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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2017)

A facile and low-cost route based on thermodynamic principles of surface amorphous films (SAFs), intergrainular films (IGFs), and cation surface segregation benefits electrochemical performances of electrode materials for lithium-ion batteries and sodium-ion batteries.

SAFs as a facile and generic surface modification method is utilized to significantly improve the rate performance and cycling stability of cathode materials for lithium-ion batteries. A thermodynamic framework of SAFs is proposed. These nanoscale SAFs form spontaneously and uniformly upon mixing and annealing at a thermodynamic equilibrium, and they exhibit a self-regulating or “equilibrium” thickness due to a balance of attractive and repulsive interfacial interactions acting on the films. Specially, spontaneous formation of nanoscale Li3PO4-based SAFs has been demonstrated in two proof-of-concept systems LiCoO2 and LiNi0.5Mn1.5O4. Furthermore, SAFs introduced by nitridation can also benefit the performance of TiO2 anode material for sodium-ion batteries. The amorphous intergrainular films (IGFs) are found in the system of Sn doped Si anode for lithium-ion batteries. The coexistence of IGFs and porous secondary structure (characterized by FIB/SEM on the cross section) results in an enhanced performance. SAFs and IGFs can be used to guide future experiments of other material systems.

Utilizing anisotropic surface segregation to thermodynamically control the particle morphology and the surface composition is another economic, facile, and effective method to significantly improve the electrochemical performance of battery electrodes. WO3 doping and anisotropic surface segregation can change the facet relative surface energy to tailor the particle Wulff shape of LiMn1.5Ni0.5O4 spinel materials and the surface Mn/Ni ratio and benefits performances. The WO3 surface segregation can also improve Co-free Li-rich layered oxide Li1.13Ni0.3Mn0.57O2 cathode material performance. X-ray photoelectron spectroscopy in conjunction with ion sputtering has shown that W segregates to the particle surfaces and decreases the surface Ni/Mn atomic ratio; high-resolution transmission electron microscopy has further suggested that the segregation of W increases the structural disorder at the particle surfaces, which may also benefit the rate performance.

    Cover page: Enhancing Electrochemical Performance of Electrode Materials for Li-ion Batteries and Na-ion Batteries via Thermodynamic Surface/Interface Contro
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2016)
      Cover page: Stabilization of nanocrystalline alloys at high temperatures via utilizing high-entropy grain boundary complexions
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2018)
        Cover page: Enhancing the electrochemical performance of Li-rich layered oxide Li1.13Ni0.3Mn0.57O2 via WO3 doping and accompanying spontaneous surface phase formation
        • Article
        • Peer Reviewed
        UC San Diego Previously Published Works (2016)
          Cover page: Communication—Enhancing the Electrochemical Performance of Lithium-Excess Layered Oxide Li1.13Ni0.3Mn0.57O2 via a Facile Nanoscale Surface Modification
          • Article
          • Peer Reviewed
          UC San Diego Previously Published Works (2017)
          Spontaneous and anisotropic surface segregation of W cations in LiMn1.5Ni0.5O4 particles can alter the Wulff shape and improve surface stability, thereby significantly improving the electrochemical performance. An Auger electron nanoprobe was employed to identify the anisotropic surface segregation, whereby W cations prefer to segregate to {110} surface facets to decrease its relative surface energy according to Gibbs adsorption theory and subsequently increase its surface area according to Wulff theory. Consequently, the rate performance is improved (e.g., by ∼5-fold at a high rate of 25C) because the {110} facets have more open channels for fast lithium ion diffusion. Furthermore, X-ray photoelectron spectroscopy (XPS) depth profiling suggested that the surface segregation and partial reduction of W cation inhibit the formation of Mn3+ on surfaces to improve cycling stability via enhancing the cathode electrolyte interphase (CEI) stability at high charging voltages. This is the first report of using anisotropic surface segregation to thermodynamically control the particle morphology as well as enhancing CEI stability as a facile, and potentially general, method to significantly improve the electrochemical performance of battery electrodes. Combining neutron diffraction, an Auger electron nanoprobe, XPS, and other characterizations, we depict the underlying mechanisms of improved ionic transport and CEI stability in high-voltage LiMn1.5Ni0.5O4 spinel materials.
            Cover page: Enhancing the Ion Transport in LiMn1.5Ni0.5O4 by Altering the Particle Wulff Shape via Anisotropic Surface Segregation
            • Article
            • Peer Reviewed
            UC San Diego Previously Published Works (2019)
            Breast cancers enduring treatment with chemotherapy may be enriched for cancer stem cells or tumor-initiating cells, which have an enhanced capacity for self-renewal, tumor initiation, and/or metastasis. Breast cancer cells that express the type I tyrosine kinaselike orphan receptor ROR1 also may have such features. Here we find that the expression of ROR1 increased in breast cancer cells following treatment with chemotherapy, which also enhanced expression of genes induced by the activation of Rho-GTPases, Hippo-YAP/TAZ, or B lymphoma Mo-MLV insertion region 1 homolog (BMI1). Expression of ROR1 also enhanced the capacity of breast cancer cells to invade Matrigel, form spheroids, engraft in Rag2-/-[Formula: see text] mice, or survive treatment with paclitaxel. Treatment of mice bearing breast cancer patient-derived xenografts (PDXs) with the humanized anti-ROR1 monoclonal antibody cirmtuzumab repressed expression of genes associated with breast cancer stemness, reduced activation of Rho-GTPases, Hippo-YAP/TAZ, or BMI1, and impaired the capacity of breast cancer PDXs to metastasize or reengraft Rag2-/-[Formula: see text] mice. Finally, treatment of PDX-bearing mice with cirmtuzumab and paclitaxel was more effective than treatment with either alone in eradicating breast cancer PDXs. These results indicate that targeting ROR1 may improve the response to chemotherapy of patients with breast cancer.
              Cover page: Inhibition of chemotherapy resistant breast cancer stem cells by a ROR1 specific antibody
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