Published on January 9th, 2014 | by Nicholas Brown


Amprius Raises $30 Million To Commercialize Li-ion Batteries

January 9th, 2014 by  

ampriusAmprius, a lithium-ion battery manufacturer, has raised $30 million of Series C funding for new, compact lithium-ion batteries which utilize silicon nanowire anodes.

In the past, silicon anode technology has experienced multiple failures, but also improvements — as have most other technologies, proving that alternative energy technologies in general deserve a chance to develop as well. Initially, a solid silicon anode was developed, but it was prone to cracking, so a nanowire version of it was developed, as the high energy density of silicon anodes was a major benefit worth pursuing (1,000 Wh/kg). However, the nanowires still weren’t reliable enough. There have been developments since then which significantly improved reliability, but now, Amprius apparently has silicon nanowire batteries ready for commercialization.

According to Green Car Congress:

“The company introduced its first generation of batteries in May 2013, and is supplying smartphone and tablet OEMs with its first two product families, based on an 1,850 mAh (580 Wh/L) battery and a 4,060 mAh (600 Wh/L) battery. Amprius’ first-generation batteries are made with silicon anodes—not silicon nanowire anodes, which will appear in the subsequent generations. The company has demonstrated greater than 650 and 700 Wh/L batteries with its second-generation and third-generation technology platforms.”

The Amprius technology was initially developed at the laboratory of Yi Cui in Stanford University. Yi Cui is a founder of Amprius.

Image Credit: Amprius

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About the Author

writes on CleanTechnica, Gas2, Kleef&Co, and Green Building Elements. He has a keen interest in physics-intensive topics such as electricity generation, refrigeration and air conditioning technology, energy storage, and geography. His website is:

  • johnBas5

    Amazing, replacing these in electric cars would with the 700Wh almost give the same range before refuelling as gasoline cars!
    Add a solar power car roof and you have an electric car winner.

    • Steve Grinwis

      Every time I’ve looked at adding solar to a car, the numbers just don’t work… For the weight and the money, you were better off with more battery.

      • johnBas5

        It’s not for range replacing but range extending and when the car is not moving to fill the battery.

        • Steve Grinwis

          Right, so, lets do the numbers again.

          The Model S has a surface area of about 10 sq meters, but a large chunk of that isn’t really usable because of the windshield and rear window glass, and also the fact that the car isn’t a rectangle, so let’s say we have roughly 7 sq meters to play with. Next we have to deal with the fact that the solar surface is horizontal instead of perpendicular to the sun. Reduce effective surface area by cos 45 (Angle off perpendicular in my neck of the woods, ( Net effective surface area is now 4.9 sq meters.

          Using a high efficiency polycrystaline panel, I can conclude we can eek out about 125 watts per square meter, so our whole array will generate about 612 watts. With my areas insolation, of around 4.2 hours of sunlight per day, we can conclude that we can make 2500 wH of juice, assuming you park in an area that never gets any shade..

          That represents about 3% of the juice held in a Model S, and because I specifically looked at high efficiency panels, would end up costing you around $900. Alternatively, You could purchase 4.5 kWh more battery for that price, have more range, and keep the solar panels for the roof of your house, where size, weight, and efficiency are less important than straight up cost.

          A third option would be to realize that electric cars these days don’t have much of a range problem as is, and we’re better of spending our money other places.

          • Bob_Wallace

            2,500 wH = 2.5 kWh.

            At roughly 0.3 kWh/mile a day of sunshine would power your ride a bit over 8 miles.

            Unless super-efficient panels became super cheap best to put panels on rooftops and plug in.

          • johnBas5

            It is meant more as a backup for other things. Small things can make a difference although not in the areas you think.

            If you don’t use it for a while that could make a large difference.
            For short-distance commuting this could make a large difference.
            For countering the self-discharging of batteries this would be a very good protection. Even if you don’t use batteries, they self-discharge.
            Providing some extra juice can lower the cost of driving a bit. For an owner, it might be nice to be able to use some gadgets while the energy gets replenished by the solar panels on the roof, you don’t have any cost of using those.

          • Steve Grinwis

            They don’t lower the cost of driving though. The solar panels aren’t free, and on a car probably won’t get the chance to run for their 25 year lifetime.

            If expect they would raise the cost if driving substantially.

