• Fayaz Ahmed

Tesla Battery Day recap with Ravindra Kempaiah, PhD Candidate at University of Illinois at Chicago

Updated: Nov 24, 2020

Fayaz Ahmed: First of all, tell us a little bit about yourself and a little about your educational and professional background.

Ravindra: I am a materials scientist working in the field of Li-ion batteries at the University of Illinois, Chicago, where I am also a PhD Candidate in the department of Mechanical Engineering.

I hold a master’s degree in Nanotechnology from the University of Waterloo, Canada and master’s in Materials Chemistry from the University of Maryland, College Park.

I am also deeply involved in the electric vehicle space and currently hold the Guinness World Record for the longest journey on an Electric bike. I am passionate about the technologies surrounding electrification of transportation and energy storage.

Fayaz Ahmed: As a researcher of battery storage technologies what’s your analysis and perspectives on the takeaways and key highlights of Tesla Battery Day.

Ravindra: In short, it was very inspiring, ambitious and truly groundbreaking!

If they deliver what they promised to do, it will change the energy storage and electric vehicle industry forever.

Tesla Battery day announcements are akin to the iPhone announcement in 2007. Apple changed the world of smartphones as we know it. Until that point, Nokia and Blackberry-like phones of the world with QWERTY keyboard ruled the market. Even though capacitative touch technologies had existed for long, it was Apple that changed the way people use phones by combining an App store + iOS and a beautiful screen. Apple also has deep vertical integration that allows them to build chips, sensors, screens with a very tight control and seamless integration with their eco-system (Facetime, iMessage etc.)

Just like that, Tesla is deeply vertically integrated, and they control the hardware, battery production and most importantly the autonomous driving software that sets Tesla apart from the rest of the industry.

18650 cells had existed for about 2+ decades but manufacturers were hesitant to make radical changes for various reasons. Tesla brought in the capital, needed vision and surplus demand. Now, Tesla’s 4680 design is particularly well suited for EVs as it provides huge power without thermal bottlenecks and because they own the gigafactories their growth rate will be much faster than the competitors.

Innovations in Anode (metallurgical-grade Silicon) and dry electrode will take some time perfect but when they do, it will change the equation drastically. Their approach to make the battery packs an integral structural unit will have some technical challenges when it comes to repair, but it will also reduce the polar moment of inertia lending their cars better handling characteristics.

Fayaz Ahmed: Since the 1990s, more than 300,000 battery-related patents have been filed (more than 30,000 in 2017 alone). So, there are lots of them (to name a few: lithium-ion batteries, solid state batteries, sodium-ion batteries, vanadium redox flow batteries etc.) what if you have to pick one breakthrough battery storage technology? Which one would you chose and why?

Ravindra: There is no one particular technology that will satisfy the energy needs. Just to provide some perspective, if you combine ALL the batteries (EV, laptop, phone, etc) in the world and make a giant battery; it won’t be able to power Lisbon for more than 1-2 hours. So, but when it comes to grid -scale energy storage, certain types of Flow batteries will be impactful. Sodium-ion and Solid-state batteries are at least 5 years away from commercialization, so we can leave them aside for now. Li-ion batteries of various chemistries i.e., NCA/NMC/LFP etc will cost less as more and more companies start scaling up and for the next 5 years, Li-ion will be the dominant technology.

Flow battery reference:


Li-ion batteries for EVs:


Fayaz Ahmed: Tesla Battery Day received harsh criticism for its multi-year timeline for the improvements and lack of concrete goals. What’s your take on this? And generally, in your opinion, what it is about commercialization of battery storage technologies that takes a lot of time. For instance, it took 40 years to get the current lithium-ion batteries to the current state of technology.

Ravindra: Their goals are very concrete and to realize the cost savings, they have to scale up considerably and build their supply chain. This process is extremely capital intensive and takes lots of time. On top of that, they have to solve some of the technical challenges. So, their timeline is actually very ambitious, and I think it may take a bit longer than what they are anticipating. Especially, the mining part is very hard. Mining Nickel in an environmentally conscious way is challenging and the rest of supply chain (from mines to processing plants to gigafactories) have tool up their factories to accommodate the demand. So, considering the capital, manpower and engineering needed, it will certainly take time.

Once they are able to produce 4680 battery packs with the new cell materials, they have validate those cells before they can be used in a production vehicle. EV battery pack validation is a very lengthy process unlike consumer electronics because one battery fire can bring huge losses. So, this validation takes significant time as well.

Fayaz Ahmed: First things first, let’s talk about fundamental chemistry of electrode materials because that’s the bottom of pyramid. They talked about the idea of replacing graphite anode design with silicon anode design. It sounds like a great idea but as you know it has its own challenges. What do you think about this idea and what engineering challenges they need to overcome in order to get silicon anode design ready to work for thousands of cycles?

