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Title: Capacity Fading Mechanism of the Commercial 18650 LiFePO 4-Based Lithium-Ion Batteries: An in Situ Time-Resolved High-Energy Synchrotron XRD Study

In this paper, in situ high-energy synchrotron XRD studies were carried out on commercial 18650 LiFePO 4 cells at different cycles to track and investigate the dynamic, chemical, and structural changes in the course of long-term cycling to elucidate the capacity fading mechanism. The results indicate that the crystalline structural deterioration of the LiFePO 4 cathode and the graphite anode is unlikely to happen before capacity fades below 80% of the initial capacity. Rather, the loss of the active lithium source is the primary cause for the capacity fade, which leads to the appearance of inactive FePO 4 that is proportional to the absence of the lithium source. Our in situ HESXRD studies further show that the lithium-ion insertion and deinsertion behavior of LiFePO 4 continuously changed with cycling. For a fresh cell, the LiFePO 4 experienced a dual-phase solid-solution behavior, whereas with increasing cycle numbers, the dynamic change, which is characteristic of the continuous decay of solid solution behavior, is obvious. Finally, the unpredicted dynamic change may result from the morphology evolution of LiFePO 4 particles and the loss of the lithium source, which may be the cause of the decreased rate capability of LiFePO 4 cells after long-termmore » cycling.« less
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  1. Indiana Univ.-Purdue Univ. Indianapolis (IUPUI), IN (United States). Dept. of Mechanical and Energy Engineering. Purdue School of Engineering and Technology; Purdue Univ., West Lafayette, IN (United States). School of Mechanical Engineering
  2. Indiana Univ.-Purdue Univ. Indianapolis (IUPUI), IN (United States). Dept. of Mechanical and Energy Engineering. Purdue School of Engineering and Technology
  3. Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Division. Advanced Photon Source
  4. Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Science and Engineering Division
  5. Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science and Engineering. School of Engineering and Applied Science
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 10; Journal Issue: 5; Journal ID: ISSN 1944-8244
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States); Indiana Univ.-Purdue Univ. Indianapolis (IUPUI), IN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
25 ENERGY STORAGE; 18650 cell; capacity fade mechanism; in situ study; LiFePO4; synchrotron XRD
OSTI Identifier: