image credit: © Denys Zazimko | Dreamstime.com
- Jul 25, 2020 9:27 pm GMTJul 20, 2020 1:18 am GMT
- 1931 views
This item is part of the Special Issue - 2020-07 - Energy Storage, click here for more
Elon Musk keeps suggesting that “Battery Day” will be really big. Originally he indicated it would be in April, delayed it to May. Then he said it will be sometime in June. As I’m starting to write this on June 20, he said that it will be combined with the upcoming shareholder meeting, which was scheduled for July7, but he is delaying that also. He now says that this combined event will be on September 22.
So I’m diving into this subject without him. I am describing the Lithium Ion chemistries he is currently using in Section 2. In Sections 3 and 4 I will discuss new findings regarding advanced technologies and materials that Elon may use. In section 5 we will look at a reasonable projection of future battery pricing. In the last section, I will briefly repeat some information from the last section of my last Elon post, and relate it to earlier information in this post.
In the earlier post, we talked about the “million mile battery”, and although this will be big news, it will not be the biggest news. I believe that an announcement of a future major reduction in battery pricing driven by improved energy density and simplified production will make the biggest headline. This will facilitate many other advancements in battery electric vehicles (BEVs), battery energy storage systems (BESS), and other technologies that depend on these (like EV supply equipment (EVSE), intermittent renewable mitigation, vehicle-to-grid (V2G) and other grid-storage applications).
To prepare for the above, Tesla appears to be prepping to build a battery research and manufacturing facility. Although Elon threatened to leave California, this facility will be in Fremont, CA where Tesla’s mothership BEV manufacturing plant is.
2. Lithium Ion Chemistries
The following are the chemistries that Tesla currently uses:
Lithium Nickel Manganese Cobalt Oxide (LiNiXMnYCoZO2), NMC: This chemistry can be optimized for power or energy-capacity by adjusting the specific cathode chemistry (X, Y and Z above). This especially applies to vehicular applications vs. battery energy storage systems (BESS). It is used for many battery electric vehicles (BEVs), but Tesla uses it for its BESS applications (Powerwall and Powerpack). The market share of the NMC chemistry is increasing as it displaces older designs.
Lithium Nickel Cobalt Aluminum Oxide (LiNiXCoYAlZO2), NCA: This chemistry is the current capacity-champion. It has characteristics similar to NMC, and costs less, but has a reduced safety tolerance. Tesla uses this chemistry for its vehicles. The reduced safety tolerance means that the battery management system must make sure that the batteries stay in a safe operating domain (over-the-air upgrades are good). I believe Tesla/Panasonic also incorporates safety devices in each cell.
LFP (LiFePO4 or 4Lithium Iron Phosphate) Tesla may be planning to use CATL’s design for a million mile battery based on this chemistry, even though it has a lower energy density than the above two. CATL is Contemporary Amperex Technology, Ltd. The Chinese company signed a two-year deal to supply batteries for Tesla's Model 3 cars in February. Its other clients include BMW, Daimler, Honda, Toyota, Volkswagen and Volvo.
At least one source has suggested that CATL may be evolving this chemistry from a graphite anode to a lithium metal anode. Batteries with a lithium metal anode are frequently referred to as lithium metal batteries. Making this upgrade to an LFP battery would roughly double the energy density of this design.
Note that a lithium metal anode also can be to upgrade other chemistries, including NMC (but not the NCA).
3. A Million and Much More
As I was reading articles on various improvements Tesla is planning for batteries, one of these gave me a link to a paper from Jeff Dahn’s team that really focuses on battery longevity. As a reminder, this team from Dalhousie University (Nova Scotia, Canada), developed an advanced design for NMC Lithium Ion batteries. Jeff (and one assumes his team) now leads Tesla’s Advanced Battery Research program in Canada.
The subject paper is referenced here. Note that this was published in September of last year. I will summarize this below, and would recommend that readers consider reading it themselves. However first, two definitions:
Discharging a battery at 1C means that the battery is discharged so that it is completely depleted in 1 hour. Thus if a battery has a capacity of 100 amp-hours at 1C, it can be discharged with an output of 100 amps for 1 hour. Note that the capacity increases with slower discharge and decreases with faster discharge. Longer discharge periods are usually formatted C/N. For instance a 2-hours discharge would be C/2.
We defined the three chemistries that Tesla is looking at in section 2. The referenced paper mostly looks at NMC. To specifically define an NMC battery you need to chemically specify the quantities of its cathode components, and the material used in its anode, like: LiNi0.5Mn0.3Co0.2O2/artificial graphite. This battery has a metallic-oxide cathode composed of lithium plus nickel, manganese and cobalt oxides (in the proportions indicated) and an artificial graphite anode. A short-hand format for this would be NMC532/AG.
