Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Mechanical and Materials Engineering

Supervisor

Sun Xueliang

Abstract

All-solid-state lithium batteries (ASSLBs) have gained substantial attention owing to their excellent safety and high energy density. However, the development of ASSLBs has been hindered by large interfacial resistance originating from the detrimental interfacial reactions, poor solid-solid contact, and lithium dendrite growth. The research in this thesis aims at achieving high-performance ASSLBs via rational interface design and understanding the interfacial reaction mechanisms.

At the cathode interface, an ideal dual core-shell nanostructure was first designed. Moreover, single-crystal LiNi0.5Mn0.3Co0.2O2 (SC-NMC532) cathode was compared with polycrystalline NMC532, the former exhibits much enhanced Li+ diffusion kinetics in ASSLIBs. Besides, it is found that the interfacial structural degradation significantly impedes interfacial Li+ transport in ASSLIBs. Fortunately, the interfacial coating is demonstrated to be effective in suppressing interfacial degradation.

Furthermore, the ionic conductivity of interfacial layer LNTO was purposely tuned to investigate the effect of interfacial ionic conductivity on ASSLIBs, it is revealed that enhancing the interfacial ionic conductivity is very crucial for high-performance ASSLBs. The conclusion was confirmed by the in-situ growth of Li3InCl6. The high Li+-conductive Li3InCl6 coated LCO demonstrates an ultra-small interfacial resistance of 0.13 W.cm-2 and excellent electrochemical performance.

At the anode interface, an inorganic-organic hybrid interlayer and a solid-state plastic crystal electrolyte were successfully engineered to prevent the interfacial reactions and lithium dendrite formation. Last but not least, a solid-liquid hybrid electrolyte was developed as interfacial solid-liquid electrolyte interphase (SLEI) to achieve high-performance ASSLBs.

In summary, the discoveries in this thesis provide important guidance to achieve high-performance ASSLBs via rational interface design.

Summary for Lay Audience

Because of the high energy density and the great safety feature, all-solid-state lithium batteries (ASSLBs) have aroused substantial attention in recent years. However, large interfacial resistance originating from the detrimental interfacial reactions, poor solid-solid contact, and lithium dendrite growth hinders the realization of ASSLBs. This thesis described various interfacial strategies to overcome large interface resistance. In addition, advanced characterizations including synchrotron radiation and high-solution transmission electron microscopy (HRTEM) were adopted to understand interfacial Li+ transport kinetics and interfacial reaction mechanism.

Specifically, an ideal dual core-shell nanostructure was first designed at the cathode interface, which demonstrates high-performance ASSLBs. Furthermore, single-crystal cathodes were found too much better than polycrystalline cathodes in ASSLBs. Besides, via HRTEM and synchrotron radiation characterization, it is found that the oxygen loss from the cathode materials can deteriorate the interfacial structure change of oxide cathodes. Fortunately, the interfacial coating is demonstrated to be effective in suppressing interfacial structure change. Moreover, it is also found that the interfacial ionic conductivity of the coating layer is very crucial for achieving high-performance ASSLIBs. Following this conclusion, a high Li+-conductive Li3InCl6 coating layer was in-situ grown on LCO surface, demonstrating an ultra-small interfacial resistance of 0.13 W.cm-2 and excellent electrochemical performance.

An inorganic-organic hybrid interlayer and a solid-state plastic crystal electrolyte were successfully engineered to prevent the interfacial reactions and lithium dendrite formation at the anode interface. Last but not least, a solid-liquid hybrid electrolyte was developed as an interfacial solid-liquid electrolyte interphase (SLEI) for high-performance solid-state batteries.

In summary, the discoveries in this thesis would provide important guidance to achieve high-performance ASSLBs.

Available for download on Saturday, January 01, 2022

Share

COinS