Envia Systems announcement may herald the first wave of DOE-supported commercial high energy density Li-ion cells with Si-C anodes

06 March 2012
 Elements in achieving the Envia 400 Wh/kg cell. Click to enlarge.

Envia Systems’ recent announcement of achieving Li-ion pouch cells with a specific energy density of 400 Wh/kg (earlier post) may be the market opener for a number of similar systems developed with US Department of Energy (DOE) support using different silicon-carbon anode materials, combined with an advanced cathode material and an appropriate electrolyte.

While Envia Systems is the first integrated cell producer to announce success with that type of combination, other providers of Si-C materials or IP—such as, but not limited to, Nanosys and the DOE’s own Argonne National Laboratory, respectively—are also currently deep in the process of development and/or commercialization. (Other silicon anode projects supported by the DOE includes those being done by Amprius, Angstrom Materials and NC State University. In addition, DOE is sponsoring a number of fundamental research projects focused on silicon anode development.) Consequently, the market may be poised for the entrance of a first wave of higher-energy density—and lower-cost—automotive Si-C cells in the 2014 or 2015 timeframe.

(As cycle life still needs to be improved for automotive applications (USABC long-term goals for EV batteries call for 1,000 cycles at 80% DOD and 10 years, earlier post), the advanced batteries with their attractive energy densities may emerge earlier in critical portable power applications. As an example, the military’s BB-2590 Li-ion battery used in a range of portable systems calls for a cycle life of ≥224 and ≥ 3 years.)

The silicon challenge. Silicon as an anode material for Li-ion batteries has attracted a great deal of R&D attention due to its much higher theoretical storage capacity than the graphitic anode materials commonly used in Li-ion batteries (LIB).

LIB capacity is limited in part by the intercalation of Li ions by the anode material—i.e., higher capacity batteries require anode materials that can accommodate more lithium ions. The theoretical capacity of the graphite anode is 372 mAh g-1; the theoretical capacity of silicon is some 10 times that.

One of the significant challenges with silicon, however, is that it undergoes an enormous volume expansion when fully lithiated. These volumetric stresses associated with lithiation/delithiation cycles result in the material crumbling, and in battery failure after a relatively short number of cycles, especially when viewed from the perspective of automotive requirements.

Hence, a significant amount of effort and funding is flowing into ways to synthesize silicon-based materials that can exploit the potential capacity while delivering acceptable cycle life. Using nanostructures has been shown by many to be one of the promising approaches to providing tolerance to the extreme changes in volume with cycling. A challenge with nanostructured silicon materials is delivering the required functionality (energy density, cycle life, safety) at an acceptable manufacturing cost.

