Development of High-Performance All-Solid-State Batteries
Abstract
All-solid-state batteries (ASSBs) with polyethylene oxide (PEO)-based solid polymer electrolytes (SPEs) or oxide-based solid-state electrolytes (SSEs) are promising candidates for electric vehicles application. However, ASSBs suffer from critical challenges including (i) low electrochemical oxidation window, (ii) poor interface contact, (iii) incompatibility between the SSE and electrode. This thesis, therefore, focuses on various strategies for addressing these problems and understanding the insight mechanisms.
To address the low oxidation window challenge of SPE, surface engineering method was used. The surface coating on LiCoO2, and/or carbon particles with lithium tantalate was conducted. This study disclosed that carbon particles/SPE interface is detrimental to the electrochemical decomposition of SPE. Further, lithium niobium oxide engineering NMC811/SPE interface was done for improving the stability of NMC811 particles and alleviating the decomposition of SPE.
Moreover, the oxidation window of SPE was increased by engineering the end functional group of PEO. Stable performance ASSBs were obtained with the dimethylamine end group SPE. Besides, the binders’ effect was studied. PEO binder are not practical for 4 V class cathodes because of its low oxidation window, while carboxyl-rich polymer binders have superior performance. Mechanism studies showed that they have higher voltage stability and work as a coating material to protect electrode/SPE interface.
The poor contact between oxide-based SSE and cathode particles was addressed with solution method synthesized Li3InCl6 SSE. The incompatibility between NASICON SSEs and sulfur cathodes is tackled with ultra-thin Al2O3 protection.
The discoveries of this thesis provide important guidance to design high performance, high energy density ASSBs.