Doctor of Philosophy
Mechanical and Materials Engineering
Sun, Xueliang A.
Lithium-ion batteries (LIBs) have become the ubiquitous energy storage technology from long range electric vehicles to portable consumer electronics. However due to their limited volumetric and gravimetric energy density, other battery chemistries and geometries must be investigated. One promising alternative is the use of anode-free batteries, which plate lithium metal directly onto or into a current collector, with the entire lithium source coming from the cathode. However, these anode-free systems face some key challenges including 1) the formation of lithium dendrites and poor cycling efficiency; 2) the construction of a robust and stable solid electrolyte interphase (SEI) on the current collector; and 3) the significant volume change of lithium plating and stripping.
This thesis focuses on the design of multiple strategies for the stabilization of the anode-free current collector and plated/stripped lithium and extending the life cycle and performance of the cell. The first part of the thesis demonstrates the use of a lithiated niobium oxide atomic layer deposition (ALD) coating to stabilize lithium deposition through the suppression of dendrite formation, extending the cycle life of the cell. Herein the total energy delivered over the life of the cell is improved by a factor of 10. In the second research chapter, an atomic/molecular layer deposition (MLD) bilayer coating is used as an artificial solid electrolyte interphase (SEI) to facilitate lithium deposition and improve the cycle life of the cell. The MLD/ALD bilayer structure is proven to act as a protective overlayer, rather than nucleation layer. In the third section, a lithiophilic nanowire mesh is utilized as an anode-free current collector to effectively host plated lithium metal and significantly improves the cycling efficiency and cycle life, while demonstrating exceptional capacity even at 12-minute charge and discharge. Finally, the last chapter investigates the relationship between the physicochemical and electrochemical properties of various SEI components generated homogeneously via a gas exposure method as a way to guide future SEI design.
Summary for Lay Audience
With the rapid development of climate crisis and consumption of fossil fuels, the development of rechargeable batteries is one of the crucial frontiers of green energy research that affects us all in everyday life. From long range electric vehicles to portable consumer electronics, lithium-ion batteries (LIBs) are the ubiquitous energy storage technology. However, due to the low storage capability of current materials, new chemistries must be investigated. One promising strategy is the use of anode-free batteries, which eliminate a significant portion of the mass and volume of the cell, allowing for longer cell lifetimes and more energy storage both per unit volume and per unit weight. However, these cells face three major difficulties: 1) how efficiently they charge and recharge and how much capacity they lose each charge-discharge cycle; 2) the ability to form a naturally protective layer on the deposited lithium metal; and 3) the large volume change each cell experiences on charge and discharge.
In this thesis, we developed some strategies to combat these 3 major challenges. First, we developed a nanoscale thin film coating to improve the efficiency of cycling and extend the cycle life of the cell, by protecting the surface of the lithium metal. This coating effectively lets lithium flow through the coating, while remaining robust and preventing cell degradation during cycling. Next, a bilayer composed of two aluminum based thin film coatings was able to act as an artificial protection layer, greatly improving the efficiency of cycling and extending the lifetime of the cell. Furthermore, the use of a nanowire copper mesh showed attraction to hosting lithium metal and massively improved performance at rapid charge and discharge speeds, while still improving the lifetime of the anode free battery. In the last section, lithium metal is exposed to various gases to create a uniform layer comprised of one of each of the various components of the naturally forming protective layer. The physical and chemical properties of these components are related to their electrochemical performance.
Doyle-Davis, Kieran Michael, "From Understanding to Performance: Interface Design of Anode-Free Batteries" (2023). Electronic Thesis and Dissertation Repository. 9844.
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