            As for negating self discharge, they might help there, but the best solution is to plug it in. This is both cheaper, and fool proof.

          • johnBas5

            Because the variable cost of solar panel elektricity on the car is 0, it can only make the cost of driving cheaper. More driving would allow them to put more juice into the battery thus implying high use.
            It is not cheaper, the solar electricity is free, plugging it in and charging costs money. The panels do their thing without the driver having to do anything at all, this is even simpler than having to do a simple plug in.

          • Steve Grinwis

            Solar electricity isn’t free though. You are going to have to spend a lot of money to add those panels to your car. This will also make the car heavier, more complicated, reduce it’s range, and increase its cost.

            Overall the levellized cost of energy from car mounted solar panels will be exorbant, which is the opposite of free. The reason why they make sense on a roof is because weight isn’t a factor, the angle can be set perfectly, and you can amortize their cost over a period of decades.

          • johnBas5

            Solar electricity is not free.
            The upfront costs are not free but once operational the variable cost is zero.

            Could be relatively much money.
            You have to compare with the rest of the car.
            Cheap car versus expensive luxury car.
            For the last one the solar panel might be a relatively cheap, compared to other things, extra.

            Heavier+ reduce it’s range.
            The solar panels weight is very low compared to the rest of the car. We can ignore it.

            More complicated.
            Cry me a river, have you any idea how complicated the motor of a car and the control systems are? Or the infotainment systems? Much, much more complicated than putting a solar panel and some DC-DC converters on it.

            Amortizing the costs over decade negates your high price, exorbitant prize argument.

            I’m getting the impression that you are trying to come up with excuses here. You have one good reason, that is the costs. All the rest is either refuted in your own post or negligible.

          • Steve Grinwis

            So, You agree that the panels will be relatively more expensive to provide power than traditionally mounted panels. Great! Lets move on from there.

            As for weight, a single 250 watt astroenergy panel on weighs 44 lbs. Now we have 875 watts worth of panels equivalent (reduced to do poor angle to 612), so the weight for just the panels is going to weigh around 154 lbs. Now we need to add the weight for the mounting equipment… A lot of this weight is going to be on the roof, which isn’t generally designed to carry much load, so the roof will have to be reinforced. Expect this to weigh in the ballpark of 30-40 lbs before you actually get all these bolted up and waterproofed. Now we need the weight for the wiring. Assuming these are all in parallel, which they should be since there’s a good chance one or more panels will be shaded, we’re going to be pushing around 50 amps total at 12v, and a bunch of that is going to have to traverse the entire length of the car. Expect there to be around 30 lbs of wiring and interconnects. Next you’re going to need a power converter of some kind to step up the 12v power to the pack voltage. Expect this, and associated wiring to weigh in the neighborhood of 10 lbs.

            All in, this is going to weigh about 220 lbs. That’s about 5% of the weight of a Model S. Now, Tesla would have two choices if they mounted this to their car. Reduce the payload capacity of the Tesla by 220 lbs, or increase the beefiness of the suspension to compensate. Tesla presumably already made the suspension as light as they could to improve energy efficiency and range, as most electric cars would do, so they probably can’t afford to lose the 220lbs of payload capacity, so now they have to increase the beefiness of their suspension. Expect adding to the beefiness of the suspension to add an additional 5-10 lbs all around as springs and struts get upgraded. Note that that is also unsprung mass, and will reduce the handling capabilities of the car.

            Note that because the car is now 5% heavier, it is also now 5% slower, clocing in around 4.3 seconds to 60, and pulling around .2 of a second from it’s quarter mile performance.

            At the same time it’s in town energy efficiency when not in direct sunlight has decreased by around the same amount, since in town fuel efficiency of an electric car is proportional to weight. On the highway, it’s not as bad, since aero-dynamics are much more significant, but probably still 2-3% less efficient. When in direct sunlight, it’s not quite as bad, but still about 4% worse in the city, and 2% on the highway.

            You can expect the manufacturer to pay around $2000 for the pleasure of making your car worse, but the price you will pay for the pleasure is presumably much higher.

          • johnBas5

            The cars that are coming out with a solar panel roof use several techniques to keep the weight low. One of them is that they use concentrator lenses instead of the heavy equipment your example has.

            This should put to rest your fears about solar panels being so bad. If the solar panels on an all-electric car can provide in the end a lower TCO.
            Putting them on hybrids is nonsense I think.

