I'm a PhD candidate in Yi Cui's group leveraging new techniques in materials characterization to study next-generation lithium-ion battery materials. My interests lie in nanocharacterization, nanomaterials, energy storage, and electronics.
Education & Certifications
B.S., University of California San Diego, Nanoengineering (2016)
Yi Cui, Doctoral Dissertation Advisor (AC)
Opportunities for Cryogenic Electron Microscopy in Materials Science and Nanoscience.
Cryogenic electron microscopy (cryo-EM) was the basis for the 2017 Nobel Prize in Chemistry for its profound impact on the field of structural biology by freezing and stabilizing fragile biomolecules for near atomic-resolution imaging in their native states. Beyond life science, the development of cryo-EM for the physical sciences may offer access to previously inaccessible length scales for materials characterization in systems that would otherwise be too sensitive for high-resolution electron microscopy and spectroscopy. Weakly bonded and reactive materials that typically degrade under electron irradiation and environmental exposure can potentially be stabilized by cryo-EM, opening up exciting opportunities to address many central questions in materials science. New discoveries and fundamental breakthroughs in understanding are likely to follow. In this Perspective, we identify six major areas in materials science that may benefit from the interdisciplinary application of cryo-EM: (1) batteries, (2) soft polymers, (3) metal-organic frameworks, (4) perovskite solar cells, (5) electrocatalysts, and (6) quantum materials. We highlight long-standing questions in each of these areas that cryo-EM can potentially address, which would firmly establish the powerful tool's broad scope and utility beyond biology.
View details for DOI 10.1021/acsnano.0c05020
View details for PubMedID 32806083
- Molecular design for electrolyte solvents enabling energy-dense and long-cycling lithium metal batteries NATURE ENERGY 2020
- Tortuosity Effects in Lithium-Metal Host Anodes JOULE 2020; 4 (4): 938–52
Improving Lithium Metal Composite Anodes with Seeding and Pillaring Effects of Silicon Nanoparticles.
Metallic lithium (Li) anodes are crucial for the development of high specific energy batteries yet are plagued by their poor cycling efficiency. Electrode architecture engineering is vital for maintaining a stable anode volume and suppressing Li corrosion during cycling. In this paper, a reduced graphene oxide "host" framework for Li metal anodes is further optimized by embedding silicon (Si) nanoparticles between the graphene layers. They serve as Li nucleation seeds to promote Li deposition within the framework even without prestored Li. Meanwhile, the LixSi alloy particles serve as supporting "pillars" between the graphene layers, enabling a minimized thickness shrinkage after full stripping of metallic Li. Combined with a Li compatible electrolyte, a 99.4% Coulombic efficiency over 600 cycles is achieved, and stable cycling of a Li||NMC532 full cell for 380 cycles with negligible capacity decay is realized.
View details for DOI 10.1021/acsnano.0c00184
View details for PubMedID 32271533
- Resolving Nanoscopic and Mesoscopic Heterogeneity of Fluorinated Species in Battery Solid-Electrolyte Interphases by Cryogenic Electron Microscopy ACS ENERGY LETTERS 2020; 5 (4): 1128–35
- Scalable synthesis of nanoporous silicon microparticles for highly cyclable lithium-ion batteries NANO RESEARCH 2020
Transient Voltammetry with Ultramicroelectrodes Reveals the Electron Transfer Kinetics of Lithium Metal Anodes
Adv. Energy Lett.
2020; 5: 701-709
View details for DOI 10.1021/acsenergylett.0c00031
- A Water Stable, Near-Zero-Strain O3-Layered Titanium-Based Anode for Long Cycle Sodium-Ion Battery ADVANCED FUNCTIONAL MATERIALS 2019
- Monolithic solid-electrolyte interphases formed in fluorinated orthoformate-based electrolytes minimize Li depletion and pulverization NATURE ENERGY 2019; 4 (9): 796–805
Preventing Li depletion and pulverization by monolithic SEI layer generated in fluorinated orthoformate based electrolytes
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000525055505258
- Cryo-EM Structures of Atomic Surfaces and Host-Guest Chemistry in Metal-Organic Frameworks MATTER 2019; 1 (2): 428–38
- Improving cyclability of Li metal batteries at elevated temperatures and its origin revealed by cryo-electron microscopy NATURE ENERGY 2019; 4 (8): 664–70
- Surface-engineered mesoporous silicon microparticles as high-Coulombic-efficiency anodes for lithium-ion batteries NANO ENERGY 2019; 61: 404–10
- Fast galvanic lithium corrosion involving a Kirkendall-type mechanism NATURE CHEMISTRY 2019; 11 (4): 382–89
Dynamic Structure and Chemistry of the Silicon Solid-Electrolyte Interphase Visualized by Cryogenic Electron Microscopy
2019; 1 (5)
View details for DOI 10.1016/j.matt.2019.09.020
Nanostructural and Electrochemical Evolution of the Solid-Electrolyte Interphase on CuO Nanowires Revealed by Cryogenic-Electron Microscopy and Impedance Spectroscopy
2019; 13 (1): 737–44
Battery performance is critically dependent on the nanostructure and electrochemical properties of the solid-electrolyte interphase (SEI) - a passivation film that exists on most lithium battery anodes. However, knowledge of how the SEI nanostructure forms and its impact on ionic transport remains limited due to its sensitivity to transmission electron microscopy and difficulty in accurately probing the SEI impedance. Here, we track the voltage-dependent, stepwise evolution of the nanostructure and impedance of the SEI on CuO nanowires using cryogenic-electron microscopy (cryo-EM) and electrochemical impedance spectroscopy (EIS). In carbonate electrolyte, the SEI forms at 1.0 V vs Li/Li+ as a 3 nm-thick amorphous SEI and grows to 4 nm at 0.5 V; as the potential approaches 0.0 V vs Li/Li+, the SEI on the CuO nanowires forms an 8 nm-thick inverted multilayered nanostructure in ethylene carbonate/diethyl carbonate (EC/DEC) electrolyte with 10 vol. % fluoroethylene carbonate (FEC) and a mosaic nanostructure in EC/DEC electrolyte. Upon Li deposition, the total SEI thickness grows to 16 nm and significant growth of the inner amorphous layer takes place in the inverted multilayered nanostructure, indicating electrolyte permeates the SEI. Using a refined EIS methodology, we isolate the SEI impedance on Cu and find that the SEI nanostructure directly correlates to macroscopic Li-ion transport through the SEI. The inverted layered nanostructure decreases the interfacial impedance upon formation, whereas the mosaic nanostructure continually increases the interfacial impedance during growth. These structural and electrochemical findings illustrate a more complete portrait of SEI formation and guide further improvements in engineered SEI.
