By Dr Kang Xu, U. S. Army Research Laboratory, USA.
Interphases enables the electrodes to operate at potentials beyond what thermodynamic stability limits of non-aqueous electrolytes would allow. The most prominent example of interphases is perhaps solid-electrolyte-interphase (SEI) on graphitic anodes in Li-ion batteries, which ensures the reversibility of Li-ion intercalation chemistries. In typical electrolytes, chemical building blocks of SEI mainly come from solvents decomposition products, and, although we often acknowledge that many aspects of SEI remain unknown, we thought we at least have established the following foundation beyond doubt: (1) semi-carbonates from the single-electron reduction of carbonate solvents constitute the major portion of SEI; (2) the formation of SEI is irreversible; and (3) SEI is ionic conductor and electron insulator. However, when taking a closer look at the “olde SEI” using a series of new techniques, we found some of those principles might need to be re-written.
In this work, I will summarize the newest understanding of this “least understood” component in Li-ion battery that was achieved in my own group and my collaborators.
Kang Xu has been doing researches on electrolyte materials and interphasial chemistry for electrochemical devices. He has been recognized multiple times by Awards both inside and outside of Department of Defense.
He has published over 140 papers in peer-reviewed journals, written/edited 3 chapters/books, and currently holds 20 issued U. S. patents. Among these he is best known in the field for the two comprehensive reviews at Chemical Reviews in 2004 and 2014, which were regarded as desk references by the researchers, and a paper at Science in 2015 that marks the seminal work on high voltage aqueous electrolytes. He is an active member of the Electrochemical Society and Materials Research Society, and often serves in various academic/governmental/industry panels as expert in energy storage technology and materials. In 2016 he was elected ARL Fellow. His publications have received 11,000+ citations in the open literature, with an h-index of 57. He was recently awarded the Electrochemical Society Battery Research award.