Li-ion? Silicon? Solid State? Who’s Going to Win the Battery Race?
Credit: Martin Katler, Unsplash
For the past two decades, investment in battery chemistries as a decarbonization strategy have rapidly developed. Though certain chemistries, including lithium, have existed for a few decades, battery performance requirements have evolved tremendously since their inception. Currently, there are multiple battery chemistries, each with their own speciality, all fighting to be the leader in the industry. However, with certain limitations that they can’t seem to shake off, how will these batteries be improved to suit current demand and performance needs?
So Many Requirements, So Many Chemistries to Pick From
Lithium iron phosphate, lithium nickel manganese cobalt, silicon, solid-state, sodium-ion. The choice is vast; but which battery chemistry has the potential to win the race? Let’s go over some of each chemistry's advantages.
Lithium Iron Phosphate (LFP)
LFP batteries use a graphitic carbon electrode with a metallic backing as the anode and lithium iron phosphate as the cathode material. They are known for their longer life span compared to certain other batteries, their low maintenance, being extremely safe and lightweight, and their improved discharge and charge efficiency. By combining this chemistry’s thermal and mechanical stability, LFPs tend to be a reliable option.
However, LFP batteries have a lower energy density, though this hasn’t deterred Tesla from using them in certain EVs, including the recently released Model 3. Nevertheless, as electrification becomes mainstream, LFP batteries won’t be enough for all vehicles, specifically electric medium-to-heavy-duty-class trucks, which have the potential for a greater impact on reducing emissions compared to passenger vehicles.
Lithium Nickel Manganese Cobalt (NMC)
NMC batteries can have either be high energy or high power, meaning they are a more favored choice for power tools, energy storage systems and the automotive industry. Indeed, NMC batteries offer a long life cycle, high energy density and come at a relatively low cost.
However, a reaction can occur between the electrolyte and oxygen that leads to high temperatures which can affect heat dissipation and mechanical stability in NMC batteries. As a result, research has been done to reduce the ratio of cobalt to mitigate safety risks with LG already working on creating such batteries using a cobalt-free chemistry,
While NMC batteries are more expensive than LFP ($80/kWh in 2020), the costs of both are expected to fall below $100/kWh by 2024. Moreover, due to higher energy density, many analysts expect NMC to become one of the most preferred chemistries for the transportation sector.
As graphite anodes reach their limit in terms of power and energy density, battery makers are turning to highly-abundant material, silicon. When used in the anode, silicon can offer 10 times more capacity than graphite, translating to higher energy density per volume. As a result, leading automakers including BMW, Ford, GM, Porsche and Tesla are all increasing their silicon battery development.
However, due to the expansion and shrinking of the silicon that occurs in the battery, these batteries are less stable and have a shorter battery life. Therefore, more manufacturers are partnering with material scientists to create new technologies that can help reduce swelling.
In Tesla’s case, they have been working on their own solution that is meant to be 6-10 times cheaper than current and previous methods used to date. By using an elastic binder and electrode design, and an elastic, ion-conducting, polymer coating, the battery is designed to work with the expansion rather than trying to prevent it.
Credit: Taneli Lahtinen, Unsplash
Over the past few months, solid-state has become the battery world’s new favorite. With many well-funded new entrants claiming to offer the next step-change in battery performance needed for an all-electric future, the world’s leading OEMs and even Bill Gates are investing billions into it.
Solid-state batteries use safer, non-flammable, more energy-dense, solid electrolytes that allow for faster charging, greater range, and longer battery life. They are also able to handle heat better, while still operating at very cold temperatures.
However, the technology is very expensive to manufacture, with research estimating that solid-state technology will cost between $400/kWh and $800/kWh by 2026. As such, it will be more difficult for the automobile industry to reach $50/kWh in the coming years.
Solid-state batteries are also more limited in terms of the total energy density that can be stored in the cathodes per unit of volume, as thicker cathodes reduce the mechanical and thermal stability of the battery. This can cause materials in the battery to degrade themselves, which leads to premature battery failure. Also, as thicker cathodes decrease power by limiting diffusion, this means that solid-state batteries still don’t crack the code for a perfectly optimized power to energy ratio, one of the main goals for all battery innovation.
Similarly to silicon that aims to use an abundant, cheap and benign material on the planet, there is a new chemistry outside the lithium-ion family: sodium. With a wider temperature range, sodium batteries are more safe and stable than LFP batteries as it is harder for thermal runaway to happen, one of the main causes for LFP batteries to catch fire.
While sodium batteries have a lower energy density similar to LFP, they are expected to replace some of LFP’s share of batteries in passenger EVs and energy storage markets. Indeed, Chinese battery maker CATL is working to improve the energy density of sodium-ion batteries by combining a certain proportion of sodium-ion and lithium-ion batteries, and integrating them into one case that is monitored by a battery management system (BMS) algorithm.
Battery Design: the Overlooked Solution that Can Create the Next Step Change in All Battery Chemistries
While battery chemistries have their advantages, they also have trade offs and with so much attention paid to chemistry, battery physics and design have yet to be sufficiently considered.
With the amount of battery chemistries on the market, battery innovation has produced a range of improvements from enhancing energy density to heat dissipation to mechanical stability and from charge time to battery life. However, improving batteries through their chemistry alone leads to limitations in their performance. As such, alterations need to be made at the electrode level.
Indeed, batteries traditionally have a 2D structure composed of a flat metal foil coated with active chemical materials. On the other hand, 3D electrodes use a porous metal structure with the active chemical material embedded inside during the coating process. Altering the structure allows physical reactions in the battery cell to be improved. Therefore, by combining battery chemistry with physics, significant upgrades across battery performance can be achieved.
Addionics’ physics-focused approach, technology and manufacturing process allow the optimal battery architecture to be designed and built to achieve the desired performance. For manufacturers, these 3D-structured batteries can be integrated into production lines at a low-cost while providing a significantly improved performance.
And the Winner Is...
As each battery chemistry has its own advantages, one chemistry alone probably won’t win this race. Nevertheless, it's only a matter of time until new battery architecture is implemented. Indeed, battery design will impact the whole industry as well as all the chemistries due to its significant positive impact.