            And quit it with the nonsense about it making your car worse.

          • Steve Grinwis

            Lightweight panels would likely reduce the amount of added weight, but they cost more, making them a worse proposition for value.

            Overall TCO of a car with solar panels would be higher than a car without them. I’ve done the math on that several times. Feel free to counter with something more than ‘But solar is free after you’ve paid for them’.

            Show me some numbers. Show me how you think that the car will be cheaper with solar panels. How much power will they generate and how much is that power worth?

            In a comment above, I did the math, and it doesn’t work out.

            I’m not being a dumbass. I’m being realistic. I’m about as big a solar supporter as you’re likely to find, the math just doesn’t add up.

            Let me repeat my numbers for our Fantasy Model S, using very optimistic numbers.

            2.5 kWh of power / day is worth $0.34 / day.

            For a year, that means it will generate $124. Over 5 years, that works out to $620. This assumes that the battery is always discharged enough to accomodate the charge, and the vehicle has never been parked in shade.

            Over 10 years it will produce $1240.
            Over 15 years it will produce $1860.

            However, the cost of the panels and DC converter, before dealership markup is somewhere around $2625. ($3 / watt, curved panels are expensive and you are going to want / need the highest efficiency panels around. Note this is before you try and add any concentrator technology, or methods of reducing weight. Expect the cost for that to hit somewhere over $3000, probably closer to $4000). Also note that this assumes a perfectly efficient DC-DC converter. Realistically there is loss there.

            You’ll note that $1860 is much smaller than either of those figures, and 15 years is much longer than I would want to hold onto a car.

            So, no, cost is still an issue. If you want to argue it’s still cost effective, please provide your own analysis. I’d love to see it, because I’d love to be wrong.

          • johnBas5

            Thank you for including the actual numbers and assumptions you use in the example.

            The specific technology choices used in your example indeed lead to that it is a bad idea and not cost effective.

            Now if we would not mess around with curved panels, not necessary and use cheaper solar cells ones to optimize for $/watt instead of watt/m² we get a different picture.

            This gets us to solar panels that have around 1 – 3 $/watt.

            A switched mode based DC-DC converter usually has a conversion efficiency that is around 95%.
            Concentrator PV designs are still being optimized in the lab:

            And what do you know, using cheap $/watt and concentrated sunlight is exactly what the car manufacturers will do:
            What if we would take the canopy as the car being under it for a few hours a day? That definatelly changes things in favour of the solar panels.

            Let’s put the cost around $1500 for the solor panels, DC DC converter and the solar concentrator canopy.

            The canopy concentrates sunlight eight times:
            And let’s say our user commutes to work and uses the canopy to let the car recharge at the companies parking.
            Let’s say we get five times as much out of it in a day compared to the whole day without canopy.

            Over 10 years, this gets us: 5*$1240 = $6080.

            This beats our material costs of $1500 and assuming dealer costs increases this into $200 – $3000 range it also beats that.

            A small remark about future developments that may change our economic examples. There is a technology in development that would allow higher than 70% solar efficiency, works over a wide spectrum efficiently and would be able to deal with heat better than current PV’s.
            At the same cost as the single junction 15%-18% efficient blue silicium based solar panels.

          • Steve Grinwis

            You are dreaming if you think you can get the canopy, cells and DC-DC converter for $1500.

            The Canopy by itself would cost more than $1500. It’s going to have to be large and steady structure with a large glass or plastic lens. If it’s plastic, expect it to need a lot of reinforcement. Don’t forget, to collect 5 times the energy, the lens has to be five times the size. So, our 7 sq.m of available space (based on our above mythical tesla from all my examples) now requires a fresnel lens that is 35 square meters. Overall, we’ve decided that fresnel lens systems make solar cells more expensive, and less reliable (the extra heat degrades the panels quickly), which is why they aren’t used in commercial applications anywhere that I’m aware of. They generally require active cooling systems that reduce efficiency and raise costs. And we haven’t even included the mess that is the autonomous driving under the canopy thing. Expect to pay way more for that system, and all it’s inherent safety problems.

            Realistically, You couldn’t even buy the cells on the car for that either. The Prius has a small solar panel on it as an option. You pay $1500 for a 60 watt panel. We’re talking about installing closer to 800 watts worth of panels (Which, due to poor angle get downrated to 612 watts for energy calculations).

