Adding silicon nanoparticles to the carbon-based anode of a lithium ion battery has been shown to dramatically improve battery performance. One company that is pursuing this technology is Paraclete Energy, which had an interesting start as a nonprofit. The company’s CEO, Jeff Norris, provided Design News with some exclusive insights into this silicon-based technology approach, its potential benefits for EVs, and where Paraclete came from and where it is going.
Design News: The use of silicon in the anode of lithium ion batteries is fairly new. Can you tell us how Paraclete got involved in this? How long have you been working in this field?
Jeff Norris: Paraclete Energy was initially formed as a philanthropic company in 2007 to produce very low-cost nanoparticle silicon inks for the room temperature production of very low-cost silicon solar cells and panels for third-world indigenous people groups. These silicon inks were made with covalently bonded, reactive functional organic and inorganic chemistry to the silicon surface to allow a much wider optical spectrum bandgap for higher photonic sensitivity. What is also relevant to the Li-ion battery industry is both Paraclete’s very low-cost production methods and the ability to make elemental nanoparticle silicon substantially oxide free.
This ability to produce cost-effective silicon nanoparticles at room temperature with nearly any organic or inorganic material covalently bonded to the surface of the silicon has been found to be very advantageous in overcoming the typical problems of working with nanoparticle silicon with Li-ion batteries. In 2012, in light of various events in the solar industry and the global move to electrify everything, Paraclete Energy focused on becoming a for-profit, sustainable supplier of nanoparticle silicon to the Li-ion battery industry.
|Jeff Norris, CEO of Paraclete Energy, will be a speaker at The Battery Show in Novi, Michigan, September 11-13. (Image source: Paraclete Energy)|
DN: What kind of advantages result in using silicon in the anode? How can these advantages improve the performance of the battery?
Jeff Norris: High capacity, cycle stable silicon in an anode enables greater range for an EV, the longer time between the need to recharge one’s phone, tablet, power tool, or other devices.
Graphite, the traditional anode material, cannot meet today’s high energy demands with a limited theoretical specific capacity of 370 mAh/g. Silicon oxide, which was used because it is air stable, has a higher capacity of 1,550 mAh/g. However, Paraclete Energy’s SM-Silicon is based on elemental silicon metal, which has a capacity of 3,590 mAh/g.
Like graphite, Paraclete’s SM-Silicon has a tap density of 0.8g/cm3 and an ICL of only 6% - 8% while being priced below graphite from a $/kWh.
DN: Fast charging has become the Holy Grail for EVs. Can silicon anodes help with that?
Jeff Norris: Fast charging is indeed not the Holy Grail, but a Holy Grail. Low cost and cycle-stable high capacity are also Holy Grails. Paraclete is presently working with some of the world’s leading fast-charging technology companies. We are assisting them by adding low cost and cycle-stable high capacity to their technology.
DN: Can you explain the mechanism by which lithium ions intercalate into the anode when silicon is used? How does it differ from graphite?
Jeff Norris: There is not much difference except that silicon has a different voltage range. Therefore, the silicon will take the charge first, then the graphite, and just the opposite on discharge: The graphite will discharge first. If the consumer is recharging their device or driving only limited miles, say less than 50 miles per day, then the silicon will not be impacted as much as if the device or EV were allowed to almost drain the battery and then recharging it. In the scenario where the device or EV is not allowed to get below 50% discharge, the silicon will last for sufficient cycles in line with the warranty. When the energy is coming primarily from the silicon, it could expand as much as over 300%, whereas the graphite only expands ~10%.
This expansion primarily causes two potential negative things:
1.) Because of the stress from the expansion, the internal conductivity of the anode could be compromised. Paraclete’s SM-Silicon has a covalently bonded surface modifier on the surface of the silicon that has reactive functional groups on the opposite end that is covalently crosslinked with the binder and carbon systems. This creates a covalently bonded network between the systems within the anode, and thereby the network will stay intact.
