Battery Technologies

Developing Better High-Energy Batteries for Transportation Applications

The need for better batteries is a recurring theme in the effort to reduce energy consumption. Electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and fuel cell vehicles all depend on rechargeable high-performance batteries to deliver an acceptable level of performance for the commercial marketplace.

But what is a better battery? Many traits characterize batteries for transportation use: long life, safety, dependability, environmental friendliness, and cost, to name just a few. As a leader in the U.S. Department of Energy’s multilaboratory research and development program on high-power lithium-ion batteries for transportation, Argonne researchers are working to better understand the mechanisms of life span, abuse tolerance, and cost, and to develop a variety of advanced materials that have the potential to address these concerns. Lithium-ion batteries are currently the primary focus of research efforts because of their light weight and high energy density, which make them ideal candidates for transportation use.

Argonne efforts to extend the life of lithium-ion batteries include

• Conducting accelerated aging of sealed cells and extensive detailed diagnostic studies on these cells to establish the mechanisms that control power fade and capacity loss in a variety of lithium-ion cell chemistries.
• Addressing the instability of conventional passivation films, which contributes to both power fade and capacity loss in conventional lithium-ion cell chemistries. This involves developing advanced cell materials that stabilize the cell chemistry for longer life, such as alternative anode materials to carbon and graphite. Also, some of the electrolyte additives being developed at Argonne are designed specifically to form more stable passivation films on both the anode and the cathode.
• Developing advanced cathodes with enhanced structural and surface stability to provide longer life.
• Studying new lithium-ion conducting salts that are more chemically and thermally stable than LiPF6. LiPF6 is believed to play a role in both the power fade and capacity fade processes for lithium-ion cells.

Argonne efforts to improve the safety of lithium-ion batteries include

• Studying the thermal reactivity of lithium-ion cell components and identifying the mechanisms that control thermal runaway in a variety of lithium-ion cell chemistries.
• Developing safer lithium-ion cell materials, such as
• Stable high-capacity intermetallic anode materials, which operate farther away from the potential of metallic lithium than do carbon-based anodes, for high-energy EV applications, as well as nanophase lithium titanate anodes which possess extremely high rate capabilities for HEVs.
• Advanced cathode materials, of a composite structure, that offer capacity densities that are more than double those achievable with SOA cathode materials
• Alternative novel solvent systems and electrolyte additives, which form more stable passivation films on the electrodes or that provide inherent overcharge tolerance via redox shuttle mechanisms.

Argonne efforts to reduce the costs of lithium-ion batteries include:

• Developing lower cost cell materials and components, e.g., manganese-based mixed metal oxide cathode materials ad nanophase lithium titanate anodes.
• Developing electrode technologies with extremely high-rate capabilities, which significantly reduce the needed cell capacity and size for HEV batteries.
• Developing redox shuttle electrolyte additives that reduce the complexity of electronic control systems.

With DOE's new initiative on plug-in hybrid electric vehicles, the emphasis of this research and development is shifting to the development of advanced cell materials that provide higher energy densities, while retaining the stability needed for long life and enhanced inherent safety.

To further support advanced battery research, Argonne’s Electrochemical Analysis and Diagnostics Laboratory is available to assist Argonne and non-Argonne battery researchers by conducting evaluations that can be used to identify potential design or materials changes that may improve battery performance.

May 16, 2007