This Small Business Innovation Research (SBIR) Phase I project will develop advanced single ion gel electrolytes and related low cost manufacturing process for high power rechargeable lithium ion batteries (LIBs) with enhanced safety. Current LIB electrolytes consist of liquid organic solvents and lithium salts. Both anions and cations can move, though the anions do not participate in electrochemical reactions and do not contribute to the power output. This not only reduces the power density, but also leads to polarization gradient, salt depletion at the cathode and risk of precipitation at the anode during high power operation. The liquid organic solvents represent significant safety risks in large size battery pack such as solvent leakage, pressure buildup from solvent vaporization, and fire hazard during vehicle accidents. Therefore, current LIBs have limited acceptance by electric vehicles. This project will develop ionomer gel electrolytes in which anions are completely immobilized and the solvents fully constrained in the gel structure. The power density and safety of the LIBs will be enhanced by the gel structure as well the electrolyte/separator assembly.
The broader impact/commercial potential of this project is related to rechargeable lithium ion batteries (LIB) with high energy density, power density, enhanced safety, and reduced cost by using an innovative single ion gel electrolyte and low-cost manufacturing process. Rechargeable LIBs have broad applications as power source for many portable electronics. However, due to the material limitations of the electrolytes and electrodes, current LIBs have limited applications in large-size high-capacity energy storage systems such as hybrid electric vehicles and grid scale energy storage system. If successful, the novel single ion conductor gel electrolytes can improve the power density, improve the safety, and reduce the manufacturing cost of LIBs and promote their wide adoption in large size high power energy storage systems.
Rechargeable lithium ion batteries (LIBs) have broad applications as power source for many portable electronics such as mobile phones, laptops, cameras, ultrabooks, e-readers, touch-pads, and power tools. The current market trend for secondary (rechargeable) lithium-ion batteries indicates a 10.3% compound annual growth rate (CAGR) in revenues ($8.4Billion in 2010), Consumer applications currently account for about 71.4% ($6.0 Billion), of total revenues, while industrial applications account for about 28.6% ($2.4 Billion) of total revenues. However, current LIB electrolytes consist of organic solvents and lithium salts. Both anions and cations can move, though the anions do not participate in electrochemical reactions and do not contribute to the power output. This not only reduces the power density, but also leads to polarization gradient, salt depletion at the cathode and risk of precipitation at the anode during high power operation. The organic solvents represent significant safety risks in large size battery pack such as solvent leakage, pressure buildup from solvent vaporization, and fire hazard during vehicle accidents. Therefore, due to the material limitations of the electrolytes and electrodes, current LIBs have limited applications in hybrid electric vehicles and grid scale energy storage system. In this NSF SBIR Phase I project, we developed ionomer gel electrolytes in which anions are completely immobilized and the solvents fully constrained in the gel structure. With proprietary chemical design, the whole ionomer for a chemically-crosslinked network whose function is similar to a "sponge" which absorbs the solvents and keeps anions immobile during battery charge-discharge process. Electrochemical test was performed to identify suitable chemical compositions for practical LIB applications. In addition, the performance of batteries with single ion conductors is modeled and compared with regular lithium ion batteries by considering the anion polarization effects. Preliminary test results confirm that coin cell with ionomer gel electrolyte has higher lithium cation transference number than regular lithium batteries. It is expected that, with future optimization of the gel chemical structures and compositions to improve their conductivity, they can significantly improve the power density and energy density of lithium ion batteries. This technology can potentially promote the application of lithium ion batteries in large size high power energy storage systems.
