Development of High Performance, Next-Generation Li-ion Battery Electrode Materials: Sulfur, Carbon and Silicon
As of late, there has been an increasing interest in research to characterize and develop a new generation of Li-ion electrode materials that exhibit Li storage performance that goes beyond the incumbent Li-ion chemistries, such as graphite and lithium cobalt oxide, or LCO. LCO, pioneered by Dr. John B. Goodenough in the 1980s, has prevailed as the most common Li-ion cathode for decades, serving as a relatively stable, energy dense intercalation material with a high operating voltage and specific energy of 3.6V (nominal) and 240 Wh/kg, respectively. As well, graphite has served as the most ubiquitous secondary battery anode for an even longer period of time. As a light, cheap and reliable material, the stacks of carbon sheets within graphite have acted as a robust host for lithium, allowing the Li ions to be inserted and removed for hundreds and thousands of cycles at a low voltage. The principle method of preparing these electrode materials has been though large-scale slurry-casting on to metal foils, calendaring, and winding into various form factors, such as cylindrical or pouch. The slurry is the term used for the suspension of active electrode material (powderized), conductive additive (nano-sized carbon), and a dissolved binder, which acts as an adhesive and/or thickening agent. While LCO and graphite have provided the energy density and power density needed to realized various technologies up until today, there is a need to push the boundaries of rechargeable chemistries in terms of energy density, rate capability (related to power density), and more sensible battery “sandwich” configurations and architectures. Three promising electrode systems for future Li-ion batteries that will improve these characteristics are sulfur cathodes, altered carbon anodes, and silicon-based anodes.