Journal
CHEMISTRY OF MATERIALS
Volume 24, Issue 19, Pages 3720-3731Publisher
AMER CHEMICAL SOC
DOI: 10.1021/cm301844w
Keywords
lithium-ion battery; high-voltage spinel; neutron diffraction; surface segregation; cation ordering; electrochemical performance
Funding
- Office of Vehicle Technologies of the U.S. Department of Energy [DE-AC02-05CH11231]
- U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division
- NSF [0923096]
- Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [0923096] Funding Source: National Science Foundation
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The high-voltage doped spinel oxides LiMn1.5Ni0.5-xMxO4 (M = Cr, Fe, and Ga; 0 <= x <= 0.08) synthesized at 900 degrees C have been investigated systematically before and after postannealing at 700 degrees C. Neutron diffraction studies reveal that the cation-ordered domain size tends to increase upon annealing at 700 degrees C. Time-of-flight secondary-ion mass spectroscopy data reveal that the dopant cations M = Cr, Fe, and Ga segregate preferentially to the surface, resulting in a more stable cathode-electrolyte interface and superior cyclability at both room temperature and 55 degrees C with conventional electrolytes. The doping with Cr and Fe stabilizes the structure with a significant disordering of the cations in the 16d sites even after postannealing at 700 degrees C, resulting in high rate capability due to low charge-transfer resistance and polarization loss. In contrast, the Ga-doped and undoped LiMn1.5Ni0.5O4 samples experience an increase in cation ordering upon postannealing at 700 degrees C, resulting in degradation in the rate capability due to an increase in the charge-transfer resistance and polarization loss.
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