Valence's U-Charge RT power systems feature built-in battery management electronics for volt-age, temperature and state-of-charge monitoring and cell balancing, and they also include internal disconnects, which makes them extremely fault tolerant since each battery system can protect itself from potentially damaging conditions. The batteries are capable of peak power rates of 500 to 1700 continuous Watts, and as many as 30 of these battery systems can be connected in series.

Valence's Saphion I technology uses natural, phosphate-based cathode material in place of the less stable and more costly cobalt-oxide, used in other Li-ion batteries.

GM's Savagian noted that nanotechnology firms' focus on advanced treatment of the electrode in Li-ion batteries, along with other chemistry. Changes in the electrode composition allow high rates of charge and a high power-to-energy ratio, which has potential for further reduction in battery mass.

Nanoexa (www.nanoexa.com) and Decktron (www.decktron.com) are partnering to develop and commercialize lithium battery technology originally developed at the U.S. Department of Energy's Argonne National Laboratory (www.anl.gov). The firms plan to develop batteries with increased power output, storage capacity, safety and lifetime for HEV and other applications.

Under the FreedomCAR Partnership (www.eere.energy.gov), Argonne has conducted R&D to help industrial battery developers lower cost and increase the lifetime and inherent safety of high-power lithium batteries.

Traditional Li-ion technology uses active electrode materials with particles that range in size from 5 microns to 20 microns, but A123Systems (www.a123systems.com), a nanotechnology firm, offers non-combustible active materials composed of particles smaller than 100 nm. The firm claims that faster kinetics in its next-generation Li-ion storage electrode provide higher power than possible from other chemistries; its electrode and cell designs offer high thermal conductivity and low impedance compared with other batteries of similar size, and its electrolyte system operates over a wider temperature range. The firm said batteries made from its nanoscale electrode material are 80% lighter and offer higher charge/discharge rates (charging to high capacity in five minutes or less) and longer cycle life compared to NiMH batteries.

According to A123Systems, conventional Li-ion cells extract only half their lithium content when they reach their upper cut-off voltage. In contrast, A123 materials are designed to ensure that all lithium is extracted from the cathode when the battery is fully charged, thus safety issues related to overcharging are eliminated.

Roy Graham, senior vice president, commercial development, at Altair Nanotechnologies Inc. (www.altairnano.com) said lithium-ion batteries currently use graphite for the negative electrode and most use lithium cobalt oxide for the positive electrode. Altairnano uses a patented nano-titanate material as the negative electrode in its NanoSafe batteries. Graham explained that when the highly reactive graphite is replaced with nano-titanate materials, no interaction takes place with the electrolyte, thus the battery is inherently safe.

Graham said that in current-generation Li-ion batteries, lithium ions deposit inside the graphite particles during charge; however, the rate at which the lithium ions can deposit is limited by the electrochemical properties of the graphite, and if they cannot enter the graphite particles they can collect (plate) as lithium metal on the negative electrode's surface. “This can occur if the ions are deposited too rapidly on the graphite electrode as might be the case if the battery is charged too quickly. If this plating occurs, the battery will severely degrade in performance and in extreme cases, will short, causing overheating and thermal runaway,” Graham said. “The time required to charge a Li-ion battery is restricted by the ion incorporation rate,” he continued. “This results in charge times measured in hours.” He added that charge rate can be affected by external factors such as temperature. “At low temperatures, the lithium-ion incorporation rate is significantly less than at room temperature so charging at these temperatures may take much longer. Since the charge rate is governed by fundamental properties of the materials the only option is to change the materials and chemistry of the battery.”

Graham said Altairnano's use of nano-titanate material for the negative electrode allows lithium to be deposited — and batteries charged — at high rates, thus no plating occurs, even at extremely cold temperatures. “In laboratory tests, a cell can be charged to more than 80% capacity in about one minute,” he reported. “The technology also increases battery discharge rates, which is important when bursts of power are needed, such as a freeway electric vehicle accelerating rapidly.”

Altairnano's first customer for its NanoSafe battery is Phoenix Motorcars (www.phoenixmotorcars.com), which will use the batteries in sport utility trucks. The trucks will also include 90 kW electric drive systems from Enova Systems (www.enovasys).

John Day writes about automotive electronics and other technology. He holds a BA degree in liberal arts from Northeastern University and an MA in Journalism from Penn State. He can be reached by e-mail at jhday12@sbcglobal.com.