Cathodes: The Key to Advancing Lithium-Ion Technology
The inner-workings of most commercialized batteries are typically pretty straightforward.
The lead-acid battery, which is the traditional battery used in the automotive sector, is as easy as it gets. Put two lead plates in sulphuric acid, and you’re off to the races.
However, lithium-ion batteries are almost infinitely more complex than their predecessors. That’s because “lithium-ion” refers to a mechanism – the transfer of lithium-ions – which can occur in a variety of cathode, anode, and electrolyte environments. As a result, there’s not just one type of lithium-ion battery, but instead the name acts as an umbrella that represents thousands of different formulations that could work.
THE CATHODE’S IMPORTANCE
Today’s infographic comes to us from Nano One, a Canadian tech company that specializes in battery materials, and it provides interesting context on lithium-ion battery advancements over the last couple of decades.
Since the commercialization of the lithium-ion battery in the 1990s, there have been relatively few developments in the materials or technology used for anodes and electrolytes. For example, graphite is still the material of choice for anodes, though researchers are trying to figure out how to make the switch over to silicon. Meanwhile, the electrolyte is typically a lithium salt in an organic solvent (except in lithium-ion polymer batteries).
Cathodes, on the other hand, are a very different story. That’s because they are usually made up of metal oxides or phosphates – and there are many different possible combinations that can be used.
Here are five examples of commercialized cathode formulations, and the metals needed for them (aside from lithium):
|Cathode Type||Chemistry||Example Metal Portions||Example Use|
|NCA||LiNiCoAlO2||80% Nickel, 15% Cobalt, 5% Aluminum||Tesla Model S|
|LCO||LiCoO2||100% Cobalt||Apple iPhone|
|LMO||LiMn2O4||100% Manganese||Nissan Leaf|
|NMC||LiNiMnCoO2||Nickel 33.3%, Manganese 33.3%, Cobalt 33.3%||Tesla Powerwall|
|LFP||LiFePO4||100% Iron||Starter batteries|
Lithium, cobalt, manganese, nickel, aluminum, and iron are just some of the metals used in current lithium-ion batteries out there – and each battery type has considerably different properties. The type of cathode chosen can affect the energy density, power density, safety, cycle life, and cost of the overall battery, and this is why researchers are constantly experimenting with new ideas and combinations.
For companies like Tesla, which wants the exit rate of lithium-ion cells to be faster than “bullets from a machine gun”, the cathode is of paramount importance. Historically, it’s where most advancements in lithium-ion battery technology have been made.
Cathode choice is a major factor for determining battery energy density, and cathodes also typically account for 25% of lithium-ion battery costs. That means the cathode can impact both the performance and cost pieces of the $/kWh equation – and building a better cathode will likely be a key driver for the success of the green revolution.
Luckily, the future of cathode development has many exciting prospects. These include concepts such as building cathodes with layered-layered composite structures or orthosilicates, as well as improvements to the fundamental material processes used in cathode assembly.
As these new technologies are applied, the cost of lithium-ion batteries will continue to decrease. In fact, experts are now saying that it won’t be long before batteries will hit $80/kWh – a cost that would make EVs undeniably cheaper than traditional gas-powered vehicles.