In some formulations, the Argonne NMC materials can provide an initial capacity of > 250 mAh g^-1 when discharged between 5 and 2.0V and a rechargeable capacity of up to 250 mAh g^-1 over the same window. By contrast, the practical capacity of conventional cobalt oxide electrodes is approximately 140 mAh g^-1. Spinel LiMn₂O₄ and olivine LiFePO₄, while more thermally and structurally stable than the cobalt oxides, deliver relatively low practical capacities above 3V in a lithium cell—typically 100-120 mAh g^-1.

We believe the high-capacity NMC (lithiated nickel-manganese-cobalt oxide) technology we are commercializing are the materials of the future, that will solve many of the performance issues we see today in lithium-ion batteries.

—President of Toda Kogyo’s internal Energy Solutions Company

Our agreement with Toda Kogyo is an important step toward bringing to market key advanced lithium-ion battery technologies that are being developed here at Argonne with funding from the US Department of Energy. The technologies being licensed will enhance the performance, life and inherent safety of lithium-ion cells compared to those that employ the cobalt-based cathode technology that has dominated the market since the introduction of lithium-ion batteries in 1990.

—Gary Henriksen, Manager of the Electrochemical Energy Storage Department at Argonne

Argonne’s work on this particular family of materials, which stretches back five or six years, was led by Dr. Michael Thackeray.

Lithium-ion batteries operate by transporting lithium ions electrochemically between the two electrodes, with oxidation of the anode and reduction of the cathode during discharge, and the reverse during charge.

Approximately one-half of the lithium can be extracted from LiCoO₂, without compromising the structural and chemical stability of the electrode; on this basis, LiCoO₂ offers a practical electrode capacity of 130–140 mAh g^-1. Substituted LiCo_1-xNi_xO₂ electrodes offer slightly higher capacities but also tend to suffer from structural and thermal instability when charged.

—“Advances in manganese-oxide ‘composite’ electrodes for lithium-ion batteries”

The battery industry has thus been in search of alternative cathode materials that allow lithium-ion cells to reach closer to their theoretical capacities, combined with safety and cycle life. One approach being taken to improve the electrochemical properties and structural stability of electrode materials is to use structural units, such as a layered structure or a spinel-type configuration.

Argonne started work on synthesizing structurally integrated layered-layered and layered-spinel compounds. The layered-layered (i.e., comprising two layered components) electrodes showed greater promise, and that led to further development and the licensing agreement with Toda Kogyo.

The new cathode materials—xLi₂MnO₃·(1-x)LiMO₂ (M = Mn, Ni, Co)—are based on a composite matrix using an inherently stable inactive lithium-metal oxide that is integrated with a highly active form of another lithium-metal oxide component. This composite allows for greater levels of lithium to be utilized, while reducing oxygen-induced side reactions at the electrode surface that limit cell life and safety. The enhanced stability of these materials allows the system to be charged to higher voltages, leading to a significantly higher energy storage capacity than currently available materials through both the higher voltage and higher capacity per unit weight of active material.

In the work that we’ve done, the lithium-rich version of the material has some properties that differentiate it from the stoichiometric in terms of the characteristics of the material—it’s a better high-rate material and has enhanced stability because of the integrated structure where it has the electrochemically inactive component integrated with the active component. If we use certain combinations of materials, metal oxides, within the family, we can get stability up to higher voltages, and when we do that, we can increase the specific capacity to up to 250 mAh g^-1.

The license to Toda includes materials of the type just described and processing technology. It also includes some of the work done to take the higher capacity material that operates at higher voltage, and make it more dense in terms of particle density, and to improve its rate capability.

One of our targets is to make this usable in PHEVs, so we can use the same size Li-ion system but give increased range capability.

—Gary Henriksen

This cathode technology is part of a large and diverse ongoing portfolio of lithium-ion battery research and development at Argonne that began in 1994 and spans a range from applied development to long-term fundamental materials research. Funded primarily by DOE’s Office of Vehicle Technologies, the scientists and engineers at Argonne have developed numerous technologies for improving the life, safety and performance of lithium-ion batteries, including several types of more stable advanced cathode and anode materials for higher power or higher energy storage applications and electrolyte systems that further stabilize the electrode/electrolyte interfaces.

I think there will be more licenses on this same technology, and those will probably happen fairly quickly. Some of the other people we’re talking to are interested in making a deal. We also have electrolyte additive technology which forms more stable passivation films on both positive and negative electrode. That technology is also being sought.

—Gary Henriksen

With more than 180 years of experience manufacturing and supplying high-performance materials in various markets, Toda Kogyo Corp. has established itself as a supplier of materials in the lithium-ion and nickel-metal hydride battery markets.

In addition to plants in Japan, Toda recently acquired a plant in the Detroit area that will help Toda serve US automobile manufacturers. Toda Advanced Materials Inc. in Sarnia, Ontario, Canada produces cathode materials and their precursors for lithium-ion and nickel-metal hydride batteries with a combined annual production capacity of 4,000 metric tons.

Resources

• Michael M. Thackeray, Christopher S. Johnson, John T. Vaughey, N. Li and Stephen A. Hackney, Advances in manganese-oxide ‘composite’ electrodes for lithium-ion batteries, J. Mater. Chem., 2005, 15, 2257 - 2267, DOI: 10.1039/b417616m

• Michael M. Thackeray, Sun-Ho Kang, Christopher S. Johnson, John T. Vaughey, Roy Benedek and S. A. Hackney, Li₂MnO₃-stabilized LiMO₂ (M = Mn, Ni, Co) electrodes for lithium-ion batteries, J. Mater. Chem., 2007, 17, 3112 - 3125, DOI: 10.1039/b702425h

• Energy Storage Research and Development 2007 Annual Progress Report (Vehicle Technologies Program)