Argonne and Hanyang University Develop New High-Energy Cathode Material With Improved Thermal Stability; Good Fit for PHEV Applications
|SEM of Li[Ni0.64Co0.18Mn0.18]O2 particle with concentration gradient of Ni, Co, and Mn contents. From Sun et al. (2009). Click to enlarge.|
A new high-energy cathode material that can greatly increase the safety and extend the life-span of future lithium-ion batteries has been developed through the close international collaboration of researchers led by the US Department of Energy’s (DOE) Argonne National Laboratory and Hanyang University in South Korea. The results, say the researchers, suggest that the cathode material could enable production of batteries that meet the demanding performance and safety requirements of plug-in hybrid electric vehicles.
Although layered lithium nickel-rich oxides (Li[Ni1-xMx]O2 (M=metal)) have attracted significant interest as promising cathode materials for rechargeable lithium-ion batteries owing to their high capacity, excellent rate capability and low cost, their low thermal-abuse tolerance and poor cycle life, especially at elevated temperature, have prohibited their use in practical batteries.
Addressing these problems, the Argonne and Hanyang researchers developed a concentration-gradient cathode material based on a layered lithium nickel cobalt manganese oxide. In this material (Li[Ni0.64Co0.18Mn0.18]O2), each particle has a central bulk that is rich in Ni and a Mn-rich outer layer with decreasing Ni concentration and increasing Mn and Co concentrations as the surface is approached. The former provides high capacity, whereas the latter improves the thermal stability. A paper on their work was published in the April issue of Nature Materials.
|Comparison of cycling performance of half cell based on bulk Li[Ni0.64Co0.18Mn0.18]O2 and concentration-gradient material Li[Ni0.64Co0.18Mn0.18]O2. Click to enlarge.|
A half cell using the concentration-gradient cathode material achieved a high capacity of 209 mAh g-1 and retained 96% of this capacity after 50 charge–discharge cycles under an aggressive test profile (55 °C between 3.0 and 4.4 V). Conventional cathodes have a capacity of 140 to 160 mAh g-1.
The material also showed superior performance in thermal-abuse tests compared with the bulk composition Li[Ni0.8Co0.1Mn0.1]O2 used as reference.
The new high-energy material that we developed makes up a new class of oxide materials in which the composition of each particle is changing from the bulk to the outer layer. Typically most oxide cathodes have a uniform composition throughout each particle, and offer low capacity and high surface reactivity with the electrolyte.
The basic idea behind our novel approach is to design a particle that has a very high-energy composition at the bulk and an outer layer composition that is very stable against any reactivity with electrolyte. Those two design features will be able to improve significantly the life and safety of lithium battery materials while offering very high-energy characteristics for possible use in PHEVs.—Khalil Amine, manager of the advanced battery technology group at Argonne and the project's co-principal investigator
The material has also demonstrated a very high-power capability, said Yank-Kook Sun, co-principle investigator and a professor in the Department of Chemical Engineering at Hanyang University.
The DOE Office of Vehicles Technologies funded this research. Argonne has a major role in working with the DOE Office of Vehicle Technologies to develop advanced anode and cathode materials and improve lithium-ion battery technologies for transportation applications.
Yang-Kook Sun, Seung-Taek Myung, Byung-Chun Park, Jai Prakash, Ilias Belharouak & Khalil Amine (2009) High-energy cathode material for long-life and safe lithium batteries. Nature Materials 8, 320 - 324 pp 320 - 324 doi: doi:10.1038/nmat2418