NEI Corporation developing Li-ion batteries with water-based electrolyte; targeting energy densities of 250 Wh/kg and 750 Wh/l
21 May 2014
NEI Corporation, a nanotech materials company (earlier post), is developing a lithium-ion battery in which the electrolytes are dissolved in water instead of an organic solvent. Such an aqueous-based lithium-ion battery has the potential to eliminate the risks associated with conventional lithium-ion batteries, in which the organic solvents are highly flammable. In addition, there are toxicity and other environmental concerns associated with the non-aqueous electrolyte solvents. Aqueous-based lithium-ion batteries also have the potential to reduce cost.
However, while the concept of a lithium-ion cell using a water-based electrolyte has been known and studied, a major limitation is the narrow electrochemical stability window for water, which restricts the cell voltage. The electrochemical stability window for water is within the range of 0 to 1.25V; electrolysis of water occurs outside this voltage range.
In contrast, organic solvent-based electrolytes are stable up to at least 4V. The lower the cell voltage is, the lower the energy density is, and consequently, water-based lithium-ion batteries have had low energy densities.
Recently, scientists and engineers at NEI Corporation have developed new materials concepts that can overcome the voltage stability issue of water-based lithium-ion systems.
The principal feature of the proposed effort is the use of a modified high-capacity cathode in conjunction with a functionalized anode that is capable of reaching much higher cell voltages than aqueous systems reported to date. The wider electrochemical potential, combined with the use of a high capacity cathode, will result in an increase in the energy density.
The aqueous-based technology is being developed with about $100,000 in Phase I funding from the Environmental Protection Agency’s Small Business Innovation Research (SBIR) Program (EPA Contract Number: EPD14009).
The target gravimetric and volumetric energy densities for the proposed aqueous electrolyte-based Liion system at the pack level are 250 Wh/kg and 750 Wh/l, respectively. The Phase 1 effort will entail synthesis and characterization of the modified cathode and anode, along with structural and electrochemical characterization of the cell.
In Phase 2, the structure and composition of the electrode materials will be further optimized, and the ability to fabricate the materials in large volume will be demonstrated. In addition, by working in partnership with battery manufacturers, the newly developed cathode material will be integrated into large format Li-ion batteries. Prototype cell packs will be fabricated and tested by the end of the Phase 2 program.
NEI has been a source for customized cathode and anode materials used in lithium batteries. The company specializes in developing new compositions and particle morphologies, including nanoscale particle engineering and surface modification. NEI’s MATCH service—Materials Analysis, Testing and Characterization—also plays a role in assisting new materials development.
NEI has an extensive battery characterization and research facility, which includes multi-channel cell testers, as well as conventional and customized electrode material manufacturing capabilities using both solid state and solution-based methods.
NEI Corporation currently offers cathode and anode materials (both powders and coated electrodes), and solid state electrolytes for use in lithium-ion batteries.
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