2.) The expansion also causes new bare surfaces to be formed on the silicon. The electrolyte will want to form electronically conductive solid electrolyte interphase (SEI) on these new bare surfaces. If new surfaces continue to be formed, the SEI will form its conductive layer again. If this continues, the electrolyte will eventually be consumed and the battery will fail. Paraclete addresses this by putting (on the surface of the nanoparticle silicon) a non-polymeric, semi-flexible artificial SEI that is ionically conductive, yet substantially electronically insulating. These properties act to protect the silicon from the electrolyte and the excess formation of SEI and therefore mitigates the issues caused by the expansion of the silicon.
DN: How do you envision the roll-out of this technology over the next few years? In what time frame will we see this in EVs and grid storage?
Jeff Norris: Silicon, or more specifically SiOx, is already used in most premium Li-ion batteries from the Tier 1 manufacturers, such as LG, Samsung, and Panasonic. We have seen this in commercial batteries since 2014. However, SiOx is limited to putting in less than 9% of 1,550 mAh/g, due to its high Initial Capacity Loss (ICL) of 25% - 35%. Therefore, the resulting composite will be about 430 mAh/g—far short of the potential of elemental SM-Silicon of 3,590 mAh/g.
Getting battery companies to change or move away to new technology is very, very difficult. This silicon and, frankly, the entire battery industry are brimming with hype-filled technological claims that may work in a lab, that are too exotic or too expensive to be commercially viable, or only work in the artificial test environment that they created. This hype, combined with the legitimate challenges of switching technologies, has justifiably made the market penetration bar very high. Paraclete is dealing with this by introducing a new, simple, drop-in high capacity, cycle stable product – SM-Silicon/585.
The goal is to produce a 585 mAh/g silicon/graphite composite with high capacity and cycle stability. Unlike what is on the market today at 430 mAh/g, those suppliers require you to also use their graphite and their fixed ratio of silicon to graphite. With Paraclete’s SM-Silicon/585, the customer uses the preferred graphite they wish to use and they can add less or more of the SM-Silicon/585, thereby changing the reversible capacity. SM-Silicon/585 also allows the customer to use a much cheaper graphite and add the SM-Silicon/585 until the desired capacity is achieved. This is specifically beneficial, given SM-Silicon/585 is 5x less expensive than the silicon used in the ~430 mAh/g product already on the market.
DN: Events like The Battery Show in Novi bring together a wide range of engineers and Industry leaders. Can you comment on what it means for Paraclete to take part in this event and the types of interactions that you see?
Jeff Norris: The Battery Show in Novi, Michigan is an absolute must attend and, for us, must exhibit event. This is our chance to meet personally with customers, prospects, and our other industry friends. We gain from the marketing but also the high-quality conversations that we have with the industry decision makers and thought leaders. We see a dramatic increase in traffic on our website leading up to and after TBS. Above all, it shortens our sales cycle substantially.
Paraclete Energy is a corporate sponsor of The Battery Show that takes place in Novi, Michigan on September 11-13. Jeff Norris will provide a talk titled, “Moving Beyond Theory: Is High Capacity Silicon Metal Commercially Viable? If So, How & When?” on Tuesday, September 11th.
The company is also conducting a pre-event workshop on Monday, September 10th titled “Battery Materials Overview.” This workshop will be presented by Jeff Norris and the company’s vice president of R&D, Reza Kavian, Ph.D.
Senior Editor Kevin Clemens has been writing about energy, automotive, and transportation topics for more than 30 years. He has masters degrees in Materials Engineering and Environmental Education and a doctorate degree in Mechanical Engineering, specializing in aerodynamics. He has set several world land speed records on electric motorcycles that he built in his workshop.
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The Battery Show, Sept. 11-13, 2018, in Novi, MI, will feature a talk by Jeff Norris along with more than 100 other technical discussions covering topics ranging from new battery technologies to thermal management. Register for the event, hosted by Design News’ parent company UBM.