As the global economy continues its mission to displace fossil fuel power for carbon free electrification, batteries are of course a vital storage tool to enable this energy transition, the World Economic Forum reports. Clearly, Lithium batteries will be centre stage and seen as the technology of choice for the foreseeable future, but which features of this technology will prove the most attractive and capture the market share?
The topic of which battery cell is "best" is a very broad subject so we shall cover the entire subject over a few different articles which will each focus on different aspects.
Today we will focus on the first two of these, "cell chemistry" and "cell format" and will follow up on the other aspects in future articles.
It is fair to say that Lithium batteries got a pretty bad reputation in the early days with numerous very high profile recalls and thermal events (fires) in phones, laptops and EV’s.
The "false perception" that choosing a Lithium battery automatically represents "danger" may still exist with some people, even today, until they look at the facts!
Best! – Sure, all Lithium batteries are all the same…… RIGHT?
"Lithium, Lithium-ion, Li-ion, Li-Po" are all generic terms for Lithium batteries however there are many different types with very different characteristics. These characteristics will each give a very different flavour to your choice of battery. i.e. LFP cells (Lithium Iron Phosphate) have a nominal voltage of 3.2 volts, whereas NMC and LCO have nominal voltage of 3.6 volts and 3.7 volts. All of these have a similar make-up (chemistry), and all fitting inside a cell enclosure of various shapes and sizes (cell format – prismatic, pouch or cylindrical).
Cell chemistry – why LFP is the clear choice.
Chemistry choice may seem like NO BIG DEAL! Afterall, they all have graphite anodes, lithium based cathodes and all have electrolyte……however, the differences are stark and have real world implications in terms of their voltage, lifetime and safety.
Think of Lithium batteries as an umbrella group with all chemistries under the one name.
● On the left hand side, we have the full Oxide chemistries (e.g. Lithium Cobalt Oxide, LCO) with the highest energy density, fastest degradation rate and lowest safety.
● In the middle of the umbrella, we see mixed Oxide chemistries (e.g. Lithium Nickel Manganese Cobalt Oxide, NMC) with its high energy density and better degradation rate but still suffers from safety concerns especially under abuse.
● On the right hand side of the umbrella are the non-Oxide chemistries (e.g. Lithium Iron Phosphate, LFP) which have a slightly lower energy content, but are very safe and stable even under abuse conditions and have a long cycle life due to their excellent degradation characteristics. Even though the energy density in an LFP is typically a little lower than the others in the umbrella, because of the low degradation rate, the usable lifetime is longer than the others.
Cell format – which format to use?
Battery cell formats can generally be divided into 3 main types.
● Cylindrical cells
● Prismatic cells
● Pouch cells
In simple terms "Cell format" means the outward appearance of the cell.
All three formats have merit for different areas but for the purposes of this article we will look specifically at Prismatic and Cylindrical cells only.
● Prismatic cells are encased in Aluminium or Steel for mechanical stability and are typically rectangular in shape. They are very space efficient which ensures maximum energy density but can cost a little more to manufacture than equivalent cylindrical cells. This is due to no industry standardisation for manufacturing or sizing being in existence. Modern prismatic cells are used in the electric powertrain and energy storage systems.
● Cylindrical cells are robust, usually made from stainless steel, steel or aluminium, have high energy density at the cell level, good mechanical stability and are the most commonly manufactured cell globally. Standardised and automated manufacturing processes also mean lower production costs. They also have good cycle life with long calendar life. However, cylindrical cells, due to their wasteful cylindrical shape lose their energy density advantage when they are assembled into larger packs.
Lithium batteries - New kids on the block?...... not any more
Lithium-ion batteries first appeared commercially in the early 1990s with Sony’s handheld video recorder which used Lithium Cobalt Oxide (LCO) cells. Over the past 3 decades, chemistries and formats have evolved to value safety as well as energy density.
It is widely accepted that no single battery type or format is ultimately suitable for ALL applications, however, with all things considered, the emerging trend is that high capacity, LFP, Prismatic cells in Utility Scale battery systems is ultimately the best option.
Trina Storage - Superior Performance
Trina Storage specialises in Utility Scale battery storage systems.
Each Trina Storage Elementa cabinet is equipped with ~2.2MWhrs of energy utilising State-of-the-art, High capacity, LFP, Prismatic cells. The Elementa system is fully integrated onsite with BMS, and EMS, PCS, MV equipment and transformer.
Why not give Trina Storage a call to see what Elementa can do for you?