Alkali metal ion batteries (e.g., lithium and sodium ion batteries) are regarded as the most promising energy storage devices because of their advantages such as high energy density and long life span. Cathode, anode and electrolyte are the main components that govern the electrochemical processes and performance of batteries. Most practically viable cathode materials utilize the redox chemistry of transition metals, where charge compensation takes place through alternating 3d orbital occupancies. To deliver the practical promise that alkali ion batteries hold, methods need to be established to tackle fundamental challenges in batteries, including structural and chemical transformations of cathode materials, nature of electrode-electrolyte interfacial reactions, and rate-determining steps in fast charging. These challenges are rooted in the interfacial charge transfer processes and determine the energy density, power density, and safety of batteries. However, most of the studies still focus on exploring new electrode materials containing different transition metals. Meanwhile, elements substitution and/or doping are wildly employed to eliminate the irreversible bulk structure transformations. Herein, we report the interfacial descriptors such as atomic orbitals and local coordination that drive the interfacial reactions and phase transformations. In our presentation, we will present several representative layered cathode materials to clarify the interfacial related fundamental questions. Combining scanning transmission energy microscopy-electron energy loss spectroscopy and X-ray absorption spectroscopy, we find that the electrode–electrolyte interface side reactions, surface degradation, intragranular crack are mainly responsible for the cells performance decay. Finally, we then develop a simple and efficient surface transformation method, that is controlling the characteristics of transition metal-oxygen bonds, to stabilize the interphases and accelerate the charge transfer processes and in turn improve the batteries performance by inhibiting the interfacial side reactions.

Degradation-enabled protection of cathode materials for alkali metal ion batteries

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.