I-Corps: Hybrid solid-liquid cathode to boost lithium primary battery energy

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

The broader impact/commercial potential of this I-Corps project is the development of a high energy density primary (non-rechargeable) battery to extend battery life and decrease battery size/weight for stand-alone long-lasting electronics. Primary batteries, with energy density 3x higher than lithium (Li)-ion, are critical for applications where high energy, reliability, and portability are essential, such as implantable/portable medical devices (e.g., pacemakers), unmanned vehicles, military and space devices, and remote monitoring sensors. These industries have strong unmet needs for high-energy primaries because they allow longer-duration operating time and can fit into smaller devices than rechargeable Li-ion. Despite the increasing demand, there have been few fundamental innovations in cell chemistries in the past 40 years, when all currently-known primary cathodes were extensively investigated. The proposed technology utilizes a recently developed high-energy cathode chemistry that may boost the energy density of the current market-leading system (Li-CFx) by a projected 50%, with good safety characteristics and little/no increase in cost. The high energy density of the proposed battery system may result in fewer batteries being needed overall (owing to increased battery life), mitigating environmental impacts of primary batteries given that their use is unavoidable in many applications. This I-Corps project is based on the development of a new class of energy-dense catholyte (cathode + electrolyte) utilizing liquid fluorinated reactants (LFRs). The proposed LFR cells exhibit intrinsically high energy densities and are robust and highly reproducible. Moreover, the compatibility between LFR and solid CFx enabled a significant evolution in cell design, where LFR catholytes are hybridized with solid-state cathodes to minimize the weight of inactive cell components (e.g., electrolyte solvents), and the battery materials are more efficiently used for storing energy. Results have shown a 20% boost in energy density over the current market-leading battery, and further improvement by 50% may be possible with cell structure optimization. Critically, the catholyte is injected into the cell using current production methodologies, which is consistent with established cell form factors and requires little modification to cell assembly, minimizing switching costs to battery manufacturers. Additionally, the price of the LFR is similar to that of the commercial solid cathodes, making the projected cost of the LFR cell after scaling up comparable to the state-of-the-art batteries. The proposed LFR cells also are expected to have good safety characteristics given the high thermal and chemical stability, low volatility, and low corrosivity of LFRs. 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.