Envia Systems. Envia Systems was selected for a $4-million grant from ARPA-E in the Agency’s first round of solicitation in 2009 (earlier post) and received another$1 million from the California Energy Commission (CEC). (GM is also an investor, having put $7 million into the company. Earlier post.) Envia is targeting its high energy density Li-ion cells at plug-in hybrid and electric vehicles. Envia Systems is developing large capacity pouch cells based on a novel high-voltage Manganese rich (HCMR) layered-layered Li2MnO3·LiMO2 composite cathode with a Si-carbon anode and proprietary electrolyte. Having a high amount of manganese in the structure translates to high capacity, increased safety and low cost. Envia’s HCMR cathode material is based on layered-layered cathode work licensed from Argonne National Laboratory (ANL). Envia has built on Argonne’s layered-layered chemistry to fine-tune the composition of Ni, Co, Mn and Li2MnO3. It innovated on particle morphology (particle size, shape, distribution, tap density & porosity) and also developed novel nanocoatings to enhance cycle life & safety. The HCMR cathode materials offer capacity of 220-295 mAh/g, and power of >1200 W/kg; cycle life @ 80% DOD is more than 1,000. Combined with a conventional graphite anode, the HCMR cathode would support a cell energy density of around 220-230 Wh/kg. Combined with the Si-C anode, it supports the heralded 400 Wh/kg density.  Envia’s highest capacity silicon-carbon anode. Click to enlarge. With support from the ARPA-E grant, Envia has demonstrated silicon-carbon nanocomposite anodes with very high capacity (1,530 mAh g-1) and promising cycle life. The material features nanopores with certain nanocoatings, said Dr. Sujeet Kumar, Envia Systems Co-Founder, President & CTO, in an interview with Green Car Congress at the recent ARPA-E Energy Inovation Summit (EIS). The silicon is embedded with the nanostructure. The approach is mundane and cost-efficient, he said, not exotic. The company is currently scaling up the material using a low-cost production process. Envia has also developed an electrolyte that is stable up to a voltage of 5.2V (vs Li/Li+). In cyclic voltammetry studies of standard electrolytes, as the voltage window was opened from upper cut-off of 4.3V vs Li/Li+ the electrolytes showed an increase in oxidation currents. When the voltage window was further increased to voltages above 4.5V the oxidation currents increased significantly showing that the electrolytes were almost completely oxidized at these voltages. However, Envia’s High Voltage Electrolyte showed stability up to 5.2V without any rapid increase in the oxidation currents.  We made the announcement of 400 Wh/kg to increase the confidence of the electric vehicle community.—Atul Kapadia ARPA-E tasked the Naval Service Warfare Center, Crane Division (NSWC Crane) Test & Evaluation Branch to perform Verification & Validation testing on two of the Envia pouch cells. The testing included verification of cell capacity and energy density at C/10 and C/3, 100% depth of discharge (DOD), as well as cell capacity and energy density at C/3, 80% DOD. The test results from the prototype cells tested at Crane were in line with the results obtained from the manufacturer. The claims of 400 Wh/Kg were substantiated through the cycling tests performed at Crane. Envia Systems expects it will be able to announce two commercial agreements this year, said Atul Kapadia, Chairman and CEO, in the EIS interview in which he also emphasized the importance of Envia’s focus on the automotive industry and its work with automotive partners. It has taken us 5 years to get here; the 5 years can give us an insurmountable lead. We are a part of the [vehicle] product roadmap. —Atul Kapadia Nanosys. Advanced materials company Nanosys, Inc., the developer of a silicon-graphite anode technology (SiNANOde), was awarded a$4.8 million grant from the DOE in August 2011 for the development of Li-ion cells leveraging high voltage composite cathode materials and silicon-based anodes. (Earlier post.)

