Solution-based Organic Coating for the Stabilization of Si Electrodes

In order to achieve the DOE Energy Storage Grand Challenge goals of $80/kWh cost for a 300-mile range electric vehicle battery deemed necessary for mass-adoption of electric vehicles (EVs) a substantial shift is needed in both the cost and capacity of today’s lithium ion batteries. Silicon-based anode materials contain over 10x the capacity of standard graphite materials and would provide a big step towards reaching these goals. However, during normal battery use silicon dramatically expands and contracts by 280% leading to: i) pulverization of Si active material due to internal stresses, ii) loss of electronic conductivity between silicon particles and conductive binders or other active material and iii) consumption of Lithium due to a continuously regenerating surface passivation layer (often termed solid-electrolyte-interphase or “SEI”) which collectively cause batteries with even small amounts of silicon to fail rapidly. The focus of this SBIR Phase I project is to enable highly-energy-dense, Si-containing LIBs that meet industry standard cycle lifetime requirements by solving these key problems of mechanical failure and SEI growth. Recent literature has shown that the introduction of a protective coating at the electrode/electrolyte interface can provide the extra mechanical and chemical stability needed to enable improve performance. However, until now, such coatings have only been applied using costly, low-throughput vacuum deposition techniques. Coreshell’s innovation has been to apply engineered electrode surface coatings that are deposited using a low-cost and industrially scalable process. Using such techniques, the team has demonstrated uniform and conformal coverage of coatings on all surfaces throughout the porous microstructure of typical LIB electrodes and will extend this technique to Si anodes during this Phase I project. The Phase I project ultimately aims to deliver 200 mAh pouch cells constructed from Si-containing anodes that exceed DOE Energy Storage Grand Challenge specific energy target of 400 Wh/kg, are composed of at least 30% Si, and also achieve industry-standard cycling performance of at least 80% capacity retention after 250 charge- discharge cycles. Achievement of the outlined Phase I performance goals will drive scaling of the developed technology to 2 Ah cells of 80-100% Si content in Phase II, and eventually to full-scale integration into LIB manufacturing lines. By helping reducing LIB costs to <$80/kWh, the technology will enable mass adoption of electric vehicles and potentially reduce CO2 emissions nationwide by up to 25%.