban on petrol and diesel car sales from 2035.
Lithium batteries, however, are not all the same! There are many elements that go into creating the most suitable battery for a specific application. Many different types of lithium batteries are available on the market; but behind the voltage, Ah and size of a lithium battery there is really a complex way, made up of study, research and development, technical tests and above all, the choice of the right chemistry, which may or may not be more or less suitable for the needs of your vehicle.
The 6 most commonly used lithium-based chemistries and their characteristics
We will take a closer look at the six main types of lithium batteries and their construction chemistries:
From theory to practice: using the right lithium chemistry for every application
We have outlined the 6 main types of lithium-based chemistry that are currently most widely used in the various electrification areas. But we must not think that these chemistries are in competition with each other, quite the contrary! They are all valuable and high-performing, but each lithium chemical works best in different areas of use.
This diagram shows a comparison of the various characteristics of the chemistries in terms of:
- Specific Energy or Gravimetric Density [Wh/Kg]: is the ratio of the amount of energy contained (Wh = V x Ah) to the weight of the battery.
- Safety: which is closely related to thermal stability because intrinsic safety depends very much on how thermally stable the components are
- C- Rate: charge/discharge rate, i.e. the ratio between the charge or discharge current (A) and the nominal capacity of the cell (Ah). This is a parameter closely linked to the cell’s ability to generate power.
- Life cycle: Number of times the cell can be discharged and charged until the end of life is reached, normally considered when 80% residual capacity is reached.
How to choose the most suitable type of lithium chemistry
We therefore try to explain in detail why one chemistry or the other should be chosen depending on the type of application to be electrified.
NMC and NCA batteries for the automotive sector
Why are NMC and NCA more widely used in the automotive sector? Because this requires a very high energy density, which can give a great power in a small space. Thus, in electric mobility, energy density, gravimetric density and specific power are essential elements, where charging speed is considered a key focal point, together with high acceleration power, particularly in premium models. Other performance features such as, for example, high battery life cycles are therefore not crucial in this sector, simply because they are not necessary!
A car is in fact extremely unlikely to make several cycles in the same day, if not a few days a year in the case of a long journey. On the contrary, a car normally uses only 20-30% of its charge in a day.
If we take, for example, a Tesla that can travel more than 400 km on one charge: if we consider a useful life of 400,000 km, this means that the total cycles that the battery has to endure will only be 1,000 ( 400,000 / 400 = 1,000 cycles) This explains why the life cycles for a battery with NMC chemistry do not exceed 2,000 (even less in NCA chemistry, where the life cycles are up to 1,000).
LFP and LTO batteries for the industrial sector
In industry, agriculture, or even for the electrification of special vehicles, especially if it is about highly cyclic applications that put stress on the battery, it is better to use chemistries such as LFP and LTO, where service life, reliability and safety are the most important requirements.
In the industrial world, therefore, the issue of space is less of a constraint, just as it is not essential to have excessive performance or energy density. When evaluating the choice of the right chemistry, the more important factor of safety therefore comes into play, an aspect that few people want to, and can, compromise on.
It is better to have a battery that is slightly bulkier, but provides optimum safety and has a significantly longer service life. There are vehicles, such as LGVs and AGVs which are required to be used intensively and work incessantly around the clock, as a result, their batteries will even do 3 or 4 charging cycles in a single day. The LFP chemistry will therefore easily support them with its more than 4,000 recharge cycles.
If batteries for stationary storage are necessary, then energy density would mean almost nothing, and, on the contrary, battery cost and life cycles would be the elements behind the choice of the chemistry. LFP chemistry would then find its place.
LCO and LMO batteries for small mobile applications
Ultimately, if a very small battery is needed for use in tools and mobile applications, then its main characteristic must be its light weight, otherwise the performance of the entire application will be affected by too much weight. In this case, it will be possible to choose chemistries such as LCO and LMO and accept the compromise of having a shorter life or a few more safety risks ( considering that it is a small battery), in order to be able to give the product the essential characteristics to be able to enter the market.
The BMS improves the characteristics of the chosen chemistry
Diagrams of this kind are very useful for providing an overview of the characteristics of each chemistry, and these aspects remain true over time. However, we should remember that at quantitative level we are speaking of purely indicative data, due to an important aspect that must never be underestimated: technological evolution.
Both technology and innovation in the broadest sense are constantly evolving concepts and, through them, chemistry also evolves very rapidly and each of them, after the appropriate studies and research, can in turn be developed into other variants to enhance a characteristic rather than another (e.g. to achieve high energy density, perhaps at the detriment of power or life cycle).
This is exactly why it is important to remain constantly up-to-date and, if inexperienced, to rely on an experienced manufacturer which can study and design the battery according to the specific requirements of the application to be electrified.
But chemistry is not the only determining element in defining the correct performance of a lithium battery: battery performance also derives from another important element, the BMS. An intelligent Battery Management System, in fact, can exploit the characteristics of the chosen chemistry to the full, guaranteeing reliability and equal performance over time by managing and controlling all the devices that work around the battery.
We will now learn about the main features of an intelligent BMS.