STTR Phase I: High Energy, Fast Charging, Long Cycle Life Si-based Rechargeable Batteries at Low Cost

The broader/commercial impact of this Small Business Technology Transfer (STTR) Phase I project is to achieve high energy, fast charging, long cycle life silicon-based rechargeable batteries at low cost. Silicon anodes are one of the most promising anode materials for the next-generation lithium ion batteries because of the high theoretical specific capacity (3,579 mAh g-1, which is about 10 times of the specific capacity of graphite anodes used in today’s commercial lithium ion batteries). However, the volume expansion (> 300%) of silicon during lithiation has led to continuous capacity decay as charge/discharge cycle increases. This project will address this continuous capacity decay problem using a patent-pending synthesis process to manufacture silicon nanoparticles with internal engineered voids and carbon coatings. Such engineered silicon-carbon composites will have long cycle life and be produced via a scalable, environmentally benign, low-cost manufacturing method, leading to a new-generation of lithium ion batteries with higher energy density and lower cost. This Small Business Technology Transfer (STTR) Phase I project addresses the volume expansion of silicon particles during lithiation that has traditionally resulted in continuous capacity decay, owing to mechanical fracture of the Si electrode, loss of inter-particle contact, and repeated solid electrolyte interphase layer formation and collapse. Introducing engineered voids allows silicon to expand inside the silicon particle without causing outward volume expansion and thus avoids fracture, loss of particle contact, and fracture and re-formation of the solid electrolyte interface during charge/discharge cycles. The carbon coating can force silicon expansion into the engineered voids, while improving the electronic conductivity of the silicon particle. Such engineered silicon-carbon nanocomposites will be fabricated via an innovative manufacturing method, composed of three major steps: (i) high-energy ball milling of micron-sized silicon particles to obtain silicon nanoparticles, (ii) carbon coating on the surface of silicon nanoparticles to obtain carbon-coated nanoparticles, and (iii) partial etching of the silicon core to obtain nanoparticles with internal engineered voids and carbon coating (i.e., Si@void@C particles). Different sizes of carbon-coated silicon nanoparticles require different partial etching conditions to generate different volumes of the engineering voids for different sized nanoparticles so that the cycle life will be improved while minimizing the loss in the specific capacity. This project will establish cost-effective methods to separate different silicon-carbon nanoparticles in four size groups and optimize the partial etching conditions for each size-group to achieve high specific capacity, fast charging, long cycle life Si@void@C anode materials at low cost. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2527575 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Bingyu Liu | Institution: SILICOAT ENERGY LLC, CHICAGO, IL | Award Amount: $304,997 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2527575 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2527575.html