Understanding Interfacial Chemistry Interactions in Energy-Dense Lithium-Ion Electrodes

ConspectusFor the past two decades, conversion and alloying-type materials have been heralded as the natural heir to commercially available graphite anodes due to their ability to deliver high gravimetric/volumetric power. Commercialization of batteries with these high-energy-density active materials could impact a variety of sectors including electric vehicles, grid storage, and consumer electronics and contribute toward an ever-increasing electrified world. However, the various failure mechanisms from inherent interfacial chemical instabilities associated with these materials make them unable to be merely substituted into currently available electrode fabrication and formulation processing techniques. As a result, realizing the high theoretical capacity and achieving commercial viability of these materials will rely on the careful manipulation of interfacial chemical interactions that dictate and control various kinetic and transport processes across multiple scales of the composite electrode. This has led to a plethora of research that has focused on systematically understanding properties of the different electrode components and designing carefully constructed electrode formulations to achieve composite electrodes with increased chemical stability, enhanced local mixed conductivities, or improved mechanical resilience.This Account relates recent progress in the understanding of synergetic opportunities for energy-dense, resilient composite anodes. By understanding the interplay between components of the composite electrode, we can construct enhanced well-integrated electrodes with performance metrics that surpass empirically derived architectures. Due to the increased complexity of high-volume-expanding electrodes, performance is more than the cumulative contributions of the individual components, and therefore energy and compatibility matching are important for robust electrochemical performance across cycling, rate capability, facile lithium-ion transport, and stability. In this Account, synergistic opportunities are framed from a chemistry perspective as we focus on examining interfacial interactions that span all electrode components: the active material surface, conductive agent linkage, and polymeric binder mesoscale. Control of key interfacial chemistry can be achieved through chemical functionalization, physical interactions, and other types of linkages and thereby lead to utilization of high-energy-density active materials in robust composite electrodes. Leveraging several techniques such as the Hanson solubility parameter (HSP) analysis, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy among others can be important in gaining mechanistic insights for key kinetic and transport phenomena that occur across multiple interface length scales. Importantly, understanding the underlying effect of interfacial manipulation on the mechanisms of transport and kinetic processes leads to the development of experimental toolsets and design frameworks applicable to not just current material classes but to forward-looking chemistries that can be applied to next-generation battery materials. Herein, we discuss interfacial control of the composite electrodes via chemical modification techniques toward the creation of reliable, long-lasting, energy-dense lithium-ion batteries.