Next Generation of High Energy Density Batteries at Low Cost

Lithium-ion batteries are an attractive energy storage technology because of their high energy density and excellent rate capability. Silicon shows incredible potential to replace graphite as an anode material due to its high lithium-storage capacity. However, silicon volume expansion (up to 400%) leads to pulverization and consumption of both lithium and electrolyte during cycling. Thus, lack of stability and capacity fade has limited commercial adoption of silicon-dominant anodes. NanoHydroChem’s solution is a cost-effective silicon-dominant anode material with more than 80% silicon content and stable capacity. This goal is achieved by producing micron-sized clusters containing encapsulated silicon nanoparticles in an oversized graphene-like carbon shell and carbon matrix. We use highly scalable, well-established, and cost-effective processes to produce the anode material providing a clear path to scale-up and cost reduction. Our starting materials are bulk-size metallurgical-grade silicon and/or PV-grade silicon waste from the solar and semiconductor industries. We do not use pyrophoric silane gas and any custom-made reactors in the production process. The active material is 100% drop-in without a need for special handling. Nano-sized silicon particles can accommodate significant stress without cracking while providing short electronic and ionic transport distances that improve rate capability. The porous structure is engineered to contain the silicon volume expansion while providing maximum contact with the carbon shell. The carbon shell protects silicon from exposure to the electrolyte while enhancing electronic conductivity. The thin carbon shell allows for excellent lithiation/delithiation kinetics, which enables extreme fast charging. The carbon matrix inside the pores enhances the conductivity and creates a robust structure that mitigates any stress and compression force (especially during calendaring) on the structure. Over the past year, we successfully demonstrated the scale-up process in 100 grams per batch to produce the silicon-based anode active material with silicon content up to 80% using well-known commercially scalable processes. Our preliminary battery performance data show great promise, although room for improvement remains. Our main objective in this phase I project is to identify the most optimized anode material composition based on the full cell data. Specifically, we will produce nine variations (70, 80, and 90% Si content; each with 150, 250, and 350% porosity size) of the anode material and test their electrochemical performance in coin cells and single-layer pouch cells. Based on the performance data, we will identify three best compositions to prototype and test pouch cells with a minimum capacity of 200 mAh. Pouch cells with the final best composition will be delivered to DoE. The budget that we need for this Phase I project includes $200,000 for personnel, materials, supplies, and equipment beyond what is currently available. Subsequent phases of the SBIR program will further scale the process and battery testing toward electric vehicle applications, exceeding 2 Ah capacity in Phase II. Commercial feasibility and impact of this project are substantial. The demand for high energy density batteries is massive and growing. The lithium-ion battery market is projected to exceed $77B in 2024. As it grows, the market is looking for new materials to increase battery performance. Use of silicon as an anode material in Li-ion batteries is not new. However, combining performance and large-scale production feasibility has been a persistent challenge. Companies and research institutes have studied silicon-based lithium-ion batteries for over a decade, but none have reached large market applications such as cell phones and electric vehicles, presumably because of their failure to achieve cost-effective production at the scales required for such markets. Those that have been commercialized are being used in satellites and other niche applications, and have significantly lower performance than we have achieved in our laboratory-scale experiments. Thus, we believe that our innovative material and production process has great potential to scale up high performance and cost-effective silicon-carbon anodes by using well-known chemical processing technologies.