Silicon Savvy

The flight from climate-damaging fossil fuels and the electrification of vehicles have manufacturers scrambling to design and produce efficient energy storage.   So far that has meant the lithium ion battery.  Unfortunately, many view the lithium ion battery in its typical configuration as inadequate to power electric vehicles for the mass market.  The primary obstacle is delivering adequate power at an affordable cost.

The recent post “Better Battery” described the efforts of one company to improve the lithium ion battery with more efficient and lower cost materials.  Sila Technologies touts its silicon-based anode as significantly more efficient than the graphite anodes currently in use.  BMW has agreed to put Sila’s silicon-based anodes in batteries planned for BMW’s 2023 electric vehicle models.

Silicon is seen as a superior material because it has a high specific capacity.  A lithium ion battery relies on an electrode called the anode to grab and store lithium ions when it is charged.  A silicon atom has the capacity to bind to four lithium ions, making it an attractive material to replace graphite anodes used in conventional lithium ion batteries.  A graphite atom has the capacity to bind with only one lithium ion.  Each gram of graphite in an anode stores enough energy to watch a two-hour movie on a smartphone.  A silicon anode would power ten hours of binge watching.

The greater energy density offered by silicon will make it possible to design longer-range electric car batteries with the same form factor as conventional batteries or to just scrap current designs and create a smaller, lighter battery.  Mobile devices could require less frequent charging and reach 100% charge in a shorter time.    

Sila has some competition in the quest to perfect silicon materials for battery anodes. All have one issue in common  -  developing a work-around for one of silicon’s inherent deficiencies. Silicon-based anode materials experience large volume change during the battery charge and discharge steps.  Silicon can swell to six times its original size.  The stress leads to pulverization of the silicon, loss of electric contact and errant chemical reactions.  The result is poor cycle life that has so far made silicon uneconomic for battery electrodes.  Consequently, much of the discussion about each of the developers of silicon materials centers on a fix for the deficiency.

Company		Location		Stage		Capital Source
Amprius, Inc.	amprius.com		Development		Venture
BioSolar, Inc.	biosolar.com		Development		BSRC:  OTCMKTS
Enevate Corp.	enevate.com		Development		Venture
Enovix	enovix.com		Volume production		Strategic partners
EnerG2	energ2.com		Commercial		Div. of BASF Venture
Group 14 Technologies	group14technologies.com		Development		EnerG2; DOE grants
Nexeon	nexeon.co.uk		Commercial		Private equity, venture
Sila Technologies	silanano.com		Development		Venture
SiNode Systems	sinodesystems.com		Development		USABC, Strategic partners

The post “Better Battery” explored how Sila Nanotechnologies is enclosing silicon in rigid nanostructures that keep their original shape while the silicon expands and contracts within.  Following are examples of other approaches that reveal there is a building body of ‘silicon savvy’.

·        Amprius is using silicon nanowires that leave room for the thin hairs of silicon to swell and shrink as the silicon atoms absorb (charge) and give away the lithium atom (discharge). 

·        A carbon matrix has been designed by BioSolar to surround and mechanically protect the silicon.

·        Enevate has formulated a silicon-dominant composite anode.  It is a single-particle material composed of more than 70% silicon.

·        Enovix is using semiconductor manufacturing techniques to produce silicon-based anodes from solar-grade silicon wafers.

·        Polymer chemistry is the foundation of EnerG2’s synthetic carbon-silicon materials.  Silicon is incorporated into the material before it is carbonized yielding a drop-in material for ultra-capacitor and lead acid battery performance enhancement.  EnerG2 was recently acquired by BASF’s venture arm.

·        Group 14 Technologies is a spin-off of EnerG2 for the purpose of commercializing EnerG2’s composite anode material as a replacement for graphite anodes in lithium ion batteries.

·        Nexeon is developing binder polymers that allow more silicon to be used as a partial replacement for carbon in battery anodes.

·        SiNode Systems is in partnership with PPG (PPG:  NYSE) to perfect SiNode’s silicon-graphene composite materials as an alternative anode.

Graphite-based anodes with a limited amount of silicon are easy enough to implement.  Both Nexeon and EnerG2 have achieved commercial success with such silicon performance enhancement materials for graphite anodes.  However, the additives are diluted silicon compounds such as silicon oxide and the silicon amounts are limited.  Silicon wafers and silicon nanowires are able to incorporate more significant amounts of silicon and therefore increase energy density in the battery.  However, these solutions may be difficult to manufacture. 

Sila Technologies is the first to announce a major commercial application for a silicon-based anode.  The race is on to capture market share.  The next post in this series on silicon applications in battery storage with look at market opportunity.

Neither the author of the Small Cap Strategist web log, Crystal Equity Research nor its affiliates have a beneficial interest in the companies mentioned herein.