Lithium-ion batteries (LIBs) play a pivotal role in advancing transportation electrification, offering a crucial solution to address climate change and fossil fuel depletion, but the current energy density of LIBs remains unsatisfying, limiting electric transportation range. To address this limitation, extensive efforts focus on developing novel electrode materials, including high-voltage cathodes and high-specific-capacity electrodes. However, the pursuit of higher energy densities introduces safety concerns due to the higher possibility of thermal runaway and flammable nature of conventional liquid electrolytes. In this doctoral thesis, I will present several innovative strategies for high-performance lithium battery systems aimed at enhancing the mileage of electric transportation without compromising or even enhancing safety.
The first part (Chapter 3) discusses a novel design for structural batteries. Structural batteries are the energy storage devices with enhanced mechanical properties integrated as structural components in vehicles to reduce vehicle weights and increase mileage. Through the development of a scalable and feasible tree-root-like lamination at the electrode/separator interface, an 11-fold enhancement in the flexural modulus of pouch cells is achieved, and the underlying mechanism is revealed by finite element simulations. This lamination has a minimal impact on the electrochemical performance of LIBs and the smallest reported specific energy reduction of ~3% in structural batteries. The prototype "electric wings" showcases stable flight for an aircraft model, highlighting the effectiveness and scalability of engineering interfacial adhesion in developing structural batteries with superior mechanical and electrochemical properties.
The second part (Chapter 4) presents a design rule for polymer electrolytes to enhance lithium metal battery safety. Lithium metal batteries are attractive for electric transportation due to their high energy densities, but their application is hindered by the safety concerns from dendrite growth. In this work, we observe that if the compositions of polyethylene oxide (PEO) electrolytes are near the boundary between amorphous and polymer-rich regions, concentration polarization in electrolytes will induce a phase transformation and create a PEO-rich phase at the electrode surface. This new phase is mechanically rigid with a Young’s modulus of ∼1-3 GPa so that it can suppress lithium dendrites, which allows Li/PEO/LiFePO₄ cells with such a phase transformation demonstrate superior lithium reversibility without dendrites for 100 cycles.
The third part (Chapter 5) proposes an innovative cathode design for all-solid-state Li-S batteries (ASSLSBs) which have ultra-high energy densities and enhanced battery safety. However, conventional cathode designs of filling sulfur in carbon hosts suffer from accelerated decomposition of electrolytes and sulfur detachment, leading to significant capacity loss. As a solution, I propose that nonconductive polar hosts allow long cycling life of ASSLSBs via stabilizing the adjacent electrolytes and bonding sulfur/Li₂S steadily to avoid detachment. By using a mesoporous SiO₂host filled with 70 wt.% sulfur as the cathode, we demonstrate steady cycling in ASSLSBs with a capacity reversibility of 95.1% in the initial cycle and a discharge capacity of 1446 mAh g-1 after 500 cycles at C/5.
| Identifer | oai:union.ndltd.org:columbia.edu/oai:academiccommons.columbia.edu:10.7916/2nhc-3164 |
| Date | January 2024 |
| Creators | Jin, Tianwei |
| Source Sets | Columbia University |
| Language | English |
| Detected Language | English |
| Type | Theses |
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