In this project, Nanosys and LG Chem Power are developing a 700~1000 mAh g-1 Si anode (SiNANOde) with a target cycle-life of >800, and an eventual goal of achieving an energy density of 1,600 mAh g-1 at the end of the program. Combined with an innovative 255 mAh g-1 cathode (Mn-rich) and unique large format cell the Si anode is expected to enable a cell with 350 Wh/kg at a cell level cost target of <$150/kWh. This project will also use a layered-layered cathode material licensed from Argonne (which LG Chem Power and GM have licensed from Argonne (earlier post). With this technology LGCP has demonstrated a cathode specific energy of 255 mAh g-1. Nanosys grows silicon nanowires on graphite particles for its anode solution (SiNANOde); the intention is to provide the material as powder to battery manufacturers who can then integrate the powder into their existing production processes, Vijendra J (VJ) Sahi, Vice President of Corporate Development, told Green Car Congress in an interview at the ARPA-E EIS. To achieve the goals of the DOE project, Nanosys will need to improve SiNANOde capacity from 650 mAh g-1 to 700~1000 mAh g-1 in Phase I and subsequently to 1,600 mAh g-1. The Si content in the powder will need to be increased to 40%. Graphite particle size and morphology will be further optimized to achieve this goal. Achieve increased endurance of cycle-life will need to increase from 220 to >800. To achieve this requires surface modification of the Si nanowire anode for improved stability and SEI formation, as well as optimization of the electrolyte and binder chemistry will be optimized. The company has so far achieved 700 cycles with 70% capacity retention at 100% DOD (depth of discharge), and 300 cycles with 80% retention, Sahi said. Argonne National Laboratory. Argonne, with funding from ARPA-E, has developed a process to synthesize silicon-graphene composites as anode materials for Li-ion batteries. When combined with Argonne’s high energy composite cathode material, the resulting cell will offer more than 340 Wh/kg, according to Dr. Junbing Yang, one of the inventors of the Si-graphene material. Argonne has filed two patent applications on this technology, which it also was highlighting at the EIS. Argonne’s gas phase deposition approach embeds nano-scale silicon particles into the graphene layers, which is the key for longer cycle life, Dr. Yang says. California Lithium Battery. California Lithium Battery has entered into a Work for Others (WFO) program with Argonne National Laboratory to commercialize an advanced Li-ion battery combining ANL’s Si-graphene anode materials with other advanced battery materials into a Very Large Format (400 Ah) prismatic cell. The primary application for this GEN3 Li-ion battery is for grid-scale storage and electric vehicles, the company said. CalBattery has an option for exclusive and non-exclusive rights to the ANL Si-graphene process. CalBattery, a joint venture between Ionex Energy Storage Systems and CALib Power, was a runner-up in the DOE “America’s Next Top Energy Innovator” Challenge. (Earlier post.) The company says it plans to start manufacturing a line of lowest cost per watt cells for these markets in the US starting in 2014. Resources Comments It looks like a lot of progress being made. It's been more then 100 years that battery researchs exist and as long as gasoline and ice exist there is nothing better to discover and battery and gasoline are unsustainable. In less then 10 years they discovered more technology with hydrogen fuelcell but now they invented battery brainwash to avoid hydrogen technology. I understand that hydrogen with the increase in efficiency can put to unnemployment millions of employees and petrol traders but that will be a cleaning of the environment and the economy. These could become the first next generation higher performance (2X) batteries at lower price. Those batteries could see the arrival of: improved lighter HEVs at about the price as ICEVs; more affordable, higher performance PHEVs; and the very first generation of affordable highway capable BEVs. Post 2014 will be more interesting. It is not about putting people out of work, but the vast size of what has been built over a long period of time. We have SO many vehicles that run on fossil fuels and such a HUGE sunk investment that it will not change much in the short term. That is why people saying everyone will drive EVs in 10 years is not realistic. If we believed that, we would just stop everything else and wait ten years, then after 10 years we would still have millions of fossil fueled vehicles and be importing even more oil. SJC, You can't argue anything about hydrogen with AD (actually he goes by gorr on other blogs). He is totally irrational and applies no logic to it. He believes in all kinds of wild conspiracy theories and thinks that hydrogen is literally lying around to be taken for free and we're all ignoring it because we're being paid and/or brainwashed not to use it. 400 Wh/kg at the cell level would certainly be a step improvement for BEV and PHEV batteries, but wouldn’t this battery chemistry also find an earlier large market in portable electronics, where size and weight are at a premium and 500 life cycles are acceptable from batteries with cathodes based on cobalt, an expensive heavy metal? The more applications for this chemistry, the faster would be the progress down the learning curve. Also, the “USABC long-term goals for (B)EV batteries call for 1,000 cycles at 80% DOD and 10 years” but these goals miss the point that a battery with half this capability - 500 cycles and 5 years – and half the cost is also acceptable. In fact, using such a cheapo battery would be more economic over 10 years since half of the cost of a USABC-type battery is deferred for 5 years, and maybe a bit more. Furthermore, the cheapo’s replacement would likely be even less expensive and better than the original cheapo battery after 5 years of technology/manufacturing improvement. If they can make this work it would be great. If they can get metal air batteries to work it would be great. I am not waiting for either, action is required now. So the wishing and hoping has to stop and the practical doing must begin. We can not remain dependent on imported oil any longer and we will not all be driving EVs tomorrow. SJC.....a 50+ mpg Prius III+ will take you to the days of affordable BEVs in 2020-2025. @NorthernPiker: consumer electronics are small potatoes compared to what would be in store for electric cars if technologies like this get into mass production for cheap. Besides, consumer electronics aren't generally running up against their energy limit -- my iPhone 4S goes 2 days before I need to recharge it, thats fine, and I can plug in a lot of places (work, home, in my car's USB port, etc). Four days on a charge with my phone or 25 hours of battery life on my iPad don't do consumers a lot of good. At most, Apple will make a thinner device but thats all we get out of it. A big battery wont do a whole lot of good, considering that phones and laptops are thermally limited, that is the heat given off by the multitude of processors and silicon chips inside are preventing the unit from using more power than it is now. Electric transport is what so desperately needs the innovation. Let's say there are 30,000 EVs sold in the U.S. in 2012. That is the LEAF, Volt and others combined. Perhaps that number will be 40,000 in 2013 and so on. Now let's say that there are 1 million EVs out of more than 200 million cars on the road in the U.S. by 2020. That might reduce oil consumption 0.1%, but we will use 10% more because of miles driven and cars on the road. You can see the situation. This is the main point I have been trying to make. These are more realistic projections, it is not what we should do, but rather what is likely to occur. SJC....by that time, China may have 800+ million e-bikes and 50+ million e-three-four-six and eight+ wheel e-vehicles on their roads plus some 100,000 Km of very high speed e-trains. It is very doubtful if we will ever catch up. I am not advocating catching up with any country, I am urging everyone in the U.S. to do what needs to be done to reduce imported oil. We can mix in issues like air quality, GDP, trade balance, currency valuations and other factors. The one issue that has been front and center in the U.S. for about 40 years has been imported oil. Some 100+ million (about 40% of current fleet) highly fuel efficient (very low cost - below$10K) very light weight (much below one tonne) Tata Nano Megapixel PHEV with aluminium mini one-cyl 325 cc genset, a 13 Kwh battery pack for 54+ miles e-range, 500+ miles total range, a mere 138-inch long for easy city parking, enough room for 2+, with less than one gallon of liquid fuel for 200+ miles, in normal driving conditions etc would do a lot to reduce imported crude oil.

