Materials Science & Engineering

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Author: search.filters.author.Dai, Jiaqi

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    Printable, high-performance solid-state electrolyte films
    (AAAS, 2020-11-18) Ping, Weiwei; Wang, Chengwei; Wang, Ruiliu; Dong, Qi; Lin, Zhiwei; Brozena, Alexandra H.; Dai, Jiaqi; Luo, Jian; Hu, Liangbing
    Current ceramic solid-state electrolyte (SSE) films have low ionic conductivities (10−8 to 10−5 S/cm ), attributed to the amorphous structure or volatile Li loss. Herein, we report a solution-based printing process followed by rapid (~3 s) high-temperature (~1500°C) reactive sintering for the fabrication of high-performance ceramic SSE films. The SSEs exhibit a dense, uniform structure and a superior ionic conductivity of up to 1 mS/cm. Furthermore, the fabrication time from precursor to final product is typically ~5 min, 10 to 100 times faster than conventional SSE syntheses. This printing and rapid sintering process also allows the layer-by-layer fabrication of multilayer structures without cross-contamination. As a proof of concept, we demonstrate a printed solid-state battery with conformal interfaces and excellent cycling stability. Our technique can be readily extended to other thin-film SSEs, which open previously unexplores opportunities in developing safe, high-performance solid-state batteries and other thin-film devices.
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    Single-digit-micrometer thickness wood speaker
    (Springer Nature, 2019-11-08) Gan, Wentao; Chen, Chaoji; Kim, Hyun-Tae; Lin, Zhiwei; Dai, Jiaqi; Dong, Zhihua; Zhou, Zhan; Ping, Weiwei; He, Shuaiming; Xiao, Shaoliang; Yu, Miao; Hu, Liangbing
    Thin films of several microns in thickness are ubiquitously used in packaging, electronics, and acoustic sensors. Here we demonstrate that natural wood can be directly converted into an ultrathin film with a record-small thickness of less than 10 μm through partial delignification followed by densification. Benefiting from this aligned and laminated structure, the ultrathin wood film exhibits excellent mechanical properties with a high tensile strength of 342 MPa and a Young’s modulus of 43.6 GPa, respectively. The material’s ultrathin thickness and exceptional mechanical strength enable excellent acoustic properties with a 1.83-times higher resonance frequency and a 1.25-times greater displacement amplitude than a commercial polypropylene diaphragm found in an audio speaker. As a proof-of-concept, we directly use the ultrathin wood film as a diaphragm in a real speaker that can output music. The ultrathin wood film with excellent mechanical property and acoustic performance is a promising candidate for next-generation acoustic speakers.
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    Nanomaterials for Garnet Based Solid State Energy Storage
    (2018) Dai, Jiaqi; Hu, Liangbing; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Solid state energy storage devices with solid state electrolytes (SSEs) can potentially address Li dendrite-dominated issues, enabling the application of metallic lithium anodes to achieve high energy density with improved safety. In the past several decades, many outstanding SSE materials (including conductive oxides, phosphates, hydrides, halides, sulfides, and polymer-based composites) have been developed for solid-state batteries. Among various SSEs, garnet-type Li7La3Zr2O12 (LLZO) is one of the most important and appealing candidates for its high ionic conductivity (10-4~10-3 S/cm) at room temperature, wide voltage window (0.0-6.0V), and exceptional chemical stability against Li metal. However, its applications in current solid state energy storage devices are still facing various critical challenges. Therefore, in this quadripartite thesis I focus on developing nanomaterials and corresponding processing techniques to improve the comprehensive performance of solid state batteries from the perspectives of electrolyte design, interface engineering, cathode improvement, and full cell construction. The first part of the thesis provides two novel designs of garnet-based SSE with outstanding performance enabled by engineered nanostructures: a 3D garnet nanofiber network and a multi-level aligned garnet nanostructure. The second part of the thesis focuses on negating the anode|electrolyte interfacial impedance. It consists of several processing techniques and a comprehensive understanding, through systematic experimental analysis, of the governing factors for the interfacial impedance in solid state batteries using metallic anodes. The third part of the thesis reports several processing techniques that can raise the working voltage of Li2FeMn3O8 (LFMO) cathodes and enable the self-formation of a core-shell structure on the cathode to achieve higher ionic conductivity and better electrochemical stability. The development and characterization of a solid state energy storage device with a battery-capacitor hybrid design is included in the last part of the thesis.