High5ive™ advanced high-voltage cells

Lithium-ion batteries introduced in the early 1990s are the energy storage backbone of the today's portable power products.

While the characteristics of the LiCoO2/Graphite electrochemical system are acceptable for the portable electronics market, significant improvements in the safety and lifetime of lithium-ion must be achieved in order for large-scale lithium-ion batteries to become a viable solution for vehicle propulsion.

At the present time, the LiFePO4/Graphite electrochemical couple offers the most promise as it provides power, safety and cycle life beyond those of mature cobalt-based systems.

Although LiFePO4 has many advantages, it suffers from low potential (3.45 volt, vs. Li+/Li), and low material density (3.6 g cm−3). Batteries based on this cathode have relatively low energy-density: approximately 50% that of the cobalt-based system.

New battery systems that have the positive attributes of the LiCoO2 and the LiFePO4 systems, while overcoming their respective deficits, are in great demand.

Spinel advantages

High voltage spinel oxides are promising candidates. This type of cathode chemistry has been studied for a number of years. However, the high voltage has detrimental effects which until now have thwarted its wider implementation in commercial batteries:

• Oxidation of the electrolyte solvent resulting in damage to the anode and cathode SEI structures, in mechanical blockage of electrode active sites and in parasitic reactions.
• PPM concentrations of HF due to residual moisture in the electrolyte - resulting in partial dissolution of metal ions in the cathode and in damage to the anode and cathode SEI structures.

To address these challenges and develop a breakthrough lithium-ion battery cell, ETV Motors assembled an R&D team with a proven track record in developing disruptive electro-chemistries that have reached the commercial marketplace. In collaboration with the renowned electrochemistry team at Bar Ilan University's Department of Chemistry, it is developing a 4.7V Lithium Manganese Nickel Oxide (LMNS) cathode that overcomes the problems experienced by other researchers.

High voltage

We believe strongly, and many of leading centers of advanced energy research agree, that high voltage cathodes represent one of the major potential routes to achieve the increased energy density so important to automotive batteries.

High voltage not only increases the energy and power densities [E(Wh/kg) = Ah/kg x V; P(W/kg) = A/kg x V] but also reduces the number of cells per battery pack. Given that EV batteries are of high voltage (typically 300-600V), series connection of cells to achieve the required voltage is the common practice. Making use of 4.7 volt cells vs. the state-of-the-art, conventional 3.2 volt or 3.7 volt cells reduces the overall number of cells by 30-45%.

And since all EV battery packs require battery management (BMS) and heat management systems (HMS), a reduction in the number of cells per battery pack has a very positive impact in reducing the weight, volume and cost of the battery pack. Thus cells like High5ive cells, having higher voltage, deliver extra value by reducing the BMS and heat management circuitry overhead - a considerable advantage.

The laboratory work of the past two years has involved the development of proprietary and patent-pending techniques and materials that include special coating of the LMNS raw materials; a novel LMNS synthesis process; coating (in situ) of cathode with nanometric polymeric layers; and novel developments affecting the anode and the cell membrane.