In depth study of charge compensation mechanism in novel 2D layered anode materials for Lithium and Sodium Ion Batteries

Soares, Cindy and Tapia Ruiz, Nuria (2021) In depth study of charge compensation mechanism in novel 2D layered anode materials for Lithium and Sodium Ion Batteries. PhD thesis, Lancaster University.

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Abstract

The development of high-performance electrode materials has become a critical area of research in the lithium and sodium-ion battery (LIBs and SIBs) community to meet the high energy and power density demands of the current and future electrical energy storage applications. So far, the progress in the development of suitable anode materials has been mostly limited to carbon-based materials, metal sulphides and oxides to a minor extent. Overall, these electrodes show room for improvement given their low voltage, low gravimetric density and poor long-term cyclability. Thus, at this juncture, alternative anodes to these with an excellent rate performance and a high capacity with long cyclability must be sought. The discovery of graphene initiated a surge of interest in other two-dimensional (2D) atomically thin materials, such as transition metal dichalcogenides (TMDs). These types of materials have been studied as promising materials for a broad range of applications for decades. The rising interest in these materials is due to their earth-abundant presence in nature, excellent mechanical properties, ability to tune interlayer spacing, good performance when large current densities are applied, long life capability and wide operation range temperatures. Although the excellent theoretical properties of these materials have not yet been reached, TMDs are a group of very promising materials to be used in energy storage. This thesis is a proof of concept to study the viability of two different TMD materials (WTe2 and TaTe2) as anode materials for both LIBs and SIBs. With this study, we will shed a light on the charge compensation mechanisms for these materials during lithium and sodium ion intercalation. The structure of the materials studied in this work was characterised using XRD, SEM and TEM. Their electrochemical response was tested using electrochemical techniques such as galvanostatic cycling, CV and EIS to probe ion (de)intercalation into the electrode crystal structure. Moreover, electrochemical tests were coupled with operando synchrotron XRD and XANES spectroscopy to understand the structural evolution upon ion insertion and extraction.