Ravindra: Using Silicon as an anode has been a hot topic of research for the past 12+ years. Prof. Yi Cui’s group at Stanford has done seminal work in this area and there are lots of technical challenges before it can be realized in large-scale deployment in EVs.

I will highlight a few of the engineering challenges:

The fundamental issue with Silicon is the large volume change (400%) when Li- enters the structure. This causes high internal stress and pulverizes the particles.

Once this pulverization occurs, the particles lose contact and the conductive pathway for Li-ions is broken. This leads to active material loss or loss of capacity (driving range to speak).

Another issue is that the large volume change and pulverization accelerates the formation of new SEI (solid electrolyte interphase) layers thereby depleting Li-ions and further reducing voltage and capacity.

To contain the volume expansion, to keep the SEI formation minimal and retain the conductive pathway is a challenging job. There have been some innovations in this area (look into Sila Nanotechnologies) but this is a longer term problem and won’t make it into the battery packs until 2023 or later.

Fayaz Ahmed: What do you think about their idea of committing to cobalt-free cathodes and moving towards a high nickel cathode design? What engineering challenges they need to overcome before mass manufacturing of high nickel content cathodes?

Ravindra: A lot of very promising research has been done in this space by Prof. Jeff Dahn’s group in Canada. They have shown that it is possible to remove Cobalt without sacrificing capacity or cycle life. The issue is more to do with high Nickel content cathodes. At very high Ni content, the structure undergoes phase transformation, and the safety can be compromised but I believe the research community is working on new electrolyte mixtures to mitigate this risk. We are already at NMC-811 and very soon this will mass manufactured. To go beyond NMC-811 and retain all the safety characteristics and capacity, this is already in the works and will become public in a matter of 8-10 months. Checkout this paper:


Fayaz Ahmed: Talking about battery cell design. Tesla says its new cell design should give its vehicles a 16% increase in range thanks to a 5x increase in energy. Cylindrical cells have been there for many decades but they seem to have come up with the radically different idea of building these cylindrical cells, right? Please tell us a bit about new cell design and what’s so innovative and exciting about it.

Ravindra: The energy increases because we have increased the cell size but the increase in energy density is close to 4-5% and this comes from higher Nickel cathode and Silicon anode and small portion of it is from the size itself.

The most exciting thing about this design is that it will simplify cooling and enable extremely fast charging of batteries, which is crucial for semitrucks and Cybertruck. Extreme fast charging is an issue in the current 1865 and 2170 cells and by moving the several tabs to the bottom of the negative terminal, it makes cooling easier as they only need to cool the bottom plate. I think Tesla has deep expertise in this area and they will optimize the cell and cooling to get the required performance and longevity.

Fayaz Ahmed: I also liked the idea of dry coating manufacturing setup for battery cells, removing the need for solvents and water to put electrodes into the jelly roll of the battery cell, what do you think about this idea?

Ravindra: Tesla acquired the Maxwell company so they could utilize the Maxwell dry electrode process. It is a great idea but there are some technical challenges as Elon noted that they are in revision 4 and will need a few more revisions before they can scale it up.

Please see this video where we discussed technology in detail: https://youtu.be/18MYRkx_Vr4?t=3721

Fayaz Ahmed: Tesla understands that significant reduction in battery costs is fundamental for the adoption of electric vehicles. Tesla Battery Day claims to reduce the cost of the battery pack at the pack level by 56% thanks to these production and manufacturing innovations they plan to implement over the years. How confident you are about Tesla achieving these numbers and what main bottlenecks and engineering challenges they will have to face in order to make it happen?

Ravindra: If there is any company that can make this happen, it is undoubtedly Tesla. They have the necessary funding, scale and engineering prowess to make it happen.

Most EV startups fail because the necessary funding runs out before they can get the technology to mature. Tesla is beyond that stage and they are building giga factories at a tremendous pace (Giga Shanghai for example). Giga Austin and Berlin are on the way. They are consolidating the supply chain and will start producing their own cells. So, if they can put all the pieces together, they will do it.

In my understanding, getting the Silicon anode to work, perfecting the dry battery electrode will take some time. 4680 form factor is already optimized and gearing the supply chain to obtain enough Nickel and Lithium in high-quality but low-cost will be their challenge. So, they may miss their timeline by a years but they have a pretty good chance at revolutionizing the space.

Fayaz Ahmed: How optimistic you are about Tesla’s goal of reaching 3TWh of battery manufacturing capacity by 2030.

Ravindra: I am neutral. From 2010 to 2020, we have seen amazing innovation. From 1 GWhr to ~35+ GWhr in their Nevada facility but going from 100 to 3 TWhr is not a huge scaling problem, they have to get the whole supply chain along with it. So, I would say 1 TWhr might be possible but I am not holding my breath on 3 TWhr.

Ravindra Kempaiah,

PhD Candidate at University of Illinois at Chicago

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