[ChBE-Grad] ChBE Seminar this Tuesday- students

[Solano, Nicolette]

It is mandatory for the groups of Harold, Grabow, Epling, Balakotaiah and Rimer to attend. All others may join if they wish. Thank you!




UH ChBE Dept. Seminar
9:00am-10:00am, Tuesday , February 23, 2016
Cemo Hall, room 105
Controlling the Surface Chemistry of Electrode Materials for High Energy Rechargeable Batteries
Feng Lin
Lawrence Berkeley National Laboratory


ABSTRACT: Chemical evolution and structural transformations at the surface of an electrode material influence greatly the key performance metrics of lithium batteries, including energy density, power capability, safety and cycle life. This presentation will discuss how we bridge the design principles of surface chemistry in electrode materials with advanced characterization tools, in pursuit of safer and durable lithium batteries. First, a high-throughput analytical method, based on synchrotron X-ray spectroscopy, is developed to investigate the surface phase irreversibility of lithium ion battery materials, a phenomenon that has been widely observed yet poorly understood. It is found that, in the technologically important LiNi1−x−yMnxCoyO2 cathode materials, surface reconstruction from a layered to a rock-salt structure is commonly observed under a variety of battery operating conditions, particularly in high energy Ni-rich compositions. This phenomenon results in poor high-voltage cycling performance, impeding attempts to improve the energy density by widening the potential window at which these electrodes operate. Subsequently, both experimental and computational approaches, including selective surface metal segregation and aliovalent substitution, are developed to optimize LiNi1−x−yMnxCoyO2 materials. The tailored surface metal segregation (i.e., Mn-rich and Ni-poor) results in superior resistance to surface reconstruction compared with those of conventional LiNi1−x−yMnxCoyO2 materials, due to the minimized unpaired Ni3d-eg electrons at the outmost layer of LiNi1−x−yMnxCoyO2 materials. On the other hand, an examination of the structural and electronic modifications reveals that aliovalent substitution of Co3+ sites by Ti4+ can largely reduce the structural distortions during delithiation, which could be ascribed to the larger cation radius of Ti4+ relative to Co3+ and the presence of an electron polaron on the Mn cations induced by Ti4+. The successful Ti aliovalent substitution in the LiNi1−x−yMnxCoyO2 composite leads to improved capacity and cycle life of the cells. This presentation will demonstrate the great importance of controlling surface chemistry of cathode materials for the successful development of high-energy lithium batteries. It is expected that this work could help accelerate the implementation of LiNi1−x−yMnxCoyO2 materials in electric vehicles and other energy storage facilities.

BIO: Dr. Feng Lin is currently a Senior Member of Technical Staff at a stealth energy company in Silicon Valley, and an affiliate scholar at Lawrence Berkeley National Laboratory (LBNL). In 2013-2015, he performed postdoctoral research in Dr. Marca Doeff’s group at LBNL, on the topics of rechargeable batteries, electrocatalysis and synchrotron core-level spectroscopy. He holds a Bachelor’s degree (2009) in Materials Science and Engineering from Tianjin University, and an MSc degree (2011) and a PhD degree (2012) in Materials Science from Colorado School of Mines. His graduate research was co-advised by Prof. Ryan Richards, Dr. Anne Dillon and Dr. Chaiwat Engtrakul at National Renewable Energy Laboratory and Colorado School of Mines, where he developed multicomponent inorganic materials for electrochromic smart windows and catalysis. Dr. Feng Lin served the electrochemistry community of Northern California as the Chair of the Electrochemical Society-San Francisco Section during 2013-2014 (currently as the Past Chair).  In 2015, he received Spicer Young Investigator Award from SLAC National Accelerator Laboratory, and was a finalist of Young Scientists Award of International Society for Solid State Ionics. His research in batteries was selected to the Top 10 Scientific Achievements by Brookhaven National Laboratory in 2014. Dr. Feng Lin is currently serving the Users Executive Committee of Stanford Synchrotron Radiation Lightsource on a 3-year term (2015-2017).

















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