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 Al₂O₃/AlF₃-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 LiNO₃ and TMSP to design an electrolyte that can form good CEI/SEI. Based on the...[ Read more ]

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 Al₂O₃/AlF₃-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 LiNO₃ and TMSP to design an electrolyte that can form good CEI/SEI. Based on the decomposition mechanism of LiNO₃ 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 LiNO₃, due to its low solubility, a small amount of LiNO₃ is insufficient for protecting the negative electrode. Therefore, in Chapter 5, I further explored the factors affecting the solubility and electrochemical stability of LiNO₃. By adjusting the components and increasing LiNO₃ 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.