Some of the details I took away from this paper is that there are many methods to extend battery longevity. These include: specific battery design elements, how batteries are charged, stored and discharged, and battery operating temperature. Secondary elements can be used to control all of the above use-related and environment-related elements. For instance, improved cooling and battery-packaging can reduce the operating temperature and thus extend the lifetime (see chart below).
In the above chart, note that the blue lines are for BEVs (top numbers, note that 1 million miles is roughly 1.6 million km) and the black lines are for BESS. DOD is depth of discharge, 20°C is 68°F and 40°C is 104°C. Also note that Tesla’s BEV designs use the heat pump or air conditioner to cool their battery packs.
Use cycles for BESS are much easier to control than for BEVs. However as battery packs become larger in the latter application, many of the elements of the use-cycle (like operating temperature) become easier to control. Larger battery packs could be driven by the desire for more mileage, higher performance and/or applications with larger vehicles (read: Tesla Simi).
4. Dry Battery Electrode (DBE)
Tesla recently bought Maxwell whose primary products are energy storage devices, albeit ones with substantial differences from lithium ion batteries. Maxwell makes ultracapacitors. These devices can charge and discharge much more rapidly than batteries, but have a lower energy density.
However, it is believed that Elon’s primary interest in them is NOT ultracapacitors, but instead a major component of these devices that can be also be used in batteries: the dry battery electrode. The primary source for this section is a paper written by the primary developers of this technology, and referenced here.
…Unlike conventional slurry cast wet coated electrode, Maxwell’s DBE offers significantly high loading and produces a thick electrode that allows for high energy density cells without compromising physical properties and electrochemical performance. Maxwell’s DBE exhibits better discharge rate capability than those of wet coated electrode. Maxwell has demonstrated scalability by producing robust self-supporting dry coated electrode film in roll form with excellent long-term electrochemical cycle performance, and established large pouch cell prototypes in greater than 10Ah format…
Maxwell Technologies is a San Diego-based ultracapacitor manufacturer that uses a proprietary solvent-free electrode production process. Advanced process development without the need for solvents has enabled Maxwell’s dry coating electrode production lines to operate at high throughput using a minimal manufacturing footprint. This unique electrode manufacturing process does not introduce any volatile waste products into the atmosphere or require complex manufacturing plant arrangements. It begins with dry raw materials and maintains its liquid-free state throughout the subsequent processing steps to ultimately produce a robust high-performance ultracapacitor electrode.
For the past several years, Maxwell has been engaged in research and development efforts to expand the application space of its dry coating electrode process technology to apply to battery electrode manufacturing processes. Cell performance using prototype dry coated lithium-ion battery electrodes has been demonstrated. Dry coated electrode configuration with various architectures using a wide range of materials can be produced at thicknesses ranging from about 50 microns to about 1 millimeter. In addition to manufacturing flexibility, the cohesion and adhesion properties of electrodes derived from the dry coating process are superior in the presence of electrolyte at high temperatures compared with those produced using the wet coating technology.
This unique electrode process technology offers significant saving in manufacturing cost and helps curb CO2 pollution in the battery electrode manufacturing process. By eliminating the use of any solvents, and the associated coating and drying complexity inherent in wet coating technology, the dry coating electrode process is environmentally friendly, and can be readily installed and commissioned with a much lower start-up capital investment. Thus, dry coating electrode manufacturing is economically attractive and socially responsible.
Maxwell’s proprietary dry coating electrode technology is comprised of three steps: (i) dry powder mixing, (ii) powder to film formation and (iii) film to current collector lamination; all executed in a solventless fashion. Maxwell’s dry coating electrode process is scalable, and can accommodate current lithium ion battery chemistry and advanced battery electrode materials. In this report, the robustness of the dry coating electrode process is demonstrated using a host of commercially available anode materials such as silicon based materials and lithium titanate (LTO), as well as cathode materials such as layered Li(NixMnyCoz)O2 (NMC), LiNi0.8Co0.15Al0.05O2 (NCA), LiFePO4 (LFP) and sulfur. All dry powder materials were mixed using Maxwell’s proprietary dry coating process to yield a final powder mixture consisting of active material, binder and conductive additive as shown in figure below (left). This powder mixture was calendered to form a continuous self-supporting dry coated electrode film that is wound in roll form (right). A wide range of dry coated electrode configurations can be produced by the adjustment of film processing conditions to control material loading weights and active layer thickness.
