Researchers Enhance the Energy-Storage Capability of Polymer-Based Nanocomposites

  • [2020-05-28]

    Recently, a research team led by Prof. LI Xiaoguang from University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS), in collaboration with Prof. SHEN Yang from Tsinghua University, made important progress in the field of flexible capacitors with high energy storage density. Researchers used negatively charged nanosheets to enhance the energy-storage capability of polymer-based nanocomposites. The results demonstrated a new horizon of high-energy-density flexible capacitors and was published in Advanced Materials.

    Dielectric materials with an intrinsic fast charge–discharge capability exhibit the highest power density among all currently available electric energy storage materials. Thus, they are crucial for advanced electronic devices and power grids.

    Flexible polymers with relatively higher breakdown strength become a preferred choice for dielectric energy storage. Polymer-based dielectric materials play a key role in advanced electronic devices and electric power systems. Although extensive research has been devoted to improve their energy-storage performances, it is a great challenge to increase the breakdown strength of polymer nanocomposites in terms of achieving high energy density and good reliability under high voltages.

    In this work, significantly enhanced energy storage capabilities are demonstrated in different flexible polymer-based nanocomposites by the addition of negatively charged Ca2Nb3O10 (CNO) nanosheets. The CNO nanosheets eventually lead to the simultaneously enhanced relative dielectric constant and breakdown strength of poly (vinylidene fluoride) (PVDF)-based nanocomposites.

    The significantly enhanced breakdown strength of 792 MV m−1 and the record-high recoverable energy density of 36.2 J cm−3 are demonstrated in PVDF-based nanocomposite capacitors with negatively charged CNO nanosheets. Similar substantial enhancements in break-down strength and energy density have also been obtained in PS-based polymer composite capacitors filled with these nanosheets.

    The strategy generalizability is verified by the similar substantial enhancements of breakdown strength and energy density in polystyrene-based nanocomposites. Phase-field simulations demonstrate that the further enhanced breakdown strength is ascribed to the local electric field, produced by the negatively charged Ca2Nb3O10 nanosheets sandwiched with the positively charged polyethyleneimine, which suppresses the secondary impact-ionized electrons and blocks the breakdown path in nanocomposites.

    All these results will arouse an extensive attention to the excellent energy storage performance of nanocomposites with negatively charged nanofillers, and their work provides a very competitive strategy to further improve energy storage performance of flexible polymer-based capacitor devices.

    Phase-field simulations for the breakdown phase evolution (Image by LI Xiaoguang et al.)

    Paper link:

    https://onlinelibrary.wiley.com/doi/full/10.1002/adma.201907227

    (Written by LI Xiaoxi, edited by LU Hongyu, USTC News Center)


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