The role of Li doping in layered/layered NaxLiyNi0.4Fe0.2Mn0.4O2 intergrowth electrodes for sodium ion batteries
- Boise State Univ., ID (United States)
- Florida State Univ., Tallahassee, FL (United States)
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Argonne National Laboratory (ANL), Argonne, IL (United States). Center for Nanoscale Materials (CNM)
- Boise State Univ., ID (United States); Argonne National Laboratory (ANL), Argonne, IL (United States). Center for Nanoscale Materials (CNM)
Here, the layered NaTMO2 (TM = Ni, Fe, Mn) materials with the O3-type structure are attractive as positive electrodes for sodium ion batteries because of their high theoretical capacity. Additionally, Li doping in these materials has been shown to offer substantial enhancements to their electrochemical properties by promoting the formation of intergrowth structures, which are combinations of specific phases. However, the mechanism by which the intergrowth modifies the electrochemical properties is often unclear. Systematic variation of Li content in NaxLiyNi0.4Fe0.2Mn0.4O2 (NFM-Liy) was conducted to identify its role in structural modification and electrochemical performance. Li contents of 0.15 and greater generate a layered/layered Na-O3/Li-O’3 intergrowth structure. 7Li and 23Na nuclear magnetic resonance and x-ray absorption spectroscopy identify that when the total solubility for alkali ions in the layered structure is exceeded, Li continues to form the Li-O’3 phase while the excess Na forms residual sodium compounds such as Na2O. Higher Li content is associated with improved capacity retention in the initial cycles from the superior stability of the mechanically linked NaO3/Li-O’3 structure that suppresses the P3 to OP2 phase transition during charge. However, high Li contents are associated with increased rates of parasitic side reactions that reduce long-term cycling stability. These side reactions are associated with the instability of the cathode-electrolyte interphase, which can be partially mitigated by atomic layer deposition (ALD) coating with alumina, which significantly enhances the capacity retention and Coulombic efficiency over many cycles. Overall, we find that the layered/layered Na-O3/Li-O’3 intergrowth structure is able to provide structural stability and suppress undesired phase transformations but is overwhelmed by the increased reactivity of the surface if not protected by surface coating.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)
- Grant/Contract Number:
- SC0019121; AC02-06CH11357; AC05-00OR22725; SC0014664
- OSTI ID:
- 2570542
- Journal Information:
- Nano Energy, Journal Name: Nano Energy Vol. 134; ISSN 2211-2855
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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