Van Marum Colloquium: Electrocatalytic transformations in Li-ion Battery Electrolytes
- Dr. Dusan Strmcnik (Argonne National Laboratory)
- Thursday 7 December 2023
Niels Bohrweg 2
2333 CA Leiden
In the pursuit of sustainable transportation solutions, lithium-ion batteries (LiBs) have emerged as a pivotal technology, revolutionizing the automotive industry by powering electric vehicles (EVs) and hybrid electric vehicles (HEVs). Their remarkable features, including high energy density, extended lifespan, and rapid charging capabilities, have positioned them as a viable alternative to conventional internal combustion engines. With continuous advancements in battery technology, EVs have become more accessible and cost-effective, promoting a greener and cleaner transportation ecosystem. Furthermore, the integration of renewable energy sources with LiBs enables the storage and distribution of clean electricity, setting the stage for a renewable-powered transportation future.
Despite their widespread use and decades of research, commercial LiBs continue to grapple with significant challenges, primarily concerning performance degradation over time. A consensus in the scientific community identifies the solid-electrolyte interphase (SEI), forming on the anode side of the LiB during the initial charging cycles, as a one of the critical drivers of efficiency loss. Furthermore, while current LiB technology boasts impressive energy and power density, high coulombic efficiency, and extended lifespan, further enhancements are urgently needed to meet the stringent requirements of electrifying the transportation sector, a major contributor to fossil fuel consumption and greenhouse gas emissions. These requirements include improving vehicle autonomy range, affordability, and safety.
To achieve these goals, it is imperative to enhance battery energy density by increasing the capacity of battery electrode materials or raising the battery's operating voltage. Since capacity is approaching the theoretical limit of the Li-ion battery concept, increasing voltage becomes a paramount objective to achieve high-energy densities. This necessitates the development of high-voltage cathode materials capable of operating at 4.5 V and beyond. However, the pursuit of higher voltages strains the inherent stability of cathode-electrolyte interface (CEI).
Addressing these challenges in existing and emerging LiB technologies requires a comprehensive understanding of the degradation processes at both the anode- and cathode-electrolyte interfaces. Unfortunately, this understanding remains underdeveloped in non-aqueous electrolytes when compared to aqueous systems. In the realm of LiB electrolytes, the complexity stemming from numerous possible competing and interrelated (electro)-chemical reactions, determined by electrolyte components and compounded by the nature and morphology of the electrode material, hampers the understanding of electrochemical interfaces at atomic/molecular level. Consequently, the physical and chemical properties of SEI and CEI are subjects of ongoing and vigorous debate, often yielding substantially different interpretations of their nature, structure, and origin.
In this seminar, we will delve into the electrochemistry of the most common components of LiB electrolytes, exploring their behavior on well-defined metal and carbon electrodes. The use of model systems enables us to accurately assess the contributions of individual chemical and electrochemical processes at the cathode and anode interfaces and relate them to electrode and electrolyte properties, double layer structure, impurity content, and more. We will demonstrate that most electrochemical reactions in the LiB environment adhere to general principles of electrocatalysis and draw parallels between LiB and aqueous electrolytes.