THESIS
2023
1 online resource (xxvi, 202 pages) : illustrations (chiefly color)
Abstract
Nowadays, lithium-ion batteries are widely used in our life. However, the energy density
is not enough. Improving energy density always induces decreased cycling stability and
electrolyte influence greatly to the stability. Therefore, it is essential to design suitable new
electrolytes to improve the cycling stability of high-energy-density lithium batteries.
In Chapter 3, by using AIP as an additive, I formed Al
2O
3/AlF
3-rich CEI on the cathode.
This CEI can protect NCM and decrease electrolyte decomposition, achieving a 97.8% (200
cycles) of 4.3V NCM811‖Li cells, higher than the control group's 78.7%. Since the electrolyte
design in Chapter 3 only focuses on the positive electrode CEI, in Chapter 4, I used LiNO
3 and
TMSP to design an electrolyte that can form good CEI/SEI. Based on the...[
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Nowadays, lithium-ion batteries are widely used in our life. However, the energy density
is not enough. Improving energy density always induces decreased cycling stability and
electrolyte influence greatly to the stability. Therefore, it is essential to design suitable new
electrolytes to improve the cycling stability of high-energy-density lithium batteries.
In Chapter 3, by using AIP as an additive, I formed Al
2O
3/AlF
3-rich CEI on the cathode.
This CEI can protect NCM and decrease electrolyte decomposition, achieving a 97.8% (200
cycles) of 4.3V NCM811‖Li cells, higher than the control group's 78.7%. Since the electrolyte
design in Chapter 3 only focuses on the positive electrode CEI, in Chapter 4, I used LiNO
3 and
TMSP to design an electrolyte that can form good CEI/SEI. Based on the decomposition
mechanism of LiNO
3 at high voltage, I designed BTSN and FTSN, and achieved 80% (800
cycles) of 4.6V LCO‖Li batteries. Although Chapter 4 explored the oxidation mechanism of
LiNO
3, due to its low solubility, a small amount of LiNO
3 is insufficient for protecting the negative electrode. Therefore, in Chapter 5, I further explored the factors affecting the solubility
and electrochemical stability of LiNO
3. By adjusting the components and increasing LiNO
3
concentration, I finally achieved 95% (200 cycles) of 4.6V LCO‖Li batteries and higher Li‖Cu
efficiency compared to Chapter 4. In Chapter 6, continuing the idea of polymer CEI, I used
Lewis base additives to promote the elimination polymerization reaction of fluorinated
carbonate and designed electrolytes with Lewis base. I found electrolytes can influence CEI
morphology. Finally, I achieved almost no attenuation after 200 cycles of 4.6V LCO‖Li
batteries, and the cycling stability exceeded 95% (500 cycles).
My work focuses on exploring the relationship between lithium battery electrolyte design,
CEI/SEI composition, and cycling stability, which will help the development of future high-energy-density lithium batteries.
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