            Do you really think that you’ll be able to get 800 watts worth of panels for $1500? I certainly don’t. Expect to pay 1000’s. Then pay $1000’s more for that canopy structure, only to have it destroy your panels in months (Since there is no mention of Ford solving the fresnel lens solar panel degradation problem). That canopy is the utter height of ridiculousness, which is why I haven’t included it in any of my numbers. Also, as the panel heats, it’s efficiency is reduced, so you’ll either need a larger lens, or you’ll need to cool the panels some how, or you’ll have to accept less energy than your calculations have.

            If we can get really efficient cells, that is awesome, but I think we’re decades away from that (70%). Also, that won’t really help the case for car mounted cells, since you can take those cheap high power cells, mount them on the roof of a house, and generate more power, more cheaply than you could on the car, since the angle is better.

          • johnBas5

            I take it that the optimal case is a bit unrealistic. Agreed.

            Your $1500 for a 60W panel is far off. Solar panel power is specified in watt peak. THe canopy does not increases the light and heat load by hundreds of times but 7 times.
            I’m assuming they found a good balance between the trade-offs. Other things they have going is relatively large-volume so you can get contracts with solar panel manufacturers to get a cheaper price. Since we don’t know much about the specific prices the car manufacturer is going to pay this leads us to a bit of a dead-end though.

            The future efficient cells are being developed in the lab. The researchers are expecting to have the research done in the next years. Not decades. It’s a very different technology than current PV, that’s why then can target that efficiency.

          • Steve Grinwis

            The article you linked has a comment that said it well:

            “Hmm, when the fresnel lens on the carport is replaced with normal solar cells feeding into the grid and the solar cells on the car replaced with a wireless charging pod, you have a system that is cheaper, yields more energy, is safer and does not destroy the paint of the car.”

          • johnBas5

            The charging pod modification contains all the elements from the solar panels on car and ADDS an wireless charging connection.

            This cannot be cheaper because it is by definition more than the solar panels on car situation.

          • Steve Grinwis

            Except, you can get higher performance out of the stationary panels, and the panels don’t have be crazy fresnel lens engineered monstrosities that modern engineering has already dismissed.

            So, you get more power to work with, you can leverage standardized panels that have higher mass production values, standard inverter techniques, the ability to backfeed to the grid to be reimbursed for extra power, They don’t make the car appreciably heavier.

            And, if you can do some handwavy magic and say that solar panels are canopies are dirt cheap, then I can do the same, and say that wireless chargine stations are going to be so cheap they’re free without providing any supporting documentation of such!

            As such, the charging structure, A La Supercharger stations that Tesla have is the better route. Q.E.D.

            –Summer Glau

          • johnBas5

            The reason I’m giving the canopy an easy time is because it could be made of cheap plastic, while the wireless charger has to contain the electronics that have to handle a pretty high power level. A wireless charger also has risk including burning the paint of your car.
            Inverter techniques or DC-DC converters use a lot the same technology and both are mature.
            The weight won’t be as much as you fear, that stays my position on the weight question.

            The supercharger stations are a good way to get power.

          • Steve Grinwis

            You want to place the car in a solar oven, But you think a wireless charger will damage the paint….


          • johnBas5

            Some paints had iron particles in them. These would absorb the wireless electricity and heat up the paint.

          • Steve Grinwis

            Please show me any evidence that this is possible. Modern cars are subjected to high magnetic fields all the time from spark plug coils. If what you are saying is true, then there would be burnt spots on the hoods of all our cars…

            (i.e. I call bullshit)

          • johnBas5

            You don’t know much about how a spark plug works, do you.
            I’m getting the impression you don’t know much and are trying to come up with some distractions.

          • Steve Grinwis

            Spark plug *coil*… The coil is another inductive transformer, similar to some wireless chargers. It takes low voltage, high current, and outputs low current high voltage. The resulting magnetic flux density is pretty awesome. Exactly the same kind of technology as exists in wireless chargers, and spark ignition engines don’t have burn marks on their hoods, do they? That’s probably because the inductive moment of the paint in the hood is tiny. So small, it’s not worth writing about. And guess what? That doesn’t change with a 4 kW inductive charger either.

            So, once again, I pose a challenge to you: Give me a single example of a wireless charger damaging paint. I claim it’s never happened, and can’t happen.

