A Leader of Lithium Lifepo4 Battery in China Since 2006

is tesla building the right battery? part 2: the silicon disruption

by:GSL ENERGY     2020-06-13
Battery technology experts have long realized that silicon has the potential to greatly increase the energy storage of lithium-ion batteries.
At a conference call on July, Elon Musk acknowledged Tesla (NASDAQ:TSLA)
Use a small amount of silicon to get a higher performance of the battery pack at 90 KW.
A recent study by a group of scientists at Stanford University suggests that silicon-based lithium-ion batteries may be closer to reality than previously thought.
Is Tesla ready for a silicon outage?
Source: Fortune-telling gasoline is out of date. One way to think about the current situation of battery energy storage is compared with gasoline.
Converted into units commonly used in BEV energy storage, there are about 12 gasoline stores.
9 KW mAh/kg energy.
Tesla Panasonic 18650 battery store 0.
264 kWh/kg currently configured in the 85 pack package.
This is a big difference, but the gap in available energy is not as big as it seems.
The internal combustion engine wastes most of the chemical energy stored in gasoline as the Heat discharged from the tail pipe or from the radiator.
Only about 25% of the energy in gasoline is converted into mechanical energy.
Three-phase induction motor (
Type used by Tesla)
The efficiency in converting electrical energy to mechanical energy is much higher, usually about 85-97%.
For Tesla, we also need to consider the efficiency of inverter Electronics, which may be about 90% in the case of a conservative comprehensive efficiency coefficient of 75%.
In the table below, I summarize the effective energy storage when considering efficiency factors.
In terms of normalized energy density, the humble 18650 battery is not far from gasoline, and an increase in energy density of four times will narrow most of the gap.
Getting roughly the same energy density as gasoline may make gasoline obsolete as a car\'s energy source, as a general cost of ownership parity has been achieved, as I discussed in the first part.
Using Silicon as an anode for lithium-ion batteries, rather than graphite currently in use, theoretically increases the energy storage by 10 times.
In fact, researchers at Northwestern University proved a factor of 2.
4 Improvement in testing cells in the study reported in 2012. Dr.
Jeff Dane, a battery technology researcher and professor at the University of Dalhousie, now has a contract with Tesla and talks about the potential of Silicon (
As cited in an article in Fortune: The problem with silicon is that making it superior to the properties of energy storage can cause silicon to quickly self-destruct when used in lithium-ion batteries.
Silicon when the battery is charged (
For battery anode or negative terminal)
Expansion of lithium atoms.
The volume change can reach 40%.
When the battery is discharged, the lithium atom leaves the silicon, causing the silicon to shrink.
Repeated charge/discharge cycles can cause solid silicon decomposition, which can cause battery failure.
Nanoparticles pair (Partial)
Most of the solutions to this problem involve creating nanometers.
The scale structure of silicon can be either a line or a particle.
For example, nexon, a British company, sells silicon nano wires for lithium-ion battery anode.
However, the production cost of Si nanoparticles is high, and it will still eventually break up and fail.
This is a very interesting part of the Stanford team.
As reported in the journal Nature Energy in February 2016, the team started with Micron-grade particles and encapsulated them with graphene shells, creating an engineering silicon material (
Composed of carbon atoms).
The size of the graphene housing allows closed silicon particles to expand and contain debris when the silicon particles disintegrate during repeated charging.
Source: Natural energy because the shell is quite hard, the effective volume of the material remains the same.
Most importantly, the housing maintains an electrical interface (
Called solid electrolyte interface layer (SEI for short)
This allows the battery to continue to work efficiently.
The Stanford group has made a little better progress (2. 7)
In terms of energy storage than Northwest group.
Although the researchers did not test their experimental batteries in many cycles (about 100)
They have achieved very high efficiency in Cullen.
Cullen efficiency is only the ratio of the amount of electricity released when the battery is discharged to the amount of electricity consumed during charging.
Cullen has never been 100% efficient. As Dr.
In an online lecture, Dahn noted that Cullen is more efficient than 99.
5% is a good indicator of long battery life (Loop 1000 s)
That\'s what researchers at Stanford do.
Although there is still a lot of verification and development work to be done, it seems that the Stanford Group has addressed the basic problem of preventing the large amount of silicon from being used for lithium-ion batteries.
Because the silicon particles are relatively large, it can be produced in batches at a cheap price.
The graphene Shell process is an expensive part and may require some development to make it affordable.
Most importantly, the life problem seems to have been solved, and the energy density increase that can be achieved in the actual battery may be two to three times.
In fact, the silicon battery reduces the size of the battery pack in a given range through this improvement factor.
One of my concerns about Tesla\'s continued use of cylindrical batteries is whether they can accommodate silicon anode.
The cylindrical battery does not appear to be able to cope with the bulk expansion of the silicon anode material.
With Sanford solution, the volume of the material is established by the graphene shell around the silicon particles, so that there is no bulk expansion of the anode.
This makes this material suitable as a replacement for the current graphite anode.
Whether lucky or visionary, Tesla has adopted a battery format that will apply to the silicon anode for lithium-ion batteries most likely to be implemented on a large scale.
Tesla\'s investment in the Gigabit plant and its commitment to cylindrical batteries do not seem to be at much risk because the emergence of Stanford Silicon materials will be out of date.
Stanford\'s engineering silicon materials are expected to disrupt the lithium-ion battery industry, but will not undermine Tesla\'s basic approach to producing battery packs.
Tesla will be able to produce cylindrical batteries using this material and most, if not all, machinery is currently installed at gigabit plants.
Since this material may be much more expensive than graphite, the expected energy density increase coefficient is about 3 times and may not be converted into equal cost savings.
The cost factor may control the proportion of the materials used in the new 2170 battery.
However, the cost of anode material is not the largest contributor to the total cost of manufacturing the battery pack, and for a given range capability, reducing the size of the package may significantly reduce the overall cost of the package.
Is there any reason for Tesla\'s competitors not to use Stanford Silicon? Probably not.
The competition will continue to develop efficient, low-cost production processes for materials that can be expanded according to the needs of BEV manufacturers.
Given Panasonic and Tesla\'s investment in the Gigabit plant, investing in the development of Stanford materials could be a natural extension of the work currently under way.
Tesla could be an early adop for Stanford materials as it already has experience with silicon as a current battery additive and an investment in Gigabit plants.
Stanford\'s engineering silicon material has the potential to significantly improve the economy of battery electric vehicles.
This can reduce the cost and size of the battery pack and increase the maximum mileage of Tesla cars.
Any other car company in Rabbi tesy could benefit more from the silicon disruption.
Disclosure: I/we have no positions in any of the stocks mentioned and no plans to start any positions in the next 72 hours.
This article was written by myself and expressed my views.
I received no compensation (
In addition to Seeking Alpha).
I have no business relationship with any stock company mentioned in this article.
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