期刊
CHEMISTRY OF MATERIALS
卷 22, 期 21, 页码 5845-5855出版社
AMER CHEMICAL SOC
DOI: 10.1021/cm101698b
关键词
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资金
- DOE [DE-SC0002626]
- U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy through the Oak Ridge National Laboratory's High Temperature Materials Laboratory
- Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy
- Taiwan Merit Scholarship [TMS-94-2A-019]
- Lawrence Livermore National Laboratory
- Thailand Center of Excellence in Physics
- U.S. Department of Energy (DOE) [DE-SC0002626] Funding Source: U.S. Department of Energy (DOE)
An objective in battery development for higher storage energy density is the design of compounds that can accommodate maximum changes in ion concentration over useful electrochemical windows. Not surprisingly, many storage compounds undergo phase transitions in situ, including production of metastable phases. Unique to this environment is the frequent application of electrical over- and underpotentials, which are the electrical analogs to undercooling and superheating. Surprisingly, overpotential effects on phase stability and transformation mechanisms have not been studied in detail. Here we use synchrotron X-ray diffraction performed in situ during potentiostatic and galvanostatic cycling, combined with phase-field modeling, to reveal a remarkable dependence of phase transition pathway on overp(o)tential in the model olivine Lit-x FePO4. For a sample of particle size similar to 113 nm, at both low (e.g., < 20 mV) and high ( > 75 mV) overpotentials a crystal-to-crystal olivine transformation dominates, whereas at intermediate overpotentials a crystalline-to-amorphous phase transition is preferred. As particle sizes decrease to the nanoscale, amorphization is further emphasized. Implications for battery use and design are considered.
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