Image Credit: John Benson
Various dry coated battery electrodes were fabricated, including NMC811, NCA, LFP, LTO, sulfur/carbon and silicon composite, using Maxwell’s dry coating electrode technology. Maxwell’s dry coating electrode technology can be used to produce advanced high capacity NMC811 cathode and silicon-graphite composite anode that can deliver designed discharge capacity… The NMC811 dry coated electrode exhibited typical discharge profile with stable voltage plateau at the end of the discharge process. The Si/Graphite composite dry coated electrode produced electrochemical characteristic of delithiation (The removal of lithium from an electrode of a lithium-ion battery) of silicon at around 0.5V that significantly enhances energy density…
In addition to higher power performance demonstrated in high energy density cells using dry coating, electrodes derived from a solvent-free process can also be robustly cycled at 100% depth of discharge using a charge/discharge rate of 0.5C/1C, respectively.
5. The Magic Number
There is a “magic number” in the electric vehicle (EV) industry: $100 per kWh. Why is this a magic number? Read on.
The battery pack is the most expensive component in a mass-produced EV. When the cost of this battery reaches roughly $100 per kWh of capacity, BEVs will reach initial purchase price parity with internal combustion powered vehicles (ICVs). BEVs already have many inherent advantages over ICVs. I wrote one of my first posts on BEVs over two years ago, and this is linked below. In section 4 of this paper, I pointed out the intrinsic and political advantages BEVs have over ICVs.
An analysis in reference 2 above shows that Tesla is approaching the magic number, and will likely pass this within a few years. In addition to the components reviewed in this post, I believe this is also because of their much greater experience in mass producing battery packs for BEV and operating experience by those BEVs, than any other BEV manufacturer.
Increasing cap and trade and carbon tax adders to the price of gasoline and diesel will make the operating cost of ICVs much more expensive than BEVs (it’s already significantly higher – read the above linked post).
6. Previous Design Elements
In early 2019 Jeff Dahn and his team at the Dalhousie University (Nova Scotia, Canada), developed an advanced design for NMC Lithium Ion batteries. Tesla has filed for a new patent on which Jeff Dahn and his team are listed as inventors… They claim it reduces costs, enhances performance and lifetime of Li-ion batteries.
I’m guessing that the above design is compatible with dry battery electrodes (section 3), which would explain why Elon bought Maxwell.
Another innovation from Mr. Dahn’s team is a battery systems with fewer operative, electrolyte additives. This design seems to be compatible with both BEVs and large BESS. This improvement also enhances performance and lifetime of Li-ion batteries, while reducing costs verses other systems that rely on more additives.
I wouldn’t be surprised if Maxwell had tested Mr. Dahn’s additives.
Less than a year ago Tesla acquired a battery manufacturing and engineering company: Hibar Systems. This company specialized in building manufacturing equipment for different processes in battery manufacturing. Hibar’s offerings include an advanced Automated Vacuum Filling Systems for Lithium-ion batteries. Recently, it offered a full 'high-speed Lithium-ion battery manufacturing system.
Note that most of the above components and processes (including dry battery electrodes) simplify and accelerate the manufacturing of lithium ion batteries. Also most (if not all) of the above are heavily protected (read: patents or proprietary designs). It is clear Mr. Musk wants to go to a place where no one else can follow (including ICVs). It should be fun watching Tesla dominate the BEV and BESS markets.
 M. Corey Goldman, The Street, “Tesla-Digs-Deeper-Into-California-With-New-Battery-Facility”, June 25, 2020, https://www.thestreet.com/video/tesla-digs-deeper-into-california-with-new-battery-facility
 Juan Carlos Zuleta, Seeking Alpha, “Why Tesla Should Be Aware Of The New 'Holy Grail' In Lithium Batteries”, June 10, 2020, https://seekingalpha.com/article/4352962-why-tesla-should-be-aware-of-new-holy-grail-in-lithium-batteries
 Jessie E. Harlow, Xiaowei Ma1, Jing Li, Eric Logan, et al, Dalhousie University, “A Wide Range of Testing Results on an Excellent Lithium-Ion Cell Chemistry to be used as Benchmarks for New Battery Technologies”, Sep 6, 2019, https://iopscience.iop.org/article/10.1149/2.0981913jes
 Hieu Duong, Joon Shin & Yudi Yudi, Maxwell Technologies, Inc., “Dry Electrode Coating Technology”, http://www.powersourcesconference.com/Power%20Sources%202018%20Digest/docs/3-1.pdf