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Title: Mechanism of Na-Ion Storage in Hard Carbon Anodes Revealed by Heteroatom Doping

Hard carbon is the candidate anode material for the commercialization of Na-ion batteries the batteries that by virtue of being constructed from inexpensive and abundant components open the door for massive scale up of battery-based storage of electrical energy. Holding back the development of these batteries is that a complete understanding of the mechanism of Na-ion storage in hard carbon has remained elusive. Although as an amorphous carbon, hard carbon possesses a subtle and complex structure composed of domains of layered rumpled sheets that have local order resembling graphene within each layer but complete disorder along the c-axis between layers. Here, we present two key discoveries: first that characteristics of hard carbon s structure can be modified systematically by heteroatom doping, and second, that these changes greatly affect Na-ion storage properties, which reveal the mechanisms for Na storage in hard carbon. Specifically, P, S and B doping was used to engineer the density of local defects in graphenic layers, and to modify the spacing between the layers. While opening the interlayer spacing through P or S doping extends the low-voltage capacity plateau, and increasing the defect concentration with P or B doping high first sodiation capacity is achieved. Furthermore, wemore » observe that the highly defective B-doped hard carbon suffers a tremendous irreversible capacity in the first desodiation cycle. Our combined first principles calculations and experimental studies revealed a new trapping mechanism, showing that the high binding energies between B-doping induced defects and Na-ions are responsible for the irreversible capacity. The understanding generated in this work provides a totally new set of guiding principles for materials engineers working to optimize hard carbon for Na-ion battery applications.« less
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  1. Oregon State Univ., Corvallis, OR (United States). Dept. of Chemistry
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical and Engineering Materials Division
  3. Hewlett Packard Labs., Palo Alto, CA (United States)
  4. Univ. of California, Riverside, CA (United States). Materials Science and Engineering
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Advanced Energy Materials
Additional Journal Information:
Journal Volume: 7; Journal Issue: 18; Journal ID: ISSN 1614-6832
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org:
USDOE Office of Science (SC); National Science Foundation (NSF)
Country of Publication:
United States
36 MATERIALS SCIENCE; 25 ENERGY STORAGE; hard carbon anodes; heteroatom doping; local structures; mechanisms; Na-ion batteries
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1393301