            You might want to read up since spark ignition is apparently a foreign concpet to you.

          • johnBas5

            Wrong, a coil and transformer behave very differently.

            This is really basic science and engineering.

            Thinking a coil = inductor and a transformer are the same thing clearly shows you don’t know enough about this subject. You further more try to compare an spark ignition coil with an inductive charger coil. The technologies may contains something that has inductance but are very different.

            The paint burning thing is as likely as the paint burning of the car because of the canopy it’s amplification of the sunlight.

            Iron containing paint exists:

            Another thing you did not know is:


            You don’t mention the energy going into the magnetic flux, which is really the crux of the matter about it. This ignores the bigger gaps in you knowledge that almost all the energy in a spark plug is converted into heating the fuel mixture because of joule heating when the spark occurs.

            Your link does not quantify power levels or magnetic field strengths and there for does not say anything.
            You very clearly don’t know anything about electronics.

          • Steve Grinwis

            Read the wiki article on Induction Coils. The first line reads as follows:

            “This article is about a specific type of transformer.”

            I’ve glossed over some details, but they’re the same basic technology, collapsing fields on coils and such.

            I knew iron containing paint existed… What you have yet to prove, despite asking repeatedly, is a single example of a wireless charger damaging paint. Give me a single cite or I shall take it as an admission you made it up. Your extraordinary claim, your evidence required.

          • johnBas5

            The paint thing is far-fetched claim since you brought up the lame-ass made-up claim that the canopy would burn the paint of the car.
            Fair to say it is not a good argument.
            Just as the burn from the canopy is.

            The setup of the transformer is very different for a spark plug than it is for a wireless charger. That they both some kind of transformer is not the whole story.
            The primary difference is that in the spark plug.
            Almost all (<99%) of the magnetic field stays contained in the transformer core. The energy never comes out the spark plug as magnetic field. Whereas the magnetic fields with an inductive charger do happen at the outside of a car. The outside of the car does come into contact with the magnetic fields from the wireless charger, unlike the spark plug.

            Since you can't even use the terminology right or understand what your sources are telling you, I'm not going to waste more time with you.

            A smartphone and a high-end gaming pc are both computers. They describe the CPU in the smartphone as a CPU. Just as they describe the spark coil… Odd that, isn't it?

          • Steve Grinwis

            What terminology did I get mixed up on, specifically? My electromagnetics class was a decade ago, so that will happen. I do like how you backtracked from ‘Behave very differently’, to ‘the energy never comes out’. Very confidence inspiring.

            And, speaking as a computer engineer, the CPU in a smart phone and a PC are very similar, so it’s a great analogy as far as I can tell. Different architecture, but same basic idea. Surprised you don’t know that considering that you claim to be an electronics expert.

            As for I can tell, You’ve just been really hand-wavy on costs, never providing any numbers, and apparently launched off on a tirade about a comment that wasn’t even my own… I was quoting a comment on a site YOU linked, and commented it as such. The point of that comment was to point out that the system was more complicated, more expensive, and less effective than traditionally mounted solar panels that back feed the grid, something you have still failed to address.

            Good job. Top marks.

          • johnBas5

            Equating the canopy with it’s measly 7 – 8 times concentration without thermally isolating enclosure to a solar oven is just wrong.
            The wireless charger has disadvantages.

          • Steve Grinwis

            Your blasting 8000 watts / sq meter onto a surface, that’s not ‘measly’. And onto a dark surface specifically designed to absorb sunlight. Temperatures are going to skyrocket.

          • johnBas5

            Compare that to current high concentration setups where the sunlight is concentrated 200 – 1000 times. The 8 times is almost nothing. It’s with high efficiency solar panels used. Not the ordinary blue ones that are really quite bad at taking extra heat.

          • Steve Grinwis

            Also: An inductive charger is just a transformer with a larger air gap. Pretty simple, pretty cheap, well understood. And definitely not microwaving paint off of cars.

          • johnBas5

            Including the transmitter and receiver electronics.
            The inclusion of the necessary electronics of the inductive charger is implied.

          • Bob_Wallace

            How well do they work to keep the battery charged if you park in a garage for a few weeks?

          • johnBas5

            The garage could have some light coming in.
            And if not, it won’t do anything.
            Of course a car owner could actually do something against this particular problem.

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