Date of Award

6-2024

Degree Name

Doctor of Philosophy

Department

Chemical and Paper Engineering

First Advisor

Dr. Qingliu Wu, Ph.D.

Second Advisor

Dr. Dewei Qi, Ph.D.

Third Advisor

Dr. Kecheng Li, Ph.D.

Fourth Advisor

Dr. Wenquan Lu, Ph.D.

Keywords

Fast charging, graphite anode, lithium plating/dendrite, lithium-ion batteries, screen printing, secondary pore network electrode

Abstract

The rapid growth of the electric vehicle (EV) market has demanded lithium-ion batteries (LIBs) with high energy density and fast charging capability. However, charging energy-dense LIBs with thick graphite electrodes at high current densities is typically facing challenges and leading to adverse performance, such as low energy density, short cycle life, rapid temperature rises and safety issues. The root cause is the onset of Li plating. During fast charging application, the sluggish lithium ions accumulated at the surface of graphite due to kinetic limitation and formed Li plating, especially when lithiated to a high state of charge (SOC). It has been well recognized that introducing a secondary porous network (SPN) into the electrodes can effectively improve the electrochemical performance of LIBs, especially under fast-charging operations. However, the process complexity and high cost limit the wide adoption of electrodes with SPNs into the electrical vehicle (EV) batteries.

To address this issue, this work firstly proposed a facile screen-printing process to produce graphite electrodes with SPNs. To identify the best anode material in Chapter 2, we studied the effect of particle size on the electrochemical behavior of electrodes containing graphite with various particle sizes (D50 6.5 to 22.4 μm) under fast charge operations. Results from both experimental and theoretical studies exhibited the superiority of small particles over big particles in terms of suppressing the onset of Li plating and growth of plated Li particles. In Chapter 3, the rheological properties of inks with various formulas were studied. Results from the rheology measurements indicated that the slurry viscosity plays a key parameter in determining the processibility of the printing process and quality of final products. Compared to particle size, the solid content has a more significant influence on the viscosity of the graphite slurries. Based on the results from printing trials, a printability window was established and validated to guide the slurry fabrication for high quality printing process and printed products. In Chapter 4 and 5, appropriate graphite electrodes were fabricated through the screen printing with designed patterned pore channels with selected graphite and developed formula by using the slurries with the formula identified in Chapter 3. The examined results demonstrated the advantages of the printing process in manufacturing graphite electrodes with precisely controlled porous structure including pore diameter and pore-to-pore distance. Used as anodes, the printed graphite electrodes demonstrated superior rate capability and durability over the conventional electrodes with uniform porous architectures at high rates.

In summary, this work firstly proposed and successfully developed a facile screen-printing process to manufacture high energy density electrodes with designed porous architecture. These printed patterned electrodes showed a great success in the fast-charging applications through effectively suppressing the Li plating, high rate capability and long cycle life. Combining with the advantages of low cost and high throughput, this technology has the potential of replacing traditional process to manufacture electrodes for fast-charging application.

Access Setting

Dissertation-Open Access

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