Of course, this low cost PHEV could NOT be built locally but their import cost ($1,000 B) would be offset within 5 years or so with reduced crude oil imports. The total$ gain in lower pollution and lower health care cost could be very interesting.

"I am urging everyone in the U.S. to do what needs to be done to reduce imported oil."

BINGO! This, THIS, is when we start to pull our economy out of the toilet. We can't afford half a billion dollars in trade imbalance for foreign oil every year and we can't afford the extra military costs associated with keeping the middle east open.

DaveD... there are two sure ways to do that. 1) produce more liquid fuels locally. 2) consume less fossil liquid fuels but more NG and electricity.

Both solutions are possible within a few short years if the majority pulls in the same direction.

Buy many more locally built 50 mpg HEVs, like the Prius and many more PHEVs and BEVs. Convert 5+M heavy vehicles and locomotives to NG. Convert all oil home heating to electricity with heat pumps. Replace most current low efficiency A/C + heating systems with very high efficiency heat pumps.

@Anthony F: I agree that the power usage of individual mobile electronic devices will not appreciably increase. The advantage of a higher energy battery would be a physically smaller battery and thinner and lighter devices, which would drive demand for such battery chemistry, particularly with an expected eventual savings in battery costs over the current cobalt-based batteries.

In 2015, a billion or so mobile devices will collectively use far more kWh's of batteries than the million or so EVs that are likely to be sold in 2015. In the same time frame, the 40 or 50 million e-bikes produced annually, each with several hundred Wh's of battery capacity, would represent a potential market, albeit more price-sensitive than smart phones, for large cells that would be equivalent to a million PHEVs.

DOE and Argonne make good progress at 400Wh/kg. Glad to see some of the dollars invested in various battery projects are starting to pay off.

1,600 mAh g-1 is a good goal. And a 20kWh battery @ \$3k is also an excellent target.

Consuming less liquid fuel is the first and best way, but with synthetic liquid fuels AND using less with hybrids, telecommuting and other methods we reduce imported oil even more.

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