The exact scope of the materials included in the licensing deal with Argonne is confidential, according to Dr. Prashant Chintawar, Senior Manager of BASF Future Business NA, but does include formulations from the Argonne patented xLi₂MnO₃·(1-x)LiMO₂ (M= Mn, Ni, Co) structures (also called NMC). An electrochemically inactive Li₂MnO₃ component integrated with an electrochemically active LiMO₂ component provides improved structural and electrochemical stability at high potentials.

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. Argonne also licensed these composite materials to Toda Kogyo Corp. of Japan in 2008. (Earlier post.)

The combination of lithium and manganese rich mixed metal oxides extends the operating time between charges, increases the calendar life and improves the inherent safety of lithium-ion cells. Moreover, the enhanced stability of the composite material permits battery systems to charge at higher voltages, which leads to a substantially higher energy storage capacity than currently available material through both the higher voltage and higher capacity per unit weight of active material.

Based on customer feedback, according to Dr. Chintawar, BASF believes these NMC formulations can offer the right combination of safety, capacity and cost to serve as the next generation of dominant cathode material in the evolving Li-ion market. Lithium cobalt oxide materials, he noted, introduced in 1991, still have a more than 60% market share. BASF plans to commercialize these new cathode materials for transportation and other applications.

Known issues with the current composite materials, said Argonne’s Dr. Michael Thackeray during the DOE 2009 merit review meetings, include a large irreversible capacity loss on the initial cycle. Furthermore, charging high-capacity xLi₂MnO₃•(1-x)LiMO₂ electrodes to a high potential (>4.4 V) damages the electrode surface and reduces the rate capability of the electrode.

Improving the rate capability of high-capacity composite electrodes particularly at room temperature is still required to meet the 40-mile range battery requirement for plug-in hybrids, Thackeray said. Ongoing work at Argonne is seeking ways to stabilize the surfaces of the composite electrodes. Flourination is one approach that is promising (earlier post), and phosphate stabilization is another pathway of interest, he noted.

Future work at Argonne in this area will continue to exploit and optimize the xLi₂MnO₃•(1-x)LiMO₂electrodes (composition and performance) with the particular goal of reaching or exceeding the energy and power goals required for 40-mile PHEVs and EVs.

There will be a focus on surface studies, using both fluorides and phosphates to improve stability and rate capability of metal oxide electrodes at high potentials.

BASF is contemplating a research collaboration with Argonne, Chintawar said.

BASF Future Business GmbH, a 100% subsidiary of BASF SE, was founded in April 2001 and owns the company’s lithium-ion battery portfolio, including the longer-term, more speculative work on lithium-sulfur batteries announced in May. (Earlier post.)

BASF currently offers a high-energy Lithium Nickel Cobalt Oxide (LNCO) cathode material.

Resources

• Layered Cathode Materials (Annual Merit Review DOE Vehicle Technologies Program)

• US Patent 6,677,082. Lithium metal oxide electrodes for lithium cells and batteries

• US Patent 6,680,143. Lithium metal oxide electrodes for lithium cells and batteries