Argonne National Laboratory (ANL) has developed composite electrodes for rechargeable lithium-ion batteries. Such electrodes offer superior cost and safety features over state-of-the-art LiCoO2 electrodes that power conventional lithium-ion batteries. Moreover, they demonstrate outstanding cycling stability and can be charged and discharged at high rates, making them excellent candidates to replace LiCoO2 for consumer electronic applications and hybrid electric vehicles.
In ANL's patented technology, the electrodes are defined as having composite xLi2M'O3·(1-x) LiMO2 structures in which an electrochemically inactive Li2M'O3 component is integrated with an electrochemically active LiMO2 component to provide improved structural and electrochemical stability. The preferred M' ions are manganese, titanium and zirconium, whereas the preferred M ions are manganese and nickel, which can be used in combination with other metals such as cobalt. For example, the composite electrode 0.10Li2MnO3·0.90LiMn0.26Ni0.37Co0.37O2, which can also be represented in conventional layered notation as Li[Li0.0475Mn0.3175Ni0.3175 Co0.3175]O2, shows outstanding electrochemical properties. The structural compatibility between the two components, both of which have layered configurations, allows integration to occur at the atomic level.
During charge and discharge of a lithium-ion cell, Li+ ions are electrochemically removed from and reinserted into the LiMO2 component. An additional advantage of using electrode structures with manganese and nickel ions in the LiMO2 component is that these structures can accommodate additional lithium; they form layered Li2MO2 structures without compromising the reversibility of the reaction, thereby providing additional capacity to the electrode. The Li2M'O3 component not only provides structural stability but also ensures, with its high lithium content, that the lithium layers in the composite electrodes are not contaminated by small amounts of transition metal ions, such as Ni2+ ions.
For further information, contact Steve Lake at the Office of Technology Transfer, Argonne National Laboratory, 630-252-5685, or slake@anl.gov.