View details for DOI 10.1021/acsnano.8b08012
View details for Web of Science ID 000456749900075
View details for PubMedID 30589528
Evolution of the Solid-Electrolyte Interphase on Carbonaceous Anodes Visualized by Atomic-Resolution Cryogenic Electron Microscopy.
The stability of modern lithium-ion batteries depends critically on an effective solid-electrolyte interphase (SEI), a passivation layer that forms on the carbonaceous negative electrode as a result of electrolyte reduction. However, a nanoscopic understanding of how the SEI evolves with battery aging remains limited due to the difficulty in characterizing the structural and chemical properties of this sensitive interphase. In this work, we image the SEI on carbon black negative electrodes using cryogenic transmission electron microscopy (cryo-TEM) and track its evolution during cycling. We find that a thin, primarily amorphous SEI nucleates on the first cycle, which further evolves into one of two distinct SEI morphologies upon further cycling: (1) a compact SEI, with a high concentration of inorganic components that effectively passivates the negative electrode; and (2) an extended SEI spanning hundreds of nanometers. This extended SEI grows on particles that lack a compact SEI and consists primarily of alkyl carbonates. The diversity in observed SEI morphologies suggests that SEI growth is a highly heterogeneous process. The simultaneous emergence of these distinct SEI morphologies highlights the necessity of effective passivation by the SEI, as large-scale extended SEI growths negatively impact lithium-ion transport, contribute to capacity loss, and may accelerate battery failure.
View details for DOI 10.1021/acs.nanolett.9b01515
View details for PubMedID 31322896
- Correlating Structure and Function of Battery Interphases at Atomic Resolution Using Cryoelectron Microscopy JOULE 2018; 2 (10): 2167–77
Core-Shell Nanofibrous Materials with High Particulate Matter Removal Efficiencies and Thermally Triggered Flame Retardant Properties.
ACS central science
2018; 4 (7): 894–98
Dust filtration is a crucial process for industrial waste gas treatment. Great efforts have been devoted to improve the performance of dust filtration filters both in industrial and fundamental research. Conventional air-filtering materials are limited by three key issues: (1) Low filtration efficiency, especially for particulate matter (PM) below 1 mum; (2) large air pressure drops across the filter, which require a high energy input to overcome; and (3) safety hazards such as dust explosions and fires. Here, we have developed a "smart" multifunctional material which can capture PM with high efficiency and an extremely low pressure drop, while possessing a flame retardant design. This multifunctionality is achieved through a core-shell nanofiber design with the polar polymer Nylon-6 as the shell and the flame retardant triphenyl phosphate (TPP) as the core. At 80% optical transmittance, the multifunctional materials showed capture efficiency of 99.00% for PM2.5 and >99.50% for PM10-2.5, with a pressure drop of only 0.25 kPa (0.2% of atmospheric pressure) at a flow rate of 0.5 m s-1. Moreover, during direct ignition tests, the multifunctional materials showed extraordinary flame retardation; the self-extinguishing time of the filtrate-contaminated filter is nearly instantaneous (0 s/g) compared to 150 s/g for unmodified Nylon-6.
View details for PubMedID 30062118
Engineering stable interfaces for three-dimensional lithium metal anodes.
2018; 4 (7): eaat5168
Lithium metal has long been considered one of the most promising anode materials for advanced lithium batteries (for example, Li-S and Li-O2), which could offer significantly improved energy density compared to state-of-the-art lithium ion batteries. Despite decades of intense research efforts, its commercialization remains limited by poor cyclability and safety concerns of lithium metal anodes. One root cause is the parasitic reaction between metallic lithium and the organic liquid electrolyte, resulting in continuous formation of an unstable solid electrolyte interphase, which consumes both active lithium and electrolyte. Until now, it has been challenging to completely shut down the parasitic reaction. We find that a thin-layer coating applied through atomic layer deposition on a hollow carbon host guides lithium deposition inside the hollow carbon sphere and simultaneously prevents electrolyte infiltration by sealing pinholes on the shell of the hollow carbon sphere. By encapsulating lithium inside the stable host, parasitic reactions are prevented, resulting in impressive cycling behavior. We report more than 500 cycles at a high coulombic efficiency of 99% in an ether-based electrolyte at a cycling rate of 0.5 mA/cm2 and a cycling capacity of 1 mAh/cm2, which is among the most stable Li anodes reported so far.
View